定义布局文件

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<?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:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical"
              android:padding="20dp"
              tools:context=".MainActivity">
    <!--    启动服务-->
    <Button
            android:id="@+id/btn_start"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="StartService"
            android:textAllCaps="false"
            android:textSize="30sp"
            android:enabled="true"/>
    <!--    结束服务-->
    <Button
            android:id="@+id/btn_stop"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="StopService"
            android:textAllCaps="false"
            android:textSize="30sp"
            android:enabled="false"/>
    <!--    绑定服务到Activity-->
    <Button
            android:id="@+id/btn_bind"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="BindService"
            android:textAllCaps="false"
            android:textSize="30sp" />
    <!--通过BindService实现了Activity与Service的通信，然后访问Service的对应方法-->
    <Button
            android:id="@+id/btn_operate"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="OperateService"
            android:textAllCaps="false"
            android:textSize="30sp" />
    <!--和Activity解除绑定-->
    <Button
            android:id="@+id/btn_unbind"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="UnBindService"
            android:textAllCaps="false"
            android:textSize="30sp" />
    <!--    执行耗时操作-->
    <Button
            android:id="@+id/btn_intent"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="IntentService"
            android:textAllCaps="false"
            android:textSize="30sp" />
    <Button
            android:id="@+id/btn_foreground"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="ForegroundService"
            android:textAllCaps="false"
            android:textSize="30sp" />
</LinearLayout>

新建Service

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package com.example.servicetest;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {
    private static final String TAG = MyService.class.getSimpleName();
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public void onCreate() {
        Log.d(TAG, "onCreate: ThreadId"+Thread.currentThread().getId());
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand: StartId"+startId);
        Log.d(TAG, "onStartCommand: ThreadId"+Thread.currentThread().getId());
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.d(TAG, "onDestroy: ThreadId"+Thread.currentThread().getId());
        super.onDestroy();
    }
}
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package com.example.servicetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();

    private Button mBtnStart, mBtnStop;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d(TAG, "onCreate: ThreadId"+Thread.currentThread().getId());

        initView();
        initClick();
    }

    private void initClick() {
        mBtnStart.setOnClickListener((View view)->{
            mBtnStart.setEnabled(false);
            mBtnStop.setEnabled(true);
            Intent intent = new Intent(this, MyService.class);;
            startService(intent);
        });
        mBtnStop.setOnClickListener((View view)->{
            mBtnStop.setEnabled(false);
            mBtnStart.setEnabled(true);
            Intent intent = new Intent(this, MyService.class);;
            stopService(intent);
        });
    }

    private void initView() {
        mBtnStart = findViewById(R.id.btn_start);
        mBtnStop = findViewById(R.id.btn_stop);
    }
}

通过如下按钮操作

  • 点击三次StartService
  • 点击一次Stop
  • 点击一次Stop
  • 点击一次StartService

输出结果

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D/MainActivity: onCreate: ThreadId2

D/MyService: onCreate: ThreadId2
D/MyService: onStartCommand: StartId1
D/MyService: onStartCommand: ThreadId2
D/MyService: onStartCommand: StartId2
D/MyService: onStartCommand: ThreadId2
D/MyService: onStartCommand: StartId3
D/MyService: onStartCommand: ThreadId2

D/MyService: onDestroy: ThreadId2

D/MyService: onCreate: ThreadId2
D/MyService: onStartCommand: StartId1
D/MyService: onStartCommand: ThreadId2

分析

ThreadId相同，故在同一程序中的本地Service与Activity在同一UI线程中执行

第一次启动Service时，会调用onCreate()方法，然后调用onStartCommand()方法

允许多次启动Service，startId将会累加

调用stopService后将回调onDestroy()方法

再次启动又从startId=1开始

绑定Service

MyService.java

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package com.example.servicetest;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

public class MyService extends Service {
    private static final String TAG = MyService.class.getSimpleName();
    public class MyBinder extends Binder {
        public MyService getService (){
            return MyService.this;
        }
    }
    private MyBinder myBinder = new MyBinder();
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.d(TAG, "onBind: bind");
        return myBinder;
    }

    @Override
    public void onCreate() {
        Log.d(TAG, "onCreate: ThreadId"+Thread.currentThread().getId());
        super.onCreate();
    }

    public String doSomeOperation(String str) {
        Log.i(TAG,"doSomeOperation: bind");
        return str+"value";
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand: StartId"+startId);
        Log.d(TAG, "onStartCommand: ThreadId"+Thread.currentThread().getId());
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.d(TAG, "onDestroy: ThreadId"+Thread.currentThread().getId());
        super.onDestroy();
    }
}

MainActivity.java

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package com.example.servicetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();

    private Button mBtnStart, mBtnStop;
    private Button mBtnBind, mBtnOperate, mBtnUnBind;


    private Intent intent;

    private MyService.MyBinder myBinder;
    private MyService myService;

    private ServiceConnection conn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intent = new Intent(this, MyService.class);
        Log.d(TAG, "onCreate: ThreadId"+Thread.currentThread().getId());
        conn = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder binder) {
                Log.d(TAG, "ServiceConnected");
                myBinder = (MyService.MyBinder) binder;
                myService = myBinder.getService();
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {
                Log.d(TAG, "ServiceDisconnected");
                myBinder = null;
                myService = null;
            }
        };
        initView();
        initClick();
    }
    private void initClick() {
        mBtnStart.setOnClickListener((View view)->{
            startService(intent);
        });
        mBtnStop.setOnClickListener((View view)->{
            stopService(intent);
        });

        mBtnBind.setOnClickListener((View view)->{
            bindService(intent, conn, BIND_AUTO_CREATE);
        });
        mBtnOperate.setOnClickListener((View view)->{
            if(myService != null) {
                String ret = myService.doSomeOperation("abc");
                Toast.makeText(this, ret, Toast.LENGTH_SHORT).show();
            }
        });
        mBtnUnBind.setOnClickListener((View view)->{
            if(myBinder != null){
                unbindService(conn);
            }
        });
    }

    private void initView() {
        mBtnStart = findViewById(R.id.btn_start);
        mBtnStop = findViewById(R.id.btn_stop);

        mBtnBind = findViewById(R.id.btn_bind);
        mBtnOperate = findViewById(R.id.btn_operate);
        mBtnUnBind = findViewById(R.id.btn_unbind);
    }
}

IntentService

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package com.example.servicetest;

import android.app.IntentService;
import android.content.Intent;
import android.util.Log;

import androidx.annotation.Nullable;

public class MyIntentService extends IntentService {
    private static final String TAG = MyIntentService.class.getSimpleName();
    public MyIntentService() {
        super(TAG);
    }
    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * @param name Used to name the worker thread, important only for debugging.
     */
    public MyIntentService(String name) {
        super(name);
    }

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

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

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

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

    @Override
    protected void onHandleIntent(@Nullable Intent intent) {
        int count = intent.getExtras().getInt("count");
        Log.d(TAG, "onHandleIntent: count="+count);

        while (count > 0) {
            count--;
            Log.d(TAG, "onHandleIntent: count="+count);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

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mBtnIntent.setOnClickListener((View view)->{
    Intent intent1 = new Intent(this, MyIntentService.class);
    intent1.putExtra("count",20);
    startService(intent1);
    intent1.putExtra("count",5);
    startService(intent1);
});

AndroidManifest.xml

application中加入

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

前台Service

Android系统对运行的进程按优先级划分了四种进程类型

  1. 前台进程 (Foreground Process)
  2. 可见进程 (Visible Process)
  3. 服务进程 (Service Process)
  4. 后台进程 (Background Process)

当系统内存不足时，系统优先杀死后台进程，为防止后台的Service被杀，故可申请为前台进程
MainActivity.java中的点击事件

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mBtnForeground.setOnClickListener((View view)-> {
    Intent intent1 = new Intent(this, MyForegroundService.class);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        startService(intent1);
    }
});

MyForegroundService.java

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package com.example.servicetest;

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.os.Build;
import android.os.IBinder;

import androidx.core.app.NotificationCompat;

public class MyForegroundService extends Service {
    public MyForegroundService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public void onCreate() {
        super.onCreate();
        showNotification();
    }

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

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    public void showNotification() {
        String channelId = "MyChannel01";
        // Notification点击后跳转到MainActivity
        Intent intent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent, PendingIntent.FLAG_CANCEL_CURRENT);
        NotificationManager notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(channelId, "MyChannel", NotificationManager.IMPORTANCE_LOW);
            notificationManager.createNotificationChannel(channel);
        }

        Notification notification = new NotificationCompat.Builder(this,channelId)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle("前台服务")
                .setContentText("This is a foreground")
                .setContentIntent(pendingIntent)
                .setLargeIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher))
                .build();
        startForeground(1, notification);
    }
}

最终的AndroidManifest.xml文件

声明前台Service权限，声明几个service

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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.servicetest">
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ServiceTest">

        <service
            android:name=".MyForegroundService"
            android:enabled="true"
            android:exported="true"></service>
        <service android:name=".MyIntentService" />
        <service
            android:name=".MyService"
            android:enabled="true"
            android:exported="true" />

        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

最终的MainActivity.java

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package com.example.servicetest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Build;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();

    private Button mBtnStart, mBtnStop;
    private Button mBtnBind, mBtnOperate, mBtnUnBind;

    private Button mBtnIntent;
    private Button mBtnForeground;
    private Intent intent;

    private MyService.MyBinder myBinder;
    private MyService myService;

    private ServiceConnection conn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intent = new Intent(this, MyService.class);
        Log.d(TAG, "onCreate: ThreadId"+Thread.currentThread().getId());
        conn = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder binder) {
                Log.d(TAG, "ServiceConnected");
                myBinder = (MyService.MyBinder) binder;
                myService = myBinder.getService();
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {
                Log.d(TAG, "ServiceDisconnected");
                myBinder = null;
                myService = null;
            }
        };
        initView();
        initClick();
    }
    private void initClick() {
        mBtnStart.setOnClickListener((View view)->{
            startService(intent);
        });
        mBtnStop.setOnClickListener((View view)->{
            stopService(intent);
        });

        mBtnBind.setOnClickListener((View view)->{
            bindService(intent, conn, BIND_AUTO_CREATE);
        });
        mBtnOperate.setOnClickListener((View view)->{
            if(myService != null) {
                String ret = myService.doSomeOperation("abc");
                Toast.makeText(this, ret, Toast.LENGTH_SHORT).show();
            }
        });
        mBtnUnBind.setOnClickListener((View view)->{
            if(myBinder != null){
                unbindService(conn);
            }
        });
        mBtnIntent.setOnClickListener((View view)->{
            Intent intent1 = new Intent(this, MyIntentService.class);
            intent1.putExtra("count",20);
            startService(intent1);
            intent1.putExtra("count",5);
            startService(intent1);
        });
        mBtnForeground.setOnClickListener((View view)-> {
            Intent intent1 = new Intent(this, MyForegroundService.class);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                startService(intent1);
            }
        });
    }

    private void initView() {
        mBtnStart = findViewById(R.id.btn_start);
        mBtnStop = findViewById(R.id.btn_stop);

        mBtnBind = findViewById(R.id.btn_bind);
        mBtnOperate = findViewById(R.id.btn_operate);
        mBtnUnBind = findViewById(R.id.btn_unbind);

        mBtnIntent = findViewById(R.id.btn_intent);

        mBtnForeground = findViewById(R.id.btn_foreground);
    }
}