Android学习笔记（四）定时器Timer

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Android考虑到线程安全问题，不允许在线程中执行UI线程。

所以在线程中不允许有UI操作

可以利用Handler机制来接收Timer每隔一秒发出的信息，也可以直接利用handler机制的

1、方法一:Handler+Thread

package com.example.yuyin_lixian;import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;import java.util.Timer;
import java.util.TimerTask;import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;/**
* handler定时器
*
* @author Smalt
*
*/
public class MainActivity extends Activity {
TextView tvShow;
private int i = 0; @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvShow = (TextView) findViewById(R.id.textView1);
new Thread(new ThreadShow()).start();
} // handler类接收数据
Handler handler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 1) {
tvShow.setText(Integer.toString(i++));
System.out.println("receive....");
}
};
}; // 线程类
class ThreadShow implements Runnable { @Override
public void run() {
// TODO Auto-generated method stub
while (true) {
try {
Thread.sleep(1000); //每隔一秒执行一次
Message msg = new Message();
msg.what = 1;
handler.sendMessage(msg);
System.out.println("send...");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("thread error...");
}
}
}
}
}

2、方法二:Handler类自带的postDelyed

其中使用PostDelayed方法，1秒后调用此Runnable对象
handler.postDelayed(runnable, 1000); 实际上也就实现了一个1s的一个定时器

如果想要关闭此定时器，可以这样操作
handler.removeCallbacks(runnable);

package com.example.yuyin_lixian;import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView; /**
* handler定时器使用postDelyed实现
*
* @author Smalt
*
*/
public class MainActivity extends Activity {
TextView tvShow;
private int i = 0;
private int TIME = 1000; @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvShow = (TextView) findViewById(R.id.textView1);
handler.postDelayed(runnable, TIME); //每隔1s执行
} Handler handler = new Handler();
Runnable runnable = new Runnable() { @Override
public void run() {
// handler自带方法实现定时器
try {
handler.postDelayed(this, TIME);
tvShow.setText(Integer.toString(i++));
System.out.println("do...");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println("exception...");
}
}
}; }

3、方法二:Handler+Timer+TimerTask

package com.example.yuyin_lixian;import java.util.Timer;
import java.util.TimerTask; import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView; /**
* 定时器实现:Handler+Timer+TimerTask
*
* @author Smalt
*
*/
public class MainActivity extends Activity {
TextView tvShow;
private int i = 0;
private int TIME = 1000; @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvShow = (TextView) findViewById(R.id.textView1);
timer.schedule(task, 1000, 1000); // 1s后执行task,经过1s再次执行
} Handler handler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 1) {
tvShow.setText(Integer.toString(i++));
}
super.handleMessage(msg);
};
};
Timer timer = new Timer();
TimerTask task = new TimerTask() { @Override
public void run() {
// 需要做的事:发送消息
Message message = new Message();
message.what = 1;
handler.sendMessage(message);
}
};
}