java samples fix (clear view before drawing frame) of 'dirty' FPS display bug

samples/android/15-puzzle/src/org/opencv/samples/puzzle15/SampleCvViewBase.java

@@ -105,6 +105,7 @@ public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHol
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - bmp.getWidth()) / 2, (canvas.getHeight() - bmp.getHeight()) / 2, null);
                     mHolder.unlockCanvasAndPost(canvas);
                 }

samples/android/face-detection/src/org/opencv/samples/fd/SampleCvViewBase.java

@@ -110,6 +110,7 @@ public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHol
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - bmp.getWidth()) / 2, (canvas.getHeight() - bmp.getHeight()) / 2, null);
                     mFps.draw(canvas, (canvas.getWidth() - bmp.getWidth()) / 2, 0);
                     mHolder.unlockCanvasAndPost(canvas);

samples/android/image-manipulations/src/org/opencv/samples/imagemanipulations/SampleCvViewBase.java

@@ -111,6 +111,7 @@ public abstract class SampleCvViewBase extends SurfaceView implements SurfaceHol
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - bmp.getWidth()) / 2, (canvas.getHeight() - bmp.getHeight()), null);
                     mFps.draw(canvas, (canvas.getWidth() - bmp.getWidth()) / 2, 0);
                     mHolder.unlockCanvasAndPost(canvas);

samples/android/tutorial-0-androidcamera/src/org/opencv/samples/tutorial0/SampleViewBase.java

@@ -218,6 +218,7 @@ public abstract class SampleViewBase extends SurfaceView implements SurfaceHolde
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - getFrameWidth()) / 2, (canvas.getHeight() - getFrameHeight()) / 2, null);
                     mHolder.unlockCanvasAndPost(canvas);
                 }

samples/android/tutorial-1-addopencv/src/org/opencv/samples/tutorial1/SampleViewBase.java

@@ -218,6 +218,7 @@ public abstract class SampleViewBase extends SurfaceView implements SurfaceHolde
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - getFrameWidth()) / 2, (canvas.getHeight() - getFrameHeight()) / 2, null);
                     mHolder.unlockCanvasAndPost(canvas);
                 }

samples/android/tutorial-3-native/src/org/opencv/samples/tutorial3/SampleViewBase.java

@@ -218,6 +218,7 @@ public abstract class SampleViewBase extends SurfaceView implements SurfaceHolde
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - getFrameWidth()) / 2, (canvas.getHeight() - getFrameHeight()) / 2, null);
                     mHolder.unlockCanvasAndPost(canvas);
                 }

samples/android/tutorial-4-mixed/src/org/opencv/samples/tutorial4/SampleViewBase.java

@@ -218,6 +218,7 @@ public abstract class SampleViewBase extends SurfaceView implements SurfaceHolde
             if (bmp != null) {
                 Canvas canvas = mHolder.lockCanvas();
                 if (canvas != null) {
+                    canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                     canvas.drawBitmap(bmp, (canvas.getWidth() - getFrameWidth()) / 2, (canvas.getHeight() - getFrameHeight()) / 2, null);
                     mHolder.unlockCanvasAndPost(canvas);
                 }