Android Camera Preview question

Question

Hello all.

I am writing a program to study Android Camera functions. Now, I have some problems about Camera preview operation:

My program will create a surfaceview object in the main activity (ActivityMain)'s onCreate() function and then set it to the content.

    super.onCreate(savedInstanceState);

    m_surface = new MyCameraSurface(this);        
    // remove title bar
    requestWindowFeature(Window.FEATURE_NO_TITLE);        
    setContentView(m_surface);

Then startPreview() will be called when surfaceChanged() is running.

public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    Log.d(TAG, "*** surfaceChanged >>>>> ***");
    Log.d(TAG, "format=" + format + ", width=" + width + ", height=" + height);

    if(m_control.IsCameraClosed() == false) {
        if(m_control.IsPreviewRun() == false) {             
            m_control.startPreview();
        }
    }

    Log.d(TAG, "*** surfaceChanged <<<<< ***");
}

My problem is: at the beginning my program always receives "GetNextPreviewFrame Error/1 frame:0x0, buffer:0x0" error:

07-22 06:47:46.727: DEBUG/MyCameraSurface(2313): *** surfaceChanged <<<<< ***
07-22 06:47:46.735: DEBUG/SurfaceFlinger(1276): commiting overlay changes
07-22 06:47:46.735: INFO/TIOverlay(1276): Nothing to do!
07-22 06:47:46.735: INFO/ActivityManager(1276): Displayed activity com.hykwok.CameraEffect/.ActivityMain: 7866 ms (total 7866 ms)
07-22 06:47:47.792: ERROR/CameraHal(1052): GetNextPreviewFrame Error/1 frame:0x0, buffer:0x0
07-22 06:47:48.477: DEBUG/dalvikvm(1276): GC freed 2299 objects / 119216 bytes in 143ms
07-22 06:47:48.793: ERROR/CameraHal(1052): GetNextPreviewFrame Error/1 frame:0x0, buffer:0x0
07-22 06:47:49.794: ERROR/CameraHal(1052): GetNextPreviewFrame Error/1 frame:0x0, buffer:0x0
07-22 06:47:50.794: ERROR/CameraHal(1052): GetNextPreviewFrame Error/1 frame:0x0, buffer:0x0

However, when I switch to another activity (ActivityCameraSetting) and then go back to the main activity, the output becomes normal.

Could anyone give some suggestion to me to fix it?

I am using Motorola Milestone. Firmware version is 2.1-update1 and build number is SHOLS_U2.02.36.0.

I am not sure other Android phones whether have this problem or not.

Another question is: Is it possible to get preview frame data by the preview callback function without set surfaceview holder?

Thank you for your help.

Source codes can be downloaded from here:

Source codes link