Android App开发学习第十二天：service

什么是Service

能够在后台长时间运行，并且没有用户界面的应用程序组件。
Service的分类
StartedService:
通过Activity调用startService(),启动Service
BoundService:
通过Activity调用bindService(),启动后，当activity停止则service停止

service的基本用法

1.创建与配置

package com.example;

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

import java.util.ArrayList;

public class MyService extends Service {
    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() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                int i = 0;
                while(isRunning()){//如果Service正在运行
                    Log.i("Service",String.valueOf(++i));
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

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

    @Override
    public void onDestroy() {
        super.onDestroy();
    }
    //判断service是否正在运行
    public boolean isRunning(){
        ActivityManager activityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        //获取所有正在运行的Service
        ArrayList<ActivityManager.RunningServiceInfo> runningService = (ArrayList<ActivityManager.RunningServiceInfo>);
        for (int i = 0; i < runningService.size(); i++) {
            if (runningService.service.getClassName.toString.equals("com.example.MyService"))
                return true;
        }
        return false;
    }
}

2.启动和停止
启动Service:startService()
停止Service
1.由Service调用stopSelf()停止
2.由其他组件调用stopService()停止

Started Service的生命周期

调用startService()->onCreate()->onStartCommand()->Service运行中->
stopSelf()或stopService()->停止Service->onDestroy()->Service被关闭

package com.example;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button1 = findViewById(R.id.btn_start);
        final  Intent intent = new Intent(MainActivity.this,MyService.class);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startService(intent);

            }
        });
        Button button2 = findViewById(R.id.btn_stop);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    stopService(intent);
            }
        });

    }
}

使用service实现音乐的播放和停止

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivity">

   <Button
       android:id="@+id/btn_start"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="播放音乐"/>


</LinearLayout>

package com.example;

import android.app.ActivityManager;
import android.app.ActivityManager.RunningServiceInfo;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;
import android.util.Log;

import java.util.ArrayList;

public class MyService extends Service {
    static boolean isplay;//记录当前的播放状态
    MediaPlayer player;
    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() {
        //创建MediaPlayer对象，并加载播放的音频文件
//        player = MediaPlayer.create(this,R.raw.music);
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (!player.isPlaying()){
            player.start();//播放音乐
            isplay = player.isPlaying();//设置当前状态为正在播放音乐
        }
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        player.stop();//停止音乐的播放
        isplay = player.isPlaying();//设置当前状态为停止播放音乐
        player.release();//释放资源
        super.onDestroy();
    }

}

package com.example;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button1 = findViewById(R.id.btn_start);
        final  Intent intent = new Intent(MainActivity.this,MyService.class);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //启动和停止MusicService
                if (MyService.isplay == false){
                    startService(intent);//启动service
                    button1.setText("停止播放音乐");
                }else {
                    stopService(intent);//停止service
                    button1.setText("启动播放音乐");
                }

            }
        });
        Button button2 = findViewById(R.id.btn_stop);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    stopService(intent);
            }
        });

    }

    @Override
    protected void onStart() {
        startService(new Intent(MainActivity.this,MyService.class));//启动service
        super.onStart();
    }
}

BoundService

Bound Service的生命周期

实现Bound Service的基本步骤
1.创建内部内类MyBinder继承Binder类，并创建getService()方法返回service
2.在Service中的onBind()方法中返回IBinder对象,即返回创建的内部类MyBinder
3.在Activity中实例化ServiceConnection对象，并重写其onServiceConnected(),onServiceDisconnected()方法，
在绑定成功后回调onServiceConnected()方法，获取service对象。
4.在Activity的onStart()方法中使用bindService()方法绑定service
5.在Acitivity的onStop()方法中使用unbindService()方法解绑service

使用Bound Service 实现模拟双色球彩票的随机选号

<?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:background="@drawable/bg2"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="机选号码"
        android:textColor="#BE2020"
        android:textSize="26sp"
        android:layout_gravity="center"
        android:gravity="center"
        android:layout_marginTop="50dp"/>



    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp">

        <TextView
            android:id="@+id/tv_1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D" />

        <TextView
            android:id="@+id/tv_2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>

        <TextView
            android:id="@+id/tv_3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>

        <TextView
            android:id="@+id/tv_4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>

        <TextView
            android:id="@+id/tv_5"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>

        <TextView
            android:id="@+id/tv_6"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>

        <TextView
            android:id="@+id/tv_7"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#CC0D0D"
            android:layout_marginLeft="5dp"/>
    </LinearLayout>

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="随机选号"
        android:background="#DF2121"/>

</LinearLayout>

package com.example;

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

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class BinderService extends Service {
    public BinderService() {
    }
    //创建MyBinder内部类
    public class MyBinder extends Binder{
        public BinderService getService(){//创建获取Service的方法
            return BinderService.this;//返回当前的Service类

        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        return new MyBinder();//返回MyBinder  Service对象
    }
    //自定义方法，用于生成随机数
    public List getRandomNumber(){
        List resArr = new ArrayList();
        String strNumber = "";//用与保存生成的随机数
        for (int i = 0; i < 7; i++) {
            int number  = new Random().nextInt(33)+1;//生成指定范围的随机整数
            if (number<10){
                strNumber = "0" + String.valueOf(number);
            }else {
                strNumber = String.valueOf(number);
            }
            resArr.add(strNumber);//把转换后的字符串添加到Liset集合中
        }
        return resArr;
    }

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

package com.example;

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.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    BinderService binderService;//声明Service类的对象
    int[] tvid = {R.id.tv_1,R.id.tv_2,R.id.tv_3,R.id.tv_4,R.id.tv_5,R.id.tv_6,R.id.tv_7};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn_random  = findViewById(R.id.btn);//获取随机选号按钮

        btn_random.setOnClickListener(new View.OnClickListener() {//单击按钮，获取随机彩票号码
            @Override
            public void onClick(View v) {
                List number = binderService.getRandomNumber();
                for (int i = 0; i < number.size(); i++) {
                    TextView tv = findViewById(tvid[i]);//获取文本框组件
                    tv.setText(number.get(i).toString());//显示生成的随机号码
                }
            }
        });
    }
    //创建serviceConnection对象
    private ServiceConnection conn = new ServiceConnection() {
        //连接成功回调此方法
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            binderService = ((BinderService.MyBinder)service).getService();//获取后台Service
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

    @Override
    protected void onStart() {
        super.onStart();
        Intent intent = new Intent(MainActivity.this, BinderService.class);
        bindService(intent,conn,BIND_AUTO_CREATE);//第三个参数可以设置绑定成功后是否自动创建service
    }

    @Override
    protected void onStop() {
        super.onStop();
        unbindService(conn);
    }
}

IntentService的基本用法

为什么要使用IntentService
Service无法自动开启线程来执行耗时任务和自动停止服务，而IntentService可以。

package com.example;

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

/**
 * An {@link IntentService} subclass for handling asynchronous task requests in
 * a service on a separate handler thread.
 * <p>
 * TODO: Customize class - update intent actions, extra parameters and static
 * helper methods.
 */
public class MyIntentService extends IntentService {
    // TODO: Rename actions, choose action names that describe tasks that this
    // IntentService can perform, e.g. ACTION_FETCH_NEW_ITEMS
    private static final String ACTION_FOO = "com.example.action.FOO";
    private static final String ACTION_BAZ = "com.example.action.BAZ";

    // TODO: Rename parameters
    private static final String EXTRA_PARAM1 = "com.example.extra.PARAM1";
    private static final String EXTRA_PARAM2 = "com.example.extra.PARAM2";

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

    /**
     * Starts this service to perform action Foo with the given parameters. If
     * the service is already performing a task this action will be queued.
     *
     * @see IntentService
     */
    // TODO: Customize helper method
    public static void startActionFoo(Context context, String param1, String param2) {
        Intent intent = new Intent(context, MyIntentService.class);
        intent.setAction(ACTION_FOO);
        intent.putExtra(EXTRA_PARAM1, param1);
        intent.putExtra(EXTRA_PARAM2, param2);
        context.startService(intent);
    }

    /**
     * Starts this service to perform action Baz with the given parameters. If
     * the service is already performing a task this action will be queued.
     *
     * @see IntentService
     */
    // TODO: Customize helper method
    public static void startActionBaz(Context context, String param1, String param2) {
        Intent intent = new Intent(context, MyIntentService.class);
        intent.setAction(ACTION_BAZ);
        intent.putExtra(EXTRA_PARAM1, param1);
        intent.putExtra(EXTRA_PARAM2, param2);
        context.startService(intent);
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        Log.i("IntentService:","Service已启动");
        long endTime  = System.currentTimeMillis()+20*1000;//结束时间
        while(System.currentTimeMillis()<endTime){
            synchronized (this){
                try {
                    wait(endTime-System.currentTimeMillis());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Override
    public void onDestroy() {
        Log.i("IntentService:","Service已停止");
        super.onDestroy();
    }

    /**
     * Handle action Foo in the provided background thread with the provided
     * parameters.
     */
    private void handleActionFoo(String param1, String param2) {
        // TODO: Handle action Foo
        throw new UnsupportedOperationException("Not yet implemented");
    }

    /**
     * Handle action Baz in the provided background thread with the provided
     * parameters.
     */
    private void handleActionBaz(String param1, String param2) {
        // TODO: Handle action Baz
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

package com.example;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {

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

        Button button2 = findViewById(R.id.btn_2);
       
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startService(new Intent(MainActivity.this,MyIntentService.class));
            }
        });
    }
}

本文地址：https://blog.csdn.net/NikerunZoo/article/details/109627265