Service和Activity通讯的3种常用方式

阳光穿透心脏的1/2处 2022-08-20 13:23 115阅读 0赞

一般的Android业务开发中，Service的使用十分常见。稍微复杂点的业务逻辑，都需要Serivice在执行某些耗时操作后通知Activity。总结常见的三种方法。

分别是：（1）binder持有Activity的Handler对象，或者持有一个Activity的callbackInterface.

（2）AIDL实现，完美支持IPC。

（3）startService+broadcastReceiver实现。

另外还有几种不推荐的方式，都有很高的局限性。比如Service执行后的结果持久化，通过startActivity在目标Activity中的OnNewIntent()处理（需要Activity是单例的)。

（1）Binder持有Activity的Handler，这里推荐Handler弱引用Activity实现。

关键代码如下：

public class WeakReferenceHandlerActivity extends Activity { 
        private MyHandler mHandler;
        public static int FLAG = 10;
        public ProgressBar progressBar;
        private Button bindButton;
        private Button nextButton;
        private UseHandlerService.MyBinder myBinder;  
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.handler_layout);
            progressBar = (ProgressBar)this.findViewById(R.id.progress);
            bindButton = (Button)this.findViewById(R.id.bind);
            nextButton = (Button)this.findViewById(R.id.next);
            mHandler = new MyHandler(this);
    
            bindButton.setOnClickListener(new OnClickListener() {
    
                @Override
                public void onClick(View v) {
                    bindService();
                    Log.d("","startDownLoad() --> click");
                }
            });
            nextButton.setOnClickListener(new OnClickListener() {
    
                @Override
                public void onClick(View v) {
                    startActivity(new Intent(WeakReferenceHandlerActivity.this,AndroidAidlActivity.class));
                }
            });
        }
    
    
    
        private ServiceConnection connection = new ServiceConnection() {  
    
            @Override 
            public void onServiceDisconnected(ComponentName name) {  
    
            }  
    
            @Override 
            public void onServiceConnected(ComponentName name, IBinder service) { 
                Log.d("","startDownLoad() --> onbind");
                myBinder = (UseHandlerService.MyBinder) service;  
                myBinder.setCallBackHandler(mHandler);
                myBinder.startDownLoad();
    
            }  
        };  
    
        @Override
        protected void onResume() {
    
            super.onResume();
        }
    
        @Override
        protected void onPause() {
            unBindService();
            super.onPause();
        }
    
        public void bindService(){
            Intent bindIntent = new Intent(this, UseHandlerService.class);  
            bindService(bindIntent, connection, BIND_AUTO_CREATE);  
        }
    
        public void unBindService(){
            unbindService(connection);
        }
    
        @Override
        protected void onDestroy() {
            // Remove all Runnable and Message.
            mHandler.removeCallbacksAndMessages(null);
    
            super.onDestroy();
        }
    
        public MyHandler getHandler(){
            return mHandler;
        }
    
        public class MyHandler extends Handler { 
            // WeakReference to the outer class's instance.
            private WeakReference<weakreferencehandleractivity> mOuter;
    
            public MyHandler(WeakReferenceHandlerActivity activity) {
                mOuter = new WeakReference<weakreferencehandleractivity>(activity);
            }
    
            @Override
            public void handleMessage(Message msg) {
                WeakReferenceHandlerActivity outer = mOuter.get();
                if (outer != null) {
                    // Do something with outer as your wish.
                    if(!outer.isFinishing()){
                        int progress = msg.what;
                        progressBar.setProgress(progress);
                    }
                }
            }
        }
    }

public class UseHandlerService extends Service{ 
        /** * 进度条的最大值 */
        public static final int MAX_PROGRESS = 100; 
        /** * 进度条的进度值 */
        private int progress = 0;
        /** * 更新进度的回调接口 */
        private MyHandler myHandler;
        private MyBinder mBinder = new MyBinder();  
        private String TAG = "UseHandlerService";
        /** * 注册回调接口的方法，供外部调用 * @param onProgressListener */
        public void setHandler(MyHandler handler) {
            myHandler = handler;
        }
        /** * 增加get()方法，供Activity调用 * @return 下载进度 */
        public int getProgress() {
            return progress;
        }
        @Override 
        public void onCreate() {  
            super.onCreate();  
            Log.d(TAG, "onCreate() executed");  
        }  
    
        @Override 
        public int onStartCommand(Intent intent, int flags, int startId) {  
            Log.d(TAG, "onStartCommand() executed");  
            return super.onStartCommand(intent, flags, startId);  
        }  
    
        @Override 
        public void onDestroy() {  
            super.onDestroy();  
            Log.d(TAG, "onDestroy() executed");  
        }  
    
        /** * 返回一个Binder对象 */
        @Override
        public IBinder onBind(Intent intent) {
            return mBinder;
        }
    
        public class MyBinder extends Binder{ 
            /** * 获取当前Service的实例 * @return */
            public UseHandlerService getService(){
                return UseHandlerService.this;
            }
    
            public void setCallBackHandler(MyHandler handler){
                myHandler = handler;
            }
    
            public void startDownLoad(){
                Log.d("","startDownLoad() inBinder-->");
                new Thread(new Runnable() {
                    public void run() {
                        while(progress < MAX_PROGRESS){
                            progress += 5;
                            Log.d("","startDownLoad() run-->");
                            //进度发生变化通知调用方
                            if(myHandler != null){
                                myHandler.sendEmptyMessage(progress);
                            }
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }).start();
            }
        }
    }

弱引用的实现，是出于防止Service不销毁，一直导致目标Activity也不能会回收的考虑。

（2）AIDL实现，同样还是进度条的UI更新。

public class AndroidAidlActivity extends Activity { 
        /** Called when the activity is first created. */
        public static final int MAX_PROGRESS = 100; 
        /** * 进度条的进度值 */
        private int progress = 0;
        public ProgressBar progressBar;
        private Button bindButton;
    
        private MyAIDLService mService;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.handler_layout);
    
            progressBar = (ProgressBar)this.findViewById(R.id.progress);
            bindButton = (Button)this.findViewById(R.id.bind);
            bindButton.setOnClickListener(new OnClickListener() {
    
                @Override
                public void onClick(View v) {
                    bindService();
                    Log.d("","startDownLoad() --> click");
                }
            });
            this.findViewById(R.id.next).setVisibility(View.GONE);
        }
    
        private ICallBack.Stub mCallback = new ICallBack.Stub() {
    
             @Override
             public void showResult(final int result) {
                 Log.d("", "showresult -->" + result);
                 progressBar.setProgress(result);
             }
        };
    
        private ServiceConnection connection = new ServiceConnection() {  
            @Override 
            public void onServiceDisconnected(ComponentName name) {  
                mService = null;
            }  
            @Override 
            public void onServiceConnected(ComponentName name, IBinder service) { 
                Log.d("","startDownLoad() --> onbind");
                mService = MyAIDLService.Stub.asInterface(service);
                try {
                    mService.registerCallback(mCallback);
                    mService.startDownload();
                } catch (RemoteException e) {
                    Log.e("", "", e);
                }
    
            }  
        };  
    
        @Override
        protected void onResume() {
            super.onResume();
        }
    
        @Override
        protected void onPause() {
            unBindService();
            super.onPause();
        }
    
        public void bindService(){
            Intent bindIntent = new Intent(this, AidlService.class);  
            bindService(bindIntent, connection, BIND_AUTO_CREATE);  
        }
    
        public void unBindService(){
            unbindService(connection);
        }
    
        @Override
        protected void onDestroy() {
            // Remove all Runnable and Message.
            super.onDestroy();
        }
    
    
    }
    public class AidlService extends Service { 
    
        private RemoteCallbackList<icallback> mCallbacks = new RemoteCallbackList<icallback>();
    
            MyAIDLService.Stub mBinder = new Stub() {
    
                @Override
                public void registerCallback(ICallBack cb) throws RemoteException {
                    if(cb != null) {
                        mCallbacks.register(cb);
                    }
                }
                @Override
                public void unregisterCallback(ICallBack cb) throws RemoteException {
                    if(cb != null) {
                        mCallbacks.unregister(cb);
                    }
                }
    
                @Override
                public void startDownload() throws RemoteException {
                    Log.d("","startDownLoad() inBinder-->");
                    new Thread(new Runnable() {
    
                        public void run() {
                            while(progress < MAX_PROGRESS){
                                progress += 5;
                                Log.d("","startDownLoad() run-->");
                                //进度发生变化通知调用方
                                if(mHandler != null){
                                    //TODO
                                    mHandler.sendEmptyMessage(progress);
                                }
    
                                try {
                                    Thread.sleep(1000);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }
                            }
    
                        }
                    }).start();
                }
            };
            /** * 进度条的最大值 */
            public static final int MAX_PROGRESS = 100; 
            /** * 进度条的进度值 */
            private int progress = 0;
            /** * 更新进度的回调接口 */
            private String TAG = "UseHandlerService";
            /** * 增加get()方法，供Activity调用 * @return 下载进度 */
            public int getProgress() {
                return progress;
            }
    
            @Override 
            public void onCreate() {  
                super.onCreate();  
                //mHandler.sendEmptyMessageDelayed(0, 1000);
                Log.d(TAG, "onCreate() executed");  
            }  
            private void callBack(Message msg) {
                int N = mCallbacks.beginBroadcast();
                try {
                    for (int i = 0; i < N; i++) {
                        Log.d("","mCallbacks -->progress"+msg.what);
                        mCallbacks.getBroadcastItem(i).showResult(msg.what);
                    }
                } catch (RemoteException e) {
                      Log.e(TAG, "", e);
                }
                mCallbacks.finishBroadcast();
            }
    
            private Handler mHandler = new Handler() {
    
                      @Override
                      public void handleMessage(Message msg) {
                           callBack(msg);
                           super.handleMessage(msg);
                      }
                };
            @Override 
            public int onStartCommand(Intent intent, int flags, int startId) {  
                Log.d(TAG, "onStartCommand() executed");  
                return super.onStartCommand(intent, flags, startId);  
            }  
    
            @Override 
            public void onDestroy() {  
                super.onDestroy();  
                Log.d(TAG, "onDestroy() executed");  
            }  
            /** * 返回一个Binder对象 */
            @Override
            public IBinder onBind(Intent intent) {
                return mBinder;
            }
    
    
        }
    还有两个AIDL文件
    package com.banking.hello;
    
    interface ICallBack {
        void showResult(int result);
    } 
    
    package com.banking.hello;
    import com.banking.hello.ICallBack;
    interface MyAIDLService {
        void registerCallback(ICallBack cb);
        void unregisterCallback(ICallBack cb);
        void startDownload();
    }

这种方式，无论Service是否是remote，都可以实现高效率通讯。

（3）第三种通过Receiver非常简单，就不上代码了。  
sendBroadCast,然后在Activity中注册一个相对应的内部receiver接受就可以了.