从附加的OnPreDrawListener对象获取ViewTreeObserver对象

Question

如何让侦听器内的观察者？ 例如：

ViewTreeObserver myObserver = myLayout.getViewTreeObserver();
myObserver.addOnPreDrawListener(new OnPreDrawListener() {
    @Override
    public boolean onPreDraw() {
        // I want to get the myLayout or myObserver here, 
        // but I don't want to use the lines below
        RelativeLayout myLayout = (RelativeLayout)findViewById(myId);
        myLayout.getViewTreeObserver().removeOnPreDrawListener(this);

Answer 1

我试过玩侦听器实例， 我不知道它有多准确，但它有效：）

final class MyOnPreDrawListener implements OnPreDrawListener
{
    private RelativeLayout myLayout;

    public void setMyLayout(RelativeLayout layout){
        myLayout = layout;
    }

    @Override
    public boolean onPreDraw() {
        // now I have myLayout here         
        return true;
    }

}

然后我打电话给

ViewTreeObserver observer = myLayout.getViewTreeObserver();
MyOnPreDrawListener myListener = new MyOnPreDrawListener();
myListener.setMyLayout(myLayout);
observer.addOnPreDrawListener(myListener);

Answer 2

将其设为最终或将其声明为实例变量，即在onCreate之前声明并初始化onCreate

final ViewTreeObserver myObserver = myLayout.getViewTreeObserver();

http://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html#accessing

ViewTreeObserver.OnPreDrawListener是由匿名内部类实现的接口。要访问变量，必须final。