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音乐播放器在没有外部存储的智能手机上运行，​​应用程序崩溃，而在有外部存储的智能手机上运行。你能告诉我为什么吗？

Java 类

    import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;

import java.io.IOException;
import java.math.BigDecimal;

public class mediaplayer extends ListActivity {
    private static final int UPDATE_FREQUENCY = 500;
    private static final int STEP_VALUE = 4000;

    private MediaCursorAdapter mediaAdapter = null;
    private TextView selelctedFile = null;
    private SeekBar seekbar = null;
    private MediaPlayer player = null;
    private ImageButton playButton = null;
    private ImageButton prevButton = null;
    private ImageButton nextButton = null;

    private boolean isStarted = true;
    private String currentFile = "";
    private boolean isMoveingSeekBar = false;

    private final Handler handler = new Handler();

    private final Runnable updatePositionRunnable = new Runnable() {
        public void run() {
            updatePosition();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.mediaplayer);
        AdView mAdView = (AdView) findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);
        selelctedFile = (TextView) findViewById(R.id.selectedfile);
        seekbar = (SeekBar) findViewById(R.id.seekbar);
        playButton = (ImageButton) findViewById(R.id.play);
        prevButton = (ImageButton) findViewById(R.id.prev);
        nextButton = (ImageButton) findViewById(R.id.next);

        player = new MediaPlayer();

        player.setOnCompletionListener(onCompletion);
        player.setOnErrorListener(onError);
        seekbar.setOnSeekBarChangeListener(seekBarChanged);

        Cursor cursor = getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null, null);

        if (null != cursor) {
            cursor.moveToFirst();

            mediaAdapter = new MediaCursorAdapter(this, R.layout.listitem, cursor);

            setListAdapter(mediaAdapter);

            playButton.setOnClickListener(onButtonClick);
            nextButton.setOnClickListener(onButtonClick);
            prevButton.setOnClickListener(onButtonClick);
        }
    }

    @Override
    protected void onListItemClick(ListView list, View view, int position, long id) {
        super.onListItemClick(list, view, position, id);

        currentFile = (String) view.getTag();

        startPlay(currentFile);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        handler.removeCallbacks(updatePositionRunnable);
        player.stop();
        player.reset();
        player.release();

        player = null;
    }

    private void startPlay(String file) {
        Log.i("Selected: ", file);

        selelctedFile.setText(file);
        seekbar.setProgress(0);

        player.stop();
        player.reset();

        try {
            player.setDataSource(file);
            player.prepare();
            player.start();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        seekbar.setMax(player.getDuration());
        playButton.setImageResource(android.R.drawable.ic_media_pause);

        updatePosition();

        isStarted = true;
    }

    private void stopPlay() {
        player.stop();
        player.reset();
        playButton.setImageResource(android.R.drawable.ic_media_play);
        handler.removeCallbacks(updatePositionRunnable);
        seekbar.setProgress(0);

        isStarted = false;
    }

    private void updatePosition() {
        handler.removeCallbacks(updatePositionRunnable);

        seekbar.setProgress(player.getCurrentPosition());

        handler.postDelayed(updatePositionRunnable, UPDATE_FREQUENCY);
    }


    private class MediaCursorAdapter extends SimpleCursorAdapter {

        public MediaCursorAdapter(Context context, int layout, Cursor c) {

            super(context, layout, c,
                    new String[]{MediaStore.MediaColumns.DISPLAY_NAME, MediaStore.MediaColumns.TITLE, MediaStore.Audio.AudioColumns.DURATION},
                    new int[]{R.id.displayname, R.id.title, R.id.duration});

        }

        @Override
        public void bindView(View view, Context context, Cursor cursor) {
            TextView title = (TextView) view.findViewById(R.id.title);
            TextView name = (TextView) view.findViewById(R.id.displayname);
            TextView duration = (TextView) view.findViewById(R.id.duration);

            name.setText(cursor.getString(
                    cursor.getColumnIndex(MediaStore.MediaColumns.DISPLAY_NAME)));

            title.setText(cursor.getString(
                    cursor.getColumnIndex(MediaStore.MediaColumns.TITLE)));

            long durationInMs = Long.parseLong(cursor.getString(
                    cursor.getColumnIndex(MediaStore.Audio.AudioColumns.DURATION)));

            double durationInMin = ((double) durationInMs / 1000.0) / 60.0;

            durationInMin = new BigDecimal(Double.toString(durationInMin)).setScale(2, BigDecimal.ROUND_UP).doubleValue();

            duration.setText("" + durationInMin);

            view.setTag(cursor.getString(cursor.getColumnIndex(MediaStore.MediaColumns.DATA)));
        }

        @Override
        public View newView(Context context, Cursor cursor, ViewGroup parent) {
            LayoutInflater inflater = LayoutInflater.from(context);
            View v = inflater.inflate(R.layout.listitem, parent, false);

            bindView(v, context, cursor);

            return v;
        }
    }

    private View.OnClickListener onButtonClick = new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.play: {
                    if (player.isPlaying()) {
                        handler.removeCallbacks(updatePositionRunnable);
                        player.pause();
                        playButton.setImageResource(android.R.drawable.ic_media_play);
                    } else {
                        if (isStarted) {
                            player.start();
                            playButton.setImageResource(android.R.drawable.ic_media_pause);

                            updatePosition();
                        } else {
                            startPlay(currentFile);
                        }
                    }

                    break;
                }
                case R.id.next: {
                    int seekto = player.getCurrentPosition() + STEP_VALUE;

                    if (seekto > player.getDuration())
                        seekto = player.getDuration();

                    player.pause();
                    player.seekTo(seekto);
                    player.start();

                    break;
                }
                case R.id.prev: {
                    int seekto = player.getCurrentPosition() - STEP_VALUE;

                    if (seekto < 0)
                        seekto = 0;

                    player.pause();
                    player.seekTo(seekto);
                    player.start();

                    break;
                }
            }
        }
    };

    private MediaPlayer.OnCompletionListener onCompletion = new MediaPlayer.OnCompletionListener() {

        @Override
        public void onCompletion(MediaPlayer mp) {
            stopPlay();
        }
    };

    private MediaPlayer.OnErrorListener onError = new MediaPlayer.OnErrorListener() {

        @Override
        public boolean onError(MediaPlayer mp, int what, int extra) {
            // returning false will call the OnCompletionListener
            return false;
        }
    };

    private SeekBar.OnSeekBarChangeListener seekBarChanged = new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
            isMoveingSeekBar = false;
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {
            isMoveingSeekBar = true;
        }

        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            if (isMoveingSeekBar) {
                player.seekTo(progress);

                Log.i("OnSeekBarChangeListener", "onProgressChanged");
            }
        }
    };}

活动 XML

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#000033"
    android:keepScreenOn="true"
    android:orientation="vertical"
    xmlns:ads="http://schemas.android.com/apk/res-auto">

    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="330dp"
        android:background="#FFFFFF" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#000033"
        android:orientation="vertical"
        android:padding="10dip">

        <TextView
            android:id="@+id/selectedfile"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:ellipsize="middle"
            android:gravity="center_horizontal"
            android:singleLine="true"
            android:text="@string/Notfileselected"
            android:textColor="@android:color/white" />

        <SeekBar
            android:id="@+id/seekbar"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:max="100"
            android:paddingBottom="10dip" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:background="#000033"
            android:gravity="center"
            android:orientation="horizontal">

            <ImageButton
                android:id="@+id/prev"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:contentDescription="@string/app_name"
                android:src="@android:drawable/ic_media_previous" />

            <ImageButton
                android:id="@+id/play"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:contentDescription="@string/app_name"
                android:src="@android:drawable/ic_media_play" />

            <ImageButton
                android:id="@+id/next"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:contentDescription="@string/app_name"
                android:src="@android:drawable/ic_media_next" />
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

列表项.xml

     <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:context=".mediaplayer$MediaCursorAdapter"
    android:keepScreenOn="true">

    <TextView
        android:id="@+id/displayname"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:ellipsize="end"
        android:singleLine="true"
        android:textSize="18sp"
        android:textStyle="bold" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/duration"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:ellipsize="end"
            android:gravity="right"
            android:singleLine="true"
            android:textSize="15sp" />
    </LinearLayout>

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ellipsize="end"
        android:singleLine="true"
        android:textSize="15sp" />

</LinearLayout>

错误日志

    java.lang.NumberFormatException: Invalid long: "null"
at java.lang.Long.invalidLong(Long.java:124)
at java.lang.Long.parseLong(Long.java:345)
at java.lang.Long.parseLong(Long.java:321)
at com.play.mediaplayer$MediaCursorAdapter.bindView(mediaplayer.java:176)
at com.play.mediaplayer$MediaCursorAdapter.newView(mediaplayer.java:193)
at android.support.v4.widget.CursorAdapter.getView(CursorAdapter.java:252)
at android.widget.AbsListView.obtainView(AbsListView.java:2344)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
at android.widget.ListView.fillFromTop(ListView.java:759)
at android.widget.ListView.layoutChildren(ListView.java:1673)
at android.widget.AbsListView.onLayout(AbsListView.java:2148)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:494)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2072)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1829)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)

    at   com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

感谢帮助

4

1 回答 1

0

由于您要求的是外部存储 ( MediaStore.Audio.Media.EXTERNAL_CONTENT_URI) 上的文件，因此没有外部存储的手机将不会为您的查询返回任何结果。

要正确处理空结果，请尝试更改：

  //...
  if (null != cursor) {
      cursor.moveToFirst();
      //...
  }

对此：

  //...
  if (null != cursor &&  cursor.moveToFirst()) {
      //...
  }

更新

如果您想从内部存储中获取文件，只需将您的查询更改为：

Cursor cursor = getContentResolver().query(MediaStore.Audio.Media.INTERNAL_CONTENT_URI, null, null, null, null);
于 2015-02-08T17:55:37.313 回答