我正在尝试从 Fragment 中的用户的音乐文件夹中获取音乐文件,但是当我这样做并在onActivityResult中接收它(并记录它)后,当我想用mediaplayer播放它时,我得到一个Nullpointer异常 . 选择文件的代码:
Button pickFile = (Button) v.findViewById(R.id.btnpick);
pickFile.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, 1);
}
});
OnActivityResult(不要忘记我在片段中)
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
getActivity();
if ((resultCode == getActivity().RESULT_OK) && (data != null)) {
Log.d("result", "okreceived");
Uri soundUri = Uri.parse(data.getData().toString());
Log.i("result", "Intent data " + data.getData().toString());
mplayergo(soundUri);
}
if (resultCode == getActivity().RESULT_CANCELED)
{
//null
}
}
public void mplayergo(Uri soundUri){
try {
mplayer.setDataSource(getActivity(), soundUri);
mplayer.start();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
这是日志:
D / result:okreceived I / result:Intent data content:// media / external / audio / media / 34839 W / System.err:java.lang.NullPointerException:尝试调用虚方法'void android.media.MediaPlayer.setDataSource (android.content.Context,android.net.Uri)'对com.package.example.GameFragment.onActivityResult(GameFragment.java)中com.package.example.GameFragment.mplayergo(GameFragment.java:764)的空对象引用:748)W / System.err:在android.support.v4.app.FragmentActivity.onActivityResult(FragmentActivity.java:156)W / System.err:at android.app.Activity.dispatchActivityResult(Activity.java:6290)W /System.err:在android.app.ActivityThread.deliverResults(ActivityThread.java:3606)W / System.err:在android.app.ActivityThread.handleSendResult(ActivityThread.java:3653)W / System.err:在android . app.ActivityThread.access $ 1400(ActivityThread.java:154)W / System.err:at android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1371)W / System.err:at android.os.Handler.dispatchMessage (H andler.java:102)W / System.err:在android.os.Looper.loop(Looper.java:135)W / System.err:在android.app.ActivityThread.main(ActivityThread.java:5300)W / System.err:at java.lang.reflect.Method.invoke(Native Method)W / System.err:at java.lang.reflect.Method.invoke(Method.java:372)W / System.err:at com . android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:904)W / System.err:at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
通过重新初始化MediaPlayer并将uri设置为源来解决此问题 .
public void mplayergo(Uri soundUri){
try {
mplayer.stop();
mplayer.reset();
mplayer.release();
mplayer = MediaPlayer.create(getActivity(), soundUri);
// mplayer.start();
} catch (Exception e) {
e.printStackTrace();
}
}
1 回答
“mplayer”未初始化 . 因此,当您尝试调用方法“setDataSource”时,它会获得空指针异常 . 尝试在调用该方法之前初始化“mplayer” .