java - android 延迟加载图库问题

Question

我尝试在异步任务中异步下载一些图像，然后在 onPostExecute() 中将图像设置为图库适配器。我已经对要在 asyntask 中下载的图像进行了硬编码，因为我什至无法到达将图像传递给适配器的构造函数的部分:/不会引发任何错误，并且 postexecute Log() 不会将任何内容发布到 logcat

谁能告诉我哪里出错了？

公共(public)类 GallerythreadedtestActivity 扩展了 Activity {

private Gallery gallery;
private AddImgAdp adapter;
private Drawable[] image;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    new downloadImages().execute();
}

public class AddImgAdp extends BaseAdapter {
    int GalItemBg;
    private Context cont;

    // Adding images.
    private Integer[] Imgid = {
    R.drawable.icon, R.drawable.icon, R.drawable.icon, R.drawable.icon
    };

    public AddImgAdp(Context c) {
    cont = c;
    TypedArray typArray = obtainStyledAttributes(R.styleable.GalleryTheme);
    GalItemBg = typArray.getResourceId(R.styleable.GalleryTheme_android_galleryItemBackground, 0);
    typArray.recycle();
    }

    public int getCount() {
    return Imgid.length;
    }

    public Object getItem(int position) {
    return position;
    }

    public long getItemId(int position) {
    return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imgView = new ImageView(cont);

    imgView.setImageDrawable(image[position]);
    // Fixing width & height for image to display
    imgView.setLayoutParams(new Gallery.LayoutParams(80, 70));
    imgView.setScaleType(ImageView.ScaleType.FIT_XY);
    imgView.setBackgroundResource(GalItemBg);

    return imgView;
    }
    }

public class downloadImages extends AsyncTask<String, Void, Void> {

    protected void onPreExecute(){
        image=new Drawable[2];
        adapter = new AddImgAdp(getApplicationContext());
        gallery = (Gallery) findViewById(R.id.examplegallery);
    }

    protected void onProgressUpdate(Void... v){

    }

    protected Void doInBackground(final String... args) {


        image[0] = ImageOperations(getApplicationContext(),"http://t3.gstatic.com/images?q=tbn:ANd9GcQidl6KX2jRWNeCA6jT_TjWG7NlI3aRiB_AcDsA9Y5owS2cr9G6","image.jpg");
        image[1] = ImageOperations(getApplicationContext(),"http://t3.gstatic.com/images?q=tbn:ANd9GcQidl6KX2jRWNeCA6jT_TjWG7NlI3aRiB_AcDsA9Y5owS2cr9G6","image.jpg");

        return null;

    }

    protected void onPostExecute(){
        Log.d("onpost","");
        gallery.setAdapter(adapter);
        gallery.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView parent, View v, int position, long id) {
            Toast.makeText(GallerythreadedtestActivity.this, "Position=" + position, Toast.LENGTH_SHORT).show();
            }
            });
    }

}

private Drawable ImageOperations(Context ctx, String url, String saveFilename) {
    try {
        InputStream is = (InputStream) this.fetch(url);
        Drawable d = Drawable.createFromStream(is, "src");
        return d;
    } catch (MalformedURLException e) {
        e.printStackTrace();
        return null;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }
}

public Object fetch(String address) throws MalformedURLException,IOException {
    URL url = new URL(address);
    Object content = url.getContent();
    return content;
}

}

Answer 1

我可以给你一个建议，请也尝试一下这个作为补充解决方案，它更好地延迟加载图像:Lazy load of images in ListView 。如果您将 xml 中的 ListView 元素更改为图库 View ，我认为这将解决您的问题。