//-------------------- SharePreferences -------------------------
    //獲取SharePreferences
    private val sp =
        context.applicationContext.getSharedPreferences(BOOK_PREFERENCES_NAME, MODE_PRIVATE)
    /**
     * SharePreferences 存數(shù)據(jù)
     */
    fun saveBookSP(book: BookBean) {
        //commit默認(rèn)為false,采用異步提交。
        sp.edit(commit = true) {
            putString(KEY_BOOK_NAME, book.name)
            putFloat(KEY_BOOK_PRICE, book.price)
            putString(KEY_BOOK_TYPE, book.type.name)
        }
    }
    /**
     * SharePreferences 獲取數(shù)據(jù)
     */
    val mBookInfo: BookBean
        get() {
            sp.apply {
                var bookName = getString(KEY_BOOK_NAME, "") ?: ""
                var bookPrice = getFloat(KEY_BOOK_PRICE, 0F)
                var bookStr = getString(KEY_BOOK_TYPE, Type.MATH.name)
                var bookType: Type = Type.valueOf(bookStr ?: Type.MATH.name)
                return BookBean(bookName, bookPrice, bookType)
            }
        }

       @Override
        public void apply() {
            final long startTime = System.currentTimeMillis();
            final MemoryCommitResult mcr = commitToMemory();
            final Runnable awaitCommit = new Runnable() {
                    @Override
                    public void run() {
                        try {
                            //采用final CountDownLatch writtenToDiskLatch = new CountDownLatch(1);
                            mcr.writtenToDiskLatch.await();
                        } catch (InterruptedException ignored) {
                        }
                       ...
                    }
                };
            QueuedWork.addFinisher(awaitCommit);
            Runnable postWriteRunnable = new Runnable() {
                    @Override
                    public void run() {
                        awaitCommit.run();
                        QueuedWork.removeFinisher(awaitCommit);
                    }
                };
            //異步執(zhí)行磁盤寫入操作
            SharedPreferencesImpl.this.enqueueDiskWrite(mcr, postWriteRunnable);
            notifyListeners(mcr);
        }

public class QueuedWork {
  private static final LinkedList<Runnable> sFinishers = new LinkedList<>();
  public static void waitToFinish() {
     ...
     Handler handler = getHandler();
     try {
        //8.0之后優(yōu)化，會主動嘗試執(zhí)行寫磁盤任務(wù)
         processPendingWork();
     } finally {
         StrictMode.setThreadPolicy(oldPolicy);
     }
     try {
         while (true) {
             Runnable finisher;
             synchronized (sLock) {
                 //從隊(duì)列中取出任務(wù)
                 finisher = sFinishers.poll();
             }
             //如果任務(wù)為空，則跳出循環(huán)，UI線程可以繼續(xù)往下執(zhí)行
             if (finisher == null) {
                 break;
             }
             //任務(wù)不為空，執(zhí)行CountDownLatch.await()，即UI線程會阻塞等待
             finisher.run();
         }
     } finally {
         sCanDelay = true;
     }
  }
 }

 @Override
 public void handleStopActivity(IBinder token, int configChanges,
            PendingTransactionActions pendingActions, boolean finalStateRequest, String reason) {
     // Make sure any pending writes are now committed.
     if (!r.isPreHoneycomb()) {
          QueuedWork.waitToFinish();
     }
    }
private void handleStopService(IBinder token) {
    QueuedWork.waitToFinish();
}

implementation 'androidx.datastore:datastore-preferences:1.0.0'

/**
 * TODO：創(chuàng)建 Preferences DataStore
 *   參數(shù)1：name：創(chuàng)建Preferences DataStore文件名稱。
 *               會在/data/data/項(xiàng)目報(bào)名/files/下創(chuàng)建名為pf_dataastore的文件
 *   參數(shù)2：corruptionHandler：如果DataStore在試圖讀取數(shù)據(jù)時(shí)，數(shù)據(jù)無法反序列化，會拋出androidx.datastore.core.CorruptionException，
 *                            此時(shí)會執(zhí)行corruptionHandler。
 *   參數(shù)3：produceMigrations：SP產(chǎn)生遷移到Preferences DataStore。ApplicationContext作為參數(shù)傳遞給這些回調(diào)，遷移在對數(shù)據(jù)進(jìn)行任何訪問之前運(yùn)行。
 *   參數(shù)4：scope：協(xié)成的作用域，默認(rèn)IO操作在Dispatchers.IO線程執(zhí)行。
 */
val Context.dataStorePf: DataStore<Preferences> by preferencesDataStore(
    //文件名稱
    name = "preferences_dataStore")

//常量
const val BOOK_PREFERENCES_NAME = "book_preferences"
const val KEY_BOOK_NAME = "key_book_name"
const val KEY_BOOK_PRICE = "key_book_price"
const val KEY_BOOK_TYPE = "key_book_type"
/**
 * TODO：創(chuàng)建 Preferences DataStore
 *   參數(shù)1：name：創(chuàng)建Preferences DataStore文件名稱。
 *               會在/data/data/項(xiàng)目報(bào)名/files/下創(chuàng)建名為pf_dataastore的文件
 *   參數(shù)2：corruptionHandler：如果DataStore在試圖讀取數(shù)據(jù)時(shí)，數(shù)據(jù)無法反序列化，會拋出androidx.datastore.core.CorruptionException，
 *                            此時(shí)會執(zhí)行corruptionHandler。
 *   參數(shù)3：produceMigrations：SP產(chǎn)生遷移到Preferences DataStore。ApplicationContext作為參數(shù)傳遞給這些回調(diào)，遷移在對數(shù)據(jù)進(jìn)行任何訪問之前運(yùn)行。
 *   參數(shù)4：scope：協(xié)成的作用域，默認(rèn)IO操作在Dispatchers.IO線程執(zhí)行。
 */
val Context.dataStorePf: DataStore<Preferences> by preferencesDataStore(
    name = "preferences_dataStore")

data class BookBean( var name: String = "",
                 var price: Float = 0f,
                 var type: Type = Type.ENGLISH) {
}

enum class Type{
    MATH,       //數(shù)學(xué)
    CHINESE,    //語文
    ENGLISH     //英語
}

  //-------------------- Preferences DataStore -------------------------
    /**
     * TODO：Preferences DataStore  保存數(shù)據(jù)
     */
    fun savePD(view: View) {
        val book = BookBean("張三", 25f, Type.CHINESE)
        viewModel.saveBookPD(book)
    }

    /**
     * TODO：Preferences DataStore 獲取數(shù)據(jù)
     */
    fun getPD(view: View) {
        lifecycleScope.launch {
            viewModel.bookPfFlow.collect {
                tv_pd_data.text = it.toString()
            }
        }
    }

//-------------------- Preferences DataStore -------------------------
    /**
     * TODO：Preferences DataStore 保存數(shù)據(jù) 必須在協(xié)程中進(jìn)行
     */
    fun saveBookPD(bookBean: BookBean) {
        viewModelScope.launch {
            dataStoreRepo.saveBookPD(bookBean)
        }
    }

    /**
     * TODO：Preferences DataStore 獲取數(shù)據(jù)
     */
    val bookPfFlow = dataStoreRepo.bookPDFlow

//-------------------- Preferences DataStore -------------------------
    /**
     * Preferences DataStore 存數(shù)據(jù)
     */
    suspend fun saveBookPD(book: BookBean) {
        context.dataStorePf.edit { preferences ->
            preferences[PreferenceKeys.P_KEY_BOOK_NAME] = book.name
            preferences[PreferenceKeys.P_KEY_BOOK_PRICE] = book.price
            preferences[PreferenceKeys.P_KEY_BOOK_TYPE] = book.type.name
        }
    }
    /**
     * Preferences DataStore 獲取數(shù)據(jù)
     */
    val bookPDFlow: Flow<BookBean> = context.dataStorePf.data
        .map { preferences ->
            // No type safety.
            val name = preferences[PreferenceKeys.P_KEY_BOOK_NAME] ?: ""
            val bookPrice = preferences[PreferenceKeys.P_KEY_BOOK_PRICE] ?: 0f
            val bookType =
                Type.valueOf(preferences[PreferenceKeys.P_KEY_BOOK_TYPE] ?: Type.MATH.name)
            return@map BookBean(name, bookPrice, bookType)
        }

//SharedPreference文件名
const val BOOK_PREFERENCES_NAME = "book_preferences"
val Context.dataStorePf: DataStore<Preferences> by preferencesDataStore(
    name = "preferences_dataStore",
    //將SP遷移到Preference DataStore中
    produceMigrations = { context ->
        listOf(SharedPreferencesMigration(context, BOOK_PREFERENCES_NAME))
    })

implementation 'com.tencent:mmkv:1.2.13'

class App:Application() {
    override fun onCreate() {
        super.onCreate()
        val rootDir = MMKV.initialize(this)
        Log.e("TAG","mmkv root: $rootDir")
    }
}