I am trying to define buttons, something like setOnClickListener. I do that in the OnCreate method and when I run my code on android emulator it throws errors.
package com.example.yyy;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.net.wifi.p2p.WifiP2pManager.ActionListener;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
import android.os.Build;
public class MainActivity extends ActionBarActivity implements OnClickListener{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
Button start = (Button)findViewById(R.id.start);
start.setOnClickListener(this);
Button hs =(Button)findViewById(R.id.hs);
hs.setOnClickListener(this);
}
#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);
}
#Override
public void onClick(View v)
{
switch(v.getId())
{
case R.id.start:
Intent find = new Intent(this, Find.class);
startActivity(find);
break;
case R.id.hs:
Toast t = Toast.makeText(this, "w8", Toast.LENGTH_SHORT);
t.show();
break;
default: break;
}
}
}
This is LogCat of this application.
03-19 21:53:13.063: D/dalvikvm(1242): GC_FOR_ALLOC freed 67K, 5% free 3046K/3188K, paused 80ms, total 84ms
03-19 21:53:13.103: I/dalvikvm-heap(1242): Grow heap (frag case) to 4.937MB for 1987216-byte allocation
03-19 21:53:13.233: D/dalvikvm(1242): GC_FOR_ALLOC freed 2K, 3% free 4984K/5132K, paused 127ms, total 127ms
03-19 21:53:14.993: D/AndroidRuntime(1242): Shutting down VM
03-19 21:53:14.993: W/dalvikvm(1242): threadid=1: thread exiting with uncaught exception (group=0xb1a63ba8)
03-19 21:53:15.003: E/AndroidRuntime(1242): FATAL EXCEPTION: main
03-19 21:53:15.003: E/AndroidRuntime(1242): Process: com.example.yyy, PID: 1242
03-19 21:53:15.003: E/AndroidRuntime(1242): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.yyy/com.example.yyy.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.os.Handler.dispatchMessage(Handler.java:102)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.os.Looper.loop(Looper.java:136)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-19 21:53:15.003: E/AndroidRuntime(1242): at java.lang.reflect.Method.invokeNative(Native Method)
03-19 21:53:15.003: E/AndroidRuntime(1242): at java.lang.reflect.Method.invoke(Method.java:515)
03-19 21:53:15.003: E/AndroidRuntime(1242): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-19 21:53:15.003: E/AndroidRuntime(1242): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-19 21:53:15.003: E/AndroidRuntime(1242): at dalvik.system.NativeStart.main(Native Method)
03-19 21:53:15.003: E/AndroidRuntime(1242): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
03-19 21:53:15.003: E/AndroidRuntime(1242): at com.example.yyy.MainActivity.onCreate(MainActivity.java:28)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.Activity.performCreate(Activity.java:5231)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-19 21:53:15.003: E/AndroidRuntime(1242): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-19 21:53:15.003: E/AndroidRuntime(1242): ... 11 more
03-19 21:53:25.683: I/Process(1242): Sending signal. PID: 1242 SIG: 9
And this is main layout.
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000"
tools:context="com.example.yyy.MainActivity"
tools:ignore="MergeRootFrame" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:id="#+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:src="#drawable/cv"
/>
<ImageButton
android:id="#+id/hs"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignRight="#+id/imageView1"
android:layout_marginRight="19dp"
android:src="#drawable/bt_hs_3d"
/>
<ImageButton
android:id="#+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_marginRight="48dp"
android:layout_toLeftOf="#+id/hs"
android:src="#drawable/bt_st_3d"
/>
</RelativeLayout>
</FrameLayout>
This line in the logcat tells you what your problem is:
03-19 21:53:15.003: E/AndroidRuntime(1242): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
You have defined an ImageButton in your XML somewhere, and then in your onCreate method you are trying to cast it to a standard Button by doing this:
Button start = (Button)findViewById(R.id.start);
start.setOnClickListener(this);
Change your code to this:
ImageButton start = (ImageButton)findViewById(R.id.start);
start.setOnClickListener(this);
you are casting imagebutton to button thats why it throws this exception.change
Button start = (Button)findViewById(R.id.start);
to
ImageButton start = (ImageButton)findViewById(R.id.start);
The error is Obvious:
03-19 21:53:15.003: E/AndroidRuntime(1242): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.yyy/com.example.yyy.MainActivity}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
findViewById(R.id.start), returns ImageButton, which you're casting to Button, and hence the crash.
Button start = (Button)findViewById(R.id.start);
I would suggest 2 options:
1) Replace Button in OnCreate method to ImageButton.
Read the following example, it has been nicely explained:
[http://www.mkyong.com/android/android-imagebutton-example/][1]
2) Add android:onClick attribute to as follows...
<ImageButton
android:id="#+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_marginRight="48dp"
android:layout_toLeftOf="#+id/hs"
android:onClick="onStartAction"
android:src="#drawable/bt_st_3d"/>
And you need to implement
public void onStartAction(View v) {
//DO Some thing here....
}
Related
package kdev.circles;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText ca = (EditText)findViewById(R.id.ca);
final EditText cp = (EditText)findViewById(R.id.cp);
final EditText sv = (EditText)findViewById(R.id.sv);
final EditText r = (EditText)findViewById(R.id.radius);
final TextView log = (TextView)findViewById(R.id.log);
Button clear = (Button)findViewById(R.id.clear);
Button solve = (Button)findViewById(R.id.Solve);
clear.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ca.setText("");
cp.setText("");
sv.setText("");
r.setText("");
}
});
solve.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if((r.toString()).equals("")) {
log.setText(log.getText() + "\n" + "error, no value entered");
}else{
sv.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * Double.valueOf(String.valueOf(r.getText())) * 4 / 3 * 3.14159265));
cp.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*3.14159265*2));
ca.setText(String.valueOf(Double.valueOf(String.valueOf(r.getText()))*Double.valueOf(String.valueOf(r.getText()))*3.14159265));
log.setText(log.getText()+"\n"+"ca"+ca.getText()+"\n"+"sv"+sv.getText()+"\n"+"cp"+cp.getText());
}
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
xml file:
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Solve"
android:id="#+id/Solve"
android:width="100dp"
android:layout_alignParentBottom="true"
android:layout_alignEnd="#+id/sv" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="#+id/radius"
android:layout_alignParentTop="true"
android:layout_alignStart="#+id/editText" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="#+id/editText"
android:layout_alignParentTop="true"
android:layout_alignParentEnd="true"
android:layout_marginTop="49dp" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="#+id/editText2"
android:layout_below="#+id/editText"
android:layout_alignStart="#+id/editText" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:ems="10"
android:id="#+id/editText3"
android:layout_below="#+id/editText2"
android:layout_alignStart="#+id/editText2" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="circle's perimeter"
android:id="#+id/cp"
android:layout_above="#+id/editText2"
android:layout_alignParentStart="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="circle's area"
android:id="#+id/ca"
android:layout_above="#+id/editText3"
android:layout_alignParentStart="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="sphere's volume"
android:id="#+id/sv"
android:layout_alignBottom="#+id/editText3"
android:layout_alignParentStart="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="radius"
android:id="#+id/textView3"
android:layout_alignBottom="#+id/radius"
android:layout_alignParentStart="true" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="clear"
android:id="#+id/clear"
android:layout_alignBottom="#+id/Solve"
android:layout_alignStart="#+id/editText3" />
<TextView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="#+id/log"
android:layout_below="#+id/editText3"
android:layout_centerHorizontal="true"
android:layout_marginTop="57dp" />
Everything is working fine till i try opening it, i couldn't find the error, because my android virtual device wasn't connected to android studio properly. I am not sure what i should do. I did have another problem before but i realised that it was due to me using the findviewbyid function before the whole layout was loaded. I have solved that problem and tried a few different techniques to solve this problem but nothing worked.
When i try and run the app it just crashes, i am not sure why?
Any help will be usefull, thank you.
this is the logcat:
12-10 15:21:18.030 1907-1907/kdev.circles W/art﹕ Verification of java.lang.CharSequence android.support.v7.widget.ResourcesWrapper.getQuantityText(int, int) took 123.881364ms
12-10 15:21:18.520 1907-1907/kdev.circles D/AndroidRuntime﹕ Shutting down VM
12-10 15:21:18.520 1907-1907/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kdev.circles, PID: 1907
java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
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.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
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.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
12-10 15:21:27.230 1907-1907/kdev.circles I/Process﹕ Sending signal. PID: 1907 SIG: 9
12-10 15:21:31.360 2153-2153/kdev.circles D/AndroidRuntime﹕ Shutting down VM
12-10 15:21:31.360 2153-2153/kdev.circles E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: kdev.circles, PID: 2153
java.lang.RuntimeException: Unable to start activity ComponentInfo{kdev.circles/kdev.circles.MainActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
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.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatTextView cannot be cast to android.widget.EditText
at kdev.circles.MainActivity.onCreate(MainActivity.java:21)
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.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
Check your view types in Java code and their matching id's in xml. They have to be of same type.
You have EditText in Java, but matching view id in xml is TextView
For instance:
final EditText ca = (EditText)findViewById(R.id.ca);
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="circle's area"
android:id="#+id/ca"
android:layout_above="#+id/editText3"
android:layout_alignParentStart="true" />
I am trying to make a simple android app that will add two numbers and display the output.However, I am getting the following error continuously.
"calculator.com.process stopped unexpectedly"
I used API 10 for rendering layout and API 17 as compiler and Target SDK.
Could post the code finally after all these trouble.
This is the code of main_activity.java
package com.example.calculator;
import android.support.v7.app.ActionBarActivity;
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 android.widget.TextView;
public class MainActivity extends ActionBarActivity {
EditText txtNum1;
EditText txtNum2;
TextView Display;
Button bCal;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txtNum1=(EditText) findViewById(R.id.Num1);
txtNum1=(EditText) findViewById(R.id.Num2);
Display=(TextView)findViewById(R.id.tvDisplay);
bCal=(Button)findViewById(R.id.bAdd);
bCal.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View Tawfiq) {
// TODO Auto-generated method stub
double x=Double.parseDouble(txtNum1.getText().toString());
double y=Double.parseDouble(txtNum2.getText().toString());
double total=x+y;
Display.setText("Sum is"+total);
}
});
}
#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);
}
}
The xml code:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/bAdd"
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="com.example.calculator.MainActivity" >
<EditText
android:id="#+id/Num1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="50dp"
android:ems="10"
android:inputType="numberDecimal" >
<requestFocus />
</EditText>
<EditText
android:id="#+id/Num2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/Num1"
android:layout_below="#+id/Num1"
android:layout_marginTop="33dp"
android:ems="10"
android:inputType="numberDecimal" />
<Button
android:id="#+id/bAdd"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/tvDisplay"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:text="Button" />
<TextView
android:id="#+id/tvDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/Num2"
android:layout_centerHorizontal="true"
android:layout_marginTop="30dp"
android:text="Sum"
android:textAppearance="?android:attr/textAppearanceLarge" />
</RelativeLayout>
This is the logcat.
01-24 16:06:39.840: D/AndroidRuntime(1130): Shutting down VM
01-24 16:06:39.870: W/dalvikvm(1130): threadid=1: thread exiting with uncaught exception (group=0xb60164f0)
01-24 16:06:39.950: E/AndroidRuntime(1130): FATAL EXCEPTION: main
01-24 16:06:39.950: E/AndroidRuntime(1130): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.calculator/com.example.calculator.MainActivity}: java.lang.ClassCastException: android.widget.RelativeLayout
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.os.Handler.dispatchMessage(Handler.java:99)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.os.Looper.loop(Looper.java:130)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread.main(ActivityThread.java:3683)
01-24 16:06:39.950: E/AndroidRuntime(1130): at java.lang.reflect.Method.invokeNative(Native Method)
01-24 16:06:39.950: E/AndroidRuntime(1130): at java.lang.reflect.Method.invoke(Method.java:507)
01-24 16:06:39.950: E/AndroidRuntime(1130): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-24 16:06:39.950: E/AndroidRuntime(1130): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-24 16:06:39.950: E/AndroidRuntime(1130): at dalvik.system.NativeStart.main(Native Method)
01-24 16:06:39.950: E/AndroidRuntime(1130): Caused by: java.lang.ClassCastException: android.widget.RelativeLayout
01-24 16:06:39.950: E/AndroidRuntime(1130): at com.example.calculator.MainActivity.onCreate(MainActivity.java:27)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-24 16:06:39.950: E/AndroidRuntime(1130): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
01-24 16:06:39.950: E/AndroidRuntime(1130): ... 11 more
You are having problem at line no-27
Caused by: java.lang.ClassCastException: android.widget.RelativeLayout
01-24 16:06:39.950: E/AndroidRuntime(1130): at com.example.calculator.MainActivity.onCreate(MainActivity.java:27)
Change the relativeLayouts Id in the xml file.
It should not be same as for the add button.
android:id="#+id/relativeLayout"
Change it as above.
Two id in the same layout cannot be same.
Your add button and the relative layout is having the same id,.
And during the findViewById(), relative layout is being caste in the Button.
That's why class cast exception is coming.
Edit:
I compiled your code:-
the next mistake you have made is-
txtNum1=(EditText) findViewById(R.id.Num2);
It should be
txtNum2=(EditText) findViewById(R.id.Num2);
Mistake-You are not assigning the reference to the second edittext.
I am trying to create an app that lets the user click a button and it will display a random month. I have created a string array in my strings.xml file. Bellow is my main.java, strings.xml and activity.xml. I try to run the app and it just force closes.
package com.example.datebutton;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.graphics.Color;
public class Main extends Activity
{
Button btn;
#Override
public void onCreate(Bundle b)
{
super.onCreate(b);
setContentView(R.layout.activity_main);
btn = (Button) findViewById(R.id.btn1);
final String[] months = getResources().getStringArray(R.array.Months);
final TextView tv =(TextView)findViewById(R.id.text1);
btn.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
int rand = (int) (Math.random() * 12);
tv.setText(months[rand]);
}
});
}
}
here is my activity.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:id="#+id/btn1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="updateMonth"
android:text="#string/app_name" />
<TextView
android:id="#+id/text1"
android:layout_width="68dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center_vertical"
android:text="#array/Months" />
</LinearLayout>
here is my strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">DateButton</string>
<string-array name="Months">
<item>January</item>
<item>Feburary</item>
<item>March</item>
<item>April</item>
<item>May</item>
<item>June</item>
<item>July</item>
<item>August</item>
<item>September</item>
<item>October</item>
<item>November</item>
<item>December</item>
</string-array>
</resources>
I'm still getting errors and the app still says unfortunately your app closed. The logcat is below.
09-11 16:55:17.472: W/Resources(1638): Converting to string: TypedValue{t=0x1/d=0x7f0c0000 a=-1 r=0x7f0c0000}
09-11 16:55:17.512: D/AndroidRuntime(1638): Shutting down VM
09-11 16:55:17.512: W/dalvikvm(1638): threadid=1: thread exiting with uncaught exception (group=0xb3a8fba8)
09-11 16:55:17.532: E/AndroidRuntime(1638): FATAL EXCEPTION: main
09-11 16:55:17.532: E/AndroidRuntime(1638): Process: com.example.datebutton, PID: 1638
09-11 16:55:17.532: E/AndroidRuntime(1638): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.datebutton/com.example.datebutton.Main}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.Button
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.os.Handler.dispatchMessage(Handler.java:102)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.os.Looper.loop(Looper.java:136)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread.main(ActivityThread.java:5017)
09-11 16:55:17.532: E/AndroidRuntime(1638): at java.lang.reflect.Method.invokeNative(Native Method)
09-11 16:55:17.532: E/AndroidRuntime(1638): at java.lang.reflect.Method.invoke(Method.java:515)
09-11 16:55:17.532: E/AndroidRuntime(1638): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-11 16:55:17.532: E/AndroidRuntime(1638): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-11 16:55:17.532: E/AndroidRuntime(1638): at dalvik.system.NativeStart.main(Native Method)
09-11 16:55:17.532: E/AndroidRuntime(1638): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.Button
09-11 16:55:17.532: E/AndroidRuntime(1638): at com.example.datebutton.Main.onCreate(Main.java:24)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.Activity.performCreate(Activity.java:5231)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-11 16:55:17.532: E/AndroidRuntime(1638): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
09-11 16:55:17.532: E/AndroidRuntime(1638): ... 11 more
You forgot to add the line: setContentView(R.layout.activity); before trying to instantiate your button object btn.
To use layout in you Activity you have to connect them both together. Below is how your code should look like:
#Override
public void onCreate(Bundle b) {
super.onCreate(b);
setContentView(R.layout.activity);
btn = (Button) findViewById(R.id.btn1);
final String[] months = getResources().getStringArray(R.array.Months);
final TextView tv =(TextView)findViewById(R.id.text1);
btn.setOnClickListener(new View.OnClickListener(){
public void onClick(View v) {
int r, g, b;
int rand = (int) (Math.random() * 12);
tv.setText(months[rand]);
}
});
}
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 8 years ago.
i am trying to develop this simple app using Android ADT and I got null point exception error. It is returning null point exception error at line 32 which is
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
counter++;
display.setText("your total is" + counter);
}
});
My whole java code is
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
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.widget.*;
public class MainActivity extends ActionBarActivity {
int counter;
Button add , subtract;
TextView display;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById(R.id.badd1);
subtract = (Button) findViewById(R.id.bsub1);
display = (TextView) findViewById(R.id.textView1);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
counter++;
display.setText("your total is" + counter);
}
});
subtract.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
counter--;
display.setText("your total is" + counter);
}
});
}
#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;
}
}
MY xml CODE IS
<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:gravity="center_horizontal"
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="com.example.newboston.MainActivity$PlaceholderFragment" >
<TextView
android:id="#+id/textView1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:text="your total is 0"
android:textSize="45dp" />
<Button
android:id="#+id/badd1"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_below="#+id/textView1"
android:layout_marginTop="34dp"
android:layout_centerHorizontal="true"
android:text="add one"
android:textSize="20dp" />
<Button
android:id="#+id/bsub1"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/badd1"
android:layout_below="#+id/badd1"
android:layout_marginTop="34dp"
android:text="subtract one"
android:textSize="20dp" />
</RelativeLayout>
My logCat file is
03-25 23:10:29.219: D/AndroidRuntime(1211): Shutting down VM
03-25 23:10:29.229: W/dalvikvm(1211): threadid=1: thread exiting with uncaught exception (group=0xb2b10ba8)
03-25 23:10:29.279: E/AndroidRuntime(1211): FATAL EXCEPTION: main
03-25 23:10:29.279: E/AndroidRuntime(1211): Process: com.example.newboston, PID: 1211
03-25 23:10:29.279: E/AndroidRuntime(1211): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.newboston/com.example.newboston.MainActivity}: java.lang.NullPointerException
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.os.Looper.loop(Looper.java:136)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-25 23:10:29.279: E/AndroidRuntime(1211): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 23:10:29.279: E/AndroidRuntime(1211): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 23:10:29.279: E/AndroidRuntime(1211): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-25 23:10:29.279: E/AndroidRuntime(1211): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-25 23:10:29.279: E/AndroidRuntime(1211): at dalvik.system.NativeStart.main(Native Method)
03-25 23:10:29.279: E/AndroidRuntime(1211): Caused by: java.lang.NullPointerException
03-25 23:10:29.279: E/AndroidRuntime(1211): at com.example.newboston.MainActivity.onCreate(MainActivity.java:32)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.Activity.performCreate(Activity.java:5231)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-25 23:10:29.279: E/AndroidRuntime(1211): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-25 23:10:29.279: E/AndroidRuntime(1211): ... 11 more
03-25 23:10:36.449: I/Process(1211): Sending signal. PID: 1211 SIG: 9
If you're using more than one layout file (e.g layout-land, layout-sw360dp), make sure all elements you reference exist on all of them.
This is my very first app. All I need is five buttons, two that call certain phone numbers (only have created one so far) and three buttons that take the user to a certain URL. I have no errors or warnings or any direction on how to navigate the LogCat.
LogCat:
10-08 14:41:40.716: D/AndroidRuntime(793): Shutting down VM
10-08 14:41:40.716: W/dalvikvm(793): threadid=1: thread exiting with uncaught exception (group=0x41465700)
10-08 14:41:40.777: E/AndroidRuntime(793): FATAL EXCEPTION: main
10-08 14:41:40.777: E/AndroidRuntime(793): java.lang.RuntimeException: Unable to start activity ComponentInfo{acps.mhs/acps.mhs.MainActivity}: java.lang.NullPointerException
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.os.Handler.dispatchMessage(Handler.java:99)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.os.Looper.loop(Looper.java:137)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread.main(ActivityThread.java:5103)
10-08 14:41:40.777: E/AndroidRuntime(793): at java.lang.reflect.Method.invokeNative(Native Method)
10-08 14:41:40.777: E/AndroidRuntime(793): at java.lang.reflect.Method.invoke(Method.java:525)
10-08 14:41:40.777: E/AndroidRuntime(793): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-08 14:41:40.777: E/AndroidRuntime(793): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-08 14:41:40.777: E/AndroidRuntime(793): at dalvik.system.NativeStart.main(Native Method)
10-08 14:41:40.777: E/AndroidRuntime(793): Caused by: java.lang.NullPointerException
10-08 14:41:40.777: E/AndroidRuntime(793): at acps.mhs.MainActivity.onCreate(MainActivity.java:25)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.Activity.performCreate(Activity.java:5133)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-08 14:41:40.777: E/AndroidRuntime(793): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
10-08 14:41:40.777: E/AndroidRuntime(793): ... 11 more
10-08 14:42:19.696: I/Process(793): Sending signal. PID: 793 SIG: 9
Mainactivity.java
package acps.mhs;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity implements View.OnClickListener {
Button mhshome, pp, mhsdir, cmhs;
#Override
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
mhshome = (Button) findViewById(R.id.mhshome);
pp = (Button) findViewById(R.id.pp);
mhsdir = (Button) findViewById(R.id.mhsdir);
cmhs = (Button) findViewById(R.id.cmhs);
mhshome.setOnClickListener(this);
pp.setOnClickListener(this);
mhsdir.setOnClickListener(this);
cmhs.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.mhshome:
Uri uri = Uri.parse("http://www2.k12albemarle.org/school/mohs/Pages/default.aspx");
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
break;
case R.id.pp:
Uri uri2 = Uri.parse("http://www2.k12albemarle.org/school/MOHS/Pages/Directory.aspx");
Intent intent2 = new Intent(Intent.ACTION_VIEW, uri2);
startActivity(intent2);
break;
case R.id.mhsdir:
Uri uri3 = Uri.parse("http://www2.k12albemarle.org/school/MOHS/Pages/Directory.aspx");
Intent intent3 = new Intent(Intent.ACTION_VIEW, uri3);
startActivity(intent3);
break;
case R.id.cmhs:
Intent callIntent = new Intent(Intent.ACTION_CALL);
callIntent.setData(Uri.parse("tel:1234567890"));
startActivity(callIntent);
break;
}
}
#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;
}
}
activity_main.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: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=".MainActivity" >
<Button
android:id="#+id/pp"
style="#style/AppBaseTheme"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/mhshome"
android:layout_centerHorizontal="true"
android:layout_marginTop="16dp"
android:text="#string/pp"/>
<Button
android:id="#+id/mhshome"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="26dp"
android:onClick="onClick"
android:text="#string/mhshome" />
<Button
android:id="#+id/mhsdir"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/pp"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:text="#string/mhsdir" />
<Button
android:id="#+id/cmhs"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/mhsdir"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:text="#string/callmhs" />
</RelativeLayout>
Its gonna be something incredibly simple I'm certain. Please point me in the right direction.
You need to call setContentView(R.layout.activity_main) :) That's why findViewById is returning null on your views.
You are not setting your layout.
Call setContentView(layout) in your onCreate() method.