Question

public class ImageDownloader extends AsyncTask<String, Void, Drawable> {
Context context;
ImageView image;
public ImageDownloader(ImageView image) {
    this.image = image;
}
protected void onPreExecute() {
}

protected Drawable doInBackground(String... urls) {
    InputStream is;
    Drawable d = null ;
    try {
        is = (InputStream)new URL(urls[0]).getContent();
        d = Drawable.createFromStream(is, "Image");
        return d;
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return d;
}
protected void onPostExecute(Drawable d) {
    if(d != null){
        d.setBounds(0, 0, d.getIntrinsicWidth(), d.getIntrinsicHeight());
        image.setBackgroundDrawable(d);
    }else{
        image.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.noimage));
        Toast.makeText(context, "No image", Toast.LENGTH_LONG).show();
    }

}

}

因为它在开始时工作但是当我下载大量图像时它会崩溃。我查看了我的LogCat，这是因为没有更多的分配。我想做一个像Pulse News这样的应用程序，它可以显示图像但不会每次都崩溃。而且我是冰淇淋三明治，以防万一。

Answer 1

您需要了解java中的SoftReference类。来吧，搜索它。你会得到你的答案

Answer 2

我找到了这个课，它工作正常，非常好！

public class LoaderImageView extends LinearLayout{

private static final int COMPLETE = 0;
private static final int FAILED = 1;

private Context mContext;
private Drawable mDrawable;
private ProgressBar mSpinner;
private ImageView mImage;

/**
 * This is used when creating the view in XML
 * To have an image load in XML use the tag 'image="http://developer.android.com/images/dialog_buttons.png"'
 * Replacing the url with your desired image
 * Once you have instantiated the XML view you can call
 * setImageDrawable(url) to change the image
 * @param context
 * @param attrSet
 */
public LoaderImageView(final Context context, final AttributeSet attrSet) {
    super(context, attrSet);
    final String url = attrSet.getAttributeValue(null, "image");
    if(url != null){
        instantiate(context, url);
    } else {
        instantiate(context, null);
    }
}

/**
 * This is used when creating the view programatically
 * Once you have instantiated the view you can call
 * setImageDrawable(url) to change the image
 * @param context the Activity context
 * @param imageUrl the Image URL you wish to load
 */
public LoaderImageView(final Context context, final String imageUrl) {
    super(context);
    instantiate(context, imageUrl);     
}

/**
 *  First time loading of the LoaderImageView
 *  Sets up the LayoutParams of the view, you can change these to
 *  get the required effects you want
 */
private void instantiate(final Context context, final String imageUrl) {
    mContext = context;

    mImage = new ImageView(mContext);
    mImage.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

    mSpinner = new ProgressBar(mContext);
    mSpinner.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

    mSpinner.setIndeterminate(true);

    addView(mSpinner);
    addView(mImage);

    if(imageUrl != null){
        setImageDrawable(imageUrl);
    }
}

/**
 * Set's the view's drawable, this uses the internet to retrieve the image
 * don't forget to add the correct permissions to your manifest
 * @param imageUrl the url of the image you wish to load
 */
public void setImageDrawable(final String imageUrl) {
    mDrawable = null;
    mSpinner.setVisibility(View.VISIBLE);
    mImage.setVisibility(View.GONE);
    new Thread(){
        public void run() {
            try {
                mDrawable = getDrawableFromUrl(imageUrl);
                imageLoadedHandler.sendEmptyMessage(COMPLETE);
            } catch (MalformedURLException e) {
                imageLoadedHandler.sendEmptyMessage(FAILED);
            } catch (IOException e) {
                imageLoadedHandler.sendEmptyMessage(FAILED);
            }
        };
    }.start();
}

/**
 * Callback that is received once the image has been downloaded
 */
Handler.Callback call = new Handler.Callback() {
    public boolean handleMessage(Message msg) {
        switch (msg.what) {
        case COMPLETE:
            mImage.setImageDrawable(mDrawable);
            mImage.setVisibility(View.VISIBLE);
            mSpinner.setVisibility(View.GONE);
            break;
        case FAILED:
        default:
            // Could change image here to a 'failed' image
            // otherwise will just keep on spinning
            break;
        }
        return true;
    }
};
private final Handler imageLoadedHandler =new Handler(call);


/**
 * Pass in an image url to get a drawable object
 * @return a drawable object
 * @throws IOException
 * @throws MalformedURLException
 */
private static Drawable getDrawableFromUrl(final String url) throws IOException, MalformedURLException {
    return Drawable.createFromStream(((java.io.InputStream)new java.net.URL(url).getContent()), "name");
}

}

要使用它，很简单：

 LoderImageView image = (LoaderImageView) findViewById(R.id.myid);
 image.setImageDrawable(url);

还有另一种从网址显示图像的方法吗？

2 个答案: