We Keep Coding

How to draw circles on button click at a certain location?

I am pretty new to Android so I apologize ahead of time if I am missing something, but my problem is that I am trying to draw a circle at a certain location everytime I click on the screen.
I have tried logging and it does return an int where it matches my if statement but nothing gets drawn.
public boolean onTouchEvent(MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
drawCirc = true;
xTouch = event.getX();
Log.d("keyboard", "xpos" + xTouch);
yTouch = event.getY();
break;
case MotionEvent.ACTION_UP:
drawCirc = false;
}
return true;
}
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setColor(Color.RED);
if(drawCirc) {
if (xTouch < 150 && xTouch>0) {
paint.setColor(Color.RED);
canvas.drawCircle(150, 500, 100, paint);
isPlayer1 = false;
invalidate();
}
}
}

#Javanator is right, you should do invalidate in touch listener.
Meanwhile, you can try out the code below, which adds animation when circle being drawn.
Paint paint = new Paint();
{
paint.setColor(Color.RED);
}
// The radius of the circle you want to draw
// 0 by default
private int radius = 0;
// The animator to animate circle drawing
private ObjectAnimator radiusAnimator;
public void setRadius(int newRadius) {
this.radius = newRadius;
this.invalidate();
}
private void showCircle(boolean show) {
ObjectAnimator animator = this.getRadiusAnimator();
if (show) {
animator.start();
} else {
animator.reverse();
}
}
private ObjectAnimator getRadiusAnimator() {
if (this.radiusAnimator == null) {
this.radiusAnimator = ObjectAnimator.ofInt(this, "radius", 0, 100);
}
return this.radiusAnimator;
}
public boolean onTouchEvent(MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
// drawCirc = true;
xTouch = event.getX();
Log.d("keyboard", "xpos" + xTouch);
yTouch = event.getY();
showCircle(true);
break;
case MotionEvent.ACTION_UP:
// drawCirc = false;
showCircle(false);
}
return true;
}
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (xTouch < 150 && xTouch > 0) {
canvas.drawCircle(xTouch, yTouch, radius, paint);
}
/*
if(drawCirc) {
if (xTouch < 150 && xTouch>0) {
paint.setColor(Color.RED);
canvas.drawCircle(150, 500, 100, paint);
isPlayer1 = false;
invalidate();
*/
}

public class CustomView extends View {
boolean drawCirc;
float xTouch;
boolean isPlayer1;
float yTouch;
public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
drawCirc=true;
xTouch = event.getX();
yTouch = event.getY();
invalidate();
}
return false;
}
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setColor(Color.RED);
if (drawCirc) {
paint.setColor(Color.RED);
canvas.drawCircle(xTouch, yTouch, 100, paint);
isPlayer1 = false;
invalidate();
}
}}
I have solved your functionality and Implemented sample code. I have checked it and it's working and you have not put a code in onTouch Listener that's why it's not worked but now I have solved. if you want area limit then put yourif (xTouch < 150 && xTouch>0)

Drawing rectangle on ImageView - not drawing upwards/leftwards

I've created a class which extends the ImageView allowing me to draw rectangles onto the ImageView on touch.
I can draw rectangles however they only display when I'm dragging the rectangle from the starting point downward and to the right.
If I drag the rectangle from the starting point upwards or to the left then no rectangle is drawn. OnDraw() fires but nothing displays.
My class:
public class TagImageView extends ImageView {
private float downX;
private float downY;
private float upX;
private float upY;
private Paint paint;
public TagImageView(Context context) {
super(context);
init();
}
public TagImageView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public TagImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
}
private void init() {
paint = new Paint();
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(3);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
downX = event.getX();
downY = event.getY();
invalidate();
return true;
case MotionEvent.ACTION_MOVE:
upX = event.getX();
upY = event.getY();
invalidate();
return true;
case MotionEvent.ACTION_UP:
invalidate();
return true;
case MotionEvent.ACTION_CANCEL:
break;
default:
break;
}
return super.onTouchEvent(event);
}
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawRect(downX, downY, upX, upY, paint);
}
}
Edit: Not sure if this is relevant? https://stackoverflow.com/a/24168545/2380071

Well, I just ended up modifying my OnDraw() method to check the values of the downX, downY and upX, upY points. Trivial, really... although not sure if it's the most efficient. Welcome to any suggestions (or, er.. pointers)!
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (downX < upX && downY < upY)
canvas.drawRect(downX, downY, upX, upY, paint);
else if (downX > upX && downY < upY)
canvas.drawRect(upX, downY, downX, upY, paint);
else if (downX < upX && downY > upY)
canvas.drawRect(downX, upY, upX, downY, paint);
else
canvas.drawRect(upX, upY, downX, downY, paint);
}

How to erase image with finger in Android

I'm developing an app that need the feature in object.
I have an Image A that cover an Image B. With finger I need to erase the Image A to show the Image B.
Erase must follow your finger flowing image A
I'm trying some code but still I couldn't erase the image A. this is the code that i'm using to draw a line on image (_imageToErase is Image A):
Canvas canvas;
Paint paint;
float downx = 0, downy = 0, upx = 0, upy = 0;
ImageView _imageToErase;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.g_layout);
_imageToErase = (ImageView) findViewById(R.id.image_to_erase);
_imageToErase.setOnTouchListener(this);
}
#Override
public void onWindowFocusChanged(boolean hasFocus){
int width = _imageToErase.getWidth();
int height = _imageToErase.getHeight();
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
canvas = new Canvas(bitmap);
paint = new Paint();
paint.setColor(Color.WHITE);
paint.setStrokeWidth(25);
paint.setAntiAlias(true);
_imageToErase.setImageBitmap(bitmap);
}
public boolean onTouch(View v, MotionEvent event) {
int action = event.getAction();
switch (action){
case MotionEvent.ACTION_DOWN:
downx = event.getX();
downy = event.getY();
break;
case MotionEvent.ACTION_MOVE:
upx = event.getX();
upy = event.getY();
canvas.drawLine(downx, downy, upx, upy, paint);
_imageToErase.invalidate();
downx = upx;
downy = upy;
break;
case MotionEvent.ACTION_UP:
break;
case MotionEvent.ACTION_CANCEL:
break;
default:
break;
}
return true;
}
This code produce only a line that follow the finger but not erase the image.
How to modify this code to erase the image? Thanks
EDIT
The link suggested in comments not solved my problem. Simply add this line:
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));
not work for me.

PaintView.java
public class PaintView extends View implements View.OnTouchListener {
private static final String TAG = "PaintView";
Bitmap Bitmap1, Bitmap2;
Bitmap Transparent;
int X = -100;
int Y = -100;
Canvas c2;
private boolean isTouched = false;
Paint paint = new Paint();
Path drawPath = new Path();
public PaintView(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
this.setOnTouchListener(this);
DisplayMetrics metrics = context.getResources().getDisplayMetrics();
int width = metrics.widthPixels;
int height = metrics.heightPixels;
Transparent = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Bitmap1 = BitmapFactory.decodeResource(getResources(), R.drawable.cake1);
Bitmap2 = BitmapFactory.decodeResource(getResources(), R.drawable.cake2);
c2 = new Canvas();
c2.setBitmap(Transparent);
c2.drawBitmap(Bitmap2, 0, 0, paint);
paint.setAlpha(0);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
paint.setAntiAlias(true);
}
private static Point getDisplaySize(final Display display) {
final Point point = new Point();
point.x = display.getWidth();
point.y = display.getHeight();
return point;
}
#Override
protected void onDraw(Canvas canvas) {
System.out.println("onDraw");
if(isTouched)
{
canvas.drawBitmap(Bitmap1, 0, 0, null);
}
canvas.drawBitmap(Transparent, 0, 0, null);
}
#Override
public boolean onTouch(View v, MotionEvent event) {
isTouched = true;
X = (int) event.getX();
Y = (int) event.getY();
paint.setStrokeWidth(60);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(X, Y);
c2.drawPath(drawPath, paint);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(X, Y);
c2.drawPath(drawPath, paint);
break;
case MotionEvent.ACTION_UP:
drawPath.lineTo(X, Y);
c2.drawPath(drawPath, paint);
drawPath.reset();
count=0;
break;
default:
return false;
}
invalidate();
return true;}}class Point {
float x, y;
#Override
public String toString() {
return x + ", " + y;
}}
MainActivity.java
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new PaintView(this));
}}

Finally I found a library that works very well for me and implementation is pretty simple
https://github.com/winsontan520/Android-WScratchView
Import library in your project and then in layout.xml
<com.winsontan520.WScratchView
android:layout_width="287dp"
android:layout_height="212dp"
android:layout_centerHorizontal="true"
android:layout_marginTop="80dp"
android:adjustViewBounds="true"
android:scaleType="centerInside"
android:id="#+id/image_to_erase"/>
in onCreate:
_imageToErase = (WScratchView) findViewById(R.id.image_to_erase);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.img_erase);
_imageToErase.setScratchBitmap(bitmap);
_imageToErase.setOnScratchCallback(new WScratchView.OnScratchCallback() {
#Override
public void onScratch(float percentage) {
updatePercentage(percentage);
}
#Override
public void onDetach(boolean fingerDetach) {
if (mPercentage > 40) {
_imageToErase.setScratchAll(true);
updatePercentage(100);
}
}
});
and
private void updatePercentage(float percentage) {
mPercentage = percentage;
// System.out.println("percentage = "+percentage);
}
Thanks everybody

Rectangle line and Dash Line

If I draw with Rectangle line and after that I want to draw with dash line my rectangle line will be transformed in dash line. I use this code:
This is MyLine.java
public class MyLine { // line
public float x,y;
public float xStart,yStart,xEnd,yEnd;
public Paint paint = new Paint();
Path path = new Path();
public MyLine()
{
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.STROKE);
paint.setPathEffect(new DashPathEffect(new float[]{20,30}, 0));
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(5f);
path = new Path();
}
public void mouseDown(Path path,float xDown,float yDown){
path.moveTo(xDown, yDown);
path.lineTo(xDown, yDown);
xStart = xDown;
yStart = yDown;
}
public void mouseUp(Path path,float xUp,float yUp){
path.lineTo(xUp, yUp);
xEnd = xUp;
yEnd = yUp;
}
public void draw(Canvas c){
paint.setColor(Color.GREEN);
paint.setStyle(Paint.Style.STROKE);
paint.setPathEffect(new DashPathEffect(new float[]{10,20}, 0));
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(5f);
path = new Path();
c.drawLine(xStart,yStart,xEnd,yEnd,paint);
}
public void changeColor(int color){
paint = new Paint(paint);
paint.setColor(color);
//myPaint.setColor(color);
}
}
Here is some code from CanvasView.java where I think is problem.
public void setDashLine(){
dashedLine = true;
paint = new Paint();
paint.setPathEffect(dashEffect);
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(STROKE_WIDTH);
myCanvas = new Canvas();
path = new Path();
}
public void setNormalLine(){
paint.setColor(Color.RED);
paint = new Paint();
paint.setPathEffect(null);
paint.setStyle(Paint.Style.STROKE);
paint.setPathEffect(null);
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(STROKE_WIDTH);
myCanvas = new Canvas();
path = new Path();
}
protected void onDraw(Canvas canvas) {
paint.setPathEffect(null);
if(bitmap!=null){
canvas.drawBitmap(bitmap, 0, 0, paint);
for(MyCircle circle:circleList){// draw circles
myCanvas.drawCircle(getCircleMidPointX(circle.firstX, circle.lastX),getCircleMidPointY(circle.firstY, circle.lastY),circle.radius,myPaint);
}
}
for(MyLine line:lineList){ //draw lines
if(dashedLine)
line.paint.setPathEffect(dashEffect);
else
line.paint.setPathEffect(null);
canvas.drawLine(line.xStart, line.yStart, line.xEnd, line.yEnd, line.paint);
}
final OnTouchListener drawLineListener = new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
FirstActivity.ll.setVisibility(LinearLayout.GONE);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
undonePaths.clear();
path.reset();
myLine = new MyLine();
myLine.xStart = event.getX();
myLine.yStart = event.getY();
return true;
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
myLine.xEnd = event.getX();
myLine.yEnd = event.getY();
invalidate();
lineList.add(myLine);
break;
default:
Log.d("mock it up", "Unknown touch event " + event.toString());
return false;
}
return true;
}
};
final OnTouchListener drawDashedLineListener = new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
FirstActivity.ll.setVisibility(LinearLayout.GONE);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
myLine = new MyLine();
return true;
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
invalidate();
lineList.add(myLine);
break;
default:
Log.d("mock it up", "Unknown touch event " + event.toString());
return false;
}
return true;
}
};
If you can see something where is wrong please tell me how can make to be useful.

How can I erase my objects without Background Image?

I want to erase my bitmap but I don't want to erase background image. When I try to erase is white and it draw very hard in frames.
This is from CanvasView
erasePaint.setColor(Color.WHITE);
//erasePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
erasePaint.setAntiAlias(true);
erasePaint.setStyle(Paint.Style.STROKE);
erasePaint.setStrokeJoin(Paint.Join.ROUND);
erasePaint.setStrokeWidth(12);
//....
protected void onDraw(Canvas canvas) {
paint.setPathEffect(null);
if(bitmap!=null){
for(MyEraser e:eraserList){
canvas.drawPath(e.p,erasePaint);
invalidate();
}
final OnTouchListener eraseListener = new OnTouchListener() {
public boolean onTouch(View v, MotionEvent event) {
// erasePaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
//FirstActivity.ll.setVisibility(LinearLayout.GONE);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
myEraser = new MyEraser();
lastTouchX = event.getX();
lastTouchY = event.getY();
myEraser.mouseDown(event.getX(), event.getY());
return true;
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
resetDirtyRect(event.getX(),event.getY());
int historySize = event.getHistorySize();
for(int i=0;i<historySize;i++){
float historicalX = event.getHistoricalX(i);
float historicalY = event.getHistoricalY(i);
expandDirtyRect(historicalX, historicalY);
myEraser.mouseUp(historicalX, historicalY);
}
myEraser.mouseUp(event.getX(), event.getY());
eraserList.add(myEraser);
break;
default:
Log.d("mock it up", "Unknown touch event " + event.toString());
return false;
}
invalidate(
(int) (dirtyRect.left - HALF_STROKE_WIDTH),
(int) (dirtyRect.top - HALF_STROKE_WIDTH),
(int) (dirtyRect.right + HALF_STROKE_WIDTH),
(int) (dirtyRect.bottom + HALF_STROKE_WIDTH));
lastTouchX = event.getX();
lastTouchY = event.getY();
return true;
}
};
}
}
This is MyEraser
public class MyEraser {
Paint paint = new Paint();
Path p = new Path();
public MyEraser(){
paint.setColor(Color.WHITE);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(5);
}
public void mouseDown(float x, float y) {
//path.addCircle(x,y,5,Path.Direction.CW);
p.moveTo( x, y );
// path.lineTo(x, y);
}
public void mouseMove(Path path, float x, float y) {
// path.addCircle(x,y,5,Path.Direction.CW);
}
public void mouseUp(float x, float y){
//path.addCircle(x,y,5,Path.Direction.CW);
p.lineTo(x, y);
}
public void draw(Canvas c,Path path){
//paint.setColor(Color.WHITE);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
paint.setStyle(Paint.Style.STROKE);
paint.setAntiAlias(true);
paint.setStrokeJoin(Paint.Join.ROUND);
paint.setStrokeWidth(7);
c.drawPath(p, paint);
}
}

EDIT: Started over for better explanation :)
I am not familiar with Android, in fact I have never used it. Use this code as an example of how to organize your code, rather than a functional code.
class MyView extends View {
private Eraser myEraser;
private Bitmap myBackgroundImage;
private Canvas myForegroundCanvas;
public MyView(Context context, Attributes, attrs) {
myEraser = new Eraser()
myBackgroundImage = BitmapFactory.decodeResource(getResources(), R.drawable.your_background_name);
Bitmap image = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); // the width and height of the view
myForegroundCanvas = new Canvas(image);
}
public boolean onTouchEvent(MotionEvent event) {
// update your eraser path
return true;
}
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(myBackgroundImage, 0, 0, null);
//for (Eraser item : eraserList) {
// if you have multiple eraser, add them to a list
myEraser.draw(myForegroundCanvas);
//}
canvas.drawCanvas(myForegroundCanvas, 0, 0, null);
}
}
The main idea is to keep the separation between your background and foreground images. That way, you could easily change the background and it would be updated. You could also have a reset on the foreground to erase everything, etc.
I hope this helps you.