SharedPreference ClassCastException問題Android

Question

第一次在這裏發佈海報，所以請原諒任何發佈錯誤。也是Android的新手，我有一個問題試圖找出共享首選問題。我聲明我的常數如下

private static SharedPreferences mSharedPreferences; 
    static final String TWEET = null; 

    static final String MEAL_ID = null; 

和我的共享偏好如下

mSharedPreferences = getApplicationContext().getSharedPreferences(
      "MyPref", 0); 

我的簡單測試代碼如下：

String msgTemp = "testing"; 
long iDTest = 234; 
Editor e = mSharedPreferences.edit(); 
e.putLong(MEAL_ID, iDTest); 
e.putString(TWEET, msgTemp); 
e.commit(); 
String tempMsg = mSharedPreferences.getString(TWEET, ""); 
long tempId = mSharedPreferences.getLong(MEAL_ID, 0); 
    Toast.makeText(getApplicationContext(), 
    "Msg: " + tempMsg + " " + "ID: " + tempId, Toast.LENGTH_LONG).show(); 

返回以下錯誤：

03-25 15:47:41.386: E/AndroidRuntime(28321): java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Long03-25 15:47:41.386: E/AndroidRuntime(28321): at android.app.SharedPreferencesImpl.getLong(SharedPreferencesImpl.java:228) 

howev呃，如果我切換2「把」線路中的代碼是這樣的：

String msgTemp = "testing"; 
long iDTest = 234; 
Editor e = mSharedPreferences.edit(); 
e.putString(TWEET, msgTemp); 
e.putLong(MEAL_ID, iDTest); 
e.commit(); 
String tempMsg = mSharedPreferences.getString(TWEET, ""); 
long tempId = mSharedPreferences.getLong(MEAL_ID, 0); 
    Toast.makeText(getApplicationContext(), 
    "Msg: " + tempMsg + " " + "ID: " + tempId, Toast.LENGTH_LONG).show(); 

我收到以下錯誤：

03-25 15:50:16.551: E/AndroidRuntime(28838): java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String 03-25 15:50:16.551: E/AndroidRuntime(28838): at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:205) 

所以，在我看來，該值是進入喜好以錯誤的順序，但我不知道爲什麼。我試過在輸入新值之前清除這些值，如下所示：

String msgTemp = "testing"; 
long iDTest = 234; 
Editor e = mSharedPreferences.edit(); 
e.remove(MEAL_ID); 
e.remove(TWEET); 
e.putLong(MEAL_ID, iDTest); 
e.putString(TWEET, msgTemp); 
e.commit(); 
String tempMsg = mSharedPreferences.getString(TWEET, ""); 
long tempId = mSharedPreferences.getLong(MEAL_ID, 0); 
    Toast.makeText(getApplicationContext(), 
    "Msg: " + tempMsg + " " + "ID: " + tempId, Toast.LENGTH_LONG).show(); 

但是那樣做什麼也沒有。任何人都可以爲我闡明這一點嗎？

Answer 1

給你的常數的值：

MEAL_ID =「meal_id」