如何从imageview获取可绘制内容并将其转换为位图？

Question

I have create app which load picture from facebook. I use Picasso. Picasso will set image result to my Imageview. I want to get that image convert to bitmap.

Here is my Code to get Image from Facebook:

 URL imageURL = new URL("https://graph.facebook.com/"+id+"/picture?type=large");                
 Picasso.with(getBaseContext()).load(imageURL.toString()).into(ImageView);

Here is my Code to get Image and convert to bitmap: (not work)

BitmapDrawable drawable = (BitmapDrawable) ImageView.getDrawable();
Bitmap bitmap = drawable.getBitmap();
bitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
ImageViewTest.setImageBitmap(bitmap);

ImageView.getDrawable() always return null.

I need your help. Thank you

Answer 1

Does it seem like loading the image into the ImageView is working? What's probably happening is that you are calling ImageView.getDrawable() before Picasso has finished loading the image. When do you call the getDrawable code? Try doing something like:

Picasso.with(getBaseContext()).load(imageURL.toString())
  .into(ImageView, new com.squareup.picasso.Callback() {
      @Override
      public void onSuccess() {
          BitmapDrawable drawable = (BitmapDrawable) ImageView.getDrawable();
          ...
      }

      @Override
      public void onError() {

      }
});

Answer 2

You should use the Picasso API to accomplish what you are looking to do.

One option would be to provide a Target listener to perform the Bitmap manipulation before setting it on the ImageView like this:

Picasso.with(getBaseContext())
        .load("https://graph.facebook.com/" + id + "/picture?type=large")
        .into(new Target() {
            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                // Manipulate image and apply to ImageView
            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {

            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {

            }
        });

Or better yet, use Picasso to perfom the resize operation and do not do any Bitmap manipulation yourself, like so:

Picasso.with(getBaseContext())
        .load("https://graph.facebook.com/" + id + "/picture?type=large")
        .resize(70, 70)
        .into(ImageView);

Answer 3

// Your imageview declaration
ImageView iv;
// Enable cache of imageview in oncreate
iv.setDrawingCacheEnabled(true);
// Get bitmap from iv
Bitmap bmap = iv.getDrawingCache();

Answer 4

This should be inside an AsyncTask:

try {
    URL url = new URL("http://....");
    Bitmap image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
} catch(IOException e) {
    System.out.println(e);
}

Answer 5

You can do it by the following code

 ImageView img;
 img.setDrawingCacheEnabled(true);
 Bitmap scaledBitmap = img.getDrawingCache();