ANR free implementation of SharedPreference

NoMainThreadWriteSharedPreferences.kt

/*
 * Copyright 2020 AVAST Software s.r.o.
 *
 * 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 com.avast.android.utils

import android.content.SharedPreferences
import android.util.Log
import androidx.annotation.RequiresApi
import androidx.annotation.VisibleForTesting
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors


/**
 * ANR free implementation of SharedPreferences.
 *
 * Fast fix for ANR caused by writing all non written changes on main thread during activity/service start/stop.
 *
 * Disadvantage of current implementation:
 *  - OnSharedPreferenceChangeListener is called after all changes are written to disk.
 *  - If somebody will call edit() apply() several times after each other it will also several times write whole prefs file.
 *
 *  Usage:
 *
 *  Override this method in your Application class.
 *
 *  public SharedPreferences getSharedPreferences(String name, int mode) {
 *      return NoMainThreadWriteSharedPreferences.getInstance(super.getSharedPreferences(name, mode), name);
 *  }
 *
 *  You need to override also parent activity, because if somebody will use activity context instead
 *  of the application one, he will get a different implementation, you can do something like
 *
 *  public SharedPreferences getSharedPreferences(String name, int mode) {
 *      return getApplicationContext().getSharedPreferences(name, mode);
 *  }
 *
 * @author Tomáš Procházka (prochazka)
 */
@RequiresApi(11)
class NoMainThreadWriteSharedPreferences private constructor(private val sysPrefs: SharedPreferences, val name: String) :
    SharedPreferences {

    private val preferencesCache: MutableMap<String, Any?> = HashMap()

    companion object {
        private val executor: ExecutorService = Executors.newSingleThreadExecutor()
        private val INSTANCES: MutableMap<String, NoMainThreadWriteSharedPreferences> = HashMap()

        @JvmStatic
        fun getInstance(sharedPreferences: SharedPreferences, name: String): SharedPreferences {
            return INSTANCES.getOrPut(name, { NoMainThreadWriteSharedPreferences(sharedPreferences, name) })
        }

        /**
         * Remove all instances for testing purpose.
         */
        @VisibleForTesting
        @JvmStatic
        fun reset() {
            INSTANCES.clear()
        }
    }

    init {
        preferencesCache.putAll(sysPrefs.all)
    }

    override fun contains(key: String?) = preferencesCache[key] != null

    override fun getAll() = HashMap(preferencesCache)

    override fun getBoolean(key: String, defValue: Boolean): Boolean {
        return preferencesCache[key] as Boolean? ?: defValue
    }

    override fun getInt(key: String, defValue: Int): Int {
        return preferencesCache[key] as Int? ?: defValue
    }

    override fun getLong(key: String, defValue: Long): Long {
        return preferencesCache[key] as Long? ?: defValue
    }

    override fun getFloat(key: String, defValue: Float): Float {
        return preferencesCache[key] as Float? ?: defValue
    }

    override fun getStringSet(key: String, defValues: MutableSet<String>?): MutableSet<String>? {
        @Suppress("UNCHECKED_CAST")
        return preferencesCache[key] as MutableSet<String>? ?: defValues
    }

    override fun getString(key: String, defValue: String?): String? {
        return preferencesCache[key] as String? ?: defValue
    }

    override fun edit(): SharedPreferences.Editor {
        return Editor(sysPrefs.edit())
    }

    override fun registerOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener) {
        sysPrefs.registerOnSharedPreferenceChangeListener(listener)
    }

    override fun unregisterOnSharedPreferenceChangeListener(listener: SharedPreferences.OnSharedPreferenceChangeListener) {
        sysPrefs.unregisterOnSharedPreferenceChangeListener(listener)
    }

    inner class Editor(private val sysEdit: SharedPreferences.Editor) : SharedPreferences.Editor {

        private val modifiedData: MutableMap<String, Any?> = HashMap()
        private var keysToRemove: MutableSet<String> = HashSet()
        private var clear = false

        override fun commit(): Boolean {
            submit()
            return true
        }

        override fun apply() {
            submit()
        }

        private fun submit() {
            synchronized(preferencesCache) {
                storeMemCache()
                queuePersistentStore()
            }
        }

        private fun storeMemCache() {
            if (clear) {
                preferencesCache.clear()
                clear = false
            } else {
                preferencesCache.keys.removeAll(keysToRemove)
            }
            keysToRemove.clear()
            preferencesCache.putAll(modifiedData)
            modifiedData.clear()
        }

        private fun queuePersistentStore() {
            try {
                executor.submit {
                    sysEdit.commit()
                }
            } catch (ex: Exception) {
                Log.e("NoMainThreadWritePrefs", "NoMainThreadWriteSharedPreferences.queuePersistentStore(), submit failed for $name")
            }
        }

        override fun remove(key: String): SharedPreferences.Editor {
            keysToRemove.add(key)
            modifiedData.remove(key)
            sysEdit.remove(key)
            return this
        }

        override fun clear(): SharedPreferences.Editor {
            clear = true
            sysEdit.clear()
            return this
        }

        override fun putLong(key: String, value: Long): SharedPreferences.Editor {
            modifiedData[key] = value
            sysEdit.putLong(key, value)
            return this
        }

        override fun putInt(key: String, value: Int): SharedPreferences.Editor {
            modifiedData[key] = value
            sysEdit.putInt(key, value)
            return this
        }

        override fun putBoolean(key: String, value: Boolean): SharedPreferences.Editor {
            modifiedData[key] = value
            sysEdit.putBoolean(key, value)
            return this
        }

        override fun putStringSet(key: String, values: MutableSet<String>?): SharedPreferences.Editor {
            modifiedData[key] = values
            sysEdit.putStringSet(key, values)
            return this
        }

        override fun putFloat(key: String, value: Float): SharedPreferences.Editor {
            modifiedData[key] = value
            sysEdit.putFloat(key, value)
            return this
        }

        override fun putString(key: String, value: String?): SharedPreferences.Editor {
            modifiedData[key] = value
            sysEdit.putString(key, value)
            return this
        }
    }
}

I will think about it if there is no synchronization issue. But generally, I think that it will bring no difference. Because system shared preference itself loading whole properties file to memory anyway. So preferencesCache.putAll(sysPrefs.all) is just an in-memory operation that will be much faster than loading and parsing files from the storage.

how do u make sure all the apps are using custom SharedPreferences,
You also need to implement file creating and management part

how do u make sure all the apps are using custom SharedPreferences,
You also need to implement file creating and management part

It is not enough explained in the class-level documentation. You need to use a custom Application class and all 3rd party libraries that will use a standard way context.getSharedPreferences() will then use the implementation provided by your application class.

convert to java pls