LinearLayout & CameraSource don't fill screen

Question

I am trying to build a full-screen barcode scanner within my app and I cannot get the LinearLayout which only contains my CameraSource to fill the entire screen (bottom of this post is a screenshot of my result with an emulated camera in the simulator).

Here is my layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/topLayout"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.mattdonders.android.wppcalculator.barcode.CameraSourcePreview
        android:id="@+id/camera_preview"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

</LinearLayout>

Here is my onCreate method from my BarcodeScanner activity:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_barcode_scanner);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

    mPreview = (CameraSourcePreview) findViewById(R.id.camera_preview);

    // Check for the camera permission before accessing the camera.  If the
    // permission is not granted yet, request permission.
    int rc = ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA);
    if (rc == PackageManager.PERMISSION_GRANTED) {
        createCameraSource();
    } else {
        requestCameraPermission();
    }
}

Here is the constructor of the CameraSource class:

public CameraSourcePreview(Context context, AttributeSet attrs) {
    super(context, attrs);
    mContext = context;
    mStartRequested = false;
    mSurfaceAvailable = false;

    mSurfaceView = new SurfaceView(context);
    mSurfaceView.getHolder().addCallback(new SurfaceCallback());
    addView(mSurfaceView);
}

Screenshot of the view not being completely filled.

Answer 1

As mentioned above in the comments to my original post, the answer to this lies in the onLayout method of the CameraSourcePreview class. Based on implementing a few solutions mentioned in a Github issue, this answer has worked the best for me and I have copy / pasted the code below so the answer to this question is not just a link.

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    int previewWidth = 320;
    int previewHeight = 240;
    if (mCameraSource != null) {
        Size size = mCameraSource.getPreviewSize();
        if (size != null) {
            previewWidth = size.getWidth();
            previewHeight = size.getHeight();
        }
    }

    // Swap width and height sizes when in portrait, since it will be rotated 90 degrees
    if (isPortraitMode()) {
        int tmp = previewWidth;
        previewWidth = previewHeight;
        previewHeight = tmp;
    }

    final int viewWidth = right - left;
    final int viewHeight = bottom - top;

    int childWidth;
    int childHeight;
    int childXOffset = 0;
    int childYOffset = 0;
    float widthRatio = (float) viewWidth / (float) previewWidth;
    float heightRatio = (float) viewHeight / (float) previewHeight;

    // To fill the view with the camera preview, while also preserving the correct aspect ratio,
    // it is usually necessary to slightly oversize the child and to crop off portions along one
    // of the dimensions.  We scale up based on the dimension requiring the most correction, and
    // compute a crop offset for the other dimension.
    if (widthRatio > heightRatio) {
        childWidth = viewWidth;
        childHeight = (int) ((float) previewHeight * widthRatio);
        childYOffset = (childHeight - viewHeight) / 2;
    } else {
        childWidth = (int) ((float) previewWidth * heightRatio);
        childHeight = viewHeight;
        childXOffset = (childWidth - viewWidth) / 2;
    }

    for (int i = 0; i < getChildCount(); ++i) {
        // One dimension will be cropped.  We shift child over or up by this offset and adjust
        // the size to maintain the proper aspect ratio.
        getChildAt(i).layout(
                -1 * childXOffset, -1 * childYOffset,
                childWidth - childXOffset, childHeight - childYOffset);
    }

    try {
        startIfReady();
    } catch (IOException e) {
        Log.e(TAG, "Could not start camera source.", e);
    }
}