The preview of the camera will be drawn on a 1x1 pixel surface. At this point the preview input of the camera will be analysed at a given interval. To detect a movement the picture will be dived into tiles. For each tile the average brightness will be calculated. If a average value of a single tile differs from the previous value, a motion is registered.

1. Copy all classes of the subpackge motiondetection into your project. Adapt the package names.
2. There must be a SurfaceView in your layout:

<SurfaceView
    android:layout_width="1dp"
    android:layout_height="1dp"
    android:id="@+id/surfaceView" />

3. create instance of MotionDetector

motionDetector = new MotionDetector(this, (SurfaceView) findViewById(R.id.surfaceView));

4. call lifecycle methods: motionDetector.onResume() and .onPause()
5. register callbacks

motionDetector.setMotionDetectorCallback(new MotionDetectorCallback() {
    @Override
    public void onMotionDetected() {
        txtStatus.setText("Bewegung erkannt");
    }

    @Override
    public void onTooDark() {
        txtStatus.setText("Zu dunkel hier");
    }
});

there are some important parameters that can be adjusted at runtime.

1. Permissions must be given in the AndroidManifest.xml

<uses-feature android:name="android.hardware.camera" />
<uses-permission android:name="android.permission.CAMERA"/>

2. if targetSdkVersion is greater than 21 you have to implement Runtime Permissions
3. the detection is only running while the activity is active. It may make sense to build in a Wake-Lock.
4. Parts of the code is taken from https://github.com/phishman3579/android-motion-detection

Jonas Gehring Apache license 2.0