Android四大组件Service之前台进程(201807最新源码)

想写一个守护进程，到github上找源码，发现基本都是比较过时的。其中比较典型的是，google已经修复了不少原来可以利用的漏洞，而且NotificationCompat.Builder也已经强制要求输入NotificationChannel的信息，所以这里你必须自己用NotificationManager 来创建NotificationChannel，并把ID传给Builder，后面有详细源码，不再细述。

这里给出的，是一个android上标准的前台进程。大致思路如下，

一般在后台运行的Service的系统优先级都比较低的，当系统出现内存不足情况时，会成为优先回收的对象。当希望Service可以一直保持运行状态时，就要提高Service的优先级，其中的一个办法就是使用前台Service。其相关函数：使用startForeground可把Service设置为前台Service。取消则使用stopForeground。

至于broadcast模式，严格来说只能说是同类唤醒，好比你安装了某公司的Aapp，在安装Bapp时，它会检查你有没有装Aapp，如果有启动Aapp，就会把她唤醒（这真是一个糟糕的做法，我们的手机，大部分情况下就是这么被拖死的）。

言归正传，先看效果图，其中显示Foreground那个，就是我们的进程。

再看源码，

activity_main.xml

<?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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn_white"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/service_white" />    

    <Button
        android:id="@+id/btn_background_service"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/service_general" />

</LinearLayout>

MainActivity.java

package com.spacesoftwares.spacecapture;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.spacesoftwares.spacecapture.service.BackgroundService;
import com.spacesoftwares.spacecapture.service.GrayService;
import com.spacesoftwares.spacecapture.service.WhiteService;

public class MainActivity extends AppCompatActivity {

    private Button mBtnWhite, mBtnGray, mBtnBlack, mBtnGeneral;

    private final static String TAG = MainActivity.class.getSimpleName();
    /**
     * 黑色唤醒广播的action
     */
    private final static String BLACK_WAKE_ACTION = "com.wake.black";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //View view = getWindow().getDecorView();
        mBtnWhite = findViewById(R.id.btn_white);
        mBtnGray = findViewById(R.id.btn_gray);
        mBtnBlack = findViewById(R.id.btn_black);
        mBtnGeneral = findViewById(R.id.btn_background_service);
        setListener();
    }

    private void setListener(){
        OnClick onClick = new OnClick();
        mBtnWhite.setOnClickListener(onClick);
        mBtnGray.setOnClickListener(onClick);
        mBtnBlack.setOnClickListener(onClick);
        mBtnGeneral.setOnClickListener(onClick);
    }

    private class  OnClick implements  View.OnClickListener{
        @Override
        public void onClick(View view) {
            int viewId = view.getId();
            if (viewId == R.id.btn_white) {         // 正常的Service
                Intent whiteIntent = new Intent(MainActivity.this, WhiteService.class);
                startService(whiteIntent);
            
            } else if (viewId == R.id.btn_background_service) {//普通的后台进程
                Log.i(TAG, "MAIN: btn_background");
                //Context context = getApplicationContext();
                Intent bgIntent = new Intent(MainActivity.this, BackgroundService.class);
                startService(bgIntent);
            }
        }
    }
}

WhiteService.java

package com.spacesoftwares.spacecapture.service;

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Build;
import android.os.IBinder;
import android.provider.Settings;
import android.support.annotation.Nullable;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

import com.spacesoftwares.spacecapture.MainActivity;
import com.spacesoftwares.spacecapture.R;

import java.io.IOException;
import java.nio.channels.Channel;

public class WhiteService extends Service {

    private final static String TAG = WhiteService.class.getSimpleName();
    private final static int FOREGROUND_ID = 1000;

    public WhiteService(){}

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        //return null;
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public void onCreate() {
        Log.i(TAG, "WhiteService->onCreate");
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.i(TAG, "WhiteService->onStartCommand");

        //NotificationManager manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        String NOTIFICATION_CHANNEL_ID = "my_channel_id_01";

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "My Notifications", NotificationManager.IMPORTANCE_HIGH);

            // Configure the notification channel.
            notificationChannel.setDescription("Channel description");
            notificationChannel.enableLights(true);
            notificationChannel.setLightColor(Color.RED);
            notificationChannel.setVibrationPattern(new long[]{0, 1000, 500, 1000});
            notificationChannel.enableVibration(true);
            notificationManager.createNotificationChannel(notificationChannel);
        }

        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
        builder.setSmallIcon(R.mipmap.ic_launcher);
        builder.setContentTitle("Foreground");
        builder.setContentText("Text shown on Notification bar");
        builder.setContentInfo("Content Info");
        builder.setWhen(System.currentTimeMillis());

        Intent activityIntent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 1, activityIntent, PendingIntent.FLAG_UPDATE_CURRENT);
        builder.setContentIntent(pendingIntent);
        Notification notification = builder.build();
        startForeground(FOREGROUND_ID, notification);
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.i(TAG, "WhiteService->onDestroy");
        super.onDestroy();
    }
}

backgroundService.java

package com.spacesoftwares.spacecapture.service;

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

public class BackgroundService extends Service {

    public BackgroundService(){
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        //return null;
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }
    private final static String TAG = BackgroundService.class.getSimpleName();

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

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


    @Override
    public int onStartCommand(Intent intent, int flags, final int startId) {
        Log.i(TAG, "service start command, id: "+String.valueOf(startId));
        new Thread(new Runnable() {
            @Override
            public void run() {
                int i = 0;

                    Log.i(TAG, "SERVICE"+String.valueOf(startId)+" IS RUNNING for " + String.valueOf(i++) + " seconds");
                    try {
                        Thread.sleep(1000);
                    }catch (InterruptedException e){
                        e.printStackTrace();
                    }
                    stopSelf();
            }
        }).start();
        return super.onStartCommand(intent, flags, startId);
    }

}

最后，不要忘记在AndroidManifest.xml中添加service。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.spacesoftwares.spacecapture">

    <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/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service
            android:name=".service.WhiteService"
            android:enabled="true"
            android:exported="false"
            android:process=":white" />      
        <service
            android:name=".service.BackgroundService"
            android:enabled="true"
            android:exported="true"
            android:process=":bg"/>     
    </application>
</manifest>