android中handler中 obtainmessge与New message区别

时间:2021-05-02 15:03:42

obtainmessage()是从消息池中拿来一个msg 不需要另开辟空间new

new需要重新申请,效率低,obtianmessage可以循环利用;

//use Handler.obtainMessage(),instead of msg = new Message();
//because if there is already an Message object,that not be used by
//any one ,the system will hand use that object,so you don't have to
//create and object and allocate memory.
//it is also another example of object recycling and reusing in android.
Message msg = mHandler.obtainMessage();
msg.what = UPDATE_LISTVIEW;
msg.obj = current + "/" + total + "songs";
//this method is called from worker Thread,so we cannot update UI from here.
msg.sendToTarget();

在看下面代码:

Message msg = handler.obtainMessage();
msg.arg1 = i;
msg.sendToTarget(); Message msg=new Message();
msg.arg1=i;
handler.sendMessage(msg);

第一种写法是message 从handler 类获取,从而可以直接向该handler 对象发送消息,第二种写法是直接调用 handler 的发送消息方法发送消息。