android中设置控件获得焦点

android中，要使控件获得焦点，需要先setFocus,再requestFocus。

以Button为例：
                btn.setFocusable(true);
                btn.setFocusableInTouchMode(true);
                btn.requestFocus();
                btn.requestFocusFromTouch();

 

//获得失去焦点的监听器

btn.setOnFocusChangeListener(new OnFocusChangeListener() {
  
  @Override
  public void onFocusChange(View v, boolean hasFocus) {
   // TODO Auto-generated method stub
   if (hasFocus) {
    btn_box.setBackgroundResource(R.drawable.book_green);
   }else {
    btn_box.setBackgroundResource(R.drawable.book);
   }   
  }
 });

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