This is a very simple android app. I'm just learning to write code for android now and I am unsure why the line: add.setOnClickListener(new View.OnClickListener() throws a NullPointerException.
public class StartingPoint extends ActionBarActivity{
int counter;
Button add, sub;
TextView display;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_starting_point);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
counter = 0;
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
counter--;
display.setText("Your total is " + counter);
}
});
}
Here is the XML code:
<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="com.thenewboston.jaredh.StartingPoint$PlaceholderFragment" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="#string/total"
android:textSize="40sp"
android:id="#+id/tvDisplay"
/>
<Button
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/tvDisplay"
android:layout_below="#+id/tvDisplay"
android:layout_gravity="center"
android:text="#string/addButton"
android:textSize="20sp"
android:id="#+id/bAdd" />
<Button
android:layout_width="250dp"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/bAdd"
android:layout_below="#+id/bAdd"
android:layout_gravity="center"
android:text="#string/subButton"
android:textSize="20sp"
android:id="#+id/bSub"/>
Logcat Error:
03-29 17:44:24.930: D/AndroidRuntime(25367): Shutting down VM
03-29 17:44:24.930: W/dalvikvm(25367): threadid=1: thread exiting with uncaught exception (group=0x41831898)
03-29 17:44:24.940: E/AndroidRuntime(25367): FATAL EXCEPTION: main
03-29 17:44:24.940: E/AndroidRuntime(25367): java.lang.RuntimeException: Unable to start activity ComponentInf{com.thenewboston.jaredh/com.thenewboston.jaredh.StartingPoint}: java.lang.NullPointerException
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2305)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2359)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread.access$700(ActivityThread.java:165)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1326)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.os.Handler.dispatchMessage(Handler.java:99)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.os.Looper.loop(Looper.java:137)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread.main(ActivityThread.java:5455)
03-29 17:44:24.940: E/AndroidRuntime(25367): at java.lang.reflect.Method.invokeNative(Native Method)
03-29 17:44:24.940: E/AndroidRuntime(25367): at java.lang.reflect.Method.invoke(Method.java:525)
03-29 17:44:24.940: E/AndroidRuntime(25367): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
03-29 17:44:24.940: E/AndroidRuntime(25367): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
03-29 17:44:24.940: E/AndroidRuntime(25367): at dalvik.system.NativeStart.main(Native Method)
03-29 17:44:24.940: E/AndroidRuntime(25367): Caused by: java.lang.NullPointerException
03-29 17:44:24.940: E/AndroidRuntime(25367): at com.thenewboston.jaredh.StartingPoint.onCreate(StartingPoint.java:39)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.Activity.performCreate(Activity.java:5372)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
03-29 17:44:24.940: E/AndroidRuntime(25367): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
03-29 17:44:24.940: E/AndroidRuntime(25367): ... 11 more
As you can see it is a very simple app just adding 1 to the text field when either button is clicked. Any help could be greatly apprecitated. Just unsure why the NullPointerException is being caused.
I would guess that the XML you presented (without saying which file it really is, and despite that the XML text is not even valid) is the layout of the PlaceholderFragment you add at the beginning. However, the fragment is not immediately added, just scheduled to be added by the FragmentManager. Therefore when you are immediately trying to find its UI components, the activity fails to do so, and the add reference is set to null by findViewById.
Related
First of all I want to say that this is my first post so it may no be very well done, in general.
My issue is the following: I would like to use three different strings from three editTexts and display them in three TextViews in another activity. I have already been searching for different kinds of ways of doing it (arrays, bundle) but it continues crashing. Help me, please. Here you have my code:
Main activity
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
// Do something in response to button
EditText eText1 = (EditText) findViewById(R.id.editText1);
EditText eText2 = (EditText) findViewById(R.id.editText2);
EditText eText3 = (EditText) findViewById(R.id.editText3);
String m1 = eText1.getText().toString();
String m2 = eText2.getText().toString();
String m3 = eText3.getText().toString();
Intent intent = new Intent(this, DisplayMessageActivity.class);
intent.putExtra("m1",m1);
intent.putExtra("m2",m2);
intent.putExtra("m3",m3);
startActivity(intent);
}
subActivity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_message);
// Get the message from the intent
Bundle extras = getIntent().getExtras();
// get the extras
String a = extras.getString("m1");
String b = extras.getString("m2");
String c = extras.getString("m3");
// Set the text views
TextView tv1 = (TextView) findViewById(R.id.textView1);
tv1.setText(a); // This is line 23
TextView tv2 = (TextView) findViewById(R.id.textView2);
tv2.setText(b);
TextView tv3 = (TextView) findViewById(R.id.textView3);
tv3.setText(c);
}
Edit1: I have changed what #Squonk said but still crashes. I don't know how to upload the logcat because it is too large for a text but I still can't upload images.
Don't know what to do :(
Edit2: Thanks to #Squonk again. I have finally managed to add the logcat. This is the logcat for the code I recently changed in "Edit1".
03-29 16:05:39.905: E/AndroidRuntime(327): FATAL EXCEPTION: main
03-29 16:05:39.905: E/AndroidRuntime(327): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.DisplayMessageActivity}: java.lang.NullPointerException
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.os.Handler.dispatchMessage(Handler.java:99)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.os.Looper.loop(Looper.java:123)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread.main(ActivityThread.java:4627)
03-29 16:05:39.905: E/AndroidRuntime(327): at java.lang.reflect.Method.invokeNative(Native Method)
03-29 16:05:39.905: E/AndroidRuntime(327): at java.lang.reflect.Method.invoke(Method.java:521)
03-29 16:05:39.905: E/AndroidRuntime(327): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-29 16:05:39.905: E/AndroidRuntime(327): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-29 16:05:39.905: E/AndroidRuntime(327): at dalvik.system.NativeStart.main(Native Method)
03-29 16:05:39.905: E/AndroidRuntime(327): Caused by: java.lang.NullPointerException
03-29 16:05:39.905: E/AndroidRuntime(327): at com.example.myfirstapp.DisplayMessageActivity.onCreate(DisplayMessageActivity.java:23)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-29 16:05:39.905: E/AndroidRuntime(327): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-29 16:05:39.905: E/AndroidRuntime(327): ... 11 more
This is one of the textviews in fragment_display_message.xml. There are three of them. Could it be that when finding the textviews in the subactivity I have to write where to find them not to confuse with the main activity?
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="33dp"
android:layout_marginTop="43dp"
android:hint="#string/edit_message"
android:textAppearance="?android:attr/textAppearanceLarge" />
Edit3: Eureka! I have finally discovered where the problem was. I had inserted the textviews in the fragment_display_message.xml instead of activity_display_message.xml. As in the mainactivity.java I use the fragment_main.xml I thought that in a subactivity would be the same. Well, I was wrong. Thanks to all! :D
Thank you for your support
The problem is these two lines...
Bundle extras = new Bundle();
...
intent.putExtras(extras);
An Intent already carries a Bundle but what you're doing is creating a second Bundle and adding that as an 'extra'.
Remove both of those lines from your main Activity and change the following lines...
extras.putString("m1", m1);
extras.putString("m2", m2);
extras.putString("m3", m3);
...to...
intent.putExtra("m1", m1);
intent.putExtra("m2", m2);
intent.putExtra("m3", m3);
In the first activity,
Intent i = new Intent(MainActivity.this, SecondActivity.class);
i.putExtra("SomeValue", data);
startActivity(i);
// In second activity
String str2 = getIntent().getExtras().getString("SomeValue");
tvRecieve.setText(str2);
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.
I am new to android application development. I was doing this tutorial app.It's a very simple one. It adds one and subtracts one from the counter.When I run it in the emulator ,it says "Unfortunately tutorial has stopped working." There are no errors in the code. The API level is 17. Please help me out.
Code for java:
public class Startingpoint extends Activity {
int counter=0;
Button add,subtract;
TextView display;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.startingpoint);
add = (Button) findViewById(R.id.bAdd);
subtract= (Button) findViewById(R.id.bSubtract);
display= (Button) findViewById(R.id.text);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
counter++;
display.setText("The total is " + counter);
}
});
subtract.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
counter--;
display.setText("The total is " + counter);
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.startingpoint, menu);
return true;
}
}
Layout code in xml :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView android:id="#+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Your total is 0"
android:textSize="35dp"
android:layout_gravity="center"
android:gravity="center"/>
<Button android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="Add One"
android:layout_gravity="center"
android:textSize="25dp"
android:id="#+id/bAdd"/>
<Button android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="Subtract One"
android:layout_gravity="center"
android:textSize="25dp"
android:id="#+id/bSubtract"/>
</LinearLayout>
Here is the logcat :
03-02 02:45:10.730: D/AndroidRuntime(780): Shutting down VM
03-02 02:45:10.730: W/dalvikvm(780): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
03-02 02:45:10.750: E/AndroidRuntime(780): FATAL EXCEPTION: main
03-02 02:45:10.750: E/AndroidRuntime(780): java.lang.RuntimeException: Unable to start activity ComponentInfo{tutorial.example.tutorial/tutorial.example.tutorial.Startingpoint}: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.Button
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.os.Handler.dispatchMessage(Handler.java:99)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.os.Looper.loop(Looper.java:137)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread.main(ActivityThread.java:5041)
03-02 02:45:10.750: E/AndroidRuntime(780): at java.lang.reflect.Method.invokeNative(Native Method)
03-02 02:45:10.750: E/AndroidRuntime(780): at java.lang.reflect.Method.invoke(Method.java:511)
03-02 02:45:10.750: E/AndroidRuntime(780): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-02 02:45:10.750: E/AndroidRuntime(780): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-02 02:45:10.750: E/AndroidRuntime(780): at dalvik.system.NativeStart.main(Native Method)
03-02 02:45:10.750: E/AndroidRuntime(780): Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.Button
03-02 02:45:10.750: E/AndroidRuntime(780): at tutorial.example.tutorial.Startingpoint.onCreate(Startingpoint.java:22)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.Activity.performCreate(Activity.java:5104)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
03-02 02:45:10.750: E/AndroidRuntime(780): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
03-02 02:45:10.750: E/AndroidRuntime(780): ... 11 more
display= (Button) findViewById(R.id.text);
should be
display= (TextView) findViewById(R.id.text);
Since display is supposed to reference a TextView instance, but you're explictly casting into a Button, and these are not compatible types.
As you got the answer from A-C this time, but for next time in android application development a important suggestion:
Always see the logcat for error, and see the "Caused by:" tag, It specifies what was the cause of the problem with sufficient detail, Also see the line no that caused that error.
And try to find what can be wrong with that line of code.
For example: in your logcat it is showing-
Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.Button
at tutorial.example.tutorial.Startingpoint.onCreate(Startingpoint.java:22)
So you can try to read the log, and you will understand that in your file Startingpoint.java at line 22 which is located in onCreate method the error is android.widget.TextView cannot be cast to android.widget.Button. So you can easily remove your errors without any help.
Hope that helps not only you current problem but prevented your future time and efforts.
I am new to Android. I am trying to build this tiny app however every time I add the code in bold:
d = (Button) findViewById (R.id.tvDis);
the app crashes and if I remove this line, everything works fine. I am runing this on android 2.2 api 8 version and nexus s emulator.
package com.maximusstudios.numtowords;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
/**Called when the activity is first created.*/
int counter;
Button add, sub;
TextView d;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
counter = 0;
add = (Button) findViewById (R.id.bAdd);
**d = (Button) findViewById (R.id.tvDis);**
sub = (Button) findViewById(R.id.bSub);
add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
}
});
sub.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
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.activity_main, menu);
return true;
}
}
XML CODE:
<?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:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Your Total is 0"
android:textSize="20dp"
android:layout_gravity="center"
android:gravity="center"
android:id="#+id/tvDis"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add one"
android:layout_gravity="center"
android:textSize="20dp"
android:id="#+id/bAdd"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add one"
android:layout_gravity="center"
android:textSize="20dp"
android:id="#+id/bSub"
/>
</LinearLayout>
Error list:
02-10 18:00:21.452: D/AndroidRuntime(910): Shutting down VM
02-10 18:00:21.452: W/dalvikvm(910): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
02-10 18:00:21.472: E/AndroidRuntime(910): FATAL EXCEPTION: main
02-10 18:00:21.472: E/AndroidRuntime(910): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.maximusstudios.numtowords/com.maximusstudios.numtowords.MainActivity}: java.lang.ClassCastException: android.widget.TextView
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.os.Handler.dispatchMessage(Handler.java:99)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.os.Looper.loop(Looper.java:123)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread.main(ActivityThread.java:4627)
02-10 18:00:21.472: E/AndroidRuntime(910): at java.lang.reflect.Method.invokeNative(Native Method)
02-10 18:00:21.472: E/AndroidRuntime(910): at java.lang.reflect.Method.invoke(Method.java:521)
02-10 18:00:21.472: E/AndroidRuntime(910): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-10 18:00:21.472: E/AndroidRuntime(910): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-10 18:00:21.472: E/AndroidRuntime(910): at dalvik.system.NativeStart.main(Native Method)
02-10 18:00:21.472: E/AndroidRuntime(910): Caused by: java.lang.ClassCastException: android.widget.TextView
02-10 18:00:21.472: E/AndroidRuntime(910): at com.maximusstudios.numtowords.MainActivity.onCreate(MainActivity.java:23)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-10 18:00:21.472: E/AndroidRuntime(910): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
02-10 18:00:21.472: E/AndroidRuntime(910): ... 11 more
Change to
d = (TextView) findViewById (R.id.tvDis);
Your casting was wrong. With your code, when you do (Button), you are trying to cast the TextView that is returned by findViewById() into a Button, which doesn't work due to them being incompatible types.
You define d as a TextView and try to cast it to a Button
Should be
d = (TextView) findViewById (R.id.tvDis);
The error you're getting is a ClassCastException
public class screen2 extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.screen2);
final Button button1 = (Button)findViewById(R.id.button1);
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
//AInteger.parseInt(string)
System.out.println("1");
EditText et = (EditText)findViewById(R.id.editText1);
System.out.println("2");
int zipCode = Integer.parseInt(et.getText().toString());
System.out.println("3");
System.out.println(zipCode);
System.out.println("dude...5");
}
});
}
}
This code shows the errror in the logcat :
11-13 19:58:06.806: W/KeyCharacterMap(281): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
11-13 19:58:09.471: I/System.out(281): 1
11-13 19:58:09.471: I/System.out(281): 2
11-13 19:58:09.477: D/AndroidRuntime(281): Shutting down VM
11-13 19:58:09.477: W/dalvikvm(281): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
11-13 19:58:09.527: E/AndroidRuntime(281): FATAL EXCEPTION: main
11-13 19:58:09.527: E/AndroidRuntime(281): java.lang.NullPointerException
11-13 19:58:09.527: E/AndroidRuntime(281): at com.example.andtwi.screen2$1.onClick(screen2.java:23)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.view.View.performClick(View.java:2408)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.view.View$PerformClick.run(View.java:8816)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.os.Handler.handleCallback(Handler.java:587)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.os.Handler.dispatchMessage(Handler.java:92)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.os.Looper.loop(Looper.java:123)
11-13 19:58:09.527: E/AndroidRuntime(281): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-13 19:58:09.527: E/AndroidRuntime(281): at java.lang.reflect.Method.invokeNative(Native Method)
11-13 19:58:09.527: E/AndroidRuntime(281): at java.lang.reflect.Method.invoke(Method.java:521)
11-13 19:58:09.527: E/AndroidRuntime(281): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-13 19:58:09.527: E/AndroidRuntime(281): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-13 19:58:09.527: E/AndroidRuntime(281): at dalvik.system.NativeStart.main(Native Method)
Though it looks like an Null Pointer exception , i think i am doing it things exactly i found on forums. Here is code of my related xml file as well. Can anyone suggest where am i doing it wrong?
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Enter Zipcode" />
<EditText
android:id="#+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="number"
android:maxLength="5" >
<requestFocus />
</EditText>
<Button
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Get movies from Flixster" />
</LinearLayout>
The code breaks at this as well :
int zipCode = Integer.parseInt(et.getText().toString());
Try this:
Button button1 = (Button)findViewById(R.id.button1);
EditText et = (EditText)findViewById(R.id.editText1);
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
System.out.println("1");
System.out.println("2");
String zipCode = et.getText().toString();
System.out.println("3");
System.out.println(zipCode);
}
}
I think,you don't need to write String zipCode = (String)et.getText().toString(); there as it is already returns a String object.
And hope,you don't miss to include setContentView(R.layout.your_xml_file); before declaring a Button and EditText.
Edit 1:
You don't seem to get problem with
int zipCode=Integer.parseInt(et.getText().toString()); there.Try this with above code modification.
You might be getting null pointer exception because you are getting String s=et.getText().toString() as null.Please check it for null before casting it to int.
Button button1 = (Button)findViewById(R.id.button1);
EditText et = (EditText)findViewById(R.id.editText1);
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
System.out.println("1");
System.out.println("2");
String check = et.getText().toString();
int zipCode=0;
if(!check.equals(""))
zipCode=Integer.parseInt(check);
System.out.println("3");
System.out.println(zipCode);
}
}
Could you post your onCreate method, as well as line 23 on its own? The most likely problem is that you neglect to call setContentView and that is why findViewById returns null.