Xamarin.Android TextureView

The TextureView class is a view that uses hardware-accelerated 2D rendering to enable a video or OpenGL content stream to be displayed. For example, the following screenshot shows the TextureView displaying a live feed from the device's camera:

Unlike the SurfaceView class, which can also be used to display OpenGL or video content, the TextureView is not rendered into a separate window. Therefore, TextureView is able to support view transformations like any other view. For example, rotating a TextureView can be accomplished by simply setting its Rotation property, its transparency by setting its Alpha property, and so on.

Therefore, with the TextureView we can now do things like display a live stream from the camera and transform it, as shown in the following code:

public class TextureViewActivity : Activity,
    TextureView.ISurfaceTextureListener
{
    Camera _camera;
    TextureView _textureView;

    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        _textureView = new TextureView (this);
        _textureView.SurfaceTextureListener = this;

        SetContentView (_textureView);
    }

    public void OnSurfaceTextureAvailable (
        Android.Graphics.SurfaceTexture surface,
        int width, int height)
    {
        _camera = Camera.Open ();
        var previewSize = _camera.GetParameters ().PreviewSize;
        _textureView.LayoutParameters =
            new FrameLayout.LayoutParams (previewSize.Width,
                previewSize.Height, (int)GravityFlags.Center);

        try {
            _camera.SetPreviewTexture (surface);
            _camera.StartPreview ();
        } catch (Java.IO.IOException ex) {
            Console.WriteLine (ex.Message);
        }

        // this is the sort of thing TextureView enables
        _textureView.Rotation = 45.0f;
        _textureView.Alpha = 0.5f;
    }
    …
}

The above code creates a TextureView instance in the Activity's OnCreate method and sets the Activity as the TextureView's SurfaceTextureListener. To be the SurfaceTextureListener, the Activity implements the TextureView.ISurfaceTextureListener interface. The system will call the OnSurfaceTextAvailable method when the SurfaceTexture is ready for use. In this method, we take the SurfaceTexture that is passed in and set it to the camera's preview texture. Then we are free to perform normal view-based operations, such as setting the Rotation and Alpha, as in the example above. The resulting application, running on a device, is shown below:

To use the TextureView, hardware acceleration must be enabled, which it will be by default as of API Level 14. Also, since this example uses the camera, both the android.permission.CAMERA permission and the android.hardware.camera feature must be set in the AndroidManifest.xml.