让应用始终在 Android 的后台运行

Question

I have to get people's trajectory (from home to job, for example), so my app gets latitude and longitude (I have two buttons: 1. Start to get lat and lon 2. Stop to get lat and lon). However, I want that android does not kill the app, I want to keep my application running while the user use facebook, twitter (for example) or simply the user locks his smartphone. My app works fine when user use the app while using facebook or twitter (for example), but when I lock my smartphone, Android kill the app. I have tried to use intentservice and service, but they do not work when I lock the screen. Should I use PowerManager.WakeLock? I do not exactly know how it works and what it does.

This is an example that I made to try services, I don't know if I am wrong, but it does not work when: 1. I am in the app (I have started the service) 2. I tap home button (while service is running) 3. I lock screen. 4. Then the service and the app are killed by android (and the service did not finished to do its stuff)

Manifest

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        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=".MyService"
            android:exported="false"></service>

    </application>

</manifest>

activity_main

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="com.javosoft.intentservice.MainActivity">

    <Button
        android:text="start Service"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="63dp"
        android:id="@+id/button"
        android:onClick="startService"/>

    <Button
        android:text="Stop Service"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignLeft="@+id/button"
        android:layout_alignStart="@+id/button"
        android:layout_marginBottom="68dp"
        android:id="@+id/button2"
        android:onClick="stopService" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:hint="textito :D"
        android:ems="10"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:id="@+id/editText" />
</RelativeLayout>

MainActivity

package com.javosoft.intentservice;

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

public class MainActivity extends AppCompatActivity {

    private Button button;

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

        button = (Button) findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this, MyService.class);
                startService(intent);
            }
        });

    }

    public void stopService (View view){
        Intent intent = new Intent(this, MyService.class);
        stopService(intent);
    }
}

MyService class

package com.javosoft.intentservice;

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

public class MyService extends Service {

    final class MyThreadClass implements Runnable{

        int service_id;
        MyThreadClass(int service_id){
            this.service_id = service_id;
        }

        @Override
        public void run() {

            synchronized (this){
                int count = 0;
                while (count < 10){
                    Log.i("servicio", "while: " + String.valueOf(count));
                    try {
                        wait(2000);
                        count++;
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
            stopSelf(service_id);

        }
    }

    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Toast.makeText(this, "El servició ha empezado D:", Toast.LENGTH_SHORT).show();
        Log.i("servicio", "El servició ha empezado D:");


        Log.i("servicio", "onStartCommand arriba");

        Thread thread = new Thread(new MyThreadClass(startId));
        thread.start();

        Log.i("servicio", "onStartCommand abajo");
        return START_STICKY;
        //return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        //super.onDestroy();
        Toast.makeText(this, "El servicio ha padarado ._.", Toast.LENGTH_SHORT).show();
        Log.i("servicio", "El servicio ha padarado ._.");
    }

    //@Nullable
    @Override
    public IBinder onBind(Intent intent) {

        return null;

    }
}

Answer 1

Try our this

public class ForegroundService extends Service {
    private static final String LOG_TAG = "ForegroundService";

    @Override
    public void onCreate() {
        super.onCreate();
    }

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

        // Your logical code here

        return START_STICKY;
    }

    @Override
    public void onTaskRemoved(Intent rootIntent) {

        //When remove app from background then start it again
        startService(new Intent(this, ForegroundService.class));

        super.onTaskRemoved(rootIntent);
    }

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

    @Override
    public IBinder onBind(Intent intent) {
        // Used only in case of bound services.
        return null;
    }
}

On Start button click:

Intent startIntent = new Intent(MainActivity.this, ForegroundService.class);
    startService(startIntent);

In Manifest

<service
            android:name=".ForegroundService"
            android:enabled="true"
            android:stopWithTask="false" />

Answer 2

I've read that some smartphones have these kind of problems, I found that Huawei, Xiaomi among others have problems with implementation Services, and guess what: My smartphone is a Huawei. The problem comes out of programs preinstalled on these devices for energy saving. Therefore, I tried to run my program on a Nexus (simulator for this one), a Sony and a Moto G, the program ran well for these 3 devices. Thanks for help.

Answer 3

As @Gudin says, it looks to me like you stop the service after 20 seconds. However, since you say this works sometimes, I'm guessing that's just some test code. I suspect your problem is in how you start the Service. Passing the Activity's context means your Service is tied to the lifecycle of that Activity. If that is destroyed, I think your Service goes with it. (Simply going through onStop() of the Activity & not onDestroy() leaves the Service intact). Try this

    Intent intent = new Intent(getApplicationContext(), MyService.class);

I tried duplicating your problem but couldn't so I can't say for sure this is your problem. This is a good place to start though.