android Mediaplayer无法在emulator中工作

我是安卓编程的乞丐 我的问题是

我想演奏背景音乐。 所以我读了这样的代码

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但这段代码在emulator中不起作用。发生错误

我的Logcat在这里

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我不明白怎么了。。。

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请帮忙

您需要使用其中一个。WMA不是其中之一。

onCreate方法的第25行出现空指针异常。使用调试器并在第行插入断点，找出哪个对象为空。您尝试播放的歌曲是什么文件类型？我使用了wma。我读了一个android API。它解释了MediaPlayer工作的周期。大概我必须先使用setDataSource（）和prepare（）吗？。。。我想你不能直接在MediaPlayer上播放wma音频文件，看看这个链接，非常感谢！！我不知道@Ashley如果你觉得这个答案有帮助，你应该点击这个问题附近的复选框图标。谢谢

public class Welcome extends Activity {
    /** Called when the activity is first created. */

    MediaPlayer player;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);        

        player=MediaPlayer.create(Welcome.this, R.raw.song);
        player.start(); 

03-05 15:36:36.588: ERROR/AndroidRuntime(954): FATAL EXCEPTION: main
03-05 15:36:36.588: ERROR/AndroidRuntime(954): java.lang.RuntimeException: Unable to start activity ComponentInfo{younkyung.app.lord_of_spelling/younkyung.app.lord_of_spelling.Welcome}: java.lang.NullPointerException
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.os.Looper.loop(Looper.java:123)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at java.lang.reflect.Method.invokeNative(Native Method)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at java.lang.reflect.Method.invoke(Method.java:521)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at dalvik.system.NativeStart.main(Native Method)
03-05 15:36:36.588: ERROR/AndroidRuntime(954): Caused by: java.lang.NullPointerException
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at younkyung.app.lord_of_spelling.Welcome.onCreate(Welcome.java:25)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-05 15:36:36.588: ERROR/AndroidRuntime(954):     ... 11 more