title: button.setOnClickListener not working
body: <p>I have added an image and a button in the xml as follows</p>
  
  <pre><code> &lt;Button
          android:id="@+id/btnChangeImage"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Change Image" /&gt;
  
      &lt;ImageView
          android:id="@+id/imageView1"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:src="@drawable/buttonplayicon" /&gt;
  </code></pre>
  
  <p>onclick of the button I want to change the image. Below is the main_activity onclick function of the button</p>
  
  <pre><code>public void addListenerOnButton() {
  
      image = (ImageView) findViewById(R.id.imageView1);
  
      button = (Button) findViewById(R.id.btnChangeImage);
      button.setOnClickListener(new OnClickListener() {
  
      @Override
      public void onClick(View v) {
          image.setImageResource(R.drawable.player_pause);
  
          }
      });
  }
  </code></pre>
  
  <p>If I add </p>
  
  <pre><code>button.setOnClickListener(new OnClickListener() {
  
      @Override
      public void onClick(View v) {
          image.setImageResource(R.drawable.player_pause);
  
      }
  });
  </code></pre>
  
  <p>in the function, I get the message "Unfortunately app has stopped"</p>
  
  <p>has any one idea regarding this?</p>
  
  <p><strong>EDIT 1</strong></p>
  
  <p>To view logcat if I follow  ( in eclipse : Window > show view > other > android > Logcat ) steps I get Logcat(deprecated)</p>
  
  <p><strong>EDIT 2</strong>
  logcat :</p>
  
  <pre><code>06-12 13:37:43.006: E/AndroidRuntime(3159): Caused by: java.lang.NullPointerException
  06-12 13:37:43.006: E/AndroidRuntime(3159):     at com.example.play_audio_app.MainActivity.addListenerOnButton(MainActivity.java:38)
  06-12 13:37:43.006: E/AndroidRuntime(3159):     at com.example.play_audio_app.MainActivity.onCreate(MainActivity.java:30)
  06-12 13:37:43.006: E/AndroidRuntime(3159):     at android.app.Activity.performCreate(Activity.java:5231)
  06-12 13:37:43.006: E/AndroidRuntime(3159):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  06-12 13:37:43.006: E/AndroidRuntime(3159):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
  06-12 13:37:43.006: E/AndroidRuntime(3159):     ... 11 more
  06-12 13:38:41.816: D/AndroidRuntime(3304): Shutting down VM
  06-12 13:38:41.816: W/dalvikvm(3304): threadid=1: thread exiting with uncaught exception (group=0x4164eba8)
  06-12 13:38:41.816: E/AndroidRuntime(3304): FATAL EXCEPTION: main
  06-12 13:38:41.816: E/AndroidRuntime(3304): Process: com.example.play_audio_app, PID: 3304
  06-12 13:38:41.816: E/AndroidRuntime(3304): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.play_audio_app/com.example.play_audio_app.MainActivity}: java.lang.NullPointerException
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.os.Handler.dispatchMessage(Handler.java:102)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.os.Looper.loop(Looper.java:136)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread.main(ActivityThread.java:5017)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at java.lang.reflect.Method.invokeNative(Native Method)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at java.lang.reflect.Method.invoke(Method.java:515)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at dalvik.system.NativeStart.main(Native Method)
  06-12 13:38:41.816: E/AndroidRuntime(3304): Caused by: java.lang.NullPointerException
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at com.example.play_audio_app.MainActivity.addListenerOnButton(MainActivity.java:38)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at com.example.play_audio_app.MainActivity.onCreate(MainActivity.java:30)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.Activity.performCreate(Activity.java:5231)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
  06-12 13:38:41.816: E/AndroidRuntime(3304):     ... 11 more
  </code></pre>
  
  <p><strong>EDIT 3</strong></p>
  
  <pre><code>protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          if (savedInstanceState == null) {
              getFragmentManager().beginTransaction()
                      .add(R.id.container, new PlaceholderFragment()).commit();
          }
  
          addListenerOnButton();
      }
  </code></pre>