Android常用定时器的实现方式
目录
前言
android开发中，常用定时器实现方式有以下几种：
1、Handler与sleep
2、Handler与postDelayed
3、Handler与timer
注：Handler的主要作用就是用来处理接收到的信息；用Handler消息传递机制是为了多个线程并发更新UI的同时，保证线程安全；
一、Handler 与 sleep
public class HandlerAndSleep {
// 1、定义一个Handler类，用于处理接受到的Message.
Handler handler = new Handler(Looper.getMainLooper()) {
@Override
public void handleMessage(@NonNull Message msg) {
super.handleMessage(msg);
// do something eg.
Log.d("HandlerAndSleep", "HandlerAndSleep");
}
};
// 2、新建一个实现Runnable接口的线程类
class MyThread implements Runnable {
@Override
public void run() {
while (true) {
try {
Thread.sleep(10000);
Message message = new Message();
message.what = 1;
handler.sendMessage(message);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
public HandlerAndSleep() {
//3、在需要启动线程的地方加入下面语句,启动线程后，线程每10s发送一次消息
new Thread(new MyThread()).start();
}
}
结果打印如下：
2022-05-30 11:30:42.320 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:30:52.324 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:31:02.326 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:31:12.335 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:31:22.338 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:31:32.339 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
2022-05-30 11:31:42.347 17864-17864/com.yh.study D/HandlerAndSleep: HandlerAndSleep
二、Handler 与 postDelayed
public class HandleAndPostDelayed {
Handler handler = new Handler(){
@Override
public boolean sendMessageAtTime(@NonNull Message msg, long uptimeMillis) {
Log.d("HandleAndPostDelayed", "HandleAndPostDelayed");
return super.sendMessageAtTime(msg, uptimeMillis);
}
};
Runnable runnable = new Runnable() {
@Override
public void run() {
// do something
handler.postDelayed(this, 2000);
}
};
HandleAndPostDelayed() {
// 开启定时器
handler.postDelayed(runnable, 2000);
// 停止定时器
// handler.removeCallbacks(runnable);
}
}
结果打印如下：
2022-05-30 14:32:41.533 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
2022-05-30 14:32:43.534 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
2022-05-30 14:32:45.537 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
2022-05-30 14:32:47.539 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
2022-05-30 14:32:49.546 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
2022-05-30 14:32:51.550 24351-24351/com.yh.study D/HandleAndPostDelayed: HandleAndPostDelayed
三、Handler 与 timer
public class HandlerAndTimer {
private final Timer timer = new Timer();
private TimerTask task;
Handler handler = new Handler() {
@Override
public void handleMessage(@NonNull Message msg) {
// do something
Log.d("HandlerAndTimer", "HandlerAndTimer");
super.handleMessage(msg);
}
};
public HandlerAndTimer() {
task = new TimerTask() {
@Override
public void run() {
Message message = new Message();
message.what = 1;
handler.sendMessage(message);
}
};
//启动定时器 参数对应为 TimerTask 延迟时间 间隔时间
timer.schedule(task, 2000, 2000);
}
}
结果打印如下：
2022-05-30 14:43:40.922 25052-25052/com.yh.study D/HandlerAndTimer: HandlerAndTimer
2022-05-30 14:43:42.924 25052-25052/com.yh.study D/HandlerAndTimer: HandlerAndTimer
2022-05-30 14:43:44.925 25052-25052/com.yh.study D/HandlerAndTimer: HandlerAndTimer
2022-05-30 14:43:46.926 25052-25052/com.yh.study D/HandlerAndTimer: HandlerAndTimer
2022-05-30 14:43:48.927 25052-25052/com.yh.study D/HandlerAndTimer: HandlerAndTimer
在Android上常用的定时器有两种，一种是Java.util.Timer，一种就是系统的AlarmService。
public class MainActivity extends AppCompatActivity {
Handler handler = new Handler() {
@Override
public void handleMessage(@NonNull Message msg) {
tCount++;
timerTV.setText(tCount+"");
super.handleMessage(msg);
}
};
Timer timer = new Timer();
int tCount = 0;
int sCount = 0;
TextView timerTV;
TextView serviceTV;
String ALARM_RECEIVER_ACTION = "com.yh.study.AlarmReceiver";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
timerTV = findViewById(R.id.timer_tv);
serviceTV = findViewById(R.id.service_tv);
timer.schedule(new TimerTask() {
@Override
public void run() {
handler.sendEmptyMessage(0);
}
}, 2*1000, 5*1000);
AlarmReceiver alarmReceiver = new AlarmReceiver(new Handler() {
@Override
public void handleMessage(@NonNull Message msg) {
sCount++;
serviceTV.setText(sCount+"");
super.handleMessage(msg);
}
});
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(ALARM_RECEIVER_ACTION);
registerReceiver(alarmReceiver, intentFilter);
Intent intent = new Intent(ALARM_RECEIVER_ACTION);
PendingIntent pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, intent, 0);
//
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(),
pendingIntent);
}
}
public class AlarmReceiver extends BroadcastReceiver {
Handler handler;
AlarmReceiver(Handler handler) {
this.handler = handler;
}
@Override
public void onReceive(Context context, Intent intent) {
Log.d("onReceive", "onReceive");
handler.sendEmptyMessage(0);
Intent serviceIntent = new Intent(context, MyService.class);
context.startService(serviceIntent);
}
}
public class MyService extends IntentService {
public MyService() {
super("MyService");
}
@Override
protected void onHandleIntent(@Nullable Intent intent) {
AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
Intent alarmIntent = new Intent("com.yh.study.AlarmReceiver");
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, alarmIntent, 0);
alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, System.currentTimeMillis()+5*1000,
pendingIntent);
}
}
以下结论来源其他博主
（小子在验证过程中，连接usb情况正常，拔掉usb后与结论不符，可能是小子哪里写的有问题）
在Timer中，当连接USB线进行调试时，会发现一切工作正常，每5秒更新一次界面，即使是按下电源键，仍然会5秒触发一次。 当拔掉USB线，按下电源键关闭屏幕后，过一段时间再打开，发现定时器明显没有继续计数，停留在了关闭电源键时的数字。
在AlarmService中，拔掉USB线，按下电源键，过一点时间再次打开屏幕，发现定时器一直在计数。
测试机型小米8,上timer，下AlarmService
补充：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);
总结
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