https://stackoverflow.com/questions/15607406
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First, create a custom WebImageView class as follows.
public class WebImageView extends ImageView {
private Drawable placeholder, image;
public WebImageView(Context context) {
super(context);
}
public WebImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public WebImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setPlaceholderImage(Drawable drawable) {
placeholder = drawable;
if (image == null) {
setImageDrawable(placeholder);
}
}
public void setPlaceholderImage(int resid) {
placeholder = getResources().getDrawable(resid);
if (image == null) {
setImageDrawable(placeholder);
}
}
public void setImageUrl(String url) {
DownloadTask task = new DownloadTask();
task.execute(url);
}
private class DownloadTask extends AsyncTask<String, Void, Bitmap> {
@Override
protected Bitmap doInBackground(String... params) {
String url = params[0];
try {
URLConnection conn = (new URL(url)).openConnection();
InputStream is = conn.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
ByteArrayBuffer baf = new ByteArrayBuffer(50);
int current = 0;
while ((current=bis.read()) != -1) {
baf.append((byte)current);
}
byte[] imageData = baf.toByteArray();
return BitmapFactory.decodeByteArray(imageData, 0, imageData.length);
} catch (Exception e) {
return null;
}
}
@Override
protected void onPostExecute(Bitmap result) {
image = new BitmapDrawable(result);
if (image != null) {
setImageDrawable(image);
}
}
}
}
Next, in Activity use the above custom ImageView as follows:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
WebImageView imageView = (WebImageView) findViewById(R.id.webimage);
imageView.setPlaceholderImage(R.drawable.ic_launcher);
imageView.setImageUrl("http://www.google.co.in/images/srpr/logo3w.png");
}
In brief, you are setting a placeholder image for the ImageView which gets replaced by the actual image when download completes. So the GridView will render immediately without delay.
Implementation Details: So in your custom view (with an image + text) instead of using a simple ImageView, use WebImageView as shown above. When you get the JSON response set the TextView with the caption and the WebImageView with the image url. So the caption will display immediately and the Image will load lazily.
