[[420676]]

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引言

輕量級(jí)數(shù)據(jù)存儲(chǔ)適用于對(duì)Key-Value結(jié)構(gòu)的數(shù)據(jù)進(jìn)行存取和持久化操作。主要用于保存應(yīng)用的一些常用配置，并不適合存儲(chǔ)大量數(shù)據(jù)和頻繁改變數(shù)據(jù)的場(chǎng)景。用戶的數(shù)據(jù)保存在文件中，可以持久化的存儲(chǔ)在設(shè)備上。需要注意的是用戶訪問的實(shí)例包含文件所有數(shù)據(jù)，并一直加載在設(shè)備的內(nèi)存中，并通過(guò)輕量級(jí)數(shù)據(jù)存儲(chǔ)的API完成數(shù)據(jù)操作。

功能介紹

輕量級(jí)數(shù)據(jù)存儲(chǔ)向本地應(yīng)用提供的API支持本地應(yīng)用讀寫數(shù)據(jù)及觀察數(shù)據(jù)變化。數(shù)據(jù)存儲(chǔ)形式為鍵值對(duì)，鍵的類型為字符串型(String)，值的存儲(chǔ)數(shù)據(jù)類型包括整型(int)、字符串型(String)、布爾型(boolean)、浮點(diǎn)型(float)、長(zhǎng)整型(long)、字符串型Set集合(Set)。

開發(fā)指南

1. 創(chuàng)建Preferences實(shí)例。

// context為上下文對(duì)象，PREFERENCE_FILE_NAME為輕量級(jí)數(shù)據(jù)庫(kù)文件名，String類型，可以自定義 
databaseHelper = new DatabaseHelper(context); 
preferences = databaseHelper.getPreferences(PREFERENCE_FILE_NAME); 

2. 將數(shù)據(jù)寫入指定文件。

// preferences.putString()為存入String類型的數(shù)據(jù) 
preferences.putString(String key, String value); 
// flush()為異步持久化數(shù)據(jù)；flushSync()為同步持久化數(shù)據(jù) 
preferences.flush()/preferences.flushSync(); 

3.從指定文件讀取數(shù)據(jù)。

//讀取時(shí)傳入的key, 要與寫入時(shí)傳入的key一致，才能獲取對(duì)應(yīng)數(shù)據(jù)，第二個(gè)參數(shù)為默認(rèn)值。 
  preferences.getString(String key, String default) 

4. 開發(fā)者可以向Preferences實(shí)例注冊(cè)觀察者，觀察數(shù)據(jù)更新變化。

private class PreferencesObserverImpl implements Preferences.PreferencesObserver { 
    
    @Override     
    public void onChange(Preferences preferences, String key) { 
        if ("key".equals(key)) { 
           HiLog.info(LABLE, "Change Received：[key=value]");         
        }     
    } 
} 
 
 
// 向preferences實(shí)例注冊(cè)觀察者 
PreferencesObserverImpl observer = new PreferencesObserverImpl(); 
preferences.registerObserver(observer); 
// 修改數(shù)據(jù)后，observer的onChange方法會(huì)被回調(diào) 
// 向preferences實(shí)例注銷觀察者 
preferences.unRegisterObserver(observer); 

源碼如下：

1.PreferenceUtils

public class PreferenceUtils { 
 
  private static String PREFERENCE_FILE_NAME = "prefrence_file"; 
  private static Preferences preferences; 
  private static DatabaseHelper databaseHelper; 
  private static PreferencesObserver mPreferencesObserver; 
 
  private static void initPreference(Context context){ 
    if(databaseHelper==null){ 
      databaseHelper = new DatabaseHelper(context); 
    } 
    if(preferences==null){ 
      preferences = databaseHelper.getPreferences(PREFERENCE_FILE_NAME); 
    } 
 
  } 
 
  //存放、獲取時(shí)傳入的context必須是同一個(gè)context,否則存入的數(shù)據(jù)無(wú)法獲取 
  public static void putString(Context context, String key, String value) { 
    initPreference(context); 
    preferences.putString(key, value); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context 上下文 
   * @param key  鍵 
   * @return 獲取的String 默認(rèn)值為:null 
   */ 
  public static String getString(Context context, String key) { 
    initPreference(context); 
    return preferences.getString(key, null); 
  } 
 
 
  public static void putInt(Context context, String key, int value) { 
    initPreference(context); 
    preferences.putInt(key, value); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context 上下文 
   * @param key 鍵 
   * @return 獲取int的默認(rèn)值為：-1 
   */ 
  public static int getInt(Context context, String key) { 
    initPreference(context); 
    return preferences.getInt(key, -1); 
  } 
 
 
  public static void putLong(Context context, String key, long value) { 
    initPreference(context); 
    preferences.putLong(key, value); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context 上下文 
   * @param key  鍵 
   * @return 獲取long的默認(rèn)值為：-1 
   */ 
  public static long getLong(Context context, String key) { 
    initPreference(context); 
    return preferences.getLong(key, -1L); 
  } 
 
 
  public static void putBoolean(Context context, String key, boolean value) { 
    initPreference(context); 
    preferences.putBoolean(key, value); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context  上下文 
   * @param key  鍵 
   * @return 獲取boolean的默認(rèn)值為：false 
   */ 
  public static boolean getBoolean(Context context, String key) { 
    initPreference(context); 
    return preferences.getBoolean(key, false); 
  } 
 
 
  public static void putFloat(Context context, String key, float value) { 
    initPreference(context); 
    preferences.putFloat(key, value); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context 上下文 
   * @param key   鍵 
   * @return 獲取float的默認(rèn)值為：0.0 
   */ 
  public static float getFloat(Context context, String key) { 
    initPreference(context); 
    return preferences.getFloat(key, 0.0F); 
  } 
 
 
  public static void putStringSet(Context context, String key, Set<String> set) { 
    initPreference(context); 
    preferences.putStringSet(key, set); 
    preferences.flush(); 
  } 
 
  /** 
   * @param context  上下文 
   * @param key 鍵 
   * @return 獲取set集合的默認(rèn)值為：null 
   */ 
  public static Set<String> getStringSet(Context context, String key) { 
    initPreference(context); 
    return preferences.getStringSet(key, null); 
  } 
 
 
  public static boolean deletePreferences(Context context) { 
    initPreference(context); 
    boolean isDelete= databaseHelper.deletePreferences(PREFERENCE_FILE_NAME); 
    return isDelete; 
  } 
 
 
  public static void registerObserver(Context context,PreferencesObserver preferencesObserver){ 
    initPreference(context); 
    mPreferencesObserver=preferencesObserver; 
    preferences.registerObserver(mPreferencesObserver); 
  } 
 
  public static void unregisterObserver(){ 
    if(mPreferencesObserver!=null){ 
      // 向preferences實(shí)例注銷觀察者 
      preferences.unregisterObserver(mPreferencesObserver); 
    } 
  } 
 
} 

2. MainAbilitySlice

public class MainAbilitySlice extends AbilitySlice implements ClickedListener { 
  private TextField tfName; 
  private TextField tfGener; 
  private TextField tfAge; 
  private TextField tfWeight; 
  private Text tvResultQuery; 
  private Text tvResultListener; 
  private String name; 
  private boolean isMan; 
  private int age; 
  private float weight; 
 
 
  @Override 
  public void onStart(Intent intent) { 
    super.onStart(intent); 
    super.setUIContent(ResourceTable.Layout_ability_main); 
    tfName=(TextField)findComponentById(ResourceTable.Id_tf_name); 
    tfGener=(TextField)findComponentById(ResourceTable.Id_tf_isMan); 
    tfAge=(TextField)findComponentById(ResourceTable.Id_tf_age); 
    tfWeight=(TextField)findComponentById(ResourceTable.Id_tf_weight); 
    tvResultQuery=(Text) findComponentById(ResourceTable.Id_tvResultQuery); 
    tvResultListener=(Text) findComponentById(ResourceTable.Id_tvResultListener); 
    Button btSave=(Button)findComponentById(ResourceTable.Id_bt_save); 
    Button btQuery=(Button)findComponentById(ResourceTable.Id_bt_query); 
    Button btRegister=(Button)findComponentById(ResourceTable.Id_bt_regist); 
    Button btUnRegister=(Button)findComponentById(ResourceTable.Id_bt_unregist); 
    btSave.setClickedListener(this); 
    btQuery.setClickedListener(this); 
    btRegister.setClickedListener(this); 
    btUnRegister.setClickedListener(this); 
  } 
 
  @Override 
  public void onActive() { 
    super.onActive(); 
  } 
 
  @Override 
  public void onForeground(Intent intent) { 
    super.onForeground(intent); 
  } 
 
  @Override 
  public void onClick(Component component) { 
    switch (component.getId()){ 
      case ResourceTable.Id_bt_save: 
        PreferenceUtils.putString(MyApplication.mContext,"name",tfName.getText()); 
        if(tfGener.getText().equals("男")){ 
          PreferenceUtils.putBoolean(MyApplication.mContext,"gender",true); 
        } 
        try { 
          String age=tfAge.getText(); 
          String weight=tfWeight.getText(); 
          int ageInt=Integer.parseInt(age); 
          float weightFloat=Float.parseFloat(weight); 
          PreferenceUtils.putInt(MyApplication.mContext,"age",ageInt); 
          PreferenceUtils.putFloat(MyApplication.mContext,"weight",weightFloat); 
        }catch (Exception e){ 
          e.printStackTrace(); 
        } 
        new ToastDialog(this).setDuration(2000).setText("保存成功").setAlignment(LayoutAlignment.CENTER).show(); 
        break; 
      case ResourceTable.Id_bt_query: 
         name=PreferenceUtils.getString(MyApplication.mContext,"name"); 
         isMan=PreferenceUtils.getBoolean(MyApplication.mContext,"gender"); 
         age=PreferenceUtils.getInt(MyApplication.mContext,"age"); 
         weight=PreferenceUtils.getFloat(MyApplication.mContext,"weight"); 
        if(isMan){ 
          tvResultQuery.setText("查詢結(jié)果："+name+"/男/"+age+"/"+weight); 
        }else { 
          tvResultQuery.setText("查詢結(jié)果："+name+"/女/"+age+"/"+weight); 
        } 
        new ToastDialog(this).setDuration(2000).setText("查詢成功").setAlignment(LayoutAlignment.CENTER).show(); 
        break; 
      case ResourceTable.Id_bt_regist: 
        PreferenceUtils.registerObserver(this,new PreferencesObserver() { 
          @Override 
          public void onChange(Preferences preferences, String key) { 
            switch (key){ 
              case "name": 
                 name=PreferenceUtils.getString(MyApplication.mContext,"name"); 
                break; 
              case "gender": 
                 isMan=PreferenceUtils.getBoolean(MyApplication.mContext,"gender"); 
                break; 
              case "age": 
                 age=PreferenceUtils.getInt(MyApplication.mContext,"age"); 
                break; 
              case "weight": 
                 weight=PreferenceUtils.getFloat(MyApplication.mContext,"weight"); 
                break; 
            } 
            if(isMan){ 
              tvResultListener.setText("兼停結(jié)果："+name+"/男/"+age+"/"+weight); 
            }else { 
              tvResultListener.setText("兼停結(jié)果："+name+"/女/"+age+"/"+weight); 
            } 
          } 
 
        }); 
        new ToastDialog(this).setDuration(2000).setText("注冊(cè)成功").setAlignment(LayoutAlignment.CENTER).show(); 
        break; 
      case ResourceTable.Id_bt_unregist: 
        PreferenceUtils.unregisterObserver(); 
        new ToastDialog(this).setDuration(2000).setText("解除注冊(cè)成功").setAlignment(LayoutAlignment.CENTER).show(); 
        break; 
    } 
 
  } 
 
 
 
} 

3. MyApplication

public class MyApplication extends AbilityPackage { 
  public static Context mContext ; 
 
  @Override 
  public void onInitialize() { 
    super.onInitialize(); 
    mContext=this; 
  } 
} 

4.頁(yè)面布局ability_main.xml文件

<?xml version="1.0" encoding="utf-8"?> 
<DirectionalLayout 
  xmlns:ohos="http://schemas.huawei.com/res/ohos" 
  ohos:height="match_parent" 
  ohos:orientation="vertical" 
  ohos:width="match_parent"> 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="vertical" 
    ohos:left_padding="15vp" 
    ohos:right_padding="15vp" 
    ohos:top_padding="16vp"> 
    <Text 
      ohos:height="match_content" 
      ohos:width="match_content" 
      ohos:text="姓名" 
      ohos:text_size="18vp"/> 
    <TextField 
      ohos:id="$+id:tf_name" 
      ohos:height="match_content" 
      ohos:width="match_parent" 
      ohos:text_input_type="pattern_text" 
      ohos:hint="請(qǐng)輸入姓名" 
      ohos:text_size="18vp" 
      ohos:hint_color="#cccccc" 
      ohos:top_margin="8vp"/> 
    <DirectionalLayout 
      ohos:height="1vp" 
      ohos:width="match_parent" 
      ohos:top_margin="3vp" 
      ohos:background_element="#cccccc"/> 
  </DirectionalLayout> 
 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="vertical" 
    ohos:left_padding="15vp" 
    ohos:right_padding="15vp" 
    ohos:top_padding="16vp"> 
    <Text 
      ohos:height="match_content" 
      ohos:width="match_content" 
      ohos:text="性別" 
      ohos:text_size="18vp"/> 
    <TextField 
      ohos:id="$+id:tf_isMan" 
      ohos:height="match_content" 
      ohos:width="match_parent" 
      ohos:text_input_type="pattern_text" 
      ohos:hint="男/女" 
      ohos:text_size="18vp" 
      ohos:hint_color="#cccccc" 
      ohos:top_margin="8vp"/> 
    <DirectionalLayout 
      ohos:height="1vp" 
      ohos:width="match_parent" 
      ohos:top_margin="3vp" 
      ohos:background_element="#cccccc"/> 
  </DirectionalLayout> 
 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="vertical" 
    ohos:left_padding="15vp" 
    ohos:right_padding="15vp" 
    ohos:top_padding="16vp"> 
    <Text 
      ohos:height="match_content" 
      ohos:width="match_content" 
      ohos:text="年齡" 
      ohos:text_size="18vp"/> 
    <TextField 
      ohos:id="$+id:tf_age" 
      ohos:height="match_content" 
      ohos:width="match_parent" 
      ohos:text_input_type="pattern_number" 
      ohos:hint="請(qǐng)輸入年齡" 
      ohos:text_size="18vp" 
      ohos:hint_color="#cccccc" 
      ohos:top_margin="8vp"/> 
    <DirectionalLayout 
      ohos:height="1vp" 
      ohos:width="match_parent" 
      ohos:top_margin="3vp" 
      ohos:background_element="#cccccc"/> 
  </DirectionalLayout> 
 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="vertical" 
    ohos:left_padding="15vp" 
    ohos:right_padding="15vp" 
    ohos:top_padding="16vp"> 
    <Text 
      ohos:height="match_content" 
      ohos:width="match_content" 
      ohos:text="體重" 
      ohos:text_size="18vp"/> 
    <TextField 
      ohos:id="$+id:tf_weight" 
      ohos:height="match_content" 
      ohos:width="match_parent" 
      ohos:text_input_type="pattern_number" 
      ohos:hint="請(qǐng)輸入體重" 
      ohos:text_size="18vp" 
      ohos:hint_color="#cccccc" 
      ohos:top_margin="8vp"/> 
    <DirectionalLayout 
      ohos:height="1vp" 
      ohos:width="match_parent" 
      ohos:top_margin="3vp" 
      ohos:background_element="#cccccc"/> 
  </DirectionalLayout> 
 
 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="horizontal" 
    ohos:top_margin="30vp" 
    ohos:left_margin="15vp" 
    ohos:right_margin="15vp"> 
    <Button 
      ohos:id="$+id:bt_save" 
      ohos:height="40vp" 
      ohos:width="0" 
      ohos:weight="1" 
      ohos:text="保存" 
      ohos:text_size="20vp" 
      ohos:text_color="#ffffff" 
      ohos:right_margin="30vp" 
      ohos:background_element="$graphic:background_main_circle" 
      ohos:layout_alignment="center"/> 
    <Button 
      ohos:id="$+id:bt_query" 
      ohos:height="40vp" 
      ohos:width="0" 
      ohos:weight="1" 
      ohos:text="查詢" 
      ohos:text_size="20vp" 
      ohos:text_color="#ffffff" 
      ohos:right_margin="30vp" 
      ohos:background_element="$graphic:background_main_circle" 
      ohos:layout_alignment="center"/> 
  </DirectionalLayout> 
 
  <DirectionalLayout 
    ohos:height="match_content" 
    ohos:width="match_parent" 
    ohos:orientation="horizontal" 
    ohos:top_margin="30vp" 
    ohos:left_margin="15vp" 
    ohos:right_margin="15vp"> 
    <Button 
      ohos:id="$+id:bt_regist" 
      ohos:height="40vp" 
      ohos:width="0" 
      ohos:weight="1" 
      ohos:text="注冊(cè)兼停" 
      ohos:text_size="20vp" 
      ohos:text_color="#ffffff" 
      ohos:right_margin="30vp" 
      ohos:background_element="$graphic:background_main_circle" 
      ohos:layout_alignment="center"/> 
    <Button 
      ohos:id="$+id:bt_unregist" 
      ohos:height="40vp" 
      ohos:width="0" 
      ohos:weight="1" 
      ohos:text="解除注冊(cè)" 
      ohos:text_size="20vp" 
      ohos:text_color="#ffffff" 
      ohos:right_margin="30vp" 
      ohos:background_element="$graphic:background_main_circle" 
      ohos:layout_alignment="center"/> 
  </DirectionalLayout> 
 
 
 
  <Text 
    ohos:id="$+id:tvResultQuery" 
    ohos:height="match_content" 
    ohos:width="match_content" 
    ohos:text_size="18vp" 
    ohos:text="查詢結(jié)果：" 
    ohos:background_element="#cccccc" 
    ohos:layout_alignment="center" 
    ohos:top_margin="30vp" 
    ohos:padding="10vp"/> 
 
  <Text 
    ohos:id="$+id:tvResultListener" 
    ohos:height="match_content" 
    ohos:width="match_content" 
    ohos:text_size="18vp" 
    ohos:text="兼停結(jié)果：" 
    ohos:background_element="#cccccc" 
    ohos:layout_alignment="center" 
    ohos:top_margin="30vp" 
    ohos:padding="10vp"/> 
 
</DirectionalLayout> 

5.圓角背景圖形background_main_circle.xml文件

<?xml version="1.0" encoding="UTF-8" ?> 
<shape xmlns:ohos="http://schemas.huawei.com/res/ohos" 
       ohos:shape="rectangle"> 
    <corners 
        ohos:radius="10"/> 
    <solid 
        ohos:color="#00aaf5"/> 
 
</shape> 

實(shí)現(xiàn)效果視頻：https://harmonyos.51cto.com/show/7929

想了解更多內(nèi)容，請(qǐng)?jiān)L問：

51CTO和華為官方合作共建的鴻蒙技術(shù)社區(qū)

https://harmonyos.51cto.com