IdGenerator.java
/*
* Copyright 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.work.impl.utils;
import static android.content.Context.MODE_PRIVATE;
import android.content.Context;
import android.content.SharedPreferences;
import androidx.annotation.RestrictTo;
/**
* Generates unique IDs that are persisted in {@link SharedPreferences}.
*
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class IdGenerator {
/** The initial id used for JobInfos and Alarms. */
public static final int INITIAL_ID = 0;
static final String PREFERENCE_FILE_KEY = "androidx.work.util.id";
static final String NEXT_JOB_SCHEDULER_ID_KEY = "next_job_scheduler_id";
static final String NEXT_ALARM_MANAGER_ID_KEY = "next_alarm_manager_id";
private final Context mContext;
private SharedPreferences mSharedPrefs;
private boolean mLoadedPreferences;
/**
* Constructs a {@link IdGenerator}.
*
* @param context {@link Context} to get the {@link SharedPreferences} from.
*/
public IdGenerator(Context context) {
mContext = context;
}
/**
* Generates IDs for {@link android.app.job.JobInfo} jobs given a reserved range.
*/
public int nextJobSchedulerIdWithRange(int minInclusive, int maxInclusive) {
synchronized (IdGenerator.class) {
loadPreferencesIfNecessary();
int id = nextId(NEXT_JOB_SCHEDULER_ID_KEY);
if (id < minInclusive || id > maxInclusive) {
// outside the range, re-start at minInclusive.
id = minInclusive;
update(NEXT_JOB_SCHEDULER_ID_KEY, id + 1);
}
return id;
}
}
/**
* Generates IDs for {@link android.app.AlarmManager} work.
*/
public int nextAlarmManagerId() {
synchronized (IdGenerator.class) {
loadPreferencesIfNecessary();
return nextId(NEXT_ALARM_MANAGER_ID_KEY);
}
}
/**
* Returns the next available ID based on a persisted counter.
* Resets ID counter to 0 when the ID exceeded {@link Integer#MAX_VALUE}.
* @param key String matching the particular counter to retrieve
* @return next available id
*/
private int nextId(String key) {
int id = mSharedPrefs.getInt(key, INITIAL_ID);
int nextId = (id == Integer.MAX_VALUE) ? INITIAL_ID : id + 1;
update(key, nextId);
return id;
}
private void update(String key, int value) {
mSharedPrefs.edit().putInt(key, value).apply();
}
private void loadPreferencesIfNecessary() {
if (!mLoadedPreferences) {
mSharedPrefs = mContext.getSharedPreferences(PREFERENCE_FILE_KEY, MODE_PRIVATE);
mLoadedPreferences = true;
}
}
}