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POCan't seem to solve this NullPointerException
 

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  1. POCan't seem to solve this NullPointerException
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    <p>The error I'm getting is: </p> <pre><code>java.lang.NullPointerException at com.me.app.MainActivity.onCreate(MainActivity.java:34) </code></pre> <p>Lines 34-39 in <code>MainActivity.java</code> are as follows:</p> <pre><code>light_switch.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { turn_torch_on(); } }); </code></pre> <p>This leads me to believe that <code>light_switch</code> is returning <code>null</code>, despite this on line 31:</p> <pre><code>light_switch = (ImageButton)findViewById(R.id.light_switch); </code></pre> <p>I've double checked the id is correct. Is there anything that I'm missing? I'm not really sure what I can do to fix this at this moment.</p> <p>The exception log is available here: <a href="http://pastebin.com/raw.php?i=yDPRjvry" rel="nofollow">http://pastebin.com/raw.php?i=yDPRjvry</a></p> <h2>MainActivity.java</h2> <pre><code>package com.me.app; import android.app.Activity; import android.app.AlertDialog; import android.app.Fragment; import android.content.pm.PackageManager; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ImageButton; public class MainActivity extends Activity { ImageButton light_switch; private boolean has_flash; @Override 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(); } // get the light switch light_switch = (ImageButton)findViewById(R.id.light_switch); // make the light switch work light_switch.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { turn_torch_on(); } }); // check if device has flash capability has_flash = getApplicationContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH); // alert user that their device is not supported if ( !has_flash ) { AlertDialog alert = new AlertDialog.Builder(MainActivity.this).create(); alert.setTitle("Sorry :("); alert.setMessage("Your device does not have a flash"); alert.show(); return; } } /** * turn torch on */ private void turn_torch_on() { // change the layout to off toggle_layout(); } /** * toggle layout for on/off */ private void toggle_layout() { light_switch.setBackgroundResource(R.drawable.button_on); } /** * A placeholder fragment containing a simple view. */ public static class PlaceholderFragment extends Fragment { public PlaceholderFragment() { } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_main, container, false); return rootView; } } } </code></pre> <h2>fragment_main.xml</h2> <pre><code>&lt;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:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" android:background="@drawable/bg_off" tools:context=".MainActivity$PlaceholderFragment"&gt; &lt;ImageButton android:id="@+id/light_switch" android:layout_height="100dp" android:layout_width="fill_parent" android:layout_centerHorizontal="true" android:layout_centerVertical="true" android:src="@drawable/button_off" android:contentDescription="On/Off switch" /&gt; &lt;/RelativeLayout&gt; </code></pre>
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      1. POCan't seem to solve this NullPointerException
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    1. COAre you using Eclipse? Have you tried cleaning the project and building again?
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    2. COcheck light_switch in xml
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    3. COUsing Android Studio. Any idea how to clean the project/rebuild in AS?
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