ViewPager swiping lags when fragment contains camera preview

Question

I have a 3-tab setup using a ViewPager and 3 fragments. One of the fragments implements a QR Code Scanner (ZBarScanner), which populates the entire fragment with a live view of the devices camera.

I've found that this camera view causes the user interface to lag heavily. The animations for swiping between tabs are much slower and the apps CPU usage has increased heavily. Running a traceview shows that the 'onPreviewFrame' method of the scanner library is taking up the majority of processor time.

I've tried playing with the offscreenPageLimit - I find that this needs to be set to 2 to keep the camera view alive, otherwise there is incredibly heavy lag when swiping due to repeatedly starting and closing the camera view.

What can I do to reduce the lag this camera preview is creating in my application?

I can post code if it helps, but it is all fairly simplistic.

Answer 1

I spent a lot of time and coffee, but found the cause of the trouble. The problem in using SurfaceView to display a preview.

Use TextureView to display a preview.

It will be useful: How can I make my view pager more smooth?

Good luck!

UPDATED:

Added example of a TextureView

CameraModule.java

public class CameraModule implements SurfaceTextureListener {
    private Camera mCamera;

    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        mCamera = getCamera();

        try {
            mCamera.setPreviewTexture(surface);
            mCamera.startPreview();
        } catch (IOException ioe) {
            // Something bad happened
        }
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
        // Ignored, Camera does all the work for us
    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        mCamera.stopPreview();
        mCamera.release();
        return true;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        // Invoked every time there's a new Camera preview frame
    }

    private Camera getCamera() {
        Camera cam = null;

        try {
            cam = Camera.open();
        } catch (RuntimeException e) {
            loggerManager.error("Camera not available");
        }

        return cam;
    }
}

CameraFragment.java

public class CameraFragment extends Fragment {

    // You create an instance of the module. I use a singleton.
    CameraModule mCameraModule = new CameraModule();

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_camera, container, false);

        TextureView mTextureView = (TextureView) view.findViewById(R.id.camera_preview);
        mTextureView.setSurfaceTextureListener(mCameraModule);

        return view;
    }
}

fragment_camera.xml

<?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="#000"
    android:orientation="vertical">

    <TextureView
        android:id="@+id/camera_preview"
        android:layout_width="match_parent"
        android:background="#000"
        android:layout_height="match_parent" />


</RelativeLayout>

Good luck!