Programmatic screenshot on android: setDrawingCacheEnabled throws a CalledFromWrongThreadException

I'm running into an issue when trying to call content.setDrawingCacheEnabled(true) in one of my robotium tests. When i try to enable the drawing cache on the context I sometimes get a CalledFromWrongThreadException. This only seems to happen when running on an emulator. When I try this on device (Samsung S2) it works every time...

Here is the code

Calling function:

String screnshotName = String.format("SS_Cities_%s.png", s);
File ssDir = Environment.getExternalStorageDirectory();
TestUtilities.takeScreenShot(solo.getCurrentActivity(), ssDir, screnshotName);

Screenshot function (that throws exception):

public static void takeScreenShot(Activity activity, File Directory, String FileName) throws Exception {
    View content = activity.findViewById(R.id.content);

    ***// This is a horrible hack that i want to get rid of***
    // Occasiaonally setDrawingCacheEnabled throws a CalledFromWrongThreadException
    int MAX_RETRIES = 10;
    for(int i = 0; i < MAX_RETRIES; i++)
    {
        try{
            content.setDrawingCacheEnabled(true);
            continue;
        }
        catch (Exception e){}

    }

    content.buildDrawingCache();
    Bitmap b = content.getDrawingCache();
    File outpu开发者_运维知识库tFile = new File(Directory.toString() + "/" + FileName);

    try {
        if (!Directory.exists()) {
            Directory.mkdirs();
        }
        if (!Directory.canWrite()) {
            throw new Exception("Directory not writable");
        }

        FileOutputStream fos = new FileOutputStream(outputFile);

        if (fos != null) {
            b.compress(Bitmap.CompressFormat.PNG, 90, fos);
            fos.close();
        }
    } catch (Exception e) {
        String screenshotError = String.format("Error taking screenshot: %s", e.toString());
        throw new Exception(screenshotError);
    }
}

Permissions set in the application I'm testing:

<uses-permission android:name="android.permission.CHANGE_CONFIGURATION"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Android emulator doesn't always work fine with external storage. That's why you might get those errors. So I suggest that whenever you want to test apps that use external storage you do it in a real device since you won't have all the "unfixed" errors that the emulator still has.

I can't see whether you perform your takeScreenShot method from the UIThread or not but as far as I can see I think your question is being answered here:

StackOverflow: CalledFromWrongThreadException