Converting a view to Bitmap without displaying it in Android?

Question

I will try to explain what exactly I need to do.

I have 3 separate screens say A,B,C. There is another screen called say HomeScreen where all the 3 screens bitmap should be displayed in Gallery view and the user can select in which view does he wants to go.

I have been able to get the Bitmaps of all the 3 screens and display it in Gallery view by placing all the code in HomeScreen Activity only. Now, this has complicated the code a lot and I will like to simplify it.

So, can I call another Activity from HomeScreen and do not display it and just get the Bitmap of that screen. For example, say I just call HomeScreen and it calls Activity A,B,C and none of the Activities from A,B,C are displayed. It just gives the Bitmap of that screen by getDrawingCache(). And then we can display those bitmaps in Gallery view in HomeScreen.

I hope I have explained the problem very clearly.

Please let me know if this is actually possible.

Answer 1

there is a way to do this. you have to create a Bitmap and a Canvas and call view.draw(canvas);

here is the code:

public static Bitmap loadBitmapFromView(View v) {
    Bitmap b = Bitmap.createBitmap( v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888);                
    Canvas c = new Canvas(b);
    v.layout(v.getLeft(), v.getTop(), v.getRight(), v.getBottom());
    v.draw(c);
    return b;
}

if the view wasn't displayed before the size of it will be zero. Its possible to measure it like this:

if (v.getMeasuredHeight() <= 0) {
    v.measure(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    Bitmap b = Bitmap.createBitmap(v.getMeasuredWidth(), v.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
    Canvas c = new Canvas(b);
    v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
    v.draw(c);
    return b;
}

EDIT: according to this post, Passing WRAP_CONTENT as value to makeMeasureSpec() doesn't to do any good (although for some view classes it does work), and the recommended method is:

// Either this
int specWidth = MeasureSpec.makeMeasureSpec(parentWidth, MeasureSpec.AT_MOST);
// Or this
int specWidth = MeasureSpec.makeMeasureSpec(0 /* any */, MeasureSpec.UNSPECIFIED);
view.measure(specWidth, specWidth);
int questionWidth = view.getMeasuredWidth();