Own defined Layout , onDraw() method not getting called

Question

I defined a class like that：

public class TestMyFrameLayout extends FrameLayout{

    Paint mPaint;
    public TestMyFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public TestMyFrameLayout(Context context) {
        super(context);
        mPaint = new Paint();
        mPaint.setColor(Color.GREEN);
    }

    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawCircle(50f, 50f, 30, mPaint);
    }   
}

and called it like:

TestMyFrameLayout myFrameLayout = new TestMyFrameLayout(this);
LayoutParams myFrameLayoutParams = new LayoutParams(300,300);
myFrameLayout.setLayoutParams(myFrameLayoutParams);
setContentView(myFrameLayout);

But In fact TestMyFrameLayout.onDraw(Canvas canvas) function not getting called, why?

Could you show the code where you make use of it? Also add `@Override` before onDraw: this will check for typo in eclipse. — Laurent', Oct 16 '11 at 09:14
Thank you Laurent'. My problem is already solved. Add this.setWillNotDraw(false); — old_hou, Oct 16 '11 at 11:10

score 235 · Answer 1 · edited Feb 12 '14 at 09:35

235

Solved. Add this.setWillNotDraw(false); in constructor

edited Feb 12 '14 at 09:35

Girish Nair

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answered Oct 16 '11 at 12:51

old_hou

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26

It could have only been an angst ridden developer who set it to true by default! – Narcís Calvet Nov 04 '11 at 15:38
5

@RyanShao for ViewGroups it's set to true by default. – ataulm Jan 10 '16 at 14:17
2

why the hell will someone want it to be true? why?? – Kai Wang Mar 08 '17 at 20:20
2

I guess it's an optimisation for when a ViewGroup is a pure container with nothing to draw for itself – hmac Jul 21 '20 at 11:24

Own defined Layout , onDraw() method not getting called

1 Answers1

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