android AlarmManager实现定时器

ゞ浴缸里的玫瑰 2024-04-17 06:19 115阅读 0赞

能实现定时器的方法有好几种，而利用AlarmManager发送广播的方式实现相对来说还是很靠谱的，长期在后台运行会被系统列入高耗电APP，系统会自动停掉广播的发送，除非把APP加入系统白名单，上代码：

package com.example.myapplication;
    
    import android.app.AlarmManager;
    import android.app.PendingIntent;
    import android.content.BroadcastReceiver;
    import android.content.Context;
    import android.content.Intent;
    import android.content.IntentFilter;
    import android.os.Build;
    import android.os.Bundle;
    import android.os.SystemClock;
    import android.util.Log;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import androidx.annotation.Nullable;
    import androidx.fragment.app.Fragment;
    import com.example.myapplication.databinding.FragmentFirstBinding;
    import static android.content.Context.ALARM_SERVICE;
    
    public class FirstFragment extends Fragment {
    
        private FragmentFirstBinding binding;
        /**
         * 10秒
          */
        private static final int TIME_INTERVAL = 10000;
        private PendingIntent pendingIntent;
        private AlarmManager alarmManager;
        private static final String ALARM_ACTION = "com.example.myapplication.alarm.clock";
    
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            binding = FragmentFirstBinding.inflate(inflater, container, false);
            return binding.getRoot();
        }
    
        @Override
        public void onDestroyView() {
            super.onDestroyView();
            binding = null;
        }
    
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            IntentFilter intentFilter = new IntentFilter(ALARM_ACTION);
            getActivity().registerReceiver(alarmReceiver, intentFilter);
            alarmManager = (AlarmManager) getActivity().getSystemService(ALARM_SERVICE);
            pendingIntent = PendingIntent.getBroadcast(getActivity(), 0, new Intent(ALARM_ACTION), 0);
    
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                //6.0低电耗模式需要使用此方法才能准时触发定时任务
                //比setWindow()方法时效性强
                alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), pendingIntent);
            } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                //4.4以上，使用此方法触发定时任务时间更为精准
                alarmManager.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), pendingIntent);
            } else {//4.4以下，使用旧方法
                alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime(), TIME_INTERVAL, pendingIntent);
            }
        }
    
        @Override
        public void onDestroy() {
            super.onDestroy();
            getActivity().unregisterReceiver(alarmReceiver);
            alarmManager.cancel(pendingIntent);
        }
    
        private BroadcastReceiver alarmReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                //定时任务
                Log.d("Alex", "onReceive");
                if (TextUtils.equals(intent.getAction(), ALARM_ACTION)) {
                    Log.d("Alex", "todo");
                    
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        alarmManager.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                                SystemClock.elapsedRealtime() + TIME_INTERVAL, pendingIntent);
                    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
                        alarmManager.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                                SystemClock.elapsedRealtime() + TIME_INTERVAL, pendingIntent);
                    } else {//4.4以下，使用旧方法
                        alarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                                SystemClock.elapsedRealtime(), TIME_INTERVAL, pendingIntent);
                    }
                }
            }
        };
    
    }

这是一个实现的例子，首次发送闹钟广播不加延迟时间，第2次开始延迟一定的时间，这里是10秒，时间可以自己定义。

这里广播接收器用的是动态注册，根据官方文档可知，安卓8.0开始，一般情况静态注册广播接收器无效。

[广播概览 | Android 开发者 | Android Developers][_ Android _ _ Android Developers]

![ba2bbc35b21a4586a79815fb8c74ff09.png][]

再注意一些注意点：

根据性能和需求有3种发送广播的方式：

![ad1aa7dcb3d34b738e5da0790d294ebf.png][]

安全事项以及最佳做法：

![f7e56bad31064ba1b948d7472b07b491.png][]

![7af7bbe163af4eef94e3dd30b4de3dd7.png][] **总结一下就是：**

应用内尽量使用 **LocalBroadcastManager**，因为广播是跨进程的，而本地广播只在应用内有效，性能会好很多；**onReceive()** 运行在主线程中，避免使用耗时的操作。

好了，又可以愉快的玩耍了。

[_ Android _ _ Android Developers]: https://developer.android.google.cn/guide/components/broadcasts?hl=zh_cn
[ba2bbc35b21a4586a79815fb8c74ff09.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/c2bf5a10b3f74324a3f72efba4e174c5.png
[ad1aa7dcb3d34b738e5da0790d294ebf.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/0813a151e2614ecd99fef7e97499baa4.png
[f7e56bad31064ba1b948d7472b07b491.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/b9a0f6ef7a0348a6942fcfdc8fcf09fd.png
[7af7bbe163af4eef94e3dd30b4de3dd7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/15/41ae615e9d74495bbe9f379fe75a185d.png