Android四大组件之一Service

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本文详细介绍了Android中的Service组件，包括其特点、应用场景及如何使用。分别讲述了startService、bindService和IntentService三种启动方式的使用方法及生命周期。

什么是Service

1.Service是Android四大组件之一，和Activity的级别相当。
2.Service是可以长时间，运行在后台的，是不可见，是没有界面的组件。
3.Service是运行在主线程中的
4.Service可以跨进程调用

为什么要学习Service

1.大部分病毒利用service的特点，可以在不知不觉中完成预设的功能
2.作为安卓工程师，至少需要了解service是如何在后台完成预设功能
3.优先级比较高
4.在某个功能需要执行很长时间，并且在这个执行过程中，不需要让用户操作，不需要在Activity进行交互的情况下，可以通过Service在后台完成指定任务

Service有哪些应用场景

1.要在后台
2.耗时比较久

如何使用Service

startService

使用startService方式启动Service

1.新建类继承Service

package com.example.myapplication.myService;

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

/**
 * Created by lyj on 2018/6/19.
 */

public class MyService extends Service {
    private int count=0;
    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        new Thread(new Runnable() {
            @Override
            public void run() {
                while (count<100){
                    Log.e("onStartCommand", "run: "+count );
                    count++;
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }          
            }
        }).start();
        return super.onStartCommand(intent, flags, startId);
    }
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.e("onDestroy", "销毁");
    }
}

2.重写onCreate方法

 public void onCreate() {
        super.onCreate();

    }

3.实现onBind抽象方法

public IBinder onBind(Intent intent) {
        return null;
    }

4.重写onStartCommand方法
我在里面启动了一个线程

public int onStartCommand(Intent intent, int flags, int startId) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (count<100){
                    Log.e("onStartCommand", "run: "+count );
                    count++;
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
        return super.onStartCommand(intent, flags, startId);
    }

5.重写onDestory方法
6.在AndroidManifest中注册

<activity android:name=".myService.MyServiceActivity">
  <intent-filter>
      <action android:name="android.intent.action.MAIN" />
      <category android:name="android.intent.category.LAUNCHER" />
  </intent-filter>
</activity>

 <service android:name=".mybindService.BindService">
     <action android:name="com.example.myapplication.myService.MyService" />
 </service>

7.在有context环境中通过startService启动Service

 Intent intent = new Intent(MyServiceActivity.this, MyService.class);
                startService(intent);//启动service

8.在有context环境中通过stopService停止Service

 Intent intent2 = new Intent(MyServiceActivity.this, MyService.class);
                stopService(intent2);//停止service

新建类的完整代码：

package com.example.myapplication.myService;

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

/**
 * Created by lyj on 2018/6/19.
 */

public class MyService extends Service {
    private int count=0;
    @Override
    public void onCreate() {
        super.onCreate();

    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (count<100){
                    Log.e("onStartCommand", "run: "+count );
                    count++;
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();


        return super.onStartCommand(intent, flags, startId);
    }


    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.e("onDestroy", "销毁");
    }
}

activity类完整代码：

package com.example.myapplication.myService;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

import com.example.myapplication.R;

public class MyServiceActivity extends AppCompatActivity implements View.OnClickListener {
    private Button myservice_btn, myservice_start, myservice_stop;
    public static ImageView myservice_image;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_service);

        myservice_btn = findViewById(R.id.myservice_btn);
        myservice_btn.setOnClickListener(this);

        myservice_start = findViewById(R.id.myservice_start);
        myservice_start.setOnClickListener(this);

        myservice_stop = findViewById(R.id.myservice_stop);
        myservice_stop.setOnClickListener(this);

        myservice_image = findViewById(R.id.myservice_image);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
//            case R.id.myservice_btn:
//                Intent intent=new Intent(MyServiceActivity.this,MyService.class);
//                startService(intent);//启动service
//                break;
            case R.id.myservice_start:
                Intent intent = new Intent(MyServiceActivity.this, MyService.class);
                startService(intent);//启动service
                break;
            case R.id.myservice_stop:
                Intent intent2 = new Intent(MyServiceActivity.this, MyService.class);
                stopService(intent2);//停止service
                break;
            default:
                break;
        }
    }
}

startService的生命周期

context.startService()–>onCreate()–>onStartCommand()–>context.stopService()–>onDestory()–>Service stop

bindService

销毁之前一定要解绑

使用bindService方式绑定Service的步骤

1.新建类继承Service
2.重写onCreate方法
3.实现onBind抽象方法

在BindService类里新建内部类MyBinder，继承自Binder(Binder实现IBinder接口)。MyBinder提供方法返回BindService实例。

public class MyBinder extends Binder {
        BindService getService() {
            return BindService.this;
        }
    }

实例化MyBinder得到mybinder对象

private final IBinder binder = new MyBinder();

实现onBind抽象方法

public IBinder onBind(Intent intent) {
        return binder;
    }

4.重写onUnbind方法
5.重写onDestory方法
6.在AndroidManifest中注册
7.在有context环境中实现ServiceConnection接口，重写onServiceConnected()和onServiceDisconnected()方法

private ServiceConnection connection = new ServiceConnection() {

            @Override
            public void onServiceDisconnected(ComponentName name) {
                bindService = null;
            }

            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                bindService = ((BindService.MyBinder) service).getService();
                System.out.println("Service连接成功");
                // 执行Service内部自己的方法
               bindService.excute();
            }
        };

8.在有context环境中通过bindService绑定Service

Intent intent = new Intent(this, BindService.class);
        bindService(intent, connection, Context.BIND_AUTO_CREATE);

9.在有context环境中通过unbindService解绑Service

  protected void onDestroy() {
        super.onDestroy();
        unbindService(connection);
    }

bindService方法

1.Intent对象，用于传参
2.ServiceConnection接口对象
3.flag标识，常用的flag是Context.BIND_AUTO_CREATE

bindService的生命周期

context.startService()–>onCreate()–>onBind()–>Service running()–>onUnbind()–>onDestory()–>Service stop

IntentService有什么不同

bindService，startService都是运行在主线程中，如果有耗时操作，需要我们自己开线程并维护线程，IntentService不需要开启子线程

IntentService怎么用，注意事项

使用IntentService的步骤
1.新建类继承IntentService类

public class MyIntentService extends IntentService{
    private int count=0;

    public MyIntentService() {
        super("");
    }

    public MyIntentService(String name) {
        super(name);
    }
}

2.实现父类的构造方法

 public MyIntentService(String name) {
        super(name);
    }

3.重写onHandleIntent()方法

@Override
    protected void onHandleIntent(@Nullable Intent intent) {
        while (count<100){
            count++;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

其他步骤和上面的startService差不多
新建类的完整代码：

package com.example.myapplication.myIntentService;

import android.app.IntentService;
import android.content.Intent;
import android.support.annotation.Nullable;
import android.util.Log;

/**
 * Created by lyj on 2018/6/19.
 */

public class MyIntentService extends IntentService{


    public MyIntentService() {
        super("");
    }


    public MyIntentService(String name) {
        super(name);
    }

    @Override
    protected void onHandleIntent(@Nullable Intent intent) {
        int count=0;
        while (count<100){
            count++;
            Log.d("MyIntentService", "onHandleIntent: "+count);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
}

activity类完整代码：

package com.example.myapplication.myIntentService;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.example.myapplication.R;


public class MyIntentServiceActivity extends AppCompatActivity implements View.OnClickListener{
    private Button myIntentservice_start, myIntentservice_stop;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_intent_service);

        myIntentservice_start = findViewById(R.id.myIntentservice_start);
        myIntentservice_start.setOnClickListener(this);

        myIntentservice_stop = findViewById(R.id.myIntentservice_stop);
        myIntentservice_stop.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.myIntentservice_start:
                Intent intent = new Intent(MyIntentServiceActivity.this, MyIntentService.class);
                startService(intent);//启动service
                break;
            case R.id.myIntentservice_stop:
                Intent intent2 = new Intent(MyIntentServiceActivity.this, MyIntentService.class);
                stopService(intent2);//停止service
                break;
                default:
                    break;
        }

    }
}

主要事项

1.注册时候如果不加一个无参的构造方法注册表就会报错
这里写图片描述

无参构造方法这样写：

    public MyIntentService() {
        super("");
    }

2.启动Service只能用start启动Service