无法控制共享首选项中字符串集的顺序

Question

这是我的第一个 Whosebug 问题。我对此进行了很多谷歌搜索。在 Hashsets、Treesets、LinkedHashSets、Collections、Stacks（Stack class 已弃用？）...我意识到我可以只使用 SQLite，但我暂时试图避免这种情况。

我正在 Android Studio 开发应用程序。该应用程序与人打交道，列出他们并以不同方式联系他们。应用程序用户可以维护和控制三种类型的列表：最近联系、阻止和收藏夹。这些列表在共享首选项中保存为字符串集，因此它们在关闭和重新打开应用程序时仍然存在。当使用在线数据库填充列表时，各个字符串充当主键。我最关心 "recently contacted" 列表，因为这个列表的顺序很重要。

问题是，据我了解，当我声明一个字符串集时，它如下所示：

Set<String> faveArray = new LinkedHashSet<String>;

据我所知，我只能在右侧使用 HashSet、LinkedHashSet 或 TreeSet。

因为我使用了 LinkedHashset，所以我期望当我重新打开应用程序并将数据从 sharedpreferences 中拉回时，字符串将从最近添加的（LIFO/堆栈）开始被拉出，因此当我填充了一个列表视图，它们将显示列表顶部的 "most recently contacted" 人，依此类推......或者至少我期望有某种可预测的 order/behavior 我可以使用.

所以.......我附上了我的共享偏好代码I/O class.

在我的主应用程序中，我执行如下操作：

static SharedPrefUTIL sharedPrefUTIL;

sharedPrefUTIL = new SharedPrefUTIL(this);

sharedPrefUTIL.addRecent("derp");
sharedPrefUTIL.addRecent("nerp");
sharedPrefUTIL.addRecent("gerp");
sharedPrefUTIL.addRecent("herp");

此时，代码

Log.i(TAG, set + " committed to " + key);

在 class SharedPrefUTIL Logs 的 commit() 方法中：

" [derp, nerp, gerp, herp] 致力于 recentArray "

Bur 在关闭并重新打开应用程序后，如果我们执行：

sharedPrefUTIL.toastContents("R");

结果看似乱序。 <<<< 那是我的问题。

非常感谢任何帮助。

package com.secretsoft.booberbunz;

import android.content.Context;
import android.content.SharedPreferences;
import android.util.Log;
import android.widget.Toast;

import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Queue;
import java.util.Set;
import java.util.TreeSet;

/**
* Created by Programming on 2/22/2016.
*/
public class SharedPrefUTIL {

protected static final String TAG = "CXX SharedPrefUTIL";

Context context;

SharedPreferences sharedPreferences;

Set<String> faveArray;
Set<String> blockArray;
Set<String> recentArray;

public static final Set<String> DEFAULT = new HashSet<String>(Arrays.asList("empty"));


public SharedPrefUTIL(Context context){

    this.context = context;

    // load shared prefs into static arrays (new objects to prevent problems)

    sharedPreferences = context.getSharedPreferences("prefs", Context.MODE_PRIVATE);

    recentArray = new LinkedHashSet<String>(sharedPreferences.getStringSet("recentArray",DEFAULT));
    blockArray = new LinkedHashSet<String>(sharedPreferences.getStringSet("blockArray",DEFAULT));
    faveArray = new LinkedHashSet<String>(sharedPreferences.getStringSet("faveArray",DEFAULT));

    Log.i(TAG, "SharedPrefUTIL instance created");


    if (recentArray.contains("empty")) {
        recentArray.clear();

        Log.i(TAG, "recentArray contains the string -empty- and was cleared");
    }

    if (blockArray.contains("empty")) {
        blockArray.clear();

        Log.i(TAG, "blockArray contains the string -empty- and was cleared");
    }

    if (faveArray.contains("empty")) {
        faveArray.clear();

        Log.i(TAG, "faveArray contains the string -empty- and was cleared");
    }

}

public void toastLength(String type){

    if (type == "R"){

        String temp = type + " array is this long: " + recentArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);


    }

    else if (type == "B"){

        String temp = type + " array is this long: " + blockArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);

    }

    else if (type == "F"){

        String temp = type + " array is this long: " + faveArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);

    }

    else {
        Log.i(TAG, "invalid type param given to toastLength()");
    }

}


public void toastContents(String type){

    if (type == "R"){

        for (String temp : recentArray) {

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, "recentArray contains: " + temp);

    }

    }

    else if (type == "B"){

        for (String temp : blockArray) {

            Toast.makeText(context, temp,
                    Toast.LENGTH_LONG).show();

            Log.i(TAG, "blockArray contains: " + temp);

        }

    }

    else if (type == "F"){

        for (String temp : faveArray) {

            Toast.makeText(context, temp,
                    Toast.LENGTH_LONG).show();

            Log.i(TAG, "faveArray contains: " + temp);

        }
    }

    else {
        Log.i(TAG, "invalid type param given to toastContents()");
    }



}

public void clearList(String type){
    if (type == "R"){
        recentArray.clear();

        commit("recentArray", recentArray);

        Toast.makeText(context,"recent list has been cleared.", Toast.LENGTH_LONG);
    }

    else if (type == "B"){

        blockArray.clear();

        commit("blockArray", blockArray);

        Toast.makeText(context,"blacklist has been cleared.", Toast.LENGTH_LONG);

    }

    else if (type == "F"){

        faveArray.clear();

        commit("faveArray", faveArray);

        Toast.makeText(context,"favorites have been cleared.", Toast.LENGTH_LONG);

    }

    else {
        Log.i(TAG, "invalid type param given to clearList()");
    }

}

public void addRecent(String newRecent){
    recentArray.add(newRecent);
    commit("recentArray", recentArray);
    Log.i(TAG, newRecent + " added to recentArray");
}

public void addBlocked(String newBlocked, String  nick){
    blockArray.add(newBlocked);
    commit("blockArray", blockArray);
    Toast.makeText(context, nick + " has been blacklisted!", Toast.LENGTH_SHORT);
}

public void remBlocked(String remBlocked, String nick){
    blockArray.remove(remBlocked);
    commit("blockArray", blockArray);
    Toast.makeText(context, nick + " has been unblocked.", Toast.LENGTH_SHORT);
}

public void addFave(String newFave, String nick){
    faveArray.add(newFave);
    commit("faveArray", faveArray);
    Toast.makeText(context, nick + " added to favorites!", Toast.LENGTH_SHORT);

}

public void remFave(String remFave, String nick){
    faveArray.remove(remFave);
    commit("faveArray", faveArray);
    Toast.makeText(context, nick + " removed from favorites.", Toast.LENGTH_SHORT);
}

public void commit(String key, Set<String> set){
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putStringSet(key,set);
    editor.commit();
    Log.i(TAG, set + " committed to " + key);
}




}

Answer 1

不幸的是，您只是发现了 SharedPreferences 的限制。

当您使用 orderd 哈希时，它不会在您调用 getStringSet 时按顺序加载它们。

我发现执行此操作的最简单的最快方法是将数组转换为文本、排序，然后将其保存到 SharedPreferences 中。 Android 附带一个可以执行此操作的对象 JSONArray。

http://developer.android.com/reference/org/json/JSONArray.html

这是一些伪代码，可以执行您想要的操作：

public void saveOrderedCollection(Collection collection, String key){
    JSONArray jsonArray = new JSONArray(collection);
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putString(key, jsonArray.toString());
    editor.commit();
}

public Collection loadOrderedCollection(String key){
    ArrayList arrayList = new ArrayList;
    SharedPreferences.Editor editor = sharedPreferences.edit();
    JSONArray jsonArray = new JSONArray(editor.getString(key, "[]"));
    for (int i = 0; i < jsonArray.length(); i++) {
        arrayList.put(jsonArray.get(i));
    }
    return arrayList;
}

以下是我用来制作此内容的其他一些帖子：

Is it possible to add an array or object to SharedPreferences on Android

In shared preferences how to store string array in android application

Answer 2

我已经实施了建议的更改（在保存到共享首选项时使用 JSON 字符串而不是字符串集），这是我的共享首选项 class 的新代码，以防其他人尝试做同样的事情。在故障排除日志上可能有点矫枉过正，但这就是我的方式，因为我不知道如何正确调试。

package [];

import android.content.Context;
import android.content.SharedPreferences;
import android.util.Log;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;

import java.util.LinkedHashSet;
import java.util.Set;


/**
 * Created by Programming on 2/22/2016.
 */
public class SharedPrefUTIL {

protected static final String TAG = "CXX SharedPrefUTIL";

Context context;

SharedPreferences sharedPreferences;

Set<String> recentArray;
Set<String> blockArray;
Set<String> faveArray;

JSONArray recentJArray;
JSONArray blockJArray;
JSONArray faveJArray;


public SharedPrefUTIL(Context context){

    this.context = context;

    // START load arrays from shared prefs

    sharedPreferences = context.getSharedPreferences("prefs", Context.MODE_PRIVATE);

    try {
        recentJArray = new JSONArray(sharedPreferences.getString("recentArray","[]"));
        blockJArray = new JSONArray(sharedPreferences.getString("blockArray","[]"));
        faveJArray = new JSONArray(sharedPreferences.getString("faveArray","[]"));
    } catch (JSONException e) {
        e.printStackTrace();
        Log.i(TAG, e.toString());
    }

    Log.i(TAG, "length of recentJArray is " + recentJArray.length());

    recentArray = new LinkedHashSet<String>();
    blockArray = new LinkedHashSet<String>();
    faveArray = new LinkedHashSet<String>();

    for (int i = 0; i < recentJArray.length(); i++) {

        try {
            recentArray.add(recentJArray.getString(i));
        } catch (JSONException e) {
            e.printStackTrace();
            Log.i(TAG, e.toString());
        }

    }

    for (int i = 0; i < blockJArray.length(); i++) {

        try {
            blockArray.add(blockJArray.getString(i));
        } catch (JSONException e) {
            e.printStackTrace();
            Log.i(TAG, e.toString());
        }

    }

    for (int i = 0; i < faveJArray.length(); i++) {

        try {
            faveArray.add(faveJArray.getString(i));
        } catch (JSONException e) {
            e.printStackTrace();
            Log.i(TAG, e.toString());
        }

    }

    // END load arrays from shared prefs

    Log.i(TAG, "SharedPrefUTIL instance created");

}

public void toastLength(String type){

    if (type == "R"){

        String temp = type + " array is this long: " + recentArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);


    }

    else if (type == "B"){

        String temp = type + " array is this long: " + blockArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);

    }

    else if (type == "F"){

        String temp = type + " array is this long: " + faveArray.size();

        Toast.makeText(context, temp,
                Toast.LENGTH_LONG).show();

        Log.i(TAG, temp);

    }

    else {
        Log.i(TAG, "invalid type param given to toastLength()");
    }

}


public void toastContents(String type){

    if (type == "R"){

        for (String temp : recentArray) {

            Toast.makeText(context, temp, Toast.LENGTH_LONG).show();

            Log.i(TAG, "recentArray contains: " + temp);

        }

    }

    else if (type == "B"){

        for (String temp : blockArray) {

            Toast.makeText(context, temp,
                    Toast.LENGTH_LONG).show();

            Log.i(TAG, "blockArray contains: " + temp);

        }

    }

    else if (type == "F"){

        for (String temp : faveArray) {

            Toast.makeText(context, temp,
                    Toast.LENGTH_LONG).show();

            Log.i(TAG, "faveArray contains: " + temp);

        }
    }

    else {
        Log.i(TAG, "invalid type param given to toastContents()");
    }



}

public void clearList(String type){
    if (type == "R"){
        recentArray.clear();

        commit("recentArray", recentArray);

        Toast.makeText(context,"recent list has been cleared.", Toast.LENGTH_LONG);
    }

    else if (type == "B"){

        blockArray.clear();

        commit("blockArray", blockArray);

        Toast.makeText(context,"blacklist has been cleared.", Toast.LENGTH_LONG);

    }

    else if (type == "F"){

        faveArray.clear();

        commit("faveArray", faveArray);

        Toast.makeText(context,"favorites have been cleared.", Toast.LENGTH_LONG);

    }

    else {
        Log.i(TAG, "invalid type param given to clearList()");
    }

}

public void addRecent(String newRecent){
    recentArray.add(newRecent);
    commit("recentArray", recentArray);
    Log.i(TAG, newRecent + " added to recentArray");
}

public void addBlocked(String newBlocked){
    blockArray.add(newBlocked);
    commit("blockArray", blockArray);
    Toast.makeText(context, newBlocked + " has been blacklisted!", Toast.LENGTH_SHORT);
}

public void remBlocked(String remBlocked){
    blockArray.remove(remBlocked);
    commit("blockArray", blockArray);
    Toast.makeText(context, remBlocked + " has been unblocked.", Toast.LENGTH_SHORT);
}

public void addFave(String newFave){
    faveArray.add(newFave);
    commit("faveArray", faveArray);
    Toast.makeText(context, newFave + " added to favorites!", Toast.LENGTH_SHORT);

}

public void remFave(String remFave){
    faveArray.remove(remFave);
    commit("faveArray", faveArray);
    Toast.makeText(context, remFave + " removed from favorites.", Toast.LENGTH_SHORT);
}

public void commit(String key, Set<String> set){

    // convert set into JSON

    JSONArray jsonArray = new JSONArray(set);

    Log.i(TAG, "During commit, jsonArray(set) is this long: " + jsonArray.length());

    //-------------------------------------------


    // commit changes
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putString(key,jsonArray.toString());
    editor.commit();
    Log.i(TAG, jsonArray.toString() + " committed to " + key);

}

}

Answer 3

使用 kotlin，您可以简单地编写扩展函数来存储一个字符串列表，该列表在您添加它们时保持顺序：

   fun SharedPreferences.Editor.putStringList(key: String, list: List<String>) {
        this.putString(key, list.joinToString(";"))
    }

   fun SharedPreferences.getStringList(key: String): List<String> {
        return this.getString(key, "")?.split(";") ?: listOf()
    }

然后您可以像这样存储您的值：

sharedPrefs.edit().putStringList("SOME_KEY", listOf("A", "B", "C"))

并像这样接收它们：

val myList = sharedPrefs.getStringList("SOME_KEY")

无法控制共享首选项中字符串集的顺序

Can't Control Order of String Set in Shared Preferences

java

android

shared

preferences

lifo