詳解Android中的Service

public class ExampleService extends Service{
  @Override
  public IBinder onBind(Intent intent) {
    return null;
  }
  @Override
  public void onCreate() {
    super.onCreate();
  }
}

<service android:name=".ExampleService" android:enabled="true" android:permission="exam02.chenqian.com.servicedemo"></service>

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

// 顯示啟動(dòng)ExampleService
Intent intent = new Intent(this,ExampleService.class);
// 啟動(dòng)ExampleService
startService(intent);

  @Override
  public void onDestroy() {
    Log.i("ServiceState","------------------>Destroy");
    super.onDestroy();
  }

//顯示關(guān)閉Service
Intent serviceIntent = new Intent(MainActivity.this,MyService.class);
//關(guān)閉Service
stopService(serviceIntent);

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:id="@+id/activity_main"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  tools:context="demo.chenqian.com.androidserverdemo.MainActivity">
  <!-- 開啟Service -->
  <Button
    android:id="@+id/btnStartService"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    android:text="@string/startService"/>
  <!-- 關(guān)閉Service -->
  <Button
    android:id="@+id/btnStopService"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    android:text="@string/stopService"/>
  <!-- 綁定Service -->
  <Button
    android:id="@+id/btnBindService"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    android:text="@string/bindService"/>
  <!-- 解綁Service -->
  <Button
    android:id="@+id/btnUnbindService"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="20dp"
    android:text="@string/unbindService"/>
</LinearLayout>

package demo.chenqian.com.androidserverdemo;
import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;
public class MyService extends Service{
　　/* 1、在下方我們定義了內(nèi)部類MyBinder，這就是為什么我們這里現(xiàn)在能定義binder的原因
　　　　2、這里我們定義binder成員變量的目的是為了在下文的MainActivity中實(shí)現(xiàn)轉(zhuǎn)型*/
  private MyBinder binder = new MyBinder();
  @Override
  public void onCreate() {
    Log.d("ServiceInfo","創(chuàng)建成功");
    super.onCreate();
  }
  @Nullable
  @Override
  public IBinder onBind(Intent intent) {
    Log.d("ServiceInfo","綁定成功");
    return null;
  }
  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    Log.d("ServiceInfo","開始執(zhí)行");
    return super.onStartCommand(intent, flags, startId);
  }
  @Override
  public boolean onUnbind(Intent intent) {
    Log.d("ServiceInfo","解綁成功");
    return super.onUnbind(intent);
  }
  @Override
  public void onDestroy() {
    Log.d("ServiceInfo","銷毀成功");
    super.onDestroy();
  }

public void 
onServiceConnected(ComponentName
   name, IBinder service)，注意這里的service是IBinder類型的，我們下方獲取MyService將會(huì)用到他*/
  class MyBinder extends Binder{
    MyService getService(){
      Log.d("ServiceInfo","成功得到當(dāng)前服務(wù)實(shí)例");
      return MyService.this;
    }
  }
}

package demo.chenqian.com.androidserverdemo;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Binder;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
  private Context mContext;
  private Button btnStartService;
  private Button btnStopService;
  private Button btnBindService;
  private Button btnUnbindService;
  private MyService myService;
  private Intent serviceIntent;
  private boolean isBond;
　　/*isBond該變量用來(lái)標(biāo)識(shí)當(dāng)前的Activity與Service是否正在綁定，因?yàn)槿绻贿M(jìn)行標(biāo)識(shí)，如果Activity沒有
　　 與Service進(jìn)行綁定，而執(zhí)行解除綁定的操作，會(huì)照成錯(cuò)誤或拋出異常，因?yàn)楫?dāng)接觸綁定時(shí)Android不允許綁定為null */
  /*注意，這里我們新建了一個(gè)connection并重寫了相關(guān)方法，為什么我們要新建這個(gè)連接，那是因?yàn)樵谙路降慕壎ê徒饨?   方法即bind和unbind需要一個(gè)connection。我們復(fù)寫相關(guān)方法一是為了方便觀察，另一個(gè)是為了在連接成功或失去關(guān)閉
   連接時(shí)，執(zhí)行相關(guān)的自定義的任務(wù)或操作*/
  private ServiceConnection connection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      Log.d("ServiceState","連接成功");
      myService = ((MyService.MyBinder)service).getService();
    }
    @Override
    public void onServiceDisconnected(ComponentName name) {
      Log.d("ServiceState","關(guān)閉連接");
　　　　　　　//當(dāng)連接指向?qū)嵗秊閚ull沒有指引的連接的實(shí)例時(shí)，好被虛擬機(jī)回收，降低占用的資源
      myService = null;
    }
  };
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //初始化數(shù)據(jù)
    mContext = this;
    isBond = false;
    //引入需要用到的組件
    btnStartService = (Button) findViewById(R.id.btnStartService);
    btnStopService = (Button) findViewById(R.id.btnStopService);
    btnBindService = (Button) findViewById(R.id.btnBindService);
    btnUnbindService = (Button) findViewById(R.id.btnUnbindService);
    //為按鈕添加單擊事件
    btnStartService.setOnClickListener(this);
    btnStopService.setOnClickListener(this);
    btnBindService.setOnClickListener(this);
    btnUnbindService.setOnClickListener(this);
  }
  @Override
  protected void onStart() {
    serviceIntent = new Intent(this,MyService.class);
    super.onStart();
  }
  @Override
  public void onClick(View v) {
    switch (v.getId()){
      case R.id.btnStartService:
        //開啟Service
        startService(serviceIntent);
        break;
      case R.id.btnStopService:
        //關(guān)閉Service
        stopService(serviceIntent);
        break;
      case R.id.btnBindService:
        //綁定Service
        isBond = bindService(serviceIntent,connection,Context.BIND_AUTO_CREATE);
        break;
      case R.id.btnUnbindService:
        //解綁Service，當(dāng)連接為null是解綁會(huì)報(bào)錯(cuò)
        if(isBond){
          unbindService(connection);
          //如果解綁成功，則修改連接標(biāo)識(shí)為假
          isBond = false;
        }
        break;
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="demo.chenqian.com.androidserverdemo">
  <application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
    <service android:name=".MyService" android:enabled="true" android:permission="demo.chenqian.com.androidserverdemo"></service>
  </application>
</manifest>