使用异步任务在gridview中加载图像,但未正确加载

时间:2014-01-09 19:21:01

标签: android gridview android-asynctask android-imageview

我正在尝试在gridview异步中加载thumnails,因为其他方式显示它需要很长时间!

当我以正常方式进行时,它会显示图像正常。 (代码和图像)

的Utils

public static Bitmap getThumbnail(Context context, Bitmap bitmap, int columns){
        WindowManager wm = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();
        Point size = new Point();
        display.getSize(size);

        int scale = size.x / columns;
        Bitmap bit = ThumbnailUtils.extractThumbnail(bitmap, scale, scale);
        return bit;
    }

适配器

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;
        if(convertView == null){
            LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.adapter_item, null);
        }
        else{
            view = convertView;
        }
        ImageView image = (ImageView)view.findViewById(R.id.img_item);
        image.setImageBitmap(Utilities.getThumbnail(context, BitmapFactory.decodeFile(((Item) this.collection.get(position)).getSrc()), 5));
        return view;
    }

Grid with images loaded

这是asyncTask的结果

的AsyncTask

public class ImageGridHandler extends AsyncTask<String, Void, Bitmap>{
    private final WeakReference<ImageView> imageViewReference;
    private Context context;

    public ImageGridHandler(Context context, ImageView img){
        imageViewReference = new WeakReference<ImageView>(img);
        this.context = context;
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        return PixzelleUtilities.getThumbnail(this.context, BitmapFactory.decodeFile(params[0]) ,5);
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        final ImageView imageView = imageViewReference.get();
        imageView.setImageBitmap(result);
    }
}

适配器

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;
        if(convertView == null){
            LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.adapter_item, null);
        }
        else{
            view = convertView;
        }
        ImageView image = (ImageView)view.findViewById(R.id.img_item);
        image.setImageBitmap(null);
        ImageGridHandler handler = new ImageGridHandler(context, image);
        handler.execute(((Item)this.collection.get(position)).getSrc());
        return view;
    }

图像是小黑色矩形。

The images don't load correctly

uris是正确的,因为我可以触摸图像并在弹出窗口中打开!

我错过了什么吗?

1 个答案:

答案 0 :(得分:1)

您需要通知适配器布局已更改,以便可以重新测量视图。然而,这是昂贵的,并且每次加载图像时都会导致重新布局。您应该通过为每个gridview切片设置固定大小来避免这种情况。目前,我的猜测是你的R.layout.adapter_item.xml的高度为wrap_content。将其更改为固定值,它应该可以解决您的问题。

如果您想要降低性能,请通过notifyDataSetChanged通知您的适配器发生了更改。

http://developer.android.com/reference/android/widget/BaseAdapter.html#notifyDataSetChanged()