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);
+        }
+    }
+}

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

@@ -29,7 +29,7 @@ import java.util.List;
 public class Preview extends ViewGroup implements SurfaceHolder.Callback, View.OnTouchListener, OnLongClickListener, View.OnClickListener,
         MediaScannerConnection.OnScanCompletedListener {
     private static final String TAG = Preview.class.getSimpleName();
-    private static final int FOCUS_AREA_SIZE = 200;
+    private static final int FOCUS_AREA_SIZE = 100;
     private static final int PHOTO_PREVIEW_LENGTH = 1000;
     private static final float RATIO_TOLERANCE = 0.1f;
 
@@ -335,6 +335,7 @@ public class Preview extends ViewGroup implements SurfaceHolder.Callback, View.O
             final List<Camera.Area> focusAreas = new ArrayList<>(1);
             focusAreas.add(new Camera.Area(focusRect, 1000));
             mParameters.setFocusAreas(focusAreas);
+            mCallback.drawFocusRect(mLastClickX, mLastClickY);
         }
 
         mCamera.setParameters(mParameters);
@@ -664,5 +665,7 @@ public class Preview extends ViewGroup implements SurfaceHolder.Callback, View.O
         int getCurrentOrientation();
 
         void videoSaved(Uri uri);
+
+        void drawFocusRect(int x, int y);
     }
 }

app/src/main/java/com/simplemobiletools/camera/activities/MainActivity.java

@@ -34,6 +34,7 @@ import android.widget.TextView;
 
 import com.simplemobiletools.camera.Config;
 import com.simplemobiletools.camera.Constants;
+import com.simplemobiletools.camera.FocusRectView;
 import com.simplemobiletools.camera.PhotoProcessor;
 import com.simplemobiletools.camera.Preview;
 import com.simplemobiletools.camera.Preview.PreviewListener;
@@ -58,12 +59,12 @@ public class MainActivity extends AppCompatActivity
     @BindView(R.id.about) View mAboutBtn;
     @BindView(R.id.last_photo_video_preview) ImageView mLastPhotoVideoPreview;
 
-    private static final String TAG = MainActivity.class.getSimpleName();
     private static final int CAMERA_STORAGE_PERMISSION = 1;
     private static final int AUDIO_PERMISSION = 2;
 
     private static SensorManager mSensorManager;
     private static Preview mPreview;
+    private static FocusRectView mFocusRectView;
     private static Handler mTimerHandler;
     private static Uri mPreviewUri;
 
@@ -160,6 +161,10 @@ public class MainActivity extends AppCompatActivity
         mPreview = new Preview(this, (SurfaceView) findViewById(R.id.camera_view), this);
         mPreview.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
         mViewHolder.addView(mPreview);
+
+        mFocusRectView = new FocusRectView(getApplicationContext());
+        mViewHolder.addView(mFocusRectView);
+
         mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
         mIsInPhotoMode = true;
         mTimerHandler = new Handler();
@@ -579,6 +584,13 @@ public class MainActivity extends AppCompatActivity
         }
     }
 
+    @Override
+    public void drawFocusRect(int x, int y) {
+        if (mFocusRectView != null) {
+            mFocusRectView.drawFocusRect(x, y);
+        }
+    }
+
     @Override
     public void mediaSaved(String path) {
         final String[] paths = {path};

app/src/main/res/layout/activity_main.xml

@@ -11,6 +11,11 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"/>
 
+    <SurfaceView
+        android:id="@+id/focus_rect_view"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"/>
+
     <ImageView
         android:id="@+id/about"
         android:layout_width="@dimen/icon_size"