Android LifecycleObserver & ScheduledThreadPoolExecutor用户可见时每隔3秒周期更新，用户不可见时暂停周期更新

缺乏、安全感 2023-10-18 11:11 45阅读 0赞

## Android LifecycleObserver & ScheduledThreadPoolExecutor用户可见时每隔3秒周期更新，不可见时暂停每隔3秒的周期更新 ##

简言之，当用户按home键把当前App切换至“后台”不可见时候（用户看不见当前App页面时候），暂停每隔3秒的周期更新操作。当用户又将App切换至前台，用户看到App页面时候，重启每隔3秒的周期性更新。关键是通过LifecycleObserver使用ScheduledThreadPoolExecutor的scheduleAtFixedRate实现。

package zhangphil.test;
    
    import android.arch.lifecycle.Lifecycle;
    import android.arch.lifecycle.LifecycleObserver;
    import android.arch.lifecycle.LifecycleRegistry;
    import android.arch.lifecycle.OnLifecycleEvent;
    import android.os.Bundle;
    import android.support.annotation.Nullable;
    import android.support.v7.app.AppCompatActivity;
    
    import java.util.concurrent.ScheduledFuture;
    import java.util.concurrent.ScheduledThreadPoolExecutor;
    import java.util.concurrent.TimeUnit;
    
    public class LiveActivity extends AppCompatActivity {
        private LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);
    
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            System.out.println("onCreate");
    
            MyLifecycleObserver mLifecycleObserver = new MyLifecycleObserver();
            getLifecycle().addObserver(mLifecycleObserver);
        }
    
        @Override
        protected void onResume() {
            super.onResume();
            System.out.println("onResume");
        }
    
        @Override
        protected void onPause() {
            super.onPause();
            System.out.println("onPause");
        }
    
        @Override
        public LifecycleRegistry getLifecycle() {
            return mLifecycleRegistry;
        }
    
        public class MyLifecycleObserver implements LifecycleObserver {
            private UpdateThread mUpdateThread;
    
            public MyLifecycleObserver() {
                mUpdateThread = new UpdateThread();
            }
    
            @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
            public void on_create() {
                System.out.println("Lifecycle.Event.ON_CREATE");
            }
    
            @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
            public void on_resume() {
                System.out.println("Lifecycle.Event.ON_RESUME");
                mUpdateThread.startUpdate();
            }
    
            @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
            public void on_pause() {
                System.out.println("Lifecycle.Event.ON_PAUSE");
                mUpdateThread.stopUpdate();
            }
        }
    
        private class UpdateThread extends Thread {
            private ScheduledThreadPoolExecutor mScheduledThreadPoolExecutor = null;
            private Runnable mRunnable = null;
            private ScheduledFuture<?> mScheduledFuture = null;
    
            public UpdateThread() {
                mScheduledThreadPoolExecutor = new ScheduledThreadPoolExecutor(1);
                mRunnable = new Runnable() {
                    @Override
                    public void run() {
                        updateAction();
                    }
                };
            }
    
            public void startUpdate() {
                //每隔3秒周期性的执行更新动作。
                mScheduledFuture = mScheduledThreadPoolExecutor.scheduleAtFixedRate(mRunnable, 0, 3, TimeUnit.SECONDS);
            }
    
            public void stopUpdate() {
                mScheduledFuture.cancel(true);
            }
        }
    
        /**
         * 从远程服务器开始更新数据到本地的动作。
         */
        private void updateAction() {
            System.out.println(Thread.currentThread().getName() + " 从远程服务器更新数据...");
        }
    }

输出：

2018-11-12 18:59:17.041 16218-16218/? I/System.out: onCreate
    2018-11-12 18:59:17.047 16218-16218/? I/System.out: Lifecycle.Event.ON_CREATE
    2018-11-12 18:59:17.188 16218-16218/? I/System.out: onResume
    2018-11-12 18:59:17.188 16218-16218/? I/System.out: Lifecycle.Event.ON_RESUME
    2018-11-12 18:59:17.191 16218-16241/? I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:20.189 16218-16241/zhangphil.test I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:23.191 16218-16241/zhangphil.test I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:24.970 16218-16218/zhangphil.test I/System.out: Lifecycle.Event.ON_PAUSE
    2018-11-12 18:59:24.970 16218-16218/zhangphil.test I/System.out: onPause
    2018-11-12 18:59:47.126 16218-16218/zhangphil.test I/System.out: onResume
    2018-11-12 18:59:47.127 16218-16218/zhangphil.test I/System.out: Lifecycle.Event.ON_RESUME
    2018-11-12 18:59:47.128 16218-16241/zhangphil.test I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:50.128 16218-16241/zhangphil.test I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:53.128 16218-16241/zhangphil.test I/System.out: pool-1-thread-1 从远程服务器更新数据...
    2018-11-12 18:59:55.211 16218-16218/zhangphil.test I/System.out: Lifecycle.Event.ON_PAUSE
    2018-11-12 18:59:55.211 16218-16218/zhangphil.test I/System.out: onPause