#2020征文-手机#HarmonyOS轻量级偏好数据库初体验

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:height="match_parent"
    ohos:width="match_parent"
    ohos:orientation="vertical">



    <Text
        ohos:id="$+id:text_helloworld"
        ohos:height="match_content"
        ohos:width="match_content"
        ohos:background_element="$graphic:background_ability_main"
        ohos:layout_alignment="horizontal_center"
        ohos:text="Hello World"
        ohos:text_size="50"
        />

    <TextField
        ohos:id="$+id:input"
        ohos:height="100vp"
        ohos:width="100vp"
        ohos:text_size="1px"></TextField>

    <Button
        ohos:id="$+id:add"
        ohos:height="match_content"
        ohos:width="match_content"
        ohos:text="添加"
        ohos:text_size="100px"></Button>

    <Button
        ohos:id="$+id:get"
        ohos:height="match_content"
        ohos:width="match_content"
        ohos:text="查询"
        ohos:text_size="100px"></Button>

    <Button
        ohos:id="$+id:del"
        ohos:height="match_content"
        ohos:width="match_content"
        ohos:text="删除"
        ohos:text_size="100px"></Button>

    <Button
        ohos:id="$+id:upd"
        ohos:height="match_content"
        ohos:width="match_content"
        ohos:text="更改"
        ohos:text_size="100px"></Button>

</DirectionalLayout>



package com.datang.myapplication.slice;

import com.datang.myapplication.ResourceTable;
import ohos.aafwk.ability.AbilitySlice;
import ohos.aafwk.content.Intent;
import ohos.agp.components.Button;
import ohos.agp.components.TextField;
import ohos.app.Context;
import ohos.data.DatabaseHelper;
import ohos.data.orm.OrmContext;
import ohos.data.orm.OrmPredicates;
import ohos.data.preferences.Preferences;
import ohos.data.rdb.ValuesBucket;
import ohos.hiviewdfx.HiLog;
import ohos.hiviewdfx.HiLogLabel;

import java.io.File;
import java.util.List;
import java.util.Map;
import java.util.Set;

//关系型数据库
public class MainAbilitySlice3 extends AbilitySlice {

    final HiLogLabel label = new HiLogLabel(HiLog.LOG_APP, 0x00201, "MY_TAG");
    Preferences preferences = null;

    @Override
    public void onStart(Intent intent) {
        super.onStart(intent);
        super.setUIContent(ResourceTable.Layout_ability_main3);
        initDB();

        insert();
        select();
        delete();
        update();


        //监听无效
        preferences.registerObserver((p, k) -> {
            HiLog.info(label, "触发了监听,key为:%{public}s", k);
        });
    }


    @Override
    public void onActive() {
        super.onActive();
    }

    public void initDB() {
        DatabaseHelper databaseHelper = new DatabaseHelper(this); // context入参类型为ohos.app.Context。
        String fileName = "test"; // fileName表示文件名，其取值不能为空，也不能包含路径，默认存储目录可以通过context.getPreferencesDir()获取。
        preferences = databaseHelper.getPreferences(fileName);
        File preferencesDir = this.getPreferencesDir();
        String absolutePath = preferencesDir.getAbsolutePath();
        HiLog.info(label, "默认路径%{public}s", absolutePath);
    }

    //增加
    public void insert() {
        Button button = (Button) findComponentById(ResourceTable.Id_add);
        button.setClickedListener(e -> {

//            preferences.putInt("intKey", 3);
//            preferences.flush();
//
//            preferences.putString("StringKey", "正经的value");
//            //同步刷新
//            preferences.flushSync();
//            //对同一个key重复添加会覆盖
//            preferences.putString("StringKey", "不正经的value");
//            //同步刷新
//            preferences.flushSync();


            TextField text = (TextField) findComponentById(ResourceTable.Id_input);
            String text1 = text.getText();
            preferences.putString(text1, text1 + "的value");
            preferences.flushSync();
            HiLog.info(label, "添加成功");
        });


    }

    //查询
    public void select() {
        Button button2 = (Button) findComponentById(ResourceTable.Id_get);
        button2.setClickedListener(e -> {
            Map<String, ?> all = preferences.getAll();
            Set<String> keys = all.keySet();
            keys.forEach(c -> {
                HiLog.info(label, "获取到的key:%{public}s", c);
                String value = preferences.getString(c, "没有" + c + "这个key");
                HiLog.info(label, "key为:%{public}s,value为:%{public}s", c, value);
            });


//            int anInt = preferences.getInt("intKey", -1);
//            HiLog.info(label, "获取到的key:%{public}d", anInt);
//
//            String string = preferences.getString("StringKey", "没有这个key");
//            HiLog.info(label, "获取到的key:%{public}s", string);
//
//            //当获取不到key时，则给出默认返回值，-1
//            int anInt2 = preferences.getInt("aaa", -1);
//            HiLog.info(label, "获取到的key:%{public}d", anInt2);
//
//            String string2 = preferences.getString("bbb", "没有这个key");
//            HiLog.info(label, "获取到的key:%{public}s", string2);
        });
    }

    //删除
    public void delete() {
        Button button3 = (Button) findComponentById(ResourceTable.Id_del);
        button3.setClickedListener(e -> {
            //这个移除实例后依然可以添加和查询,不知道是干啥的
//            DatabaseHelper databaseHelper = new DatabaseHelper(this);
//            String fileName = "test"; // fileName表示文件名，其取值不能为空，也不能包含路径。
//            databaseHelper.removePreferencesFromCache(fileName);
//            HiLog.info(label, "移除实例");


            //删除文件后依然能新增和查看
//            DatabaseHelper databaseHelper = new DatabaseHelper(this);
//            String fileName = "test"; // fileName表示文件名，其取值不能为空，也不能包含路径。
//            boolean result = databaseHelper.deletePreferences(fileName);
//            HiLog.info(label, "删除文件");
        });
    }


    //更改
    public void update() {
        Button button4 = (Button) findComponentById(ResourceTable.Id_upd);
        button4.setClickedListener(e -> {
            //这个更改也不知道干啥的
//            DatabaseHelper databaseHelper = new DatabaseHelper(this);
//            String srcFile = "/data/data/com.datang.myapplication/MainAbility/preferences/test"; // srcFile表示源文件名或者源文件的绝对路径，不能为相对路径，其取值不能为空。当srcFile只传入文件名时，srcContext不能为空。
//            String targetFile = "test2"; // targetFile表示目标文件名，其取值不能为空，也不能包含路径。
//            Context srcContext = null;
//            boolean result = databaseHelper.movePreferences(null,srcFile,targetFile);
        });
    }

}