A solution for sending messages for real-time chat or background tasks in Android.

A solution for sending messages for real-time chat or background tasks in Android.

There may be a hidden Bug in instant chat. This Bug is related to the network speed and performance of the mobile phone. For example, in instant chat, if you send a message, your network condition is not very good, at this time, the message you sent is always in the sending status. If you don't want to read it, you can quit. When Activity or Fragment is destroyed, the message is forcibly GC, to solve this problem, we can use IntentService. What is IntentService?

/*IntentService is a base class for {@link Service}s that handle asynchronous requests (expressed as {@link Intent}s) on demand. Clients send requests through {@link android.content.Context#startService(Intent)} calls; the service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work.*/

It can be seen from this explanation that it is an asynchronous service without worrying about its own lifecycle. therefore, we can use it to send messages. After the message is sent, we must notify the UI to update the UI. At this time, we need to use broadcast for convenience. we can write an IntentService as follows:

package com.softtanck.intentservicedemo.service;import android.app.IntentService;import android.content.Context;import android.content.Intent;import com.softtanck.intentservicedemo.MainActivity;/** * Created by winterfell on 11/17/2015. */public class UpLoadImgService extends IntentService {    public UpLoadImgService() {        super("ceshi");    }    /**     * Creates an IntentService.  Invoked by your subclass's constructor.     *     * @param name Used to name the worker thread, important only for debugging.     */    public UpLoadImgService(String name) {        super(name);    }    public static void startUploadImg(Context context, String path) {        Intent intent = new Intent(context, UpLoadImgService.class);        intent.setAction(MainActivity.UPLOAD_IMG);        intent.putExtra(MainActivity.EXTRA_IMG_PATH, path);        context.startService(intent);    }    @Override    protected void onHandleIntent(Intent intent) {        if (null != intent) {            String action = intent.getAction();            if (action.equals(MainActivity.UPLOAD_IMG)) {                //UpLoad file                uploadImg(intent.getStringExtra(MainActivity.EXTRA_IMG_PATH));            }        }    }    private void uploadImg(String path) {        try {            Thread.sleep(2000);            Intent intent = new Intent(MainActivity.UPLOAD_IMG);            intent.putExtra(MainActivity.EXTRA_IMG_PATH, path);            sendBroadcast(intent);        } catch (InterruptedException e) {            e.printStackTrace();        }    }}

Call the following code as needed:

UpLoadImgService.startUploadImg(MainActivity.this, "/sdcard/cache/com.softtanck.intentservice/1.png");

In addition, if IntentService is an inherited Service, how does it Implement Asynchronous threads .? Let's take a rough look at its source code:

/** Copyright (C) 2008 The Android Open Source Project ** Licensed under the Apache License, Version 2.0 (the "License "); * you may not use this file before t in compliance with the License. * You may be obtain a copy of the License at ** http://www.apache.org/licenses/LICENSE-2.0 ** Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "as is" BASIS, * without warranties or conditions of any kind, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android. app; import android. annotation. workerThread; import android. content. intent; import android. OS. handler; import android. OS. handlerThread; import android. OS. IBinder; import android. OS. logoff; import android. OS. message;/*** IntentService is a base class for {@ link Service} s that handle asynchronous * requests (expressed as {@ link Intent} s) on demand. clients send requests * through {@ link android. content. context # startService (Intent)} CILS; the * service is started as needed, handles each Intent in turn using a worker * thread, and stops itself when it runs out of work. **
This "work queue processor" pattern is commonly used to offload tasks * from an application's main thread. the IntentService class exists to * simplify this pattern and take care of the mechanic. to use it, extend * IntentService and implement {@ link # onHandleIntent (Intent )}. intentService * will receive the Intents, launch a worker thread, and stop the service as * appropriate. **
All requests are handled on a single worker thread -- they may take as * long as necessary (and will not block the application's main loop ), but * only one request will be processed at a time. * ** Developer Guides *
For a detailed discussion about how to create services, read the * Services developer guide.
* ** @ See android. OS. asyncTask */public abstract class IntentService extends Service {private volatile low.mservicelow.private volatile ServiceHandler mServiceHandler; private String mName; private boolean mRedelivery; private final class ServiceHandler extends Handler {public ServiceHandler (Looper loler) {super (looper) ;}@ Override public void handleMessage (Message msg) {onHandleIntent (Intent) msg. obj); stopSelf (msg. arg1) ;}}/*** Creates an IntentService. invoked by your subclass's constructor. ** @ param name Used to name the worker thread, important only for debugging. */public IntentService (String name) {super (); mName = name;}/*** Sets intent redelivery preferences. usually called from the constructor * with your preferred semantics. **
If enabled is true, * {@ link # onStartCommand (Intent, int, int)} will return * {@ link Service # START_REDELIVER_INTENT }, so if this process dies before * {@ link # onHandleIntent (Intent)} returns, the process will be restarted * and the intent redelivered. if multiple Intents have been sent, only * the most recent one is guaranteed to be redelivered. **
If enabled is false (the default), * {@ link # onStartCommand (Intent, int, int)} will return * {@ link Service # START_NOT_STICKY}, and if the process dies, the Intent * dies along with it. */public void setIntentRedelivery (boolean enabled) {mRedelivery = enabled;} @ Override public void onCreate () {// TODO: it wocould be nice to have an option to hold a partial wakelock // during processing, and to ha Ve a static startService (Context, Intent) // method that wowould launch the service & hand off a wakelock. super. onCreate (); HandlerThread thread = new HandlerThread ("IntentService [" + mName + "]"); // creates a HandlerThread. start (); mserviceloading = thread. getLooper (); mServiceHandler = new ServiceHandler (mserviceloader) ;}@ Override public void onStart (Intent intent, int startId) {Message msg = MServiceHandler. obtainMessage (); msg. arg1 = startId; msg. obj = intent; mServiceHandler. sendMessage (msg);}/*** You shocould not override this method for your IntentService. instead, * override {@ link # onHandleIntent}, which the system CILS when the IntentService * es a start request. * @ see android. app. service # onStartCommand */@ Override public int onStartCommand (Intent intent, int flags, I Nt startId) {onStart (intent, startId); return mRedelivery? START_REDELIVER_INTENT: START_NOT_STICKY;} @ Override public void onDestroy () {mserviceloading. quit ();}/*** Unless you provide binding for your service, you don't need to implement this * method, because the default implementation returns null. * @ see android. app. service # onBind */@ Override public IBinder onBind (Intent intent) {return null;}/*** This method is invoked on the worker thread with a request to process. * Only one Intent is processed at a time, but the processing happens on a * worker thread that runs independently from other application logic. * So, if this code takes a long time, it will hold up other requests to * the same IntentService, but it will not hold up anything else. * When all requests have been handled, the IntentService stops itself, * so you shoshould not call {@ link # stopSelf }. ** @ param intent The value passed to {@ link * android. content. context # startService (Intent )}. * // @ WorkerThread protected abstract void onHandleIntent (Intent intent );}

From the source code, we can see that a HandlerThread is initialized during OnCreat, and then a Handler communication is established through logoff Loop from the message queue, in HandlerMessage, an abstract method is called to inherit the method to be implemented in IntentService. This method is in the thread, so you do not need to start the thread again. its lifecycle is also managed by the Service.