gitHub:https://github.com/Gong-Shijie/ServiceDemo
服务Service
服务有两种启动方式：
- startService（）方式开始的服务
- bindService（）方式开启的服务
LivaData(Demo中使用到)依赖：
implementation "android.arch.lifecycle:extensions:1.1.1"
implementation "android.arch.lifecycle:viewmodel:1.1.1"
implementation "android.arch.lifecycle:livedata:1.1.1"
启动和特性
服务仍然是运行在主线程，两种服务有着不同的生命周期，也可以搭配一起使用。
两种方法都可以实现数据从活动到服务，通过在intent添加数据，可以在服务内从intent内取出数据。
//在Intent内添加数据就可以在服务内从Intent取出
startService(serviceIntent);
bindService(serviceIntent,serviceConnection,BIND_AUTO_CREATE);
在服务内获取来自intent的数据
//Bind方式启动服务时候调用，返回IBinder类型的接口供活动调用
@Override
public IBinder onBind(Intent intent) {
// intent即可取出携带数据
Log.i("gong","sevice bind");
return randomNumBinder;
}
//start方式开始服务时候会调用，如果处理耗时任务需要new线程
//startID每一次开启一个服务，都会有不同的startID
//在开启服务时候可以在intent填写数据实现交互
@Override
public int onStartCommand(Intent intent, int flags, final int startId) {
new Thread(new Runnable() {
@Override
public void run() {
Log.i("gong","startID: "+startId);
startRandomNumberGenerator();
}
}).start();
return START_STICKY;
}
start方式启动的服务
该方式的特点是和活动之间没有很强的交互性，可以利用LiveData增加数据交互性。
该种方式会调用onStartConmmand（），在该方法内我们实现需要进行的后台服务操作逻辑。
该函数的返回值的类型有三种，适用于不同类型的需求。
官方文档中的介绍
如果在服务中开启了线程，注意在服务Desdroy后，线程不会自动终止，需要自己实现在服务销毁后终止线程。线程会在执行run后终止。
bind方式启动的服务
该方式通过Binder机制，可以实现活动和服务的交互，这种交互很强，包括了数据上的交互和对服务行为上的控制。完全可以通过Binder获得Service实例从而控制调用Service内的方法。
bindService的几种类型和实现
- Local binding指在应用进程内进行bind
- Remote binding指跨进程实现的bind
注意跨进程通信即（IPC）涉及的重要概念： - IBinder接口是用来交互的桥梁
- Messenger继承自Binder也是实现IPC的一种方法
- AIDL也是用于实现IPC
local binding
remote binding
//Bind方式启动服务时候调用，返回IBinder类型的接口供活动调用
@Override
public IBinder onBind(Intent intent) {
Log.i("gong","sevice bind");
return randomNumBinder;
}
//构造返回的接口传递Service实例
class RandomNumBinder extends Binder{
MyService getService(){
return MyService.this;
}
}
绑定端代码
serviceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
randomNumBinder = (MyService.RandomNumBinder) service;
myService = randomNumBinder.getService();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
bindService(serviceIntent,serviceConnection,BIND_AUTO_CREATE);
服务service生命周期
生命周期
总结
需求选择启动方式
根据具体需要来启动Service，建立service后，可以理解为客户端和服务端。
- 如果只是需要进行数据上的交互，建议start方式+ LiveData 即可保证service内的数据通过Livedata可以在活动中获取。
- 如果还需要对服务进行行为控制，强交互，比如控制服务内的函数的调用，那么就需要我使用bindService方式启动服务，还可以搭配start方式后bind根据具体需求。
生命周期的问题：
- 结束服务：其他组件调用stopService（）或者 服务内自行调用stopself（）
- bind的service只有unbind后才可以调用stopservice来结束
- 可以开启多个服务，调用一次stopService即可结束所有服务
- bind也可以直接开启服务当所有bind的组件unbind后service就会销毁
- 如果需要启动多个service可以使用官方文档推荐的方法使用Handler机制来处理
public class HelloService extends Service {
private Looper mServiceLooper;
private ServiceHandler mServiceHandler;
// Handler that receives messages from the thread
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
// Normally we would do some work here, like download a file.
// For our sample, we just sleep for 5 seconds.
long endTime = System.currentTimeMillis() + 5*1000;
while (System.currentTimeMillis() < endTime) {
synchronized (this) {
try {
wait(endTime - System.currentTimeMillis());
} catch (Exception e) {
}
}
}
// Stop the service using the startId, so that we don't stop
// the service in the middle of handling another job
stopSelf(msg.arg1);
}
}
@Override
public void onCreate() {
// Start up the thread running the service. Note that we create a
// separate thread because the service normally runs in the process's
// main thread, which we don't want to block. We also make it
// background priority so CPU-intensive work will not disrupt our UI.
HandlerThread thread = new HandlerThread("ServiceStartArguments",
Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
// Get the HandlerThread's Looper and use it for our Handler
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
// For each start request, send a message to start a job and deliver the
// start ID so we know which request we're stopping when we finish the job
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
mServiceHandler.sendMessage(msg);
// If we get killed, after returning from here, restart
return START_STICKY;
}
@Override
public IBinder onBind(Intent intent) {
// We don't provide binding, so return null
return null;
}
@Override
public void onDestroy() {
Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
}
}
使用Handler机制细思极妙，官方文档需要经常查看。
MyServiceDemo代码
MyService.java
public class MyService extends Service {
private static final int MAX = 100;
private static final int MIN = 0;
private MutableLiveData<String> mutableLiveData = new MutableLiveData<>();
private String logStr = new String();
private int mRandomNumber=0;
private Boolean mIsRandomGeneratorOn = true;
private IBinder randomNumBinder = new RandomNumBinder();
//Bind方式启动服务时候调用，返回IBinder类型的接口供活动调用
@Override
public IBinder onBind(Intent intent) {
Log.i("gong","sevice bind");
return randomNumBinder;
}
//构造返回的接口传递Service实例
class RandomNumBinder extends Binder{
MyService getService(){
return MyService.this;
}
}
@Override
public boolean onUnbind(Intent intent) {
Log.i("gong","sevice unbind!");
return super.onUnbind(intent);
}
//start方式开始服务时候会调用，如果处理耗时任务需要new线程
//startID每一次开启一个服务，都会有不同的startID
//在开启服务时候可以在intent填写数据实现交互
@Override
public int onStartCommand(Intent intent, int flags, final int startId) {
new Thread(new Runnable() {
@Override
public void run() {
Log.i("gong","startID: "+startId);
startRandomNumberGenerator();
}
}).start();
return START_STICKY;
}
private void startRandomNumberGenerator(){
while (mIsRandomGeneratorOn){
try{
Thread.sleep(1000);
if(mIsRandomGeneratorOn){
mRandomNumber =new Random().nextInt(MAX)+MIN;
logStr = logStr + mRandomNumber+" ";
mutableLiveData.postValue(logStr);
Log.i("gong",""+mRandomNumber);
}
}catch (InterruptedException e){
}
}
}
@Override
public void onCreate() {
super.onCreate();
Log.i("gong","Service create!");
logStr = "";
mIsRandomGeneratorOn = true;
}
//销毁服务的时候记住关闭线程，线程在执行run内方法后终止
@Override
public void onDestroy() {
super.onDestroy();
Log.i("gong","Service destroy!");
mIsRandomGeneratorOn = false;
}
public int getmRandomNumber() {
return mRandomNumber;
}
//提供livadata来更新数据到活动界面
public MutableLiveData<String> getMutableLiveData() {
return mutableLiveData;
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private TextView textView ;
private TextView showLog ;
private Button startService ;
private Button bindService ;
private Button unBindService ;
private Button stopService ;
private Button getnumber;
Intent serviceIntent ;
private MyService.RandomNumBinder randomNumBinder;
private MyService myService;
ServiceConnection serviceConnection;
Boolean isBindService =false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
iniview();
serviceIntent = new Intent(this,MyService.class);
}
@Override
public void onClick(View v) {
switch(v.getId()){
case R.id.startService:
startService(serviceIntent);
break;
case R.id.bindService:
bindmService();
break;
case R.id.unBindService:
unbindmService();
break;
case R.id.stopService:
stopService(serviceIntent);
break;
case R.id.getnumber:
setObserver();
setmText(myService.getmRandomNumber());
break;
}
}
private void setmText(int getmRandomNumber) {
textView.setText(getmRandomNumber+"");
}
public void iniview(){
textView = findViewById(R.id.textView);
showLog = findViewById(R.id.showLog);
startService = findViewById(R.id.startService);
bindService = findViewById(R.id.bindService);
unBindService = findViewById(R.id.unBindService);
stopService = findViewById(R.id.stopService);
getnumber = findViewById(R.id.getnumber);
startService.setOnClickListener(this);
bindService.setOnClickListener(this);
unBindService.setOnClickListener(this);
stopService.setOnClickListener(this);
getnumber.setOnClickListener(this);
}
//bind service获取调动服务的接口myService可以来和Service交互
public void bindmService(){
serviceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
randomNumBinder = (MyService.RandomNumBinder) service;
myService = randomNumBinder.getService();
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
bindService(serviceIntent,serviceConnection,BIND_AUTO_CREATE);
isBindService = true;
}
public void unbindmService(){
if(isBindService == true){
unbindService(serviceConnection);
}
isBindService = false;
}
//根据Service内的Livedata来更新数据显示到界面
public void setObserver(){
myService.getMutableLiveData().observe(this, new Observer<String>() {
@Override
public void onChanged(String s) {
showLog.setText(s);
}
});
}
}
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