title: android studio java.langNullPointerException null object reference
body: <p>I am continually getting an error when trying to run an android app telling me that there is a <code>null</code> object reference. I am still a beginner with android and java and I would greatly appreciate any help I can get.</p>
  
  <p>Here is the <code>logcat</code>:    </p>
  
  <pre><code>01-17 17:11:49.156  27778-27778/com.example.owner.sketchy D/AndroidRuntime﹕ Shutting down VM
      --------- beginning of crash
  01-17 17:11:49.157  27778-27778/com.example.owner.sketchy E/AndroidRuntime﹕ FATAL EXCEPTION: main
      Process: com.example.owner.sketchy, PID: 27778
      java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.owner.sketchy/com.example.owner.sketchy.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.LinearLayout.getChildAt(int)' on a null object reference
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
              at android.app.ActivityThread.access$800(ActivityThread.java:144)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.LinearLayout.getChildAt(int)' on a null object reference
              at com.example.owner.sketchy.MainActivity.onCreate(MainActivity.java:33)
              at android.app.Activity.performCreate(Activity.java:5933)
              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
              at android.app.ActivityThread.access$800(ActivityThread.java:144)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  </code></pre>
  
  <p>and here is my <code>MainActivity.java</code>:</p>
  
  <pre><code>    package com.example.owner.sketchy;
  
  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.ImageButton;
  import android.widget.LinearLayout;
  
  public class MainActivity extends ActionBarActivity {
  
  
      private ImageButton currPaint;
      private DrawingView drawView;
  
      public void paintClicked(View view) {
          if (view != currPaint) {
  
              ImageButton imgView = (ImageButton) view;
              String color = view.getTag().toString();
              imgView.setImageDrawable(getResources().getDrawable(R.drawable.paint_pressed));
              currPaint.setImageDrawable(getResources().getDrawable(R.drawable.paint));
              currPaint = (ImageButton) view;
              drawView.setColor(color);
          }
      }
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          drawView = (DrawingView)findViewById(R.id.drawing);
          LinearLayout paintLayout = (LinearLayout)findViewById(R.id.paint_colors);
          currPaint = (ImageButton)paintLayout.getChildAt(0);
      }
      @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);
      }
  
  }
  </code></pre>