Google Glass Camera: setPreviewCallback - callback

Question

I have an operating android app that utilizes preview callbacks, to process the image after every frame from the preview (the preview is paused for a minute while the calculations take place). It works great! But, now I am trying to get Google Glass to do the same thing: activate Preview, activate preview callback, activating the calculations.
This issue likely has to do with how Camera is defined:
Camera mCamera = null;
but, I cannot define it as Camera.open(); with Google Glass because it fails. Thus when i get to defining the callback, I'm told it may produce a NullPointerException, and indeed I get the following error string:
Process: com.ead.glasscam.app, PID: 14231
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ead.glasscam.app/com.ead.glasscam.app.MainActivity}:
java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2235)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2285)
at android.app.ActivityThread.access$800(ActivityThread.java:138)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1236)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:149)
at android.app.ActivityThread.main(ActivityThread.java:5061)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.ead.glasscam.app.MainActivity.onCreate(MainActivity.java:100)
at android.app.Activity.performCreate(Activity.java:5236)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1089)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2285)
            at android.app.ActivityThread.access$800(ActivityThread.java:138)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1236)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:149)
            at android.app.ActivityThread.main(ActivityThread.java:5061)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:610)
            at dalvik.system.NativeStart.main(Native Method)
So, the code:
// Attach a callback for preview
mPreviewCallback camCallback = new mPreviewCallback();
mCamera.setPreviewCallback(camCallback);
What is mPreviewCallback?:
public class mPreviewCallback implements Camera.PreviewCallback {
public void onPreviewFrame(byte[] data, final Camera camera){
Log.i("CAMERA", "Triggered Preview Frame");
}
}
I really don't understand how to do this simple process on Android, with Google Glass. Thank you for reading.

Answer 1

Checkout this example from jaredsburrows, it uses the camera preview on Glass and I used it in a project once (It Works! ;) )
https://github.com/jaredsburrows/OpenQuartz/tree/master/example-apps/OG_CameraApp
public class CameraView extends SurfaceView implements SurfaceHolder.Callback
{
private SurfaceHolder surfaceHolder = null;
private Camera camera = null;
#SuppressWarnings("deprecation")
public CameraView(Context context)
{
super(context);
surfaceHolder = this.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
/*
* (non-Javadoc)
* #see android.view.SurfaceHolder.Callback#surfaceCreated(android.view.SurfaceHolder)
*/
#Override
public void surfaceCreated(SurfaceHolder holder)
{
camera = Camera.open();
// Set the Hotfix for Google Glass
this.setCameraParameters(camera);
// Show the Camera display
try
{
camera.setPreviewDisplay(holder);
}
catch (Exception e)
{
this.releaseCamera();
}
}
/*
* (non-Javadoc)
* #see android.view.SurfaceHolder.Callback#surfaceChanged(android.view.SurfaceHolder, int, int, int)
*/
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
// Start the preview for surfaceChanged
if (camera != null)
{
camera.startPreview();
}
}
/*
* (non-Javadoc)
* #see android.view.SurfaceHolder.Callback#surfaceDestroyed(android.view.SurfaceHolder)
*/
#Override
public void surfaceDestroyed(SurfaceHolder holder)
{
// Do not hold the camera during surfaceDestroyed - view should be gone
this.releaseCamera();
}
/**
* Important HotFix for Google Glass (post-XE11) update
* #param camera Object
*/
public void setCameraParameters(Camera camera)
{
if (camera != null)
{
Parameters parameters = camera.getParameters();
parameters.setPreviewFpsRange(30000, 30000);
camera.setParameters(parameters);
}
}
/**
* Release the camera from use
*/
public void releaseCamera()
{
if (camera != null)
{
camera.release();
camera = null;
}
}
}