我在android中编写了一个自定义视图。当此视图的可见性发生更改时,我需要进行一些处理。当视图/小部件的可见性改变时,是否有一些监听器被调用?
编辑:
我知道如何改变可见性,想知道当我们在视图上设置可见性时是否有一个监听器被调用!
您想在自定义视图类中进行该处理吗?如果是这样,那为什么不直接重写 setVisibility() 方法,调用 super(),然后进行自定义处理呢?
我知道如何改变可见性,想知道当我们在视图上设置可见性时是否有一个监听器被调用!
您必须继承 yourview/widget
和 override setVisibility
,并注册一个您将在其上接收通知的接口。例如:
public class MyView extends View {
public interface MyListener {
public void onSetVisibilityCalled();
}
public void registerListener(MyListener myListener) {
this.mListener = myListener;
}
public void setVisibility (int visibility) {
super.setVisibility(visibility);
if (mListener != null)
mListener.onSetVisibilityCalled();
}
}
您必须对要添加侦听器的视图进行子类化。然后,您应该覆盖onVisibilityChanged
而不是setVisibility
. onVisibilityChanged
当视图的可见性因任何原因发生更改时触发,包括更改祖先视图时。
View
如果您希望在您的可见性更改时通知不同的类,您将需要一个界面。
例子:
public class MyView extends View {
private OnVisibilityChangedListener mVisibilityListener;
public interface OnVisibilityChangedListener {
// Avoid "onVisibilityChanged" name because it's a View method
public void visibilityChanged(int visibility);
}
public void setVisibilityListener(OnVisibilityChangedListener listener) {
this.mVisibilityListener = listener;
}
protected void onVisibilityChanged (View view, int visibility) {
super.onVisibilityChanged(view, visibility);
// if view == this then this view was directly changed.
// Otherwise, it was an ancestor that was changed.
// Notify external listener
if (mVisibilityListener != null)
mVisibilityListener.visibilityChanged(visibility);
// Now we can do some things of our own down here
// ...
}
}
要更改小部件的可见性,请使用widget.setVisibility(View.Visible)
orwidget.setVisibility(View.Invisible)
方法。