Question

我是android的新手。这是我在getView（）里面得到异常的代码。我正在尝试列出音乐titlename以及音乐持续时间，点击后开始播放音乐。

MainActivity.java

    public class MainActivity extends Activity {

    Cursor c;
    int index;
    int count;
    MediaPlayer mp;

    private ArrayList<String> mnamedata = new ArrayList<String>();
    private ArrayList<String> mdurationdata = new ArrayList<String>();

    public static class ViewHolder {
        TextView mname;
        TextView mduration;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String cols[] = { MediaStore.Audio.Media.DISPLAY_NAME,
                MediaStore.Audio.Media.DURATION, MediaStore.Audio.Media.DATA };

        try {
            ContentResolver contentResolver = getContentResolver();
            Uri uri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            c = contentResolver.query(uri, cols, null, null, null);

            count = c.getCount();
            ListView lv = (ListView) findViewById(R.id.listView1);
            lv.setAdapter(new MusicAdapter(getApplicationContext()));
            mp = new MediaPlayer();

            for (int i = 0; i < c.getCount(); i++) {
                mnamedata.add(c.getString(0));
                mdurationdata.add(c.getString(1));
            }

            lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> arg0, View arg1,
                        int arg2, long arg3) {
                    // TODO Auto-generated method stub
                    c.moveToPosition(arg2);
                    String fn = c.getString(2);
                    try {
                        if (mp.isPlaying())
                            mp.reset();
                        mp.setDataSource(fn);
                        mp.prepare();
                        mp.start();

                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            });
        } catch (Exception e) {
            System.out.println("No sdcard presents");
        }

    }

    private class MusicAdapter extends BaseAdapter {

        Context music_context;
        LayoutInflater inflater;

        private MusicAdapter(Context c) {
            music_context = c;
            inflater = (LayoutInflater) music_context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return count;
        }

        @Override
        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        @Override
        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub
            ViewHolder holder;
            if (convertView == null) {
                convertView = inflater.inflate(R.layout.listinflate, null);
                holder = new ViewHolder();

                convertView.setTag(holder);

            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            holder.mname = (TextView) convertView
                    .findViewById(R.id.mname);
            holder.mduration = (TextView) convertView
                    .findViewById(R.id.mduration);
            holder.mname.setText(mnamedata.get(position));
            holder.mduration.setText(mdurationdata.get(position));

            return convertView;
        }

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

listinflate.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/mname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:layout_marginLeft="5dp"
        android:layout_marginTop="10dp"
        android:layout_weight="1"
        android:clickable="false"
        android:focusable="false"
        android:focusableInTouchMode="false"
        android:text="Name"
        android:textSize="6pt"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/mduration"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:clickable="false"
        android:focusable="false"
        android:focusableInTouchMode="false"
        android:text="Code"
        android:textSize="6pt" />

</LinearLayout>

activity_main.xml中

<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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

 <ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true" 
    >

</ListView>

</RelativeLayout>

输出

 04-29 01:02:38.455: E/AndroidRuntime(17156): FATAL EXCEPTION: main
04-29 01:02:38.455: E/AndroidRuntime(17156): java.lang.IndexOutOfBoundsException: Invalid index 1, size is 0
04-29 01:02:38.455: E/AndroidRuntime(17156):    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
04-29 01:02:38.455: E/AndroidRuntime(17156):    at java.util.ArrayList.get(ArrayList.java:304)
04-29 01:02:38.455: E/AndroidRuntime(17156):    at com.example.musiclistview.MainActivity$MusicAdapter.getView(MainActivity.java:132)
04-29 01:02:38.455: E/AndroidRuntime(17156):    at android.widget.AbsListView.obtainView(AbsListView.java:2603)
04-29 01:02:38.455: E/AndroidRuntime(17156):    at android.widget.ListView.measureHeightOfChildren(ListView.java:1253)

Answer 1

更改代码以添加c.moveToFirst（）以确保光标位于for之前的第一个位置并添加c.moveToNext（）以便将光标移动到下一个位置也可以更改为一段时间（！c.isAfterLast（））{}移动光标

...

count = c.getCount();
ListView lv = (ListView) findViewById(R.id.listView1);
lv.setAdapter(new MusicAdapter(getApplicationContext()));
mp = new MediaPlayer();
c.moveToFirst();
for (int i = 0; i < c.getCount(); i++) {
...
c.moveToNext();
}

...

在getView中获取arrayindexoutofboundException

1 个答案: