android - 使用自定义 simpleCursorAdapter

Question

我正在尝试使用自定义适配器访问列表 Activity 。我已经在不使用任何自定义适配器的情况下直接进行了尝试，它运行良好，但因为我想在 ListView 中添加更多功能，所以我想实现一个自定义适配器。现在我已经尝试过了，但我得到的是一个空的 ListView ，没有任何数据可见。列表 Activity

public class MainActivity extends ListActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";

         String[] projection = {
                    MediaStore.Audio.Media._ID,
                    MediaStore.Audio.Media.ARTIST,
                    MediaStore.Audio.Media.TITLE,
                    MediaStore.Audio.Media.DATA,
                    MediaStore.Audio.Media.DISPLAY_NAME,
                    MediaStore.Audio.Media.DURATION,

            };
            //query 

            musiccursor = this.managedQuery(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,projection,selection,null,sortOrder);
            music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA);


            int a[]= new int[]{R.id.TitleSong,R.id.Artist};


            Custom_Adapter adapter = new Custom_Adapter(this,R.layout.music_items, musiccursor, new String[]{MediaStore.Audio.Media.TITLE,MediaStore.Audio.Media.ARTIST} ,a);

            this.setAdapter(adapter);

            }
    }

自定义适配器

    public class Custom_Adapter extends SimpleCursorAdapter {


    private Context mContext;
    private Context appContext;
    private int layout;
    private Cursor cr;
    private final LayoutInflater inflater;

    public Custom_Adapter(Context context,int layout, Cursor c,String[] from,int[] to) {
        super(context,layout,c,from,to);
        this.layout=layout;
        this.mContext = context;
        this.inflater=LayoutInflater.from(context);
        this.cr=c;
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        // TODO Auto-generated method stub
        super.bindView(view, context, cursor);
     view=inflater.inflate(layout, null, false);
        TextView titleS=(TextView)view.findViewById(R.id.TitleSong);
        TextView artistS=(TextView)view.findViewById(R.id.Artist);
        int Title_index;
        int Artist_index;
        cursor.moveToFirst();
        while(cursor.isLast()){

            Title_index=cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME);
            Artist_index=cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST);
            titleS.setText(cursor.getString(Title_index));
            artistS.setText(cursor.getString(Artist_index));
            cr.moveToNext();
            }

    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub

        return convertView;
    }
}

Answer 1

扩展游标适配器时，您应该重写方法 bindView和 newView . bindView 方法用于将所有数据绑定(bind)到给定 View ，例如在 TextView 上设置文本。 newView 方法用于扩充新 View 并返回它，此时您不将任何数据绑定(bind)到 View 。大多数适配器使用 getView 函数，但在扩展游标适配器时，您应该使用 bindView 和 newView。

    public class Custom_Adapter extends SimpleCursorAdapter {

            private Context mContext;
            private Context appContext;
            private int layout;
            private Cursor cr;
            private final LayoutInflater inflater;

            public Custom_Adapter(Context context,int layout, Cursor c,String[] from,int[] to) {
                super(context,layout,c,from,to);
                this.layout=layout;
                this.mContext = context;
                this.inflater=LayoutInflater.from(context);
                this.cr=c;
            }

            @Override
            public View newView (Context context, Cursor cursor, ViewGroup parent) {
                    return inflater.inflate(layout, null);
            }

            @Override
            public void bindView(View view, Context context, Cursor cursor) {
                super.bindView(view, context, cursor);
                TextView titleS=(TextView)view.findViewById(R.id.TitleSong);
                TextView artistS=(TextView)view.findViewById(R.id.Artist);

                int Title_index=cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME);
                int Artist_index=cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST);

                titleS.setText(cursor.getString(Title_index));
                artistS.setText(cursor.getString(Artist_index));

            }

    }