安卓一行代码 服务的创建

10.3.1 创建服务

AndroidStudio是个牛逼的工具讲道理实在是太智能了，这波操作就是右键点击然后可以选择创建Service，之后两个选项

都勾着，第一个是否允许其他应用程序访问这个服务。，第二个是是否可用。

创建完之后就重写几个方法

package com.example.servicetest;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
//四大组件都需要在AndroidManifest.xml文件中进行注册才能生效，AndroidStudio自动注册好了
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");
    }
    public void onCreate(){
        //在服务创建时进行调用

        super.onCreate();
    }
    //在服务启动的时候调用
    public int onStartCommand(Intent intent,int flags,int startId)
    {
        return super.onStartCommand(intent,flags,startId);
    }
    //在服务销毁的时候调用
    public void onDestroy()
    {
        super.onDestroy();
    }
}

这里讲道理是真不错的，androidstudio已经自动帮我们的服务，在AndroidManifest.xml文件中注册好了。

10.3.2 启动和停止服务

启动服务主要是靠Intent来实现的

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

   <Button
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:id="@+id/start_service"
       android:text="Start Service"
       tools:ignore="MissingConstraints" />
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/stop_service"
        android:text="Stop Service"
        tools:ignore="MissingConstraints" />
</androidx.constraintlayout.widget.ConstraintLayout>

package com.example.servicetest;

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 startService=(Button)findViewById(R.id.start_service);
        Button  stopService=(Button)findViewById(R.id.stop_service);
        startService.setOnClickListener((View.OnClickListener) this);
        stopService.setOnClickListener((View.OnClickListener) this);
    }
    public void onClick(View v)
    {
        switch (v.getId()){
            case R.id.start_service:
                Intent startIntent=new Intent(this,MyService.class);
                startService(startIntent);
                break;
            case R.id.stop_service:
                Intent stopIntent=new Intent(this,MyService.class);
                stopService(stopIntent); //停止服务
                break;
            default:
                break;
        }
    }
}

接下来有个问题就是怎么证实服务已经成功或者停止来呢，最简单的方法就是MyService几个方法中加入打印日志

package com.example.servicetest;

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

//四大组件都需要在AndroidManifest.xml文件中进行注册才能生效，AndroidStudio自动注册好了
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");
    }
    public void onCreate(){
        //在服务创建时进行调用

        super.onCreate();
        Log.d("MyService","onCreate executed");
    }
    //在服务启动的时候调用
    public int onStartCommand(Intent intent,int flags,int startId)
    {
        Log.d("MyService","onStartCommand executed");
        
        return super.onStartCommand(intent,flags,startId);
        
    }
    //在服务销毁的时候调用
    public void onDestroy()
    {
        
        super.onDestroy();
        Log.d("MyService","onDestory executed");
    }
}

onCreate()方法是在服务第一次创建的时候调用的，而onStartCommand()方法则在每次启动服务时都会调用。

10.3.3 活动和服务进行通信

因为活动和服务在启动之后有点毫无关系的感觉，如果活动可以指挥服务的话，就需要onBind()方法了

package com.example.servicetest;

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

//四大组件都需要在AndroidManifest.xml文件中进行注册才能生效，AndroidStudio自动注册好了
public class MyService extends Service {
    private DownloadBinder mBinder=new DownloadBinder();
    class DownloadBinder extends Binder{
        public void startDownLoad()
        {
            Log.d("MyService","startDownload executed");
        }
        public int getProgress()
        {
            Log.d("MyService","getProgress executed");
            return 0;
        }
    }
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        return mBinder;
    }
    public void onCreate(){
        //在服务创建时进行调用

        super.onCreate();
        Log.d("MyService","onCreate executed");
    }
    //在服务启动的时候调用
    public int onStartCommand(Intent intent,int flags,int startId)
    {
        Log.d("MyService","onStartCommand executed");

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

    }
    //在服务销毁的时候调用
    public void onDestroy()
    {

        super.onDestroy();
        Log.d("MyService","onDestory executed");
    }
}

新建了一个DownloadBinder对象，继承Binder类，并创建了两个模拟方法，然后在onBinder方法中返回这个对象

 <Button
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:id="@+id/uBind_Service"
     android:text="UBind_Service"
     tools:ignore="MissingConstraints" />
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/Bind_Service"
        android:text="Bind Service"
        tools:ignore="MissingConstraints" />

这两个按钮是绑定服务和取消绑定的，活动和服务进行一波绑定，绑定之后就可以调用Binder提供的方法了

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

import java.nio.BufferUnderflowException;

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private MyService.DownloadBinder downloadBinder;
    private ServiceConnection connection=new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
            downloadBinder=(MyService.DownloadBinder)iBinder;
            downloadBinder.startDownLoad();
            downloadBinder.getProgress();
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button startService=(Button)findViewById(R.id.start_service);
        Button  stopService=(Button)findViewById(R.id.stop_service);
        startService.setOnClickListener((View.OnClickListener) this);
        stopService.setOnClickListener((View.OnClickListener) this);
        Button bindService=(Button)findViewById(R.id.Bind_Service);
        Button unbindService=(Button)findViewById(R.id.uBind_Service);
        bindService.setOnClickListener(this);
        unbindService.setOnClickListener(this);
    }
    public void onClick(View v)
    {
        switch (v.getId()){
            case R.id.start_service:
                Intent startIntent=new Intent(this,MyService.class);
                startService(startIntent);
                break;
            case R.id.stop_service:
                Intent stopIntent=new Intent(this,MyService.class);
                stopService(stopIntent); //停止服务
                break;
            case R.id.Bind_Service:
                Intent bindIntent=new Intent(this,MyService.class);
                bindService(bindIntent,connection,BIND_AUTO_CREATE);//绑定服务
                break;
            case R.id.uBind_Service:
                unbindService(connection);
                break;
            default:
                break;
        }
    }
}

10.5.1 使用前台服务

和通知很像，这点是真的骚

package com.example.servicetest;

import android.app.Notification;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

import androidx.core.app.NotificationCompat;

//四大组件都需要在AndroidManifest.xml文件中进行注册才能生效，AndroidStudio自动注册好了
public class MyService extends Service {
    private DownloadBinder mBinder=new DownloadBinder();
    class DownloadBinder extends Binder{
        public void startDownLoad()
        {
            Log.d("MyService","startDownload executed");
        }
        public int getProgress()
        {
            Log.d("MyService","getProgress executed");
            return 0;
        }
    }
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        return mBinder;
    }
    public void onCreate(){
        //在服务创建时进行调用

        super.onCreate();
        Log.d("MyService","onCreate executed");
        Intent intent=new Intent(this,MainActivity.class);
        PendingIntent pi=PendingIntent.getActivity(this,0,intent,0);
        Notification notification=new NotificationCompat.Builder(this).setContentText("This is content text").setContentTitle("This is content title")
                .setWhen(System.currentTimeMillis()).setSmallIcon(R.mipmap.ic_launcher).setLargeIcon(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher)).setContentIntent(pi).build();
        startForeground(1,notification);
    }
    //在服务启动的时候调用
    public int onStartCommand(Intent intent,int flags,int startId)
    {
        Log.d("MyService","onStartCommand executed");

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

    }
    //在服务销毁的时候调用
    public void onDestroy()
    {

        super.onDestroy();
        Log.d("MyService","onDestory executed");
    }
}