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PONull Pointer Exception with setOnClickListener()
 

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    <p>I sometimes get a null pointer exception with my code. Oddly enough, this does not happen every time, and I'm not sure why. Help?</p> <pre><code>package net.obviam.droidz; public class HomeView extends Activity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.menu); Button page1 = (Button) findViewById(R.id.Button01); page1.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { // Intent i = getIntent(); Intent myIntent = new Intent(view.getContext(), DroidzActivity.class); startActivityForResult(myIntent, 0); } }); } protected void onDestroy() { // Log.d(TAG, "Destroying.."); super.onDestroy(); } @Override protected void onStop() { // Log.d(TAG, "Stopping..."); super.onStop(); } } </code></pre> <p>The logcat says that the problem is with line 19, the setOnClickListener. I'm not sure what's wrong with it though. It doesn't appear to be referencing anything.</p> <p>The Logcat reads like this:</p> <pre><code>02-17 16:52:13.816: E/AndroidRuntime(23756): FATAL EXCEPTION: main 02-17 16:52:13.816: E/AndroidRuntime(23756): java.lang.RuntimeException: Unable to start activity ComponentInfo{net.obviam.droidz/net.obviam.droidz.HomeView}: java.lang.NullPointerException 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1651) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.os.Handler.dispatchMessage(Handler.java:99) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.os.Looper.loop(Looper.java:130) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread.main(ActivityThread.java:3687) 02-17 16:52:13.816: E/AndroidRuntime(23756): at java.lang.reflect.Method.invokeNative(Native Method) 02-17 16:52:13.816: E/AndroidRuntime(23756): at java.lang.reflect.Method.invoke(Method.java:507) 02-17 16:52:13.816: E/AndroidRuntime(23756): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:842) 02-17 16:52:13.816: E/AndroidRuntime(23756): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 02-17 16:52:13.816: E/AndroidRuntime(23756): at dalvik.system.NativeStart.main(Native Method) 02-17 16:52:13.816: E/AndroidRuntime(23756): Caused by: java.lang.NullPointerException 02-17 16:52:13.816: E/AndroidRuntime(23756): at net.obviam.droidz.HomeView.onCreate(HomeView.java:19) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 02-17 16:52:13.816: E/AndroidRuntime(23756): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615) 02-17 16:52:13.816: E/AndroidRuntime(23756): ... 11 more </code></pre> <p>And here is the manifest file:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android" package="net.obviam.droidz" android:versionCode="1" android:versionName="1.0" &gt; &lt;uses-sdk android:minSdkVersion="10" /&gt; &lt;application android:icon="@drawable/images" android:label="@string/app_name" android:debuggable="true"&gt; &lt;activity android:name=".HomeView" android:label="@string/app_name"&gt; &lt;intent-filter&gt; &lt;action android:name="android.intent.action.MAIN" /&gt; &lt;category android:name="android.intent.category.LAUNCHER" /&gt; &lt;/intent-filter&gt; &lt;/activity&gt; &lt;activity android:name=".DroidzActivity"&gt;&lt;/activity&gt; &lt;/application&gt; </code></pre> <p></p> <p>And here is the xml file that the button is found in:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"&gt; &lt;Button android:text="Start Game!" android:id="@+id/Button01" android:layout_width="250dp" android:textSize="18dp" android:layout_height="55dp"&gt; &lt;/Button&gt; &lt;/LinearLayout&gt; </code></pre>
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    1. COThat would mean that `page1` is null, so probably `findViewById` is failing to return a valid object.
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    2. COAlso, this problem only occurs when hitting the back key, or when trying to restart it after hitting the back key. Don't know if that's significant.
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