一、先簡單首先回顧一下Service的一些問題

1、為什么使用Service？

答：對于一些需要長時間才可執行完畢的操作放在Activity里不太合適，因為Activity關閉后導致操作不能再繼續，但后臺服務可以持續運行。

2、bindService和startService的區別？

答：１)兩者創建的service的生命周期不同

２)startService啟動的服務不能返回service的實例，bindService的可以

3、為什么不直接使用new XxxxService來創建服務？

答：在執行startService或者bindService時，android會把會啟動的服務進行記錄(未做深入研究)，以確保擁有后臺服務的進程具有較高的優先級，所以要使用startService或者bindService來創建服務。new XxxxService只是創建了一個服務類的實例，而不是一個服務。

4、為什么onServiceDisconnected一直未被調用到？

答：unbindService并不會導致onServieDisconnected被調用，只有在服務被系統銷毀的時候才會被調用。

5、可以在一個應用中使用startService跨進程啟動另外一個進程的服務嗎？

答：可以，需要設置目標進程的包名，可以使用如下代碼或者setPackage(未測試)

Java

Intent intent = new Intent();

intent.setClassName("com.zht.car.testservice", "com.zht.car.testservice.MyTestService");

startService(intent);

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Intentintent=newIntent();

intent.setClassName("com.zht.car.testservice","com.zht.car.testservice.MyTestService");

startService(intent);

6、既然可以跨進程調用startService那為什么還要使用aidl？

答：startService只能啟動另外進程的服務，最多還可以通過intent傳入一些參數，但是不能從對方進程返回數據，所以如果跨進程通訊aidl還是很有必要的。

二、bindService的開發步驟簡述

1、創建一個Service，比如本例中為MyTestService

2、在Service中定義一個Binder的子類MyServiceBinder，后面用來返回MyTestService的實例(見一、３為什么不能直接new MyTestService() )

3、定義并實例化一個MyServiceBinder對象，用來在Service的onBind函數中返回給調用者

4、在Service的onBind函數中返回MyServiceBinder實例對象，android sdk會通過各種調用將這個對象傳到ServiceConnection的onServiceConnected

5、在Activity中定義一個MyTestService對象

6、在Activity中執行bindService

7、在Activity中實例化一個ServiceConnection對象

8、在ServiceConnection對象的onServiceConnected回調函數中，將參數中的IBinder對象強制轉換為Service中定義的Binder子類(MyServiceBinder)對象

9、通過強制Binder子類對象的方法獲取MyTestService實例，至此就得到這個Service的實例了

10、綁定狀態的控制，通過一個boolean類型的變量來控制，以及其他的回調函數的設置

三、時序圖

四、代碼

１、Service的代碼

package com.zht.car.testservice;

import android.app.Service;

import android.content.Intent;

import android.os.Binder;

import android.os.Handler;

import android.os.IBinder;

public class MyTestService extends Service {

private MyServiceBinder mMyServiceBinder = new MyServiceBinder();

private OnWeightChangeListener mOnWeightChangeListener;

private int mWeight = 20;

public MyTestService() {

}

@Override

public IBinder onBind(Intent intent) {

new Handler().postDelayed(new Runnable() {

@Override

public void run() {

mWeight = mWeight * 2;

if(mOnWeightChangeListener != null){

mOnWeightChangeListener.onWeightChange(mWeight);

}

}

}, 1000);

return mMyServiceBinder;

}

class MyServiceBinder extends Binder {

MyTestService getService(){

return MyTestService.this;

}

}

public int getWeight() {

return mWeight;

}

public void setOnWeightChangeListener(OnWeightChangeListener onWeightChangeListener) {

mOnWeightChangeListener = onWeightChangeListener;

}

public interface OnWeightChangeListener {

public void onWeightChange(int weight);

}

}

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packagecom.zht.car.testservice;

importandroid.app.Service;

importandroid.content.Intent;

importandroid.os.Binder;

importandroid.os.Handler;

importandroid.os.IBinder;

publicclassMyTestServiceextendsService{

privateMyServiceBindermMyServiceBinder=newMyServiceBinder();

privateOnWeightChangeListenermOnWeightChangeListener;

privateintmWeight=20;

publicMyTestService(){

}

@Override

publicIBinderonBind(Intentintent){

newHandler().postDelayed(newRunnable(){

@Override

publicvoidrun(){

mWeight=mWeight *2;

if(mOnWeightChangeListener!=null){

mOnWeightChangeListener.onWeightChange(mWeight);

}

}

},1000);

returnmMyServiceBinder;

}

classMyServiceBinderextendsBinder{

MyTestServicegetService(){

returnMyTestService.this;

}

}

publicintgetWeight(){

returnmWeight;

}

publicvoidsetOnWeightChangeListener(OnWeightChangeListeneronWeightChangeListener){

mOnWeightChangeListener=onWeightChangeListener;

}

publicinterfaceOnWeightChangeListener{

publicvoidonWeightChange(intweight);

}

}

２、Activity代碼

package com.zht.car.testservice;

import android.app.Service;

import android.content.ComponentName;

import android.content.Intent;

import android.content.ServiceConnection;

import android.os.IBinder;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

public class MainActivity extends AppCompatActivity {

private MyTestService mMyTestService;

private String LOG_TAG = "MainActivity";

private boolean mServiceBinded = false;

private ServiceConnection mServiceConnection = new ServiceConnection() {

@Override

public void onServiceConnected(ComponentName name, IBinder service) {

MyTestService.MyServiceBinder binder = (MyTestService.MyServiceBinder) service;

mMyTestService = binder.getService();

mMyTestService.setOnWeightChangeListener(new MyTestService.OnWeightChangeListener() {

@Override

public void onWeightChange(int weight) {

Log.d(LOG_TAG, "Weight changed: " + mMyTestService.getWeight());

}

});

mServiceBinded = true;

Log.d(LOG_TAG, "Service connected.");

Log.d(LOG_TAG, "weight: " + mMyTestService.getWeight());

}

@Override

public void onServiceDisconnected(ComponentName name) {

Log.d(LOG_TAG, "Service disconnected.");

mServiceBinded = false;

}

};

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

protected void onDestroy() {

if(mServiceBinded) {

unbindService(mServiceConnection);

}

super.onDestroy();

}

public void onBindServiceClick(View view) {

if(mServiceBinded){

return;

}

Intent intent = new Intent(this, MyTestService.class);

bindService(intent, mServiceConnection, Service.BIND_AUTO_CREATE);

}

public void onUnbindServiceClick(View view) {

if(!mServiceBinded) {

return;

}

unbindService(mServiceConnection);

mServiceBinded = false;

}

}

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packagecom.zht.car.testservice;

importandroid.app.Service;

importandroid.content.ComponentName;

importandroid.content.Intent;

importandroid.content.ServiceConnection;

importandroid.os.IBinder;

importandroid.support.v7.app.AppCompatActivity;

importandroid.os.Bundle;

importandroid.util.Log;

importandroid.view.View;

publicclassMainActivityextendsAppCompatActivity{

privateMyTestServicemMyTestService;

privateStringLOG_TAG="MainActivity";

privatebooleanmServiceBinded=false;

privateServiceConnectionmServiceConnection=newServiceConnection(){

@Override

publicvoidonServiceConnected(ComponentNamename,IBinderservice){

MyTestService.MyServiceBinderbinder=(MyTestService.MyServiceBinder)service;

mMyTestService=binder.getService();

mMyTestService.setOnWeightChangeListener(newMyTestService.OnWeightChangeListener(){

@Override

publicvoidonWeightChange(intweight){

Log.d(LOG_TAG,"Weight changed: "+mMyTestService.getWeight());

}

});

mServiceBinded=true;

Log.d(LOG_TAG,"Service connected.");

Log.d(LOG_TAG,"weight: "+mMyTestService.getWeight());

}

@Override

publicvoidonServiceDisconnected(ComponentNamename){

Log.d(LOG_TAG,"Service disconnected.");

mServiceBinded=false;

}

};

@Override

protectedvoidonCreate(BundlesavedInstanceState){

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

@Override

protectedvoidonDestroy(){

if(mServiceBinded){

unbindService(mServiceConnection);

}

super.onDestroy();

}

publicvoidonBindServiceClick(Viewview){

if(mServiceBinded){

return;

}

Intentintent=newIntent(this,MyTestService.class);

bindService(intent,mServiceConnection,Service.BIND_AUTO_CREATE);

}

publicvoidonUnbindServiceClick(Viewview){

if(!mServiceBinded){

return;

}

unbindService(mServiceConnection);

mServiceBinded=false;

}

}

總結

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