Service基本使用

Service是长时间驻留在Android中的一种后台服务, 主要用于消息处理, 跨进程之间的通信. 例如, 使用手机能够边播放音乐边使用其他应用就是因为音乐应用通过Service播放.

0x10 简介

Service有两种启动方式, 分别为Start和bind方式:

0x11 生命周期

services

0x12 回调方法

0x20 代码示例

定义一个ServiceDemo.class类, 作为处理消息的主要类:

package com.killshadow.attackhms;

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

public class ServiceDemo extends Service {
    private static final String TAG = "ServiceDemo";
    private int count;
    private boolean start;

    // 用于onBind的时候返回给客户端
    private MyBinder binder = new MyBinder();
    public class MyBinder extends Binder {
        public int getCount() {
            return count;
        }
    }

    // Service最开始启动的回调方法, 如果已经onCreate, 则bindService的时候直接onBind
    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG,"ServiceDemo -> onCreate, Thread ID: " + Thread.currentThread().getId());
        this.start = true;
        // 创建一个线程动态修改count的值
        new Thread() {
            public void run() {
                while (start) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    // 每秒加1
                    count++;
                }
            }
        }.start();
    }

    // startService的时候回调用这个回调
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.i(TAG, "ServiceDemo -> onStartCommand, startId: " + startId + ", Thread ID: " + Thread.currentThread().getId());
        return START_STICKY;
    }

    // bindService的时候, 一定会调用这个回调
    @Override
    public IBinder onBind(Intent intent) {
        Log.i(TAG, "ServiceDemo -> onBind, Thread ID: " + Thread.currentThread().getId());
        return binder;
    }

    // 当service被unBind之后, 再次bind的时候会调用这个回调
    @Override
    public void onRebind(Intent intent) {
        super.onRebind(intent);
        Log.i(TAG, "ServiceDemo -> onRebind");
    }

    // 调用unbindService的时候会调用这个方法
    @Override
    public boolean onUnbind(Intent intent) {
        Log.i(TAG, "ServiceDemo -> onUnbind");
        return true;
    }

    // stopService会调用这个回调, 销毁service
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "ServiceDemo -> onDestroy, Thread ID: " + Thread.currentThread().getId());
        this.start = false;
    }
}

下面分别介绍两种启动Service的方法.

0x21 Started

Intent intent = new Intent(mContext, ServiceDemo.class);
// start-stop Service
startService(intent);
stopService(new Intent(mContext, ServiceDemo.class));

通过Start/Stop方法开启/关闭Service的方式比较简单, 发送intent即可.

0x22 Bound

ServiceDemo.MyBinder myBinder;
private ServiceConnection conn = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        Log.i(TAG, "Service Connected: " + name.getClassName());
        myBinder = (ServiceDemo.MyBinder) service;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        Log.i(TAG, "Service DisConnected: " + name.getClassName());
    }
};

button1.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // unbind的时候检查count的值
        Toast.makeText(mContext, "Count: " + myBinder.getCount(), Toast.LENGTH_SHORT).show();
        unbindService(conn);
    }
});

button2.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        bindService(new Intent(mContext, ServiceDemo.class), conn, Service.BIND_AUTO_CREATE);
    }
});