Android application crashes every time on startup

Android application crashes every time on startup - java

I started coding my first app in Android Studio, what it should do at this stage is that you click a button with the digit and it outputs it into the textfield. When i run this code the application crashes right on startup and I have no idea what's wrong.
MyActivity.java
package com.example.david.calculator;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import org.w3c.dom.Text;
public class MyActivity extends Activity {
EditText results;
private int number;
final EditText result = (EditText) findViewById(R.id.number);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
BtnPressed(1);
}
});
}
private void BtnPressed(int i) {
result.setText(Integer.toString(i));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.my, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
activity_my.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".MyActivity">
<EditText
android:layout_width="fill_parent"
android:layout_height="50dp"
android:id="#+id/number"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:hint="0"
android:background="#ffe7e7e7"
android:textSize="30sp"
android:gravity="center_vertical|right"
android:paddingRight="20dp"
android:editable="true"
android:enabled="true"
android:numeric="integer|signed|decimal" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="1"
android:id="#+id/button"
android:layout_below="#+id/number"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_marginTop="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="2"
android:id="#+id/button2"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button"
android:layout_toRightOf="#+id/button"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="3"
android:id="#+id/button3"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button2"
android:layout_toRightOf="#+id/button2"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="4"
android:id="#+id/button4"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_below="#+id/button"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="5"
android:id="#+id/button5"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button4"
android:layout_toRightOf="#+id/button4"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="6"
android:id="#+id/button6"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button5"
android:layout_toRightOf="#+id/button5"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="7"
android:id="#+id/button7"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_below="#+id/button4"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="8"
android:id="#+id/button8"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button7"
android:layout_toRightOf="#+id/button7"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="9"
android:id="#+id/button9"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button8"
android:layout_toRightOf="#+id/button8"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="0"
android:id="#+id/button11"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_below="#+id/button7"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginTop="10dp" />
<Button
android:layout_width="160dp"
android:layout_height="75dp"
android:text="="
android:id="#+id/button12"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button11"
android:layout_toRightOf="#+id/button11"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="+"
android:id="#+id/button13"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button3"
android:layout_toRightOf="#+id/button3"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="-"
android:id="#+id/button14"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button6"
android:layout_toRightOf="#+id/button6"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="*"
android:id="#+id/button15"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button9"
android:layout_toRightOf="#+id/button9"
android:layout_marginLeft="10dp" />
<Button
android:layout_width="75dp"
android:layout_height="75dp"
android:text="/"
android:id="#+id/button16"
android:textSize="50sp"
android:background="#ff0fdf22"
android:layout_alignTop="#+id/button12"
android:layout_toRightOf="#+id/button12"
android:layout_marginLeft="10dp" />
Logcat:
07-24 16:30:07.894 26564-26564/com.example.david.calculator D/AndroidRuntime﹕ Shutting down VM
07-24 16:30:07.894 26564-26564/com.example.david.calculator W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4190aba8)
07-24 16:30:07.899 26564-26564/com.example.david.calculator E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.david.calculator, PID: 26564
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.david.calculator/com.example.david.calculator.MyActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.app.Activity.findViewById(Activity.java:1884)
at com.example.david.calculator.MyActivity.<init>(MyActivity.java:18)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1208)
at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Thank you very much for all the replies.

You are setting your EditText in your main class and not in your classes onCreate method. You can't find a view if the activity hasn't been created yet.
public class MyActivity extends Activity {
EditText results;
private int number;
final EditText result = (EditText) findViewById(R.id.number);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
BtnPressed(1);
}
});
}
Should become
public class MyActivity extends Activity {
EditText results;
private int number;
private EditText result;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
result = (EditText) findViewById(R.id.number);
Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
BtnPressed(1);
}
});
}
You were getting a NullPointerException in your log, this should fix it.

You should move
final EditText result = (EditText) findViewById(R.id.number);
inside onCreate(...) after setContentView(..)
Corrected Code
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
EditText result = (EditText) findViewById(R.id.number);
Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
BtnPressed(1);
}
});
}

Check your code:
final EditText result = (EditText) findViewById(R.id.number);
This should come after setContentView() method just like with the button.

You should do this:
final EditText result = (EditText) findViewById(R.id.number);
in your onCreate after the setContentView.

Related

Button onClickListener and textView.setText won't work in AlertDialog

So I was trying to Build a Custom AlertDialog onSongCompletionListener but there's an issue...
The AlertDialog would appear if I remove the onClickListeners of buttons present in the Dialog...
But the would crash when I add the listeners..
Here is a screenshot of the Dialog, the buttons appear but won't work though as I had removed the listeners:
Heres my code;
completedSongName = (TextView) findViewById(R.id.completedSongName);
playAnotherSong = (Button) findViewById(R.id.buttonPlayAnotherSong);
replayCurrentsong = (Button) findViewById(R.id.buttonPlayAgain);
tstBtn = (Button) findViewById(R.id.testBtn);
// ON COMPLETE LISTENERS
onCompletionDialog = new Dialog(this);
testSong.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
#Override
public void onCompletion(MediaPlayer mp) {
onCompletionDialog.setContentView(R.layout.songcompletedialog);
completedSongName.setText("testSong");
playAnotherSong.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
onCompletionDialog.dismiss();
}
});
replayCurrentsong.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
testSong.start();
}
});
onCompletionDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
onCompletionDialog.show();
}
});```
Here is the XML
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:gravity="center">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:cardCornerRadius="20dp"
app:cardBackgroundColor="#color/colorGreenLight"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_marginTop="25dp"
android:layout_marginBottom="25dp">
<ImageView
android:id="#+id/musicIconFinished"
android:layout_width="64dp"
android:layout_height="64dp"
android:padding="7sp"
android:layout_centerHorizontal="true"
android:layout_marginStart="10sp"
android:background="#drawable/circle_dark_green"
android:src="#drawable/ic_library_music_white" />
<TextView
android:id="#+id/completedTextLabel"
android:layout_below="#+id/musicIconFinished"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:textAlignment="center"
android:textStyle="bold"
android:textSize="20sp"
android:textColor="#color/colorGreen"
android:layout_marginTop="20dp"
android:text="Completed"
android:fontFamily="#font/productsansregular"/>
<TextView
android:id="#+id/completedSongName"
android:layout_below="#+id/completedTextLabel"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:textAlignment="center"
android:textStyle="normal"
android:textSize="18sp"
android:textColor="#color/colorGreen1"
android:layout_marginTop="8dp"
android:hint="Completed Song Name"
android:fontFamily="#font/productsansregular"/>
<TextView
android:id="#+id/songStartTimeLabel"
android:layout_below="#+id/completedSongName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:textAlignment="textStart"
android:textStyle="normal"
android:textSize="16sp"
android:textColor="#color/colorGreen"
android:layout_marginTop="14dp"
android:text="Start Time:"
android:fontFamily="#font/productsansregular"/>
<TextView
android:id="#+id/songStartTime"
android:layout_below="#+id/completedSongName"
android:layout_toEndOf="#+id/songStartTimeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="5dp"
android:textAlignment="textStart"
android:textStyle="normal"
android:textSize="16sp"
android:textColor="#color/colorGreen1"
android:layout_marginTop="14dp"
android:hint="Start Time:"
android:fontFamily="#font/productsansregular"/>
<TextView
android:id="#+id/songEndTimeLabel"
android:layout_below="#+id/songStartTimeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:textAlignment="textStart"
android:textStyle="normal"
android:textSize="16sp"
android:textColor="#color/colorGreen"
android:layout_marginTop="4dp"
android:text="Start Time:"
android:fontFamily="#font/productsansregular"/>
<TextView
android:id="#+id/songEndTime"
android:layout_below="#+id/songStartTime"
android:layout_toEndOf="#+id/songEndTimeLabel"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="5dp"
android:textAlignment="textStart"
android:textStyle="normal"
android:textSize="16sp"
android:textColor="#color/colorGreen1"
android:layout_marginTop="4dp"
android:hint="Start Time:"
android:fontFamily="#font/productsansregular"/>
<Button
android:layout_width="200dp"
android:layout_height="wrap_content"
android:id="#+id/buttonPlayAnotherSong"
android:layout_below="#id/songEndTime"
android:layout_marginTop="20dp"
android:layout_centerHorizontal="true"
android:text="Play Another Song"
android:fontFamily="#font/productsansregular"
android:textColor="#color/textColorWhite"
android:textSize="14sp"
android:background="#drawable/button_background_green"/>
<Button
android:layout_width="200dp"
android:layout_height="wrap_content"
android:id="#+id/buttonPlayAgain"
android:layout_below="#id/buttonPlayAnotherSong"
android:layout_marginTop="16dp"
android:layout_centerHorizontal="true"
android:text="Replay current song"
android:fontFamily="#font/productsansregular"
android:textColor="#color/textColorWhite"
android:textSize="14sp"
android:background="#drawable/button_background_green"/>
</RelativeLayout>
</LinearLayout>
</android.support.v7.widget.CardView>
</RelativeLayout>
To test the code, I used a testButton ..
testButton.onClick ... pop up would appear ..
THE CULPRIT IS:
completedSongName.setText("testSong");
playAnotherSong.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
onCompletionDialog.dismiss();
}
});
replayCurrentsong.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
testSong.start();
}
});
onCompletionDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
onCompletionDialog.show();
}
What error it shows??
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.innocentapps.musicplayerstrial, PID: 7928
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:390)
at android.view.View.performClick(View.java:6600)
at android.view.View.performClickInternal(View.java:6577)
at android.view.View.access$3100(View.java:781)
at android.view.View$PerformClick.run(View.java:25912)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6923)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:870)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385)
at android.view.View.performClick(View.java:6600) 
at android.view.View.performClickInternal(View.java:6577) 
at android.view.View.access$3100(View.java:781) 
at android.view.View$PerformClick.run(View.java:25912) 
at android.os.Handler.handleCallback(Handler.java:873) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:193) 
at android.app.ActivityThread.main(ActivityThread.java:6923) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:870) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at com.innocentapps.musicplayertrial.MainActivity.showOnCompletionPopUp(MainActivity.java:564)
at java.lang.reflect.Method.invoke(Native Method) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:385) 
at android.view.View.performClick(View.java:6600) 
at android.view.View.performClickInternal(View.java:6577) 
at android.view.View.access$3100(View.java:781) 
at android.view.View$PerformClick.run(View.java:25912) 
at android.os.Handler.handleCallback(Handler.java:873) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:193) 
at android.app.ActivityThread.main(ActivityThread.java:6923) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:870) 
I/Process: Sending signal. PID: 7928 SIG: 9
Application terminated.

try this
onCompletionDialog = new Dialog(this);
onCompletionDialog .requestWindowFeature(Window.FEATURE_NO_TITLE);
onCompletionDialog .setContentView(R.layout.songcompletedialog);
completedSongName = (TextView)onCompletionDialog.findViewById(R.id.completedSongName);
playAnotherSong = (Button)onCompletionDialog.findViewById(R.id.buttonPlayAnotherSong);
replayCurrentsong = (Button) onCompletionDialog.findViewById(R.id.buttonPlayAgain);
tstBtn = (Button)onCompletionDialog.findViewById(R.id.testBtn);
and put this whenever you want the dialog to show.
onCompletionDialog.show();

use custom layout inflater in alert dialogbox
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
LayoutInflater inflater = this.getLayoutInflater();
View dialogView = inflater.inflate(R.layout.yourcustomview, null);
dialogBuilder.setView(dialogView);
dialogBuilder.setCancelable(false);
//find id by this way
View view = dialogView.findViewById(R.id.view);
AlertDialog alertDialog = dialogBuilder.create();
alertDialog.setCanceledOnTouchOutside(false);
alertDialog.show();

Android appilcation force stops on hitting the button

Im new to Android and having little problem while running this app. Whenever I hit the "ADD" button on my application it force stops. Please help me out. Im attaching my xml and java code along.
This is the error Im getting:
I/OpenGLRenderer: Initialized EGL, version 1.4
W/EGL_emulation: eglSurfaceAttrib not implemented
W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xe99d1f80, error=EGL_SUCCESS
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: akshay.com.myfirstapp, PID: 13085
java.lang.NumberFormatException: Invalid int: ""
at java.lang.Integer.invalidInt(Integer.java:138)
at java.lang.Integer.parseInt(Integer.java:358)
at java.lang.Integer.parseInt(Integer.java:334)
at akshay.com.myfirstapp.Addition$1.onClick(Addition.java:28)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Application terminated.
Here is my Addition.java
package akshay.com.myfirstapp;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Addition extends AppCompatActivity {
EditText editText2,editText3;
Button button;
TextView textView3;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_addition);
editText2=(EditText)findViewById(R.id.editText2);
editText3=(EditText)findViewById(R.id.editText3);
button=(Button)findViewById(R.id.button);
textView3=(TextView)findViewById(R.id.textView3);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
int i=Integer.parseInt(editText2.getText().toString());
int j=Integer.parseInt(editText3.getText().toString());
int ans=i+j;
textView3.setText(ans);
}
});
}
}
Here is my addition_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_addition"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="akshay.com.myfirstapp.Addition">
<EditText
android:layout_width="150dp"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="#+id/editText2"
android:layout_alignParentTop="true"
android:layout_alignLeft="#+id/editText3"
android:layout_alignStart="#+id/editText3" />
<TextView
android:text="First Number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="36dp"
android:layout_marginStart="36dp"
android:id="#+id/textView"
android:textSize="20sp"
android:layout_alignBottom="#+id/editText2"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<TextView
android:text="Second Number"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="33dp"
android:id="#+id/textView2"
android:textSize="20sp"
android:layout_below="#+id/textView"
android:layout_alignLeft="#+id/textView"
android:layout_alignStart="#+id/textView" />
<EditText
android:layout_width="150dp"
android:layout_height="wrap_content"
android:inputType="textPersonName"
android:ems="10"
android:id="#+id/editText3"
android:layout_alignBaseline="#+id/textView2"
android:layout_alignBottom="#+id/textView2"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="Add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/button"
android:layout_below="#+id/editText3"
android:layout_centerHorizontal="true"
android:layout_marginTop="71dp" />
<TextView
android:text="Sum"
android:layout_height="wrap_content"
android:id="#+id/textView3"
android:textSize="25sp"
android:layout_width="100dp"
android:layout_below="#+id/button"
android:layout_centerHorizontal="true"
android:layout_marginTop="64dp" />

An empty string cannot be converted to an Integer, so you need to check that your EditTexts are not empty first.
And as pointed out by #csabapap, the setText method on your TextView should be passed a String.
Final code could look something like this:
if (editText2.getText().length() != 0 && editText3.getText().length() != 0) {
int i=Integer.parseInt(editText2.getText().toString());
int j=Integer.parseInt(editText3.getText().toString());
int ans=i+j;
textView3.setText(String.valueOf(ans));
}
You may also want to give your EditText variables meaningful names. It is very difficult to tell which one is which, and doing this will save you valuable debugging time later on.

Call another activity from button on camera Android

I'm implementing a Camera app on Android, I'd like to have a button on it which will lead the user to the developer website, or my website.
This button is placed right of the shutter button.
I was trying to call the webview activity from this button, but it's giving me errors and I'm confused on this case, because there are plenty of examples of calling an activity inside another one, but no from a camera app.
I don't know what am I doing wrong.
Here's the piece of code in MainActivity:
public class MainActivity extends Activity /**implements OnClickListener**/ {
ImageView image;
Activity context;
Preview preview;
Camera camera;
Button exitButton;
ImageView fotoButton;
Button webButton;
LinearLayout progressLayout;
String path = "/sdcard/KutCamera/cache/images/";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context=this;
webButton = (Button) findViewById(R.id.imageView_world);
fotoButton = (ImageView) findViewById(R.id.imageView_foto);
exitButton = (Button) findViewById(R.id.button_exit);
image = (ImageView) findViewById(R.id.imageView_photo);
progressLayout = (LinearLayout) findViewById(R.id.progress_layout);
preview = new Preview(this,
(SurfaceView) findViewById(R.id.KutCameraFragment));
FrameLayout frame = (FrameLayout) findViewById(R.id.preview);
frame.addView(preview);
preview.setKeepScreenOn(true);
fotoButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
takeFocusedPicture();
} catch (Exception e) {
}
exitButton.setClickable(false);
fotoButton.setClickable(false);
webButton.setClickable(true);
progressLayout.setVisibility(View.VISIBLE);
}
});
webButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent myIntent = new Intent(MainActivity.this, WebActivity.class);
MainActivity.this.startActivity(myIntent);
}
});
}
Everytime I run it it throws me this error:
4-04 00:33:43.929 4237-4237/com.kut.kutcamera E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kut.kutcamera/com.kut.kutcamera.MainActivity}: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
at android.app.ActivityThread.access$700(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:175)
at android.app.ActivityThread.main(ActivityThread.java:5279)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button
at com.kut.kutcamera.MainActivity.onCreate(MainActivity.java:56)
at android.app.Activity.performCreate(Activity.java:5283)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
at android.app.ActivityThread.access$700(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
at android.os.Handler.dispatchMessage(Handler.java:99)at android.os.Looper.loop(Looper.java:175)
at android.app.ActivityThread.main(ActivityThread.java:5279)
at java.lang.reflect.Method.invokeNative(Native Method)at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)
The layout declaration of the world button is just Okay, I don't really think it's because of that, I guess there is something inside that camera method that doesn't allows me to properly make the call.
Can anybody shed some light on this?
Thanks in advance!
EDIT
activiy_main.xml:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity" >
<FrameLayout
android:id="#+id/preview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1" >
<SurfaceView
android:id="#+id/KutCameraFragment"
android:name="com.kut.camera.KutCameraFragment"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
<RelativeLayout
android:id="#+id/rel_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:alpha="1"
android:background="#android:color/black"
android:orientation="vertical"
android:padding="10dp" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="#+id/textViewReferan"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Photo"
android:textColor="#android:color/white"
android:textSize="16sp" />
<Button
android:id="#+id/button_exit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentTop="true"
android:background="#android:color/transparent"
android:text="Ok"
android:textColor="#2799CF" />
</RelativeLayout>
<LinearLayout
android:id="#+id/progress_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:gravity="center"
android:orientation="vertical"
android:visibility="gone" >
<ProgressBar
android:id="#+id/progressBar1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="#+id/islem_value_textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Loading..." />
</LinearLayout>
</LinearLayout>
<RelativeLayout
android:id="#+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:alpha="0.9"
android:background="#android:color/black"
android:padding="10dp" >
<ImageView
android:id="#+id/imageView_foto"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:src="#drawable/camera"
android:contentDescription="1" />
<ImageView
android:id="#+id/imageView_photo"
android:layout_width="80dp"
android:layout_height="100dp"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:layout_marginRight="5dp"
android:padding="5dp"
android:scaleType="fitCenter"
android:src="#drawable/fotocekicon"
android:contentDescription="2" />
<ImageView
android:id="#+id/imageView_world"
android:layout_width="80dp"
android:layout_height="100dp"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_marginLeft="5dp"
android:padding="5dp"
android:scaleType="fitCenter"
android:src="#drawable/world"
android:contentDescription="2" />
</RelativeLayout>
<ImageView
android:id="#+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/mark3"
android:layout_centerVertical="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
</FrameLayout>
</FrameLayout>

Hi I have update your activity class, just replace with my code let me know you still face the problem.
public class MainActivity extends Activity /**implements OnClickListener**/ {
ImageView image;
Activity context;
Preview preview;
Camera camera;
Button exitButton;
ImageView fotoButton;
ImageView webButton;
LinearLayout progressLayout;
String path = "/sdcard/KutCamera/cache/images/";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context=this;
webButton = (ImageView) findViewById(R.id.imageView_world);
fotoButton = (ImageView) findViewById(R.id.imageView_foto);
exitButton = (Button) findViewById(R.id.button_exit);
image = (ImageView) findViewById(R.id.imageView_photo);
progressLayout = (LinearLayout) findViewById(R.id.progress_layout);
preview = new Preview(this,
(SurfaceView) findViewById(R.id.KutCameraFragment));
FrameLayout frame = (FrameLayout) findViewById(R.id.preview);
frame.addView(preview);
preview.setKeepScreenOn(true);
fotoButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
try {
takeFocusedPicture();
} catch (Exception e) {
}
exitButton.setClickable(false);
fotoButton.setClickable(false);
webButton.setClickable(true);
progressLayout.setVisibility(View.VISIBLE);
}
});
webButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent myIntent = new Intent(MainActivity.this, WebActivity.class);
MainActivity.this.startActivity(myIntent);
}
});
}
Thank you

Null pointer exception on button send [closed]

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Improve this question
Please find below the main class
package com.example.myfirstapp;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
public class MainActivity extends ActionBarActivity {
public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
public void addListenerOnSpinnerItemSelection() {
spinner = (Spinner) findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(new MyOnItemSelectedListener());
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
Button buttonSend;
EditText textTo;
EditText textSubject;
EditText textMessageContact;
EditText textMessageEmail;
EditText textMessageAmount;
Spinner spinner;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
buttonSend = (Button) findViewById(R.id.buttonSend);
textTo = (EditText) findViewById(R.id.editTextSendTo);
textSubject = (EditText) findViewById(R.id.editTextName);
textMessageContact = (EditText) findViewById(R.id.editTextContact);
textMessageEmail = (EditText) findViewById(R.id.editTextEmail);
textMessageAmount = (EditText) findViewById(R.id.editTextAmount);
spinner = (Spinner) findViewById(R.id.spinner);
buttonSend.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
String to = textTo.getText().toString();
String subject = textSubject.getText().toString();
Intent email = new Intent(Intent.ACTION_SEND);
email.putExtra(Intent.EXTRA_EMAIL, new String[] { to });
email.putExtra(Intent.EXTRA_SUBJECT, subject);
email.setType("message/rfc822");
startActivity(Intent.createChooser(email,
"Choose an Email client :"));
}
});
}
}
Also please find below the xml file
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<!-- android:background="#drawable/mmm_bg" -->
<TableLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="40dip" >
<TableRow>
<TextView
android:id="#+id/textViewName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Name:"
android:textColor="#FF0000"
android:textStyle="bold" />
<EditText
android:id="#+id/editTextName"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:layout_weight="3"
android:ems="10"
android:hint="enter the name"
android:textColor="#000000"
android:textStyle="bold" >
<requestFocus />
</EditText>
</TableRow>
<TableRow>
<TextView
android:id="#+id/textViewContact"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Contact:"
android:textColor="#FF0000"
android:textStyle="bold" />
<EditText
android:id="#+id/editTextContact"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:layout_weight="3"
android:ems="10"
android:hint="enter the contact no."
android:textStyle="bold" >
<requestFocus />
</EditText>
</TableRow>
<TableRow>
<TextView
android:id="#+id/textViewEmail"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Email: "
android:textColor="#FF0000"
android:textStyle="bold" />
<EditText
android:id="#+id/editTextEmail"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:layout_weight="3"
android:ems="10"
android:hint="enter the email address"
android:textColorHint="#008080" >
<requestFocus />
</EditText>
</TableRow>
<TableRow>
<TextView
android:id="#+id/textViewProduct"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Product:"
android:textColor="#FF0000"
android:textStyle="bold" />
<Spinner
android:id="#+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="#array/product_array" />
<requestFocus />
<EditText>
</EditText>
</TableRow>
<TableRow>
<TextView
android:id="#+id/textViewAmount"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Amount:"
android:textColor="#FF0000"
android:textStyle="bold" />
<EditText
android:id="#+id/editTextAmount"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:layout_weight="3"
android:ems="10"
android:hint="enter the amount"
android:textStyle="bold" >
<requestFocus />
</EditText>
</TableRow>
<TableRow>
<TextView
android:id="#+id/textViewSendTo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="right"
android:padding="10dip"
android:text="Send To:"
android:textColor="#FF0000"
android:textStyle="bold" />
<EditText
android:id="#+id/editTextSendTo"
android:layout_height="wrap_content"
android:layout_gravity="top|center_horizontal"
android:layout_weight="3"
android:ems="10"
android:hint="reciever&apos;s email address"
android:textStyle="bold" >
<requestFocus />
</EditText>
</TableRow>
</TableLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dip"
android:gravity="center"
android:orientation="horizontal"
android:weightSum="3" >
<Button
android:id="#+id/buttonSend"
android:layout_width="0dip"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="Send" />
</LinearLayout>
</LinearLayout>
please find below the log cat
05-13 09:03:49.935: E/AndroidRuntime(14062): Caused by: java.lang.NullPointerException
05-13 09:03:49.935: E/AndroidRuntime(14062): at com.example.myfirstapp.MainActivity.onCreate(MainActivity.java:89)
05-13 09:03:49.935: E/AndroidRuntime(14062): at android.app.Activity.performCreate(Activity.java:5231)
05-13 09:03:49.935: E/AndroidRuntime(14062): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
05-13 09:03:49.935: E/AndroidRuntime(14062): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
05-13 09:03:49.935: E/AndroidRuntime(14062): ... 11 more
05-13 09:08:50.395: I/Process(14062): Sending signal. PID: 14062 SIG: 9
I am trying to create an app which has 4 to 5 textbox and spinner and send button.
On clicking the send button the email should go to the recipient with the details entered in text boxes. but there occurs null pointer exception.
I am unable to solve the problem. Why is the NPE happening and how to resolve it .
Thanks in advance. Please help me to get through this.

A null pointer exception is very common and means you're trying to access a method or property on an object that is null. Obviously it would not be possible to call such a method (as it doesn't exist).
I suspect that either textTo or textSubject is null, because those are user defined objects. If you set a breakpoint on the line where you set the variable textTo (for example), you should notice that it is null.
When you find the value that is null, then you can figure out how to remedy the situation. If it turns out to be a variable like 'textTo', then check that the resource actually exists, or that you are casting it to the correct object

Just write your if loop after declaration of your all the views in your onCreate() as below:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
buttonSend = (Button) findViewById(R.id.buttonSend);
textTo = (EditText) findViewById(R.id.editTextSendTo);
textSubject = (EditText) findViewById(R.id.editTextName);
textMessageContact = (EditText) findViewById(R.id.editTextContact);
textMessageEmail = (EditText) findViewById(R.id.editTextEmail);
textMessageAmount = (EditText) findViewById(R.id.editTextAmount);
spinner = (Spinner) findViewById(R.id.spinner);
buttonSend.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
String to = textTo.getText().toString();
String subject = textSubject.getText().toString();
Intent email = new Intent(Intent.ACTION_SEND);
email.putExtra(Intent.EXTRA_EMAIL, new String[] { to });
email.putExtra(Intent.EXTRA_SUBJECT, subject);
email.setType("message/rfc822");
startActivity(Intent.createChooser(email,
"Choose an Email client :"));
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}

Android: addTextChangedListener crash app

I have been trying to use the addTextChangedListener for three days, The log says that it is caused by java.lang.NullPointerException. When I comment the addTextChangedListener block the program runs fine.
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class calc extends ActionBarActivity {
EditText text;
private TextView textout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_calc);
text = (EditText) findViewById(R.id.fs);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
text.addTextChangedListener(new TextWatcher() {
#Override
public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
}
#Override
public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) { }
#Override
public void afterTextChanged(Editable s) {
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.calc, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_calc, container, false);
return rootView;
}
}
}
And here we have the log.
01-09 16:03:12.280 1088-1088/com.fuzato.buckconverter E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.fuzato.buckconverter, PID: 1088
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.fuzato.buckconverter/com.fuzato.buckconverter.calc}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.fuzato.buckconverter.calc.onCreate(calc.java:39)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)
The log says that the problem is found in onCreate and it is caused by a java.lang.NullPointerException.
Any thoughts?
Thanks for everything!
Layout:
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:clickable="false">
<GridLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignWithParentIfMissing="false"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginLeft="61dp"
android:layout_marginTop="43dp"
android:id="#+id/gridLayout">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Switching Freq. (Fs)"
android:id="#+id/fs"
android:layout_row="0"
android:layout_column="0" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Output Voltage (V2)"
android:id="#+id/V2"
android:layout_row="1"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/V2"
android:layout_row="1"
android:layout_column="1"
android:text="10" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Volts"
android:id="#+id/textView12"
android:layout_row="1"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Input Voltage (V1)"
android:id="#+id/textView3"
android:layout_row="2"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/V1"
android:layout_row="2"
android:layout_column="1"
android:text="10" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Volts"
android:id="#+id/textView13"
android:layout_row="2"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Duty Cycle (k)"
android:id="#+id/k"
android:layout_row="3"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/k"
android:layout_row="3"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Current Ripple (ΔI)"
android:id="#+id/textView5"
android:layout_row="4"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/deltaI"
android:layout_row="4"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Amps"
android:id="#+id/textView15"
android:layout_row="4"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Voltage Ripple (ΔV)"
android:id="#+id/textView6"
android:layout_row="5"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/deltaV"
android:layout_row="5"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Volts"
android:id="#+id/textView16"
android:layout_row="5"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Max current (Imax)"
android:id="#+id/Imax"
android:layout_row="6"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/Imax"
android:layout_row="6"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Amps"
android:id="#+id/textView17"
android:layout_row="6"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Min Current (Imin)"
android:id="#+id/Imin"
android:layout_row="7"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/Imin"
android:layout_row="7"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Amps"
android:id="#+id/textView18"
android:layout_row="7"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Inductance (L)"
android:id="#+id/Ind"
android:layout_row="8"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/L"
android:layout_row="8"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="mH"
android:id="#+id/textView19"
android:layout_row="8"
android:layout_column="2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Capacitance (C)"
android:id="#+id/cap"
android:layout_row="9"
android:layout_column="0" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/fs"
android:layout_row="0"
android:layout_column="1"
android:text="10" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hz"
android:id="#+id/textView11"
android:layout_row="0"
android:layout_column="2" />
<EditText
android:layout_width="124dp"
android:layout_height="wrap_content"
android:inputType="number"
android:ems="10"
android:id="#+id/C"
android:layout_row="9"
android:layout_column="1" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="uF"
android:id="#+id/textView20"
android:layout_row="9"
android:layout_column="2" />
</GridLayout>
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="#+id/gridLayout"
android:id="#+id/relativeLayout">
</RelativeLayout>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="apply"
android:id="#+id/button"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/enter"
android:layout_below="#+id/relativeLayout"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_marginRight="94dp"
android:text="3" />
</RelativeLayout>
I have also tried to debbug it in my phone, I get the same problem.

I'm not entirely sure why you app compiles in the first place, but the problem initially was that your findViewById() method was returning null because it couldn't find a view matching your ID.
Your current issues include:
- Your text object is declared as TextView while it should be an
EditText
- In your layout, your view with id R.id.fs is a TextView when it should be an EditText.

try change TextView text; to EditText text;

I found the problem.
My layout was on fragment_main, sorry!
Thanks for the help!!

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Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Android application crashes every time on startup - java

Check your code: final EditText result = (EditText) findViewById(R.id.number); This should come after setContentView() method just like with the button.

You should do this: final EditText result = (EditText) findViewById(R.id.number); in your onCreate after the setContentView.

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