android绘图触摸事件 [英] android drawing on touch event

问题描述

我试图创建一个应用程序，使用户能够触摸屏幕并根据用户的手指坐标绘制图像。这是我的代码：

I'm trying to make an application which enables user to touch the screen and draw image based on users' finger coordinates. Here's my code :

public class DrawingBoard extends View {

        Drawable editIcon = getResources().getDrawable(R.drawable.icon);
        Bitmap mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.background);

        float xPos = 0;
        float yPos = 0; 

        public DrawingBoard (Context context) {
            // TODO Auto-generated constructor stub
            super (context);            
        }
        @Override
        protected void onDraw (Canvas canvas) {
            super.onDraw(canvas);

            canvas.save();
            canvas.drawBitmap(mBitmap, 0, 0, null);
            canvas.translate(xPos, yPos);
            editIcon.draw(canvas);
            canvas.restore();

            invalidate();
        }
        @Override
        public boolean onTouchEvent (MotionEvent event) {

            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN : 
                    xPos = event.getX();
                    yPos = event.getY();
                    break;
            }

            return true;

        }
    }
}

每当我尝试点击模拟器中的屏幕，没有显示的图像....

But, whenever I try to click on a screen in emulator, there's no image shown....

指出我的错误... THX

pls point out my mistake... THX

推荐答案

我已经多次回答这个问题，这段代码工作100％。如果u仍有任何查询，则u可以与我联系

I have posted an answer for this question many times,This code is working 100 %. if u have still any query then u can contact me

但此代码将用于在Google Maps上绘制图像：

BUT THIS CODE WILL WORK FOR DRAWING AN IMAGE ON GOOGLE MAPS:

public boolean onTouchEvent(MotionEvent event, MapView mapView) 
     {   

        if (event.getAction() == 1) 
      {                
            GeoPoint p = mapView.getProjection().fromPixels(
                (int) event.getX(),
                (int) event.getY());
                Toast.makeText(getBaseContext(), "lat and longtd is \n "+
                    p.getLatitudeE6() / 1E6 + "," + 
                    p.getLongitudeE6() /1E6 , 
                    Toast.LENGTH_LONG).show(); //
               mapView.getOverlays().add(new MarkerOverlay(p));
                mapView.invalidate();
        } 
                return true;


    }  

  class MarkerOverlay extends Overlay
{
     private GeoPoint p;
    private Projection projection; 

     public MarkerOverlay(GeoPoint p)
     {
        this.p = p;
     }

     @Override
     public boolean draw(Canvas canvas, MapView mapView,boolean shadow, long when)
     {
        super.draw(canvas, mapView, shadow);                   

        //---translate the GeoPoint to screen pixels---
        Point screenPts = new Point();
        mapView.getProjection().toPixels(p, screenPts);

        //---add the marker---
        Bitmap bmp = BitmapFactory.decodeResource(getResources(),R.drawable.pir_pictr);            
        canvas.drawBitmap(bmp, screenPts.x, screenPts.y-50, null);

        return true;   
     }



 }

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