Draw Circle on Touch

Draw Circle on touch

I would do it this way:

public class TestActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new DrawingView(this));
    }

    class DrawingView extends SurfaceView {

        private final SurfaceHolder surfaceHolder;
        private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

        public DrawingView(Context context) {
            super(context);
            surfaceHolder = getHolder();
            paint.setColor(Color.RED);
            paint.setStyle(Style.FILL);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            if(event.getAction() == MotionEvent.ACTION_DOWN) {
                if (surfaceHolder.getSurface().isValid()) {
                    Canvas canvas = surfaceHolder.lockCanvas();
                    canvas.drawColor(Color.BLACK);
                    canvas.drawCircle(event.getX(), event.getY(), 50, paint);
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }
            return false;
        }
    }
}

Draw new Circle with each new Touch Event

The line

canvas.drawARGB(255,255,255,255);

keeps drawing over the rendered circle. Removing it means that each new circle is visible on the canvas.

Draw a circle each time I touch the screen

Try this one. Clear the imageView's bitmap inside the action ACTION_UP. Here is the example code:

First make your bitmap outside the onTouchListener like:

private var bitmap: Bitmap? = null

Then your onTouchListener will be like:

imageBody.setOnTouchListener({ v, event ->

        if(event != null){
            if (event.action == MotionEvent.ACTION_DOWN) {
                bitmap = Bitmap.createBitmap(imageBody.drawingCache)
                val pixel: Int = bitmap.getPixel(event.getX().toInt(), event.getY().toInt())
                coordX = event.getX()
                coordY = event.getY()

                val Drawable = imageBody.drawable
                val ImageBounds = Drawable.bounds
                val scaledHeight = ImageBounds.height()
                val scaledWidth = ImageBounds.width()

                OrigX = coordX / scaledHeight
                OrigY = coordY / scaledWidth

                when (pixel) {
                    Color.rgb(241,241,241) -> {
                        val canvas = Canvas(bitmap)
                        val paint = Paint()
                        paint.color = Color.rgb(255,128,0)

                        canvas.drawCircle(coordX, coordY, 15F, paint) /**DRAW CIRCLE*/

                        imageBody.setImageBitmap(bitmap)
                        imageBody.Invalidate()
                    }
                }
            }

            if (event.action == MotionEvent.ACTION_UP) {
                if (bitmap != null && !bitmap!!.isRecycled) {
                    bitmap?.recycle()
                    bitmap = null
                }
            }
        }
        true
    })

Drawing a circle on HTML5 canvas at touch location

Use clientX/Y instead and use bounding rect to compensate for canvas position:

function drawSymptomCircle(event) {

    var canvas = this;  // no need to get canvas element from DOM, this = canvas

    if (canvas.getContext){  // this test should be done once in global, not here :)
        ...

        var rect = this.getBoundingClientRect();  // absolute position of canvas
        x = event.targetTouches[0].clientX;       // relative to client win
        y = event.targetTouches[0].clientY;

        x -= rect.left;                           // adjusted to be relative to canvas
        y -= rect.top;

        ...

Also obtaining getContext() is something I would recommend you do in global/parent scope. this will represent the canvas element as the element is the default context for an event handler.

Draw circle when touched and when touch is removed in a custom view

if you are trying to draw multiple circles when the user touches the screen and touch removed, you need to use a List of circles. you can have an ExampleCircle class where it have an x,y and color field.

public class ExampleCircle{

int x,y;
Color color;
//setters and getters

}

//onTouch
//assuming you already have a List object (List circleList=new ArrayList(); )

ExampleCircle newCircle=new ExampleCircle();
 switch(event.getAction()){
   case MotionEvent.ACTION_DOWN :
    newCircle.setX((int)event.getX());
    newCircle.setY((int)event.getY()) ;
    newCircle.setColor(paint.setColor(Color.BLACK));
    break;

case MotionEvent.ACTION_UP:
    newCircle.setX((int)event.getX());
    newCircle.setY((int)event.getY()) ;
    newCircle.setColor(paint.setColor(Color.BLACK));
    break;
}

circleList.add(newCircle);
invalidate();
return true;

//on draw method

replace

    canvas.drawCircle(point.x, point.y, 5, paint);

with

for(int i=0;i<circleList.size();i++){
   ExampleCircle currentCircle=circleList.get(i);

        canvas.drawCircle(currentCircle.getX(), currentCircle.getY(), 5, paint or currentCircle.getColor());

}

---

Related Topics