android - Drag and move a circle drawn on canvas -

i working on android application should allow user draw circle on canvas , drag . have been able draw lines , circles on it.but cant seem able drag it.

is possible drag object drawn on canvas in android?.for example if detect touch within circle, how delete circle previous position , move current position? have tried invalidate().but wont work if user has drawn multiple circle , wants move of them.

it seems might have issues handling of multi-touch / drawing. there's usefull tutorials on android developer site , on android blog.

based on able create example think quite similar you're trying achieve (without complete circle drawing - circles generated single touch):

public class circlesdrawingview extends view {      private static final string tag = "circlesdrawingview";      /** main bitmap */     private bitmap mbitmap = null;      private rect mmeasuredrect;      /** stores data single circle */     private static class circlearea {         int radius;         int centerx;         int centery;          circlearea(int centerx, int centery, int radius) {             this.radius = radius;             this.centerx = centerx;             this.centery = centery;         }          @override         public string tostring() {             return "circle[" + centerx + ", " + centery + ", " + radius + "]";         }     }      /** paint draw circles */     private paint mcirclepaint;      private final random mradiusgenerator = new random();     // radius limit in pixels     private final static int radius_limit = 100;      private static final int circles_limit = 3;      /** available circles */     private hashset<circlearea> mcircles = new hashset<circlearea>(circles_limit);     private sparsearray<circlearea> mcirclepointer = new sparsearray<circlearea>(circles_limit);      /**      * default constructor      *      * @param ct {@link android.content.context}      */     public circlesdrawingview(final context ct) {         super(ct);          init(ct);     }      public circlesdrawingview(final context ct, final attributeset attrs) {         super(ct, attrs);          init(ct);     }      public circlesdrawingview(final context ct, final attributeset attrs, final int defstyle) {         super(ct, attrs, defstyle);          init(ct);     }      private void init(final context ct) {         // generate bitmap used background         mbitmap = bitmapfactory.decoderesource(ct.getresources(), r.drawable.up_image);          mcirclepaint = new paint();          mcirclepaint.setcolor(color.blue);         mcirclepaint.setstrokewidth(40);         mcirclepaint.setstyle(paint.style.fill);     }      @override     public void ondraw(final canvas canv) {         // background bitmap cover area         canv.drawbitmap(mbitmap, null, mmeasuredrect, null);          (circlearea circle : mcircles) {             canv.drawcircle(circle.centerx, circle.centery, circle.radius, mcirclepaint);         }     }      @override     public boolean ontouchevent(final motionevent event) {         boolean handled = false;          circlearea touchedcircle;         int xtouch;         int ytouch;         int pointerid;         int actionindex = event.getactionindex();          // touch event coordinates , make transparent circle         switch (event.getactionmasked()) {             case motionevent.action_down:                 // it's first pointer, clear existing pointers data                 clearcirclepointer();                  xtouch = (int) event.getx(0);                 ytouch = (int) event.gety(0);                  // check if we've touched inside circle                 touchedcircle = obtaintouchedcircle(xtouch, ytouch);                 touchedcircle.centerx = xtouch;                 touchedcircle.centery = ytouch;                 mcirclepointer.put(event.getpointerid(0), touchedcircle);                  invalidate();                 handled = true;                 break;              case motionevent.action_pointer_down:                 log.w(tag, "pointer down");                 // secondary pointers, obtain ids , check circles                 pointerid = event.getpointerid(actionindex);                  xtouch = (int) event.getx(actionindex);                 ytouch = (int) event.gety(actionindex);                  // check if we've touched inside circle                 touchedcircle = obtaintouchedcircle(xtouch, ytouch);                  mcirclepointer.put(pointerid, touchedcircle);                 touchedcircle.centerx = xtouch;                 touchedcircle.centery = ytouch;                 invalidate();                 handled = true;                 break;              case motionevent.action_move:                 final int pointercount = event.getpointercount();                  log.w(tag, "move");                  (actionindex = 0; actionindex < pointercount; actionindex++) {                     // pointer has moved, search pointer id                     pointerid = event.getpointerid(actionindex);                      xtouch = (int) event.getx(actionindex);                     ytouch = (int) event.gety(actionindex);                      touchedcircle = mcirclepointer.get(pointerid);                      if (null != touchedcircle) {                         touchedcircle.centerx = xtouch;                         touchedcircle.centery = ytouch;                     }                 }                 invalidate();                 handled = true;                 break;              case motionevent.action_up:                 clearcirclepointer();                 invalidate();                 handled = true;                 break;              case motionevent.action_pointer_up:                 // not general pointer                 pointerid = event.getpointerid(actionindex);                  mcirclepointer.remove(pointerid);                 invalidate();                 handled = true;                 break;              case motionevent.action_cancel:                 handled = true;                 break;              default:                 // nothing                 break;         }          return super.ontouchevent(event) || handled;     }      /**      * clears circlearea - pointer id relations      */     private void clearcirclepointer() {         log.w(tag, "clearcirclepointer");          mcirclepointer.clear();     }      /**      * search , creates new (if needed) circle based on touch area      *      * @param xtouch int x of touch      * @param ytouch int y of touch      *      * @return obtained {@link circlearea}      */     private circlearea obtaintouchedcircle(final int xtouch, final int ytouch) {         circlearea touchedcircle = gettouchedcircle(xtouch, ytouch);          if (null == touchedcircle) {             touchedcircle = new circlearea(xtouch, ytouch, mradiusgenerator.nextint(radius_limit) + radius_limit);              if (mcircles.size() == circles_limit) {                 log.w(tag, "clear circles, size " + mcircles.size());                 // remove first circle                 mcircles.clear();             }              log.w(tag, "added circle " + touchedcircle);             mcircles.add(touchedcircle);         }          return touchedcircle;     }      /**      * determines touched circle      *      * @param xtouch int x touch coordinate      * @param ytouch int y touch coordinate      *      * @return {@link circlearea} touched circle or null if no circle has been touched      */     private circlearea gettouchedcircle(final int xtouch, final int ytouch) {         circlearea touched = null;          (circlearea circle : mcircles) {             if ((circle.centerx - xtouch) * (circle.centerx - xtouch) + (circle.centery - ytouch) * (circle.centery - ytouch) <= circle.radius * circle.radius) {                 touched = circle;                 break;             }         }          return touched;     }      @override     protected void onmeasure(final int widthmeasurespec, final int heightmeasurespec) {         super.onmeasure(widthmeasurespec, heightmeasurespec);          mmeasuredrect = new rect(0, 0, getmeasuredwidth(), getmeasuredheight());     } } 

activity contains setcontentview(r.layout.main) there main.xml following:

<relativelayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_height="match_parent"     android:layout_width="match_parent"     android:id="@+id/scroller">     <com.example.testapp.circlesdrawingview         android:layout_width="match_parent"         android:layout_height="match_parent" /> </relativelayout>