latex中空心圆:线程的使用 三种方式 Android中常用定时器
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在Android 中,经常用到的定时器主要有以下几种实现:
一、采用Handler与线程的sleep(long )方法
二、采用Handler的postDelayed(Runnable, long) 方法
三、采用Handler与timer及TimerTask结合的方法。
下面逐一介绍:
一、采用Handle与线程的sleep(long )方法
Handler主要用来处理接受到的消息。这只是最主要的方法,当然Handler里还有其他的方法供实现,有兴趣的可以去查API,这里不过多解释。
1.定义一个Handler类,用于处理接受到的Message.
Handler handler = new Handler() {
public void handleMessage(Message msg) {
//要做的事情
super.handleMessage(msg);
}
};
2.新建一个实现Runnable接口的线程类。如下:
public class MyThread implements Runnable{
@Override
public void run() {
// TODO Auto-generated method stub
while (true) {
try {
Thread.sleep(10000);//线程暂停10秒,单位毫秒
Message message=new Message();
message.what=1;
handler.sendMessage(message);//发送消息
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}3.在需要启动线程的地方加入下面语句:
new Thread(new MyThread()).start();
4.启动线程后,线程每10s发送一次消息。实例:
Java代码
- package com.quding.thread;
- import android.app.Activity;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Looper;
- import android.os.Message;
- import android.util.Log;
- import android.widget.TextView;
- public class MyCounter extends Activity{
- private TextView mTextView;
- private Handler handler;
- private int count;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.mycounter);
- mTextView = (TextView) findViewById(R.id.mycounter_textView);
- handler = new Handler(Looper.getMainLooper()){
- @Override
- public void handleMessage(Message msg) {
- super.handleMessage(msg);
- if(msg.what == 1){
- //添加要干的事情
- count++;
- mTextView.setText(count + "");
- }
- }
- };
- new Thread(new MyThread()).start();
- Log.e("tag", "cehsi");
- }
- public class MyThread implements Runnable{
- public void run() {
- while(true){
- try {
- Message message = new Message();
- message.what = 1;
- Thread.sleep(1000); //间隔时间在这里定
- //通过handler把这个线程的线程体放到主线程的消息队列中,使得该线程在主线程中执行
- handler.sendMessage(message);
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- }
- }
package com.quding.thread;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Looper;import android.os.Message;import android.util.Log;import android.widget.TextView;public class MyCounter extends Activity{private TextView mTextView;private Handler handler;private int count;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.mycounter);mTextView = (TextView) findViewById(R.id.mycounter_textView);handler = new Handler(Looper.getMainLooper()){@Overridepublic void handleMessage(Message msg) {super.handleMessage(msg);if(msg.what == 1){//添加要干的事情count++;mTextView.setText(count + "");}}};new Thread(new MyThread()).start();Log.e("tag", "cehsi");}public class MyThread implements Runnable{public void run() {while(true){try {Message message = new Message();message.what = 1;Thread.sleep(1000); //间隔时间在这里定//通过handler把这个线程的线程体放到主线程的消息队列中,使得该线程在主线程中执行handler.sendMessage(message);} catch (Exception e) {e.printStackTrace();}}}}}
二、采用Handler的postDelayed(Runnable, long) 方法
这个实现比较简单一些:
1. Handler handler=new Handler();
Runnable runnable=new Runnable(){
@Override
public void run() {
// TODO Auto-generated method stub
//要做的事情
handler.postDelayed(this, 2000);
}
};
2.启动计时器:
handler.postDelayed(runnable, 2000);//每两秒执行一次runnable.
3.停止计时器:
handler.removeCallbacks(runnable);Java代码
- package com.quding.thread;
- import android.app.Activity;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Looper;
- import android.os.Message;
- import android.util.Log;
- import android.widget.TextView;
- public class MyCounter extends Activity{
- private TextView mTextView;
- private Handler handler;
- private int count;
- private Runnable myRunnable;
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.mycounter);
- mTextView = (TextView) findViewById(R.id.mycounter_textView);
- handler = new Handler(Looper.getMainLooper());
- myRunnable = new Runnable(){
- @Override
- public void run() {
- //此处添加每个一段时间要执行的语句
- count++;
- mTextView.setText(count + "");
- handler.postDelayed(this, 1000);
- }
- };
- //启动计时器
- handler.postDelayed(myRunnable, 1000);
- }
- @Override
- protected void onStop() {
- super.onStop();
- handler.removeCallbacks(myRunnable);
- }
- }
package com.quding.thread;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Looper;import android.os.Message;import android.util.Log;import android.widget.TextView;public class MyCounter extends Activity{private TextView mTextView;private Handler handler;private int count;private Runnable myRunnable;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.mycounter);mTextView = (TextView) findViewById(R.id.mycounter_textView);handler = new Handler(Looper.getMainLooper());myRunnable = new Runnable(){@Overridepublic void run() {//此处添加每个一段时间要执行的语句count++;mTextView.setText(count + "");handler.postDelayed(this, 1000);}};//启动计时器handler.postDelayed(myRunnable, 1000);}@Overrideprotected void onStop() {super.onStop();handler.removeCallbacks(myRunnable);}}
三、采用Handler与timer及TimerTask结合的方法。
1.定义定时器、定时器任务及Handler句柄
private final Timer timer = new Timer();
private TimerTask task;
Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
//要做的事情
super.handleMessage(msg);
}
};
2.初始化计时器任务。
task = new TimerTask() {
@Override
public void run() {
// TODO Auto-generated method stub
Message message = new Message();
message.what = 1;
handler.sendMessage(message);
}
};
3.启动定时器
timer.schedule(task, 2000, 2000);
简要说一下上面三步提到的一些内容。
1.定时器任务(TimerTask)顾名思义,就是说当定时器到达指定的时间时要做的工作,这里是想Handler发送一个消息,由Handler类进行处理。
2. java.util.Timer.schedule(TimerTask task, long delay):这个方法是说,dalay/1000秒后执行task.只执行一次。
java.util.Timer.schedule(TimerTask task, long delay, long period):这个方法是说,delay/1000秒后执行task,然后进过period/1000秒再次执行task,这个用于循环任务,执行无数次,当然,你可以用timer.cancel();取消计时器的执行。
- package com.quding.thread;
- import java.util.Timer;
- import java.util.TimerTask;
- import android.app.Activity;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Looper;
- import android.os.Message;
- import android.util.Log;
- import android.widget.TextView;
- public class MyCounter extends Activity{
- private TextView mTextView;
- private Handler handler;
- private int count;
- private Timer timer = new Timer();
- @Override
- protected void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- setContentView(R.layout.mycounter);
- mTextView = (TextView) findViewById(R.id.mycounter_textView);
- handler = new Handler(Looper.getMainLooper()){
- @Override
- public void handleMessage(Message msg) {
- super.handleMessage(msg);
- if(msg.what == 1){
- count++;
- mTextView.setText(count + "");
- }
- }
- };
- TimerTask task = new TimerTask() {
- @Override
- public void run() {
- Message msg =new Message();
- msg.what = 1;
- handler.sendMessage(msg);
- }
- };
- timer.schedule(task, 10000, 1000); // 第二个参数是定时开始计时,第三个参数是时间间隔
- }
- }