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Service学习笔记02-实战 startService 与bindService
2022-06-11 17:25:00 【双木青橙】
启动服务的两种方式
最常见启动Service的两种方式是startService 和bindService,他们之间最主要的区别可参考startService与bindService的区别
启动服务
通过绑定服务的方式可以在客户端获取对应Service的引用，从而完成与Service的交互。主要过程如下图所示：
- 首先，在继承Service的自定义服务中新建一个继承自IBinder的内部类，在IBinder中获取myService的引用
- 在服务的onBinder()方法中将Service中的IBinder对象注入（这个方法会在绑定服务成功的时候被调用，客户端可以通过这个方法获得IBinder对象，进而获取Service的引用）
- 在客户端声明一个ServiceConnection 对象，在ServiceConnection对象的onServiceContected() (这个方法就是在绑定服务成功的时候调用的)可以获得服务中的IBinder对象
- 通过获得的IBinder对象获取Service引用，可以获取Service中的数据和方法
代码实战
首先，我们先定义一个TestService，增加myBinder的内部类，在里面通过一个public类返回TestService 对象，然后重写onBind方法将Binder类返回给客户端，这是必要的一步，这样客户端就可以通过bind方式获取到我们的Service
public class TestService extends Service {
private static final String TAG = "TestService";
private static final Random generator = new Random();
//通过binder实现调用client与Service之间的通信
private MyBinder binder;
//要想自己的Service 支持bindService的启动方式，就必须在Service的OnBind方法中返回一个IBinder类型的实例
@Nullable
@Override
public IBinder onBind(Intent intent) {
Log.i(TAG, "TestService -> onBind,Thread:" + Thread.currentThread().getName());
return binder;
}
@Override
public boolean onUnbind(Intent intent) {
Log.i(TAG, "TestService -> onUnbind,Thread:" + intent.getStringExtra("from"));
return false;
}
public class MyBinder extends Binder {
public TestService getService() {
return TestService.this;
}
}
@Override
public void onCreate() {
Log.i(TAG, "TestService -> onCreate,Thread:" + Thread.currentThread().getName());
super.onCreate();
binder=new MyBinder();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "TestService -> onStartCommand,StartId: " + startId + "Thread:" + Thread.currentThread().getName());
return START_NOT_STICKY;
}
@Override
public void onDestroy() {
Log.i(TAG, "TestService -> onDestroy,Thread:" + Thread.currentThread().getName());
super.onDestroy();
}
//Service 暴露出去供client调用的公共方法
public int getRandomNumber() {
return generator.nextInt();
}
}
然后在Activity当中通过bindService来启动Service
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG="MainActivity";
private TestService service=null;
private boolean isBound=false;
private ServiceConnection connection=new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder binder) {
isBound=true;
TestService.MyBinder myBinder=(TestService.MyBinder)binder;
service= myBinder.getService();
Log.i(TAG,"MainActivity onServiceConnected");
int num=service.getRandomNumber();
Log.i(TAG,"MainActivity 中调用TestService的getRandomNumber方法，结果："+num);
}
@Override
public void onServiceDisconnected(ComponentName name) {
isBound=false;
Log.i(TAG,"MainActivity onServiceDisconnected");
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i(TAG,"MainActivity -> onCreate,Thread:"+Thread.currentThread().getName());
Button bindServiceButton=(Button)findViewById(R.id.btnBindService);
bindServiceButton.setOnClickListener(this);
}
@Override
public void onClick(View v) {
Log.i(TAG,"onClick has into");
if(v.getId()==R.id.btnBindService){
Intent intent=new Intent(this,TestService.class);
intent.putExtra("from","ActivityA");
Log.i(TAG,"MainActivity 执行 bindService");
bindService(intent,connection,BIND_AUTO_CREATE);
}else if(v.getId()==R.id.btnUnBindService){
if(isBound){
Log.i(TAG,"MainActivity 执行 unBindService");
unbindService(connection);
}
}
}
}
在MainActivity 当中先是创建一个实现了ServiceConnection 的成员变量connection,里面主要需要重写onServiceConnected方法，在里面去创建IBinder 对象，并且获取Serivice对象
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG="MainActivity";
private TestService service=null;
private boolean isBound=false;
private ServiceConnection connection=new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder binder) {
isBound=true;
TestService.MyBinder myBinder=(TestService.MyBinder)binder;
service= myBinder.getService();
Log.i(TAG,"MainActivity onServiceConnected");
int num=service.getRandomNumber();
Log.i(TAG,"MainActivity 中调用TestService的getRandomNumber方法，结果："+num);
}
@Override
public void onServiceDisconnected(ComponentName name) {
isBound=false;
Log.i(TAG,"MainActivity onServiceDisconnected");
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i(TAG,"MainActivity -> onCreate,Thread:"+Thread.currentThread().getName());
Button bindServiceButton=(Button)findViewById(R.id.btnBindService);
bindServiceButton.setOnClickListener(this);
Button unBindServiceButton=(Button)findViewById(R.id.btnUnBindService);
unBindServiceButton.setOnClickListener(this);
Button startActivityButton=(Button)findViewById(R.id.btnStartActivity);
startActivityButton.setOnClickListener(this);
Button coastRandomNumButton=(Button)findViewById(R.id.btnCoastRandomNum);
coastRandomNumButton.setOnClickListener(this);
}
@Override
public void onClick(View v) {
Log.i(TAG,"onClick has into");
if(v.getId()==R.id.btnBindService){
Intent intent=new Intent(this,TestService.class);
intent.putExtra("from","ActivityA");
Log.i(TAG,"MainActivity 执行 bindService");
bindService(intent,connection,BIND_AUTO_CREATE);
}else if(v.getId()==R.id.btnUnBindService){
if(isBound){
Log.i(TAG,"MainActivity 执行 unBindService");
unbindService(connection);
}
}else if(v.getId()==R.id.btnStartActivity){
Intent intent=new Intent(this,ActivityB.class);
Log.i(TAG,"MainActivity 启动ActivityB");
startActivity(intent);
}else if(v.getId()==R.id.btnFinish){
Log.i(TAG,"MainActivity 执行 finish");
this.finish();
}else if(v.getId()==R.id.btnCoastRandomNum){
Log.i(TAG,"MainActivity 执行 coastRandom");
Log.i(TAG,"random num :"+service.getRandomNumber());
}
}
@Override
protected void onDestroy() {
Log.i(TAG,"MainActivity -> onDestroy");
super.onDestroy();
}
}
- 问题1：在同一个Activity 重新执行bindService方法会如何？
重新执行ServiceConnection的onServiceConnected方法 - 问题2： bindService 或者unBindService 不成对出现会如何？
经过验证：重复执行bindService 方法只会执行一次Service的onBind 和onCreate 方法，bindService内部做了单例机制，但是如果多次执行unBindService方法会直接抛异常java.lang.IllegalArgumentException: Service not registered - 问题3：为什么已经执行了unBindService方法还是可以引用绑定service 的方法？
问题3 从而引起来是否存在内存泄漏的问题，通过查看
参考资料
https://blog.csdn.net/qq_33718648/article/details/79880105
https://blog.csdn.net/oudetu/article/details/79279596
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