Android：how To Change Attributes In Ondraw() By Onclicklistener

I have a simple ondraw() function. private class MyViewCircle extends View { public MyViewCircle(Context context) { super(context); // TODO Auto-gen

Solution 1:

you could set some variables to represent there attributes, for example, in your case,you can set a n int for the color, and three float for the coordinates of the center and the radius.

in your onClick() method, change the values of there variables , and then call invalidate() to redraw the image.

Solution 2:

You can use a member variable to store the state, change it onClick, and check it in onDraw.

To hook up the click event properly, make sure you call setOnClickListener in your constructor, and call invalidate in onClick to force a redraw.

privateclassMyCircleextendsViewimplementsOnClickListener {
  privatebooleanmDrawBlueCircle=false;
  privatePaintmPaint=newPaint();

  publicMyCircle(Context context) {
    super(context);
    setOnClickListener(this);
  }

  @OverrideprotectedvoidonDraw(Canvas canvas) {
    floatx=20;
    floaty=20;
    floatr=50;
    intcolor= Color.BLACK;
    if (mDrawBlueCircle) {
      x = 30;
      y = 30;
      color = Color.BLUE;
    }
    mPaint.setColor(color);
    canvas.drawCircle(x, y, r, mPaint);
  }

  @OverridepublicvoidonClick(View v) {
    mDrawBlueCircle = true;
    invalidate();
  }
}

Notice that I also store the Paint in a member variable mPaint. This prevents new objects to be created on each draw cycle and reduces garbage collection.