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POPlay random sound file on button press - Android
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13885420
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2012-12-14T19:56:43.110
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I am a beginner, I'm trying to make a very simple app, one button and 4 .ogg files in the assets folder, that button would play random file from the above mentioned. I have only one main class and one layout. Here is what I did, the code doesn't show any error but the app crash immediately when launching on emulator. My main class:- <pre><code> MediaPlayer player; AssetFileDescriptor descriptor; private String[] filelist; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_list_item); player = new MediaPlayer(); Button playSound = (Button)findViewById(R.id.button1); AssetManager aMan = this.getAssets(); try { filelist = aMan.list("/assets"); } catch (IOException e1) { e1.printStackTrace(); } playSound.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Random randomGenerator = new Random(); int randomInt = randomGenerator.nextInt(filelist.length); try { String mediaFile = filelist[randomInt]; descriptor = getAssets().openFd(mediaFile); player.setDataSource(descriptor.getFileDescriptor(),descriptor.getStartOffset(),descriptor.getLength()); descriptor.close(); player.prepare(); player.start(); } catch (Exception e) { e.printStackTrace(); } } }); } </code></pre> My layout:- <pre><code><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" tools:context=".MainActivity" > <ImageView android:id="@+id/imageView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:layout_centerHorizontal="true" android:src="@drawable/background" android:contentDescription="@string/desc" /> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentRight="true" android:layout_marginBottom="154dp" android:layout_marginRight="92dp" android:text="@string/button1" /> </RelativeLayout> </code></pre> Here is the logcat:- <pre><code>12-14 19:36:56.062: D/AndroidRuntime(540): Shutting down VM 12-14 19:36:56.062: W/dalvikvm(540): threadid=1: thread exiting with uncaught exception (group=0x409961f8) 12-14 19:36:56.072: E/AndroidRuntime(540): FATAL EXCEPTION: main 12-14 19:36:56.072: E/AndroidRuntime(540): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mbawardi.layan/com.mbawardi.layan.MainActivity}: java.lang.NullPointerException 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread.access$600(ActivityThread.java:122) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.os.Handler.dispatchMessage(Handler.java:99) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.os.Looper.loop(Looper.java:137) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread.main(ActivityThread.java:4340) 12-14 19:36:56.072: E/AndroidRuntime(540): at java.lang.reflect.Method.invokeNative(Native Method) 12-14 19:36:56.072: E/AndroidRuntime(540): at java.lang.reflect.Method.invoke(Method.java:511) 12-14 19:36:56.072: E/AndroidRuntime(540): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 12-14 19:36:56.072: E/AndroidRuntime(540): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 12-14 19:36:56.072: E/AndroidRuntime(540): at dalvik.system.NativeStart.main(Native Method) 12-14 19:36:56.072: E/AndroidRuntime(540): Caused by: java.lang.NullPointerException 12-14 19:36:56.072: E/AndroidRuntime(540): at com.mbawardi.layan.MainActivity.onCreate(MainActivity.java:39) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.Activity.performCreate(Activity.java:4465) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 12-14 19:36:56.072: E/AndroidRuntime(540): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) 12-14 19:36:56.072: E/AndroidRuntime(540): ... 11 more 12-14 19:36:59.042: I/Process(540): Sending signal. PID: 540 SIG: 9 12-14 19:37:06.032: D/AndroidRuntime(556): Shutting down VM 12-14 19:37:06.032: W/dalvikvm(556): threadid=1: thread exiting with uncaught exception (group=0x409961f8) 12-14 19:37:06.042: E/AndroidRuntime(556): FATAL EXCEPTION: main 12-14 19:37:06.042: E/AndroidRuntime(556): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mbawardi.layan/com.mbawardi.layan.MainActivity}: java.lang.NullPointerException 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread.access$600(ActivityThread.java:122) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.os.Handler.dispatchMessage(Handler.java:99) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.os.Looper.loop(Looper.java:137) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread.main(ActivityThread.java:4340) 12-14 19:37:06.042: E/AndroidRuntime(556): at java.lang.reflect.Method.invokeNative(Native Method) 12-14 19:37:06.042: E/AndroidRuntime(556): at java.lang.reflect.Method.invoke(Method.java:511) 12-14 19:37:06.042: E/AndroidRuntime(556): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 12-14 19:37:06.042: E/AndroidRuntime(556): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 12-14 19:37:06.042: E/AndroidRuntime(556): at dalvik.system.NativeStart.main(Native Method) 12-14 19:37:06.042: E/AndroidRuntime(556): Caused by: java.lang.NullPointerException 12-14 19:37:06.042: E/AndroidRuntime(556): at com.mbawardi.layan.MainActivity.onCreate(MainActivity.java:39) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.Activity.performCreate(Activity.java:4465) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 12-14 19:37:06.042: E/AndroidRuntime(556): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) 12-14 19:37:06.042: E/AndroidRuntime(556): ... 11 more </code></pre> The second logcat after applying ρяσѕρєя K's solution:- <pre><code>12-14 20:19:02.227: D/AndroidRuntime(537): Shutting down VM 12-14 20:19:02.237: W/dalvikvm(537): threadid=1: thread exiting with uncaught exception (group=0x409961f8) 12-14 20:19:02.247: E/AndroidRuntime(537): FATAL EXCEPTION: main 12-14 20:19:02.247: E/AndroidRuntime(537): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mbawardi.layan/com.mbawardi.layan.MainActivity}: java.lang.NullPointerException 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread.access$600(ActivityThread.java:122) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.os.Handler.dispatchMessage(Handler.java:99) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.os.Looper.loop(Looper.java:137) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread.main(ActivityThread.java:4340) 12-14 20:19:02.247: E/AndroidRuntime(537): at java.lang.reflect.Method.invokeNative(Native Method) 12-14 20:19:02.247: E/AndroidRuntime(537): at java.lang.reflect.Method.invoke(Method.java:511) 12-14 20:19:02.247: E/AndroidRuntime(537): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 12-14 20:19:02.247: E/AndroidRuntime(537): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 12-14 20:19:02.247: E/AndroidRuntime(537): at dalvik.system.NativeStart.main(Native Method) 12-14 20:19:02.247: E/AndroidRuntime(537): Caused by: java.lang.NullPointerException 12-14 20:19:02.247: E/AndroidRuntime(537): at com.mbawardi.layan.MainActivity.onCreate(MainActivity.java:42) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.Activity.performCreate(Activity.java:4465) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 12-14 20:19:02.247: E/AndroidRuntime(537): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) 12-14 20:19:02.247: E/AndroidRuntime(537): ... 11 more </code></pre>
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<java><android>
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Play random sound file on button press - Android
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