Android: Black screen flashes when activity resumes

I am having an issue with a TabbedActivity I have created.

I notice if I put my application in the background and then bring it back to the foreground, the screen goes black for a moment before the layout reappears. It looks as if the activity is being recreated, but I have confirmed that onCreate() is NOT being called when the app is resumed.

I set breakpoints in the onResume() and onStart() methods in the activity to see when the black screen occurs. When the app comes back to the foreground, onStart() is called, then onResume(), and THEN the screen flashes black for a split second. After this, the layout reappears. This is shown here:

I would like to note that this activity's onCreate() and onResume() methods are empty besides the calls to their superclasses. The fragment that is shown in the above gif doesn't even override the onResume() or onCreate() methods. Also, in other activities in my app that are NOT tabbed activities, this behavior does not occur - it only occurs in the TabbedActivity.

Please let me know if more information is needed and I will gladly provide it. I'm just not exactly sure where this problem could possibly be occurring.

EDIT:
I've realized when I comment out the contents of ANOTHER FRAGMENT'S onResume() method, this no longer occurs. Here is what that method looks like:

    @Override
    public void onResume() {
        super.onResume();
        System.out.println("RESUME");
        
        if (mShowCamera != null)
        {
            mShowCamera.camera = null;
        }
        mCamera = Camera.open();
        mShowCamera = new ShowCamera(getContext(), mCamera);
        mMainCamLayout = (FrameLayout)getView().findViewById(R.id.camLayout);
        mMainCamLayout.addView(mShowCamera);
        Camera.Parameters cameraParameters = mCamera.getParameters();
        cameraParameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
        if (cameraParameters.getSupportedFocusModes() != null &&
                cameraParameters.getSupportedFocusModes().contains(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO))
        {
            mCamera.setParameters(cameraParameters);

        }
    }

This has been resolved. The issue was that there was a lot of work being done when my application came back into focus. This caused the time required to load the activity to increase.

This activity has a few fragments attached to it. One contributing factor to this problem was trying to cache too many fragments like so:

ViewPager mViewPager = findViewById(R.id.view_pager);
mViewPager.setOffscreenPageLimit(4);

Minimizing the number of off-screen pages made the initial loading of my activity noticeably faster.

If your activity is taking a long time to load, try reducing the amount of work it has to do in its OnCreate and OnResume methods.