draw a rectangle on the focused area for a moment

app/src/main/java/com/simplemobiletools/camera/FocusRectView.java

@@ -0,0 +1,66 @@
+package com.simplemobiletools.camera;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.os.Handler;
+import android.view.ViewGroup;
+
+public class FocusRectView extends ViewGroup {
+    private static final int RECT_SIZE = 50;
+    private static final int RECT_DURATION = 500;
+
+    private static Paint mPaint;
+    private static Rect mRect;
+    private static Handler mHandler;
+
+    private static boolean mDrawRect;
+    private static int mPrimaryColor;
+
+    public FocusRectView(Context context) {
+        super(context);
+        setWillNotDraw(false);
+        mHandler = new Handler();
+        mPrimaryColor = getResources().getColor(R.color.colorPrimary);
+        setupPaint();
+    }
+
+    private void setupPaint() {
+        mPaint = new Paint();
+        mPaint.setStyle(Paint.Style.STROKE);
+        mPaint.setColor(mPrimaryColor);
+        mPaint.setStrokeWidth(2);
+    }
+
+    public void drawFocusRect(int x, int y) {
+        mRect = new Rect(x - RECT_SIZE, y - RECT_SIZE, x + RECT_SIZE, y + RECT_SIZE);
+        toggleRect(true);
+
+        mHandler.removeCallbacksAndMessages(null);
+        mHandler.postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                toggleRect(false);
+            }
+        }, RECT_DURATION);
+    }
+
+    private void toggleRect(boolean show) {
+        mDrawRect = show;
+        invalidate();
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int l, int t, int r, int b) {
+
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        super.onDraw(canvas);
+        if (mDrawRect) {
+            canvas.drawRect(mRect, mPaint);
+        }
+    }
+}