为什么OnDraw中没有无效后，叫（）？ [英] Why onDraw is not called after invalidate()?

问题描述

我发现计算器上很多帖子，但我还是解决不了我的问题。这是我的code片：

I have found many posts on stackoverflow but I still cannot solve my problem. Here is my code piece:

public class MyView extends RelativeLayout {

Button b1;
Button b2;
Context sContext;
public static int i = 0;
private int w = 400;
private int h = 400;
private int w2 = 100;
private int h2 = 100;

public MyView(Context context) {
    super(context);
    sContext = context;
    init();
}

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
    sContext = context;
    init();
}

private void init() {
    b1 = new Button(sContext);
    addView(b1);
    b1.setBackgroundColor(Color.YELLOW);

    b1.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            if (w >= 600) {
                MyView.this.setBackgroundColor(Color.GREEN);
                //b1.setBackgroundColor(Color.RED);
            } else {
                MyView.this.setX(100);
            }

            MyView.this.invalidate();
            w += 100;
            w2 += 20;
        }

    });
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //b1.setBackgroundColor(Color.RED);
    Toast.makeText(sContext, ""+i, Toast.LENGTH_SHORT).show();
    ++i;
}
}

请您解释一下为什么OnDraw的不叫前三次我preSS B1？因为我叫无效，每次我preSS B1。非常感谢你！

Would you please explain why onDraw is not called the first three times I press b1? Because I called invalidate everytime I press b1. Thank you very much!

推荐答案

在默认情况下所有的ViewGroup子类没有调用它的OnDraw方法，你应该调用setWillNotDraw启用它（假）<一href="http://developer.android.com/reference/android/view/View.html#setWillNotDraw%28boolean%29">link

By default all ViewGroup sub classes did not calls its onDraw method, you should enable it by call setWillNotDraw (false) link

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