如何让程序5秒钟更新一下Title.。。。。
首先我们看一下习惯了Java编程的人,在不知道Handler的用法之前是怎么样写的程序,代码如下所示:
- package
com.android.tutor;
- import
java.util.Timer;
- import
java.util.TimerTask;
- import
android.app.Activity;
- import
android.os.Bundle;
- public
class
HandlerDemo
extends
Activity {
- //title为setTitle方法提供变量,这里为了方便我设置成了int型
- private
int
title =
0
;
- public
void
onCreate(Bundle savedInstanceState) {
- super
.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- Timer timer = new
Timer();
- timer.scheduleAtFixedRate(new
MyTask(),
1
,
5000
);
- }
- private
class
MyTask
extends
TimerTask{
- @Override
- public
void
run() {
- setTitle("Welcome to Mr Wei's blog "
+ title);
- title ++;
- }
- }
- }
//title为setTitle方法提供变量,这里为了方便我设置成了int型
private int title = 0;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Timer timer = new Timer();
timer.scheduleAtFixedRate(new MyTask(), 1, 5000);
}
private class MyTask extends TimerTask{
@Override
public void run() {
setTitle("Welcome to Mr Wei's blog " + title);
title ++;
}
}
}
然而当我们执行程序,并不能达到我们预期的效果,所以Android 引进了Handler
这个特殊的类,可以说它是Runnable和Activity交互的桥梁
这个特殊的类,可以说它是Runnable和Activity交互的桥梁
,所以我们只要在run方法中发送Message,而在Handler里,通过不同的Message执行不同的任务。
所以我们修改后的代码如下:
- package
com.android.tutor;
- import
java.util.Timer;
- import
java.util.TimerTask;
- import
android.app.Activity;
- import
android.os.Bundle;
- import
android.os.Handler;
- import
android.os.Message;
- public
class
HandlerDemo
extends
Activity {
- //title为setTitle方法提供变量,这里为了方便我设置成了int型
- private
int
title =
0
;
- private
Handler mHandler =
new
Handler(){
- public
void
handleMessage(Message msg) {
- switch
(msg.what) {
- case
1
:
- updateTitle();
- break
;
- }
- };
- };
- public
void
onCreate(Bundle savedInstanceState) {
- super
.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- Timer timer = new
Timer();
- timer.scheduleAtFixedRate(new
MyTask(),
1
,
5000
);
- }
- private
class
MyTask
extends
TimerTask{
- @Override
- public
void
run() {
- Message message = new
Message();
- message.what = 1
;
- mHandler.sendMessage(message);
- }
- }
- public
void
updateTitle(){
- setTitle("Welcome to Mr Wei's blog "
+ title);
- title ++;
- }
- }