Android screenshot app - null pointer exception

Question

I am trying to test code to take screenshot on the android emulator. I have the following code to start with:

    View content = ((ViewGroup)findViewById(android.R.id.content)).getChildAt(0);
    content.setDrawingCacheEnabled(true);
    Bitmap bitmap = Bitmap.createBitmap(content.getDrawingCache());
    content.setDrawingCacheEnabled(false);

But I get null pointer exception in createBitmap at line 551.

Can someone please point out what am I doing wrong.

score 1 · Answer 1 · answered Mar 17 '12 at 02:51

1

I think your problem could come from your View content :

View content = ((ViewGroup)findViewById(android.R.id.content)).getChildAt(0);

Did you try remove getChildAt(0) or to replace it by getRootView() ?

Else, there is a good website with a sample there if it can help you (last post on the first forum page):

Capture Screen With Coding

Tell me if you find how to solve it.

answered Mar 17 '12 at 02:51

ChapMic

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I used the code : Bitmap bitmap = content.getDrawingCache(), and I did not get the null pointer exception. As the emulator has root privilege, if I ran this code on a phone, would I get an exception ? Also, why does the app not require READ_FRAME_BUFFER permission ? Thanks – Jake Mar 17 '12 at 03:17
On running on the emulator, I get bitmap = null. – Jake Mar 17 '12 at 03:23

score 0 · Answer 2 · answered Oct 02 '12 at 12:55

You must use MeasureSpec in some cases. Try this:

View content = ((ViewGroup)findViewById(android.R.id.content));
content.setDrawingCacheEnabled(true);
content.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
content.layout(0, 0, content.getMeasuredWidth(), content.getMeasuredHeight());
content.buildDrawingCache(true);
Bitmap bitmap = Bitmap.createBitmap(content.getDrawingCache());

Android screenshot app - null pointer exception

2 Answers2