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私は初心者です。アセットフォルダーに1つのボタンと4つの.oggファイルを含む非常にシンプルなアプリを作成しようとしています。そのボタンは上記のランダムファイルを再生します。

私は1つのメインクラスと1つのレイアウトしか持っていません。

コードにエラーは表示されませんが、エミュレーターで起動するとすぐにアプリがクラッシュします。

私の主なクラス:-

    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();
        }
    }
});
}

私のレイアウト:-

<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>

これがlogcatです：-

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

ρяσσρєя K のソリューションを適用した後の 2 番目の logcat:-

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
4

1 に答える 1

0

インポートから削除import android.R;して、オン プロジェクトの R ファイルをインポートします。または使用

descriptor = MainActivity.this.getAssets().openFd(mediaFile);

それ以外の

descriptor = MainActivity.this.getAssets().openFd("audioogg/"+mediaFile);
于 2012-12-14T20:12:03.053 に答える