Android -Services 使用简介

Android Services 四大组件之一，主要用于后台长时间运行。没有界面。这里讲解两种services的启动还有AIDL通信方式。

1.startservices

a.建立继承services的类，复写方法（本地服务）

public class MyServices extends Service  {

private static final String TAG="TestTag";

@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}

@Override
public void onCreate() {
Log.i(TAG, "onCreate");
super.onCreate();
}

@Override
public void onStart(Intent intent, int startId) {
Log.i(TAG, "onStart");
super.onStart(intent, startId);
}

@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
super.onDestroy();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "onStartCommand");
return super.onStartCommand(intent, flags, startId);
}

}

b.声明AndroidManifest

<service android:name=".MyServices"/>

c.启动关闭

switch(v.getId()){
case R.id.btnStart:
startService(intent);
break;
case R.id.btnStop:
stopService(intent);
break;
}

后记：

服务生命周期：context.startService() ->onCreate()- >onStart()- >onStartCommand()->Service running ->context.stopService() ->onDestroy() ->Service stop

如果Service还没有运行，则android先调用onCreate()然后调用onStartCommand()，每次调用startService(Intent)的时候，都会调用执行onStartCommand()；
如果Service已经运行，则只调用onStartCommand()。

2.bindservices

服务链接（ServiceConnection）或直接获取Service中状态和数据信息
服务链接能够获取Service的对象，因此绑定Service的组件可以调用Service中的实现的函数
使用Service的组件通过Context.bindService()建立服务链接，通过Context.unbindService()停止服务链接
如果在绑定过程中Service没有启动，Context.bindService()会自动启动Service
同一个Service可以绑定多个服务链接，这样可以同时为多个不同的组件提供服务

a.创建BindService继承Service

public class BindService extends Service {

private static final String TAG="BindService";

private BindServiceX myBinderServiceX=new BindServiceX();
public class BindServiceX extends Binder{
public BindService getBindService() {
return BindService.this;
}
}

@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
Log.i(TAG, "onBind");
return myBinderServiceX;
}

@Override
public void onCreate() {
Log.i(TAG, "onCreate");
super.onCreate();
}

@Override
public boolean onUnbind(Intent intent) {
Log.i(TAG, "onUnbind");
return super.onUnbind(intent);
}

@Override
public void onDestroy() {
Log.i(TAG, "onDestroy");
super.onDestroy();
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "onStartCommand");
return super.onStartCommand(intent, flags, startId);
}

public void ShowLog(){
Log.i(TAG, "BindService=>ShowLog");
}

}

b.声明AndroidManifest

<service android:name=".BindService"/>

c.启动使用

public void onClick(View v) {
Intent intentBind = new Intent(MainActivity.this, BindService.class);

switch (v.getId()) {
case R.id.btnStartBindService:
bindService(intentBind, conn, Context.BIND_AUTO_CREATE);
break;
case R.id.btnStopBindService:
if (isConn) {
unbindService(conn); //不可以多次调用
isConn=false;
}
break;
}

后记：

AndroidServiceActivity绑定方法，Context.BIND_AUTO_CREATE表明只要绑定存在，就自动建立Service；同时也告知Android系统，这个Service的重要程度与调用者相同，除非考虑终止调用者，否则不要关闭这个Service。

如果service没被创建，那么调用一次onCreate(),然后调用onBind()，多次绑定时，不会多次调用onBind()。

通过unbindService()函数取消绑定Servcie时，onUnbind()函数将被调用，
如果onUnbind()函数的返回true，则表示在调用者绑定新服务时，
onRebind()函数将被调用

取消绑定仅需要使用unbindService()方法，并将ServiceConnnection传递给unbindService()方法需注意的是，unbindService()方法成功后，系统并不会调用onServiceDisconnected()，因为onServiceDisconnected()仅在意外断开绑定时才被调用

3.AIDL IPC通信 services

Android系统中，各个应用都运行在自己的进程中，进程之间一般无法直接进行通信，为了实现进程通信（interprocess communication，简称IPC），android提供了AIDL Service；

Android需要AIDL（Android Interface Definition Language）来定义远程接口，这种接口定义语言并不是一种真正的变成语言，只是定义两个进程之间的通信接口；

与Java接口相似，但是存在如下几点差异：

AIDL定义接口的源代码必须以.aidl结尾；

AIDL用到的数据类型，除了基本类型、String、List、Map、CharSequence之外，其它类型全部都需要导包，即使它们在同一个包中也需要导包；

AIDL的步骤:

a.创建AIDL文件

package com.example.zcx.servicesdemo;

// Declare any non-default types here with import statements

//interface ICat {
//    /**
//     * Demonstrates some basic types that you can use as parameters
//     * and return values in AIDL.
//     */
//    void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat,
//            double aDouble, String aString);
//}
interface ICat {
String getColor();
double getWeight();
}

b.服务端编写

public class AidlService extends Service {
String[] colors = new String[] { "红色", "黄色", "黑色" };
double[] weights = new double[] { 2.3, 3.1, 1.58 };
private String color;
private double weight;
private CatBinder catBinder;
Timer timer = new Timer();

@Override
public void onCreate() {
super.onCreate();
catBinder = new CatBinder();
timer.schedule(new TimerTask() {

@Override
public void run() {
// 随机地改变service组件内的color，weight属性的值
int rand = (int) (Math.random() * 3);
color = colors[rand];
weight = weights[rand];
System.out.println("---------" + rand);
}
}, 0, 800);
}

@Override
public IBinder onBind(Intent arg0) {
/**
* 返回CatBinder对象，在绑定本地Service情况下，
* 该catBinder会直接传给客户端的ServiceConnected对象的ServiceConnected
* ()方法的第二个参数；在绑定远程Service的情况下
* ，只将catBinder对象的代理传给客户端的ServiceConnected对象的ServiceConnected()方法的第二个参数
*/
return catBinder;
}

@Override
public void onDestroy() {
timer.cancel();
}

/**
* 继承Stub,也就是实现了ICat接口，并实现了IBinder接口
*
* @author pengcx
*
*/
public class CatBinder extends ICat.Stub {
@Override
public String getColor() throws RemoteException {
return color;
}

@Override
public double getWeight() throws RemoteException {
return weight;
}
}
}

androidmanifest:

<service android:name=".AidlService" android:process=":remote">
<intent-filter>
<action android:name="org.crazyit.aidl.AIDL_SERVICE" />
</intent-filter>
</service>

c.客户端使用

首先需要建立aidl,注意要在相同的包名下,否则报错： java.lang.SecurityException: Binder invocation to an incorrect interface

// ICat.aidl
package com.example.zcx.servicesdemo;

// Declare any non-default types here with import statements

//interface ICat {
//    /**
//     * Demonstrates some basic types that you can use as parameters
//     * and return values in AIDL.
//     */
//    void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat,
//            double aDouble, String aString);
//}
interface ICat {
String getColor();
double getWeight();
}

编写客户端：

public class MainActivity extends AppCompatActivity {

private ICat catService;
private Button getButton;
private EditText colorEditText, weightEditText;

private ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceDisconnected(ComponentName name) {
catService = null;
}

@Override
public void onServiceConnected(ComponentName name, IBinder service) {
// 获取远程Service的onBinder方法返回的对象代理
catService = ICat.Stub.asInterface(service);
Log.d("zcx","catService");
}
};
public static Intent getExplicitIntent(Context context, Intent implicitIntent) {
// Retrieve all services that can match the given intent
PackageManager pm = context.getPackageManager();
List<ResolveInfo> resolveInfo = pm.queryIntentServices(implicitIntent, 0);
// Make sure only one match was found
if (resolveInfo == null || resolveInfo.size() != 1) {
return null;
}
// Get component info and create ComponentName
ResolveInfo serviceInfo = resolveInfo.get(0);
String packageName = serviceInfo.serviceInfo.packageName;
String className = serviceInfo.serviceInfo.name;
ComponentName component = new ComponentName(packageName, className);
// Create a new intent. Use the old one for extras and such reuse
Intent explicitIntent = new Intent(implicitIntent);
// Set the component to be explicit
explicitIntent.setComponent(component);
return explicitIntent;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

getButton = (Button) findViewById(R.id.getbutton);
colorEditText = (EditText) findViewById(R.id.coloredittext);
weightEditText = (EditText) findViewById(R.id.weightedittext);

// 创建所需要绑定的Service的Intent
Intent intent = new Intent();
intent.setAction("org.crazyit.aidl.AIDL_SERVICE");
//intent.setPackage(getPackageName());
Intent eintent = new Intent(getExplicitIntent(this,intent));
Log.e("zcx","eintent = "+eintent);
// 绑定远程的服务
Log.e("zcx"," "+bindService(eintent, conn, Service.BIND_AUTO_CREATE));

getButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// 获取并显示远程service的状态
try {
colorEditText.setText(catService.getColor());
weightEditText.setText(catService.getWeight() + "");
} catch (RemoteException e) {
e.printStackTrace();
}
}
});
}

@Override
protected void onDestroy() {
super.onDestroy();
// 解除绑定
this.unbindService(conn);
}
}