Android 点击EditText编辑框清除hint预设字

MainActivity：

/**
* 点击EditText窗体后，清除预设字
* @author lichao829@163.com
*
*/
public class MainActivity extends Activity{

@Override
protected void onCreate(Bundle savedInstanceState) {
  // TODO Auto-generated method stub
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  EditText username = (EditText)findViewById(R.id.username);
  EditText password = (EditText)findViewById(R.id.password);
  Button login = (Button)findViewById(R.id.login);

  /*EditText默认获取焦点行为的取消？
  解决之道：在EditText的父级控件中，
  设置： android:focusable="true"
            android:focusableInTouchMode="true"
   详见xml布局文件。*/

  //username焦点监听事件
  username.setOnFocusChangeListener(new OnFocusChangeListener() {
      public void onFocusChange(View v, boolean hasFocus) {
          EditText et=(EditText)v;
          if (!hasFocus) {// 失去焦点
          et.setHint(et.getTag().toString());
          } else {
              String hint=et.getHint().toString();
              et.setTag(hint);//保存预设字
              et.setHint(null);
          }
      }
  });
  //password焦点监听事件
  password.setOnFocusChangeListener(new OnFocusChangeListener() {
   public void onFocusChange(View v, boolean hasFocus) {
    EditText et=(EditText)v;
    if (!hasFocus) {// 失去焦点
     et.setHint(et.getTag().toString());
    } else {
     String hint=et.getHint().toString();
     et.setTag(hint);//保存预设字
     et.setHint(null);
    }
   }
  });

  login.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
     // TODO Auto-generated method stub
     Toast.makeText(MainActivity.this, "登录", Toast.LENGTH_LONG).show();
    }
  });
}
}

布局界面：

</LinearLayout>