Wifi状态更改（连接或断开与网络的连接）时如何触发JobScheduler？

Question

I want to run a piece of code when Wifi is connected or disconnected from some router. I can use service and BrodcastReceiver for this but as of Oreo, the service is killed few minutes after the app is closed (unless in foreground). So, I am trying to use JobScheduler for this but I can't figure out what triggers to provide for execution of my Job.

Answer 1

Android doesn't want to run your code each time there's a network change. These changes may occur several times per minute and your code will cause too much battery drain.

The best you can do is schedule your job to run at regular intervals (which cannot be too short — if you request less than 15 minutes, you won't get it regularly) and check what you need in there. You can request that your job runs only when there's network connectivity, but not the opposite (to run when there's no connectivity).

Answer 2

You can do this perfectly with the Firebase JobDispatcher.

Code to start the job:

fun startNetworkChangeJob() {
    // Create a new dispatcher using the Google Play driver.
    val dispatcher = FirebaseJobDispatcher(GooglePlayDriver(app))

    val myJob = dispatcher.newJobBuilder()
            // the JobService that will be called
            .setService(NetworkChangeJob::class.java)
            // uniquely identifies the job
            .setTag(app.getString(R.string.networkChangeJobId))
            // recurring job
            .setRecurring(true)
            // don't persist past a device reboot
            .setLifetime(Lifetime.FOREVER)
            // start between 0 and 60 seconds from now
            .setTrigger(Trigger.executionWindow(0, 60))
            // don't overwrite an existing job with the same tag
            .setReplaceCurrent(false)
            // retry with exponential backoff
            .setRetryStrategy(RetryStrategy.DEFAULT_EXPONENTIAL)
            // constraints that need to be satisfied for the job to run
            .setConstraints(
                    // only run on an unmetered network
                    Constraint.ON_UNMETERED_NETWORK
            )
            .build()

    dispatcher.mustSchedule(myJob)
}

Then the job itself. Here you can place your logic to determine what to do:

override fun onStartJob(job: com.firebase.jobdispatcher.JobParameters): Boolean {
    // Runs on the main thread!

    checkIfNeedToStartService()

    return false  // Answers the question: "Is there still work going on?"
}

override fun onStopJob(job: com.firebase.jobdispatcher.JobParameters): Boolean {
    // Runs on the main thread!

    return true // Answers the question: "Should this job be retried?"
}

Be sure to also add the following to your manifest:

<service
        android:name=".jobs.NetworkChangeJob"
        android:exported="false">
        <intent-filter>
            <action android:name="com.firebase.jobdispatcher.ACTION_EXECUTE" />
        </intent-filter>
    </service>