SharedPreferences putStringSet 不起作用 [英] SharedPreferences putStringSet doesn't work

问题描述

我需要将 Set 放在 SharedPreference 中，但我遇到了问题.

I need to put Set in SharedPreference, but I have a problem.

当我点击按钮时，我将从SharedPreference中获取Set并将数据添加到Set然后放回SharedPreference，但是当我销毁项目并再次打开它时，sharedPreference只在Set中获取一个字符串

when I click button, I will get Set from SharedPreference and add data to Set then put back SharedPreference, but when I destroy project and open it again, the sharedPreference only get one string in Set

SharedPreferences s = getSharedPreferences("db", 0);
Log.i("chauster", "1.set = "+s.getStringSet("set", new HashSet<String>()));

Button btn = (Button)findViewById(R.id.button1);
btn.setOnClickListener(new Button.OnClickListener() {

    @Override
    public void onClick(View v) {
        SharedPreferences ss = getSharedPreferences("db", 0);
        Set<String> hs = ss.getStringSet("set", new HashSet<String>());
        hs.add(String.valueOf(hs.size()+1));
        Editor edit = ss.edit();
        edit.putStringSet("set", hs);
        edit.commit();
        SharedPreferences sss = getSharedPreferences("db", 0);
        Log.i("chauster", "2.set = "+sss.getStringSet("set",
                new HashSet<String>()));
    }
});

当我第一次安装项目时，我点击按钮 4 次，logcat 打印它

when I install project first, and I click button 4 times, the logcat print it

1.set = []
2.set = [1]
2.set = [2, 1]
2.set = [3, 2, 1]
2.set = [3, 2, 1, 4]

将字符串放入 sharedPreference Set 看起来很成功，但是当我销毁应用程序并再次打开它时，logcat 会打印它

it's look like success to put string in sharedPreference Set, but when I destroy app and open it again, the logcat print it

1.set = [1]

意思是sharedPreference里面只有一个字符串，不知道怎么回事?请帮我.谢谢~

it means only one string in Set from sharedPreference, I don't know what's happened? Please help me. thanks~

推荐答案

在 putStringSet 之前使用 edit.clear()

use edit.clear() before putStringSet

SharedPreferences ss = getSharedPreferences("db", 0);
Set<String> hs = ss.getStringSet("set", new HashSet<String>());
hs.add(String.valueOf(hs.size()+1));
Editor edit = ss.edit();
edit.clear();
edit.putStringSet("set", hs);
edit.commit();

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