Start camera preview using API2 with surfaceview and delay

Question

I am running into an issue using camera 2 API and surface view. This is for an old embedded system and I HAVE to use surfaceview for reasons I can't explain here.

I found this sample where it is shown how it can be done:

https://android.googlesource.com/platform/frameworks/base/+/ee699a6/tests/Camera2Tests?autodive=0

What I need to start the preview with a delay after "onCreate". The code works without any delay. But if I add a delay the preview never comes on (the surface callback never gets called)

here is a snipped of code that does NOT work:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.surfaceviewtest);

    new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
        @Override
        public void run() {
            startCameraExec();
        }
    }, 2000);
}

But This works :

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.surfaceviewtest);
    startCameraExec();
}

my startCameraExec just sets up the background thread and sets up the surface callback

private void startCameraExec() {
    Log.d(TAG, "Starting API2 camera...");
    // Start a background thread to manage camera requests
    mBackgroundThread = new HandlerThread("background");
    mBackgroundThread.start();
    mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    mForegroundHandler = new Handler(getMainLooper());
    mCameraManager = (CameraManager) getSystemService(CAMERA_SERVICE);

    mSurfaceView = (SurfaceView) findViewById(R.id.mainSurfaceView);
    mSurfaceView.getHolder().addCallback(mSurfaceHolderCallback);
}

the .xml is pretty simple too:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorPrimary"
    android:orientation="vertical">

    <SurfaceView xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/mainSurfaceView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        android:layout_centerInParent="true"
        android:layout_margin="80dp"
        android:onClick="onClickOnSurfaceView" />
</RelativeLayout>

here is what what I think is the problem, this never gets called if the delay the intialization

final SurfaceHolder.Callback mSurfaceHolderCallback = new SurfaceHolder.Callback() {

... a bunch of code
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        // On the first invocation, width and height were automatically set to the view's size
        if (mCameraId == null) {
            // Find the device's back-facing camera and set the destination buffer sizes
            try {
                for (String cameraId : mCameraManager.getCameraIdList()) {
                    CameraCharacteristics cameraCharacteristics =
            ... a bunch of code

any clues how I can go around the issue?

thank you.

Answer 1

You can try to enter the delay after surfaceChanged( { // if (mCameraId == null) {

But you must keep track of all conditions required to obtain and start the camera stream. If may be safer to only delay the call to start preview.

Answer 2

I found a simpler solution. I hid the surface and made it visible only after a delay. That was what I looking for. Thank you for the inputs.

private void startCameraExec() {
    Log.d(TAG, "Starting API2 camera...");

    mSurfaceView = (SurfaceView) findViewById(R.id.mainSurfaceView);

    // This did the trick :)
    mSurfaceView.setVisibility(View.VISIBLE);
    mSurfaceView.getHolder().addCallback(mSurfaceHolderCallback);