[Offline pages] Creating BackgroundJobScheduler, which uses JobScheduler

chrome/android/java/src/org/chromium/chrome/browser/offlinepages/BackgroundJobScheduler.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.offlinepages;
+
+import android.annotation.TargetApi;
+import android.app.job.JobInfo;
+import android.app.job.JobScheduler;
+import android.content.ComponentName;
+import android.content.Context;
+import android.os.Build;
+import android.os.PersistableBundle;
+
+/**
+ * The background job scheduler class used for scheduling tasks using JobScheduler.
+ */
+@TargetApi(Build.VERSION_CODES.N)
+public class BackgroundJobScheduler extends BackgroundScheduler {
+    public static final int JOB_ID = 774322033;
+    private static final long MILLISECONDS_IN_SECOND = 1000;

[nyquist, 2017/02/16 23:49:32]

TimeUnit.SECONDS.toMillis(1)?

[fgorski, 2017/02/17 22:31:15]

Done.

+
+    public BackgroundJobScheduler(Context context) {
+        super(context);
+    }
+
+    @Override
+    public void cancel() {
+        JobScheduler jobScheduler = getJobScheduler();
+        if (jobScheduler == null) return;

[nyquist, 2017/02/16 23:49:32]

When will this be null? And if it is, would you want to fall back to using GCM
as a best effort?
And does this change over time, or could we do this in the constructor, storing
a final member with a reference to this service? Then we could have something
like a "isAvailable()" or something on the BackgroundScheduler class as an
abstract method.

[fgorski, 2017/02/17 22:31:15]

This piece of code was added, as I was trying to sort the exception, when
GcmNetworkManager was not there. I presume that OS will give me something always
and I don't have to worry. Hence removing the null check.
If I'm proven to be wrong I'll happily fix this again.
This all depends on whether context changes. If it doesn't then it may make
sense to keep the scheduler as a member variable. If it can change, which I
presume is the case, we don't plan to keep this class around. (It is not called
that commonly so discarding it does not cost much).

+        jobScheduler.cancel(JOB_ID);
+    }
+
+    @Override
+    protected void scheduleImpl(TriggerConditions triggerConditions, long delayStartSeconds,
+            long executionDeadlineSeconds, boolean overwrite) {
+        JobScheduler jobScheduler = getJobScheduler();
+        if (jobScheduler == null) return;
+
+        if (!overwrite) {
+            JobInfo existingJob = jobScheduler.getPendingJob(JOB_ID);
+            if (existingJob != null) return;
+        }
+
+        PersistableBundle taskExtras = new PersistableBundle();
+        TaskExtrasPacker.packTimeInBundle(taskExtras);
+        TaskExtrasPacker.packTriggerConditionsInBundle(taskExtras, triggerConditions);
+
+        JobInfo jobInfo =
+                new JobInfo
+                        .Builder(JOB_ID, new ComponentName(
+                                                 getContext(), BackgroundSchedulerJobService.class))
+                        .setMinimumLatency(delayStartSeconds * MILLISECONDS_IN_SECOND)

[nyquist, 2017/02/16 23:49:32]

How about something like: TimeUnit.SECONDS.toMillis(delayStartSeconds)

[fgorski, 2017/02/17 22:31:15]

Done.

+                        .setOverrideDeadline(executionDeadlineSeconds * MILLISECONDS_IN_SECOND)
+                        .setPersisted(true) // across device resets

[nyquist, 2017/02/16 23:49:32]

Nit: Double space before // and period at end of sentence.

[fgorski, 2017/02/17 22:31:15]

Done.

+                        .setRequiredNetworkType(triggerConditions.requireUnmeteredNetwork()
+                                        ? JobInfo.NETWORK_TYPE_UNMETERED
+                                        : JobInfo.NETWORK_TYPE_ANY)
+                        .setRequiresCharging(triggerConditions.requirePowerConnected())
+                        .setExtras(taskExtras)
+                        .build();
+
+        jobScheduler.schedule(jobInfo);
+    }
+
+    private JobScheduler getJobScheduler() {
+        return (JobScheduler) getContext().getSystemService(Context.JOB_SCHEDULER_SERVICE);
+    }
+}