java - 共享偏好的不当行为

Question

在你评判我之前，我想说我读了这些:

• Saving a List of Strings in Android with SharedPreferences
  
• Misbehavior when trying to store a string set using SharedPreferences
  
• getString(String key, String defValue) - Reference
  

但我仍然无法理解，无法正常工作。我的偏好完全不当。我的代码:

public static SharedPreferences sharedAppPreferences;
public static final String AppsListKey = "AppListKey";
public static final String AppsPreferences = "AppsPreferences";
public static ArrayList<String> packageNames;

public void chooseApps(View view) {
        sharedAppPreferences = getSharedPreferences(AppsPreferences, Context.MODE_PRIVATE);
        if (sharedAppPreferences.contains(AppsListKey)) {
            Set<String> buffer = new LinkedHashSet<String>(sharedAppPreferences.getStringSet(AppsListKey, new LinkedHashSet<String>()));
            packageNames = new ArrayList<String>(buffer);
        } else {
            packageNames = new ArrayList<String>();
        }
        PackageManager packageManager = getPackageManager();

        int flags = PackageManager.GET_META_DATA | PackageManager.GET_SHARED_LIBRARY_FILES | PackageManager.GET_UNINSTALLED_PACKAGES;
        List<ApplicationInfo> packageList = packageManager.getInstalledApplications(flags);

        for (ApplicationInfo pack : packageList) {

            if (((pack.flags & ApplicationInfo.FLAG_SYSTEM) == 1) || packageNames.contains(pack.loadLabel(packageManager).toString())) {
                // System application or already in array
            } else {
                // Installed by user and isnt in array
                packageNames.add(pack.loadLabel(packageManager).toString());
            }
        }
        Editor editor = sharedAppPreferences.edit();
        Set<String> buffer1 = new LinkedHashSet<String> (packageNames);
        editor.putStringSet(AppsListKey, buffer1);
        editor.commit();
        //packageNames.clear();
        //buffer1.clear();
        buffer1 = new LinkedHashSet<String>(sharedAppPreferences.getStringSet(AppsListKey, new LinkedHashSet<String>()));
        packageNames = new ArrayList<String>(buffer1);
        AppList appList = new AppList();
        appList.show(getSupportFragmentManager(), "AppList");
    }

为什么我第一次运行我的应用程序时会得到这样的列表

[Skype, Facebook, Whatsapp, Twitter, Google+]

只要应用程序正在运行就没问题......但是如果我终止我的应用程序并重新启动，我现在会得到完全不同的列表，如

[Whatsapp, Google+, Skype, Twitter, Facebook]

谁能解释一下这里有什么问题吗？

Answer 1

列表前后的唯一区别是顺序...

为了扩展我一直在谈论的内容，我刚刚意识到你的错误..

LinkedHashSet被订购。但是，您存储在

Set<String> buffer 

Set<String>没有订购...

所以它又把它弄混了。

您需要将其存储在LinkedHashSet 的参数中如下图

LinkedHashSet<String> buffer = new LinkedHashSet<String>(sharedAppPreferences.getStringSet(AppsListKey, new LinkedHashSet<String>()));

(有两次我认为这需要更改。)

编辑:

您可以做的最后一件事是，与其创建新列表，不如从共享首选项中转换现有列表 ...

 LinkedHashSet<String> buffer = (LinkedHashSet<String>)sharedAppPreferences.getStringSet(AppsListKey, new LinkedHashSet<String>());

HashSet 有替代品 here