Android: Overlay on Android Camera Preview

I'm afraid you have to implement camera preview screen yourself. In theory an overlay can be added to other application by modifying its layout or by creating an overlay window. The first way is impossible to implement and the second way can be implemented I think but it's kind of a hack and a error prone method.

Implementing you own camera activity is not a very difficult task but it's rather challenging. I would recommend you to take a look at the default Camera application. Here's its source code: https://github.com/android/platform_packages_apps_camera.

You can do that with the help of FrameLayout like this:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" >

  <android.view.SurfaceView
  android:id="@+id/surface"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" />

<ImageView
    android:id = "@+id/header"
    android:layout_width = "wrap_content"
    android:layout_height = "wrap_content" />

</FrameLayout>

This camera project will help you.

You can use SurfaceView and create a CustomView that will open the camera and you can adjust its size in the xml accordingly. Below is a pseudo code.

Create a class that extends SurfaceView and open camera inside that

CapturePreview.java

public class CapturePreview extends SurfaceView implements SurfaceHolder.Callback{

    public static Bitmap mBitmap;
    SurfaceHolder holder;
    static Camera mCamera;

    public CapturePreview(Context context, AttributeSet attrs) {
        super(context, attrs);

        holder = getHolder();
        holder.addCallback(this);
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {

        Camera.Parameters parameters = mCamera.getParameters();
        parameters.getSupportedPreviewSizes();
        mCamera.setParameters(parameters);
        mCamera.startPreview();
    }
    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        try {
            mCamera = Camera.open();
            mCamera.setPreviewDisplay(holder);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mCamera.stopPreview();
        mCamera.release();
    }
    /***
     * 
     *  Take a picture and and convert it from bytes[] to Bitmap.
     *  
     */
    public static void takeAPicture(){  

        Camera.PictureCallback mPictureCallback = new PictureCallback() {
            @Override
            public void onPictureTaken(byte[] data, Camera camera) {

                BitmapFactory.Options options = new BitmapFactory.Options();
                mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length, options);
            }
        };
        mCamera.takePicture(null, null, mPictureCallback);
    }
}

Now you have to include the view that you created using SurfaceView in your xml like this

main.xml

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

  <FrameLayout 
  android:id="@+id/mySurfaceView"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content">

  <com.cam.CapturePreview 
  android:layout_width="fill_parent"
  android:layout_height="wrap_content">
  </com.cam.CapturePreview>

  </FrameLayout>

  <LinearLayout 
  android:layout_below="@id/mySurfaceView" 
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:layout_centerInParent="true"
  android:gravity="center">

  <ImageView android:id="@+id/myImageView" 
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:src="@drawable/icon"/>
  </LinearLayout>  

</RelativeLayout>

Now you can use this main.xml in any Acitivty that will open a camera with a ImageView. Thanks....

You will have to handle the whole camera preview and taking picture yourself. Take a look at the Samples at samples/ApiDemos/src/com/example/android/apis/graphics/CameraPreview. You can have your own layout over the preview area and add your graphic to it.

Sample link

https://developer.android.com/training/camera/cameradirect#java