title: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
body: <p>I was trying to create a menu like this(Menu in gray background)-</p>
  
  <p><img src="https://i.stack.imgur.com/yTeDu.png" alt="enter image description here"></p>
  
  <p>I made it using a LayoutInflator. Its code is below-</p>
  
  <pre><code>ImageView imgv1, imgv2;
  TextView tv1, tv2, tv3;
  private Animation down;
  View child;
  
  @Override
  protected void onCreate(Bundle savedInstanceState)
  {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_home);
  
      imgv1 = (ImageView) findViewById(R.id.imageViewHA1);
      imgv2 = (ImageView) findViewById(R.id.imageViewHA2);
  
      tv1 = (TextView) findViewById(R.id.textViewMenu1);
      tv2 = (TextView) findViewById(R.id.textViewMenu2);
      tv3 = (TextView) findViewById(R.id.textViewMenu3);
  
      down = AnimationUtils.loadAnimation(this, R.anim.slide_down);
  
      imgv2.setOnClickListener(new OnClickListener()
      {
  
          @Override
          public void onClick(View v)
          {
              LinearLayout item = (LinearLayout) findViewById(R.id.linearLayout2);
              if (child == null)
              {
                  item.setAnimation(down);
                  down.start();
                  child = getLayoutInflater().inflate(R.layout.menu_layout, null);
                  item.addView(child);
              } else
              {
                  item.removeAllViews();
                  child = null;
              }
          }
      });
  
      tv3.setOnClickListener(new OnClickListener()
      {
  
          @Override
          public void onClick(View v)
          {
              System.exit(0);
          }
      });
  }
  </code></pre>
  
  <p>R.layout.menu_layout code-</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/RelativeLayout1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:orientation="vertical" &gt;
  
  &lt;LinearLayout
      android:id="@+id/menulayout1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:background="@color/White"
      android:orientation="vertical"
      android:showDividers="middle" &gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_marginLeft="3dp"
          android:layout_marginRight="3dp"
          android:layout_marginTop="2dp"
          android:background="@color/DimGray" &gt;
  
          &lt;TextView
              android:id="@+id/textViewMenu1"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center"
              android:paddingBottom="3dp"
              android:paddingLeft="10dp"
              android:paddingRight="10dp"
              android:paddingTop="3dp"
              android:text="New Group"
              android:textColor="@color/White"
              android:textStyle="bold" /&gt;
  
      &lt;/LinearLayout&gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_marginLeft="3dp"
          android:layout_marginRight="3dp"
          android:layout_marginTop="2dp"
          android:background="@color/DimGray" &gt;
  
          &lt;TextView
              android:id="@+id/textViewMenu2"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center"
              android:paddingBottom="3dp"
              android:paddingLeft="10dp"
              android:paddingRight="10dp"
              android:paddingTop="3dp"
              android:text="Contacts"
              android:textColor="@color/White"
              android:textStyle="bold" /&gt;
  
      &lt;/LinearLayout&gt;
  
      &lt;LinearLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_marginLeft="3dp"
          android:layout_marginRight="3dp"
          android:layout_marginTop="2dp"
          android:background="@color/DimGray"
          android:orientation="vertical" &gt;
  
          &lt;TextView
              android:id="@+id/textViewMenu3"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:gravity="center"
              android:paddingBottom="3dp"
              android:paddingLeft="10dp"
              android:paddingRight="10dp"
              android:paddingTop="3dp"
              android:text="Exit"
              android:textColor="@color/White"
              android:textStyle="bold" /&gt;
  
      &lt;/LinearLayout&gt;
  
  &lt;/LinearLayout&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>When I ran my code I got the exception which is in the title of this question. The LogCat details are here-</p>
  
  <pre><code>09-18 22:06:50.369: E/AndroidRuntime(952): FATAL EXCEPTION: main
  09-18 22:06:50.369: E/AndroidRuntime(952): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.os.Handler.dispatchMessage(Handler.java:99)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.os.Looper.loop(Looper.java:137)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread.main(ActivityThread.java:4745)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at java.lang.reflect.Method.invokeNative(Native Method)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at java.lang.reflect.Method.invoke(Method.java:511)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at dalvik.system.NativeStart.main(Native Method)
  09-18 22:06:50.369: E/AndroidRuntime(952): Caused by: java.lang.NullPointerException
  09-18 22:06:50.369: E/AndroidRuntime(952):  at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:58)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.Activity.performCreate(Activity.java:5008)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
  09-18 22:06:50.369: E/AndroidRuntime(952):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
  09-18 22:06:50.369: E/AndroidRuntime(952):  ... 11 more
  09-18 22:16:03.709: E/Trace(998): error opening trace file: No such file or directory (2)
  09-18 22:16:04.238: D/AndroidRuntime(998): Shutting down VM
  09-18 22:16:04.238: W/dalvikvm(998): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
  09-18 22:16:04.248: E/AndroidRuntime(998): FATAL EXCEPTION: main
  09-18 22:16:04.248: E/AndroidRuntime(998): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.ClassCastException: com.example.gchat.HomeActivity cannot be cast to android.view.View$OnClickListener
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.os.Handler.dispatchMessage(Handler.java:99)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.os.Looper.loop(Looper.java:137)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread.main(ActivityThread.java:4745)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at java.lang.reflect.Method.invokeNative(Native Method)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at java.lang.reflect.Method.invoke(Method.java:511)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at dalvik.system.NativeStart.main(Native Method)
  09-18 22:16:04.248: E/AndroidRuntime(998): Caused by: java.lang.ClassCastException: com.example.gchat.HomeActivity cannot be cast to android.view.View$OnClickListener
  09-18 22:16:04.248: E/AndroidRuntime(998):  at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:35)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.Activity.performCreate(Activity.java:5008)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
  09-18 22:16:04.248: E/AndroidRuntime(998):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
  09-18 22:16:04.248: E/AndroidRuntime(998):  ... 11 more
  09-18 22:20:33.669: E/Trace(1046): error opening trace file: No such file or directory (2)
  09-18 22:20:33.989: D/AndroidRuntime(1046): Shutting down VM
  09-18 22:20:34.029: W/dalvikvm(1046): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
  09-18 22:20:34.079: E/AndroidRuntime(1046): FATAL EXCEPTION: main
  09-18 22:20:34.079: E/AndroidRuntime(1046): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.gchat/com.example.gchat.HomeActivity}: java.lang.NullPointerException
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.os.Handler.dispatchMessage(Handler.java:99)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.os.Looper.loop(Looper.java:137)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread.main(ActivityThread.java:4745)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at java.lang.reflect.Method.invokeNative(Native Method)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at java.lang.reflect.Method.invoke(Method.java:511)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at dalvik.system.NativeStart.main(Native Method)
  09-18 22:20:34.079: E/AndroidRuntime(1046): Caused by: java.lang.NullPointerException
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at com.example.gchat.HomeActivity.onCreate(HomeActivity.java:58)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.Activity.performCreate(Activity.java:5008)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
  09-18 22:20:34.079: E/AndroidRuntime(1046):     ... 11 more
  </code></pre>
  
  <p>I searched a lot here and in Google, but couldn't found anything helpful. How can I correct this error ?</p>