android 所有焦点问题汇总【Focus】

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一. 主动获取焦点

setFocusable(true); // 是设置能否获得焦点而已。.

requestFocus(); //是让控件得到焦点

requestFocusInWindow()  //的作用应该是获取窗口的焦点

二:子类是否获取焦点

android:descendantFocusability
Defines the relationship between the ViewGroup and its descendants when looking for a View to take focus.
Must be one of the following constant values.
ConstantValueDescriptionbeforeDescendants  0The ViewGroup will get focus before any of its descendants.afterDescendants  1The ViewGroup will get focus only if none of its descendants want it.blocksDescendants  2The ViewGroup will block its descendants from receiving focus
 
具体可以看另外一篇文章： android:descendantFocusability用法简析

三：监听activity获取/失去焦点（onWindowFocusChanged）

作用：1.可以监听activity获取/失去焦点【hasFocus： true 获取焦点， false失去焦点】

2.判断activity加载完成（当所有生命周期完成后调用该方法）

@Override

public void onWindowFocusChanged(boolean hasFocus) {
    // TODO Auto-generated method stub 
    super.onWindowFocusChanged(hasFocus); 
} 