1

我的 gridview 活动当前的方式是在我的 onCreate 方法中，我启动了一个异步任务，该任务搜索我手机上的所有视频，然后使用 do while 循环将 id 和文件路径存储在 SQLite 数据库中。然后我调用一个使用后台线程的光标适配器来使用文件路径来创建缩略图并将它们显示在网格视图中。但是，我遇到的问题是，当我第一次启动活动时，gridview 中没有显示任何内容。但是，当我再次打开它时，一切都会显示。所以我的问题是，当活动首次启动时，光标中没有任何内容，因此无法显示任何内容。

我的问题是在后台线程中输入新数据时如何更新光标适配器？如何触发光标适配器使用刚刚在后台线程中输入的数据？我的代码发布在下面（抱歉有点草率）。

创建时

public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.preview);
GridView gridview = (GridView) this.findViewById(R.id.gridview);

cursor = getContentResolver().query(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, mediaColumns, null, null, null);
columnindexid = cursor.getColumnIndexOrThrow(MediaStore.Video.Media._ID);
columnindexdata = cursor.getColumnIndexOrThrow(MediaStore.Video.Media.DATA);

entry = new GridviewData(this);
entry.open();

DataEntry putitin = new DataEntry(entry);
putitin.execute();

//the cursor used in the cursor adapter
Cursor curs = entry.adapterCursor();
videoidindex = entry.Indexfinder(curs);
videopathindex = entry.Indexfinder2(curs);

config = new ImageLoaderConfiguration.Builder(this)
.imageDownloader(new BaseImageDownloader(this))
.build();

ImageLoader.getInstance().init(config);
Log.i(TAG, "Before set adapter");
gridview.setAdapter(new VideoAdapter(this, curs, flags));
 }

将数据放入数据库的异步任务

private class DataEntry extends AsyncTask<Void, Integer, GridviewData>{
Cursor cursor;
GridviewData dataentry;
DataEntry(GridviewData gridviewdata){
    this.dataentry = gridviewdata;
    this.cursor = getContentResolver().query(MediaStore.Video.Media.EXTERNAL_CONTENT_URI,
            mediaColumns, null, null, null);

         columnindexid = cursor.getColumnIndexOrThrow(MediaStore.Video.Media._ID);
         columnindexdata = cursor.getColumnIndexOrThrow(MediaStore.Video.Media.DATA);
}

@Override
protected GridviewData doInBackground(Void... params) {

    cursor.moveToFirst();
    do {

        String videoid = cursor.getString(columnindexid);
        String videopath = cursor.getString(columnindexdata);

        int result = dataentry.findVideoID(videoid);
        if (result == 1){

            //this is where data is put into the database
            dataentry.addVideoinfo(videoid, videopath);

        }

        if (result == 0){
            Log.i(TAG, "Cursor wasn't processed, no getcount");
        }
        if(result == 2){
            Log.i(TAG, "The data is already there");
        }

    } while (cursor.moveToNext());
    Log.i(TAG, "After dowhile loop");
    cursor.close();

    return dataentry;   
}   
    }

光标适配器

class VideoAdapter extends CursorAdapter {
Context context; 
public VideoAdapter(Context context, Cursor c, int flags) {
    super(context, c, flags);
    this.context = context;
    }

@Override
public void bindView(View view, Context context, Cursor cursor) {
    ViewHolder holder = (ViewHolder) view.getTag();
    String fileid = cursor.getString(videoidindex);
    String filepath = cursor.getString(videopathindex);
    BitmapDownloader bitdl = new BitmapDownloader(fileid, filepath,    holder.imageview);
    bitdl.execute();
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View eachgrid = inflater.inflate(R.layout.eachgrid, parent, false);
    ViewHolder holder = new ViewHolder();
    holder.imageview = (ImageView) eachgrid
            .findViewById(R.id.Imageview1);
    eachgrid.setTag(holder);
    return eachgrid;        
}
4

1 回答 1

2

后台线程完成后，在适配器上调用notifyDataSetChanged 。

通知附加的观察者底层数据已更改，任何反映数据集的视图都应自行刷新。

于 2013-06-16T21:17:36.980 回答