每次我的 Android 應用程序啟動時，我都會從我的服務器獲得一個arraylist, MatchingArrayList： try { JSONArray Object = new JSONArray(MatchingAsString); //for every object in the Array for (int x = 0; x < Object.length(); x++) { final JSONObject obj = Object.getJSONObject(x); MatchingArrayList.add(obj.getString("usernameMatch")); }它看起來像這樣：[+111, +222]然后我像arraylist這樣保存sharedpreferences： SharedPreferences sharedPreferencesMAL = PreferenceManager.getDefaultSharedPreferences(getApplication()); SharedPreferences.Editor editorMAL = sharedPreferencesMAL.edit(); Gson gsonMAL = new Gson(); String jsonMAL = gsonMAL.toJson(MatchingArrayList); editorMAL.putString("MatchingArrayList", jsonMAL); editorMAL.commit();所以下次使用該應用時，如果MatchingArrayList已更改為[+111, +222, +333]，例如，它將覆蓋上次使用arraylist的[+111, +222]它運行良好，除非MatchingArrayList是null或為空。sharedpreferences不更新。我試過了： if (MatchingArrayList == null) { SharedPreferences sharedPreferencesMAL = PreferenceManager.getDefaultSharedPreferences(getApplication()); SharedPreferences.Editor editorMAL = sharedPreferencesMAL.edit(); editorMAL.putString("MatchingArrayList", null); editorMAL.commit(); } else { //save MatchingArrayList into sharedpreferences so we can use it elsewhere SharedPreferences sharedPreferencesMAL = PreferenceManager.getDefaultSharedPreferences(getApplication()); SharedPreferences.Editor editorMAL = sharedPreferencesMAL.edit(); Gson gsonMAL = new Gson(); String jsonMAL = gsonMAL.toJson(MatchingArrayList); editorMAL.putString("MatchingArrayList", jsonMAL); editorMAL.commit(); } But still the last arraylist is being used. How can I fix this?
如果 arraylist 為空，如何保存到 shredpreferences？
慕婉清6462132
2022-07-27 20:07:53
