无效仅在自定义视图中有效

Question

so i created a view called "drawable view"

 class DrawableView extends View{
        Context mContext;

        int touches=0,k,Xoffs,clicks=0;


  double x_1 = 0,x_2=0;

        private float mLastTouchX, mLastTouchY;

        public DrawableView(Context context) {
        super(context);
        mContext = context;
        }

....
    @Override
    protected void onDraw(Canvas canvas){

        Paint myPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

canvas.drawColor(Color.BLUE);
myPaint.setColor(Color.WHITE);

canvas.drawCircle(200, 100, 20, myPaint);


    }

..... more code....

}

and it can only be invalidated within the ondraw command! ie: calling "invalidate();" at the end of the ondraw command causes it to loop.

I have tried many times to call g_draw.invalidate(); or g_draw.postInvalidate(); (g_draw is the name of the created Drawable View)from other classes and even the main activity class and it doesnt work. why and how can i fix it?

thanks

Answer 1

If you want continious onDraw invoking try doing it in another thread. Create a thread, and from its run method try doing postInvalidate.

It always worked for me.

Another thing is that when you draw a circle once, next time wont make any difference - it will look the same.

Answer 2

You may want to call invalidate() somewhere in your DrawableView class. For example, if you want your view to redraw itself after any touch event, you would do something like this:

public boolean onTouchEvent( MotionEvent event) {

    if(event.getAction() == MotionEvent.ACTION_UP){
        invalidate();
    }
}

This is how I draw the movable pieces in my puzzle game.