Sharedpreferences不起作用，默認值

Question

我的應用程序中有很多複選框，一個微調器，edittext和一個按鈕。當我從微調框中選擇一個項目，然後輸入一個特定的值並點擊一個按鈕時，某個複選框文本會發生變化。現在我添加了共享首選項，並有兩個問題。

第一個問題是，當我嘗試使用sharedpreferences時，應用程序崩潰（只要我啓動包含這些sharedpreferences的活動）。

private String getItemQuantity(String key){ 
    SharedPreferences itemQuantitySP = getApplicationContext().getSharedPreferences("bifrostPrefs", android.content.Context.MODE_PRIVATE); 
    String sp1 = "sp1"; 
    return itemQuantitySP.getString(key, sp1); 
} 
private void saveItemQuantity(String key, String value){ 
    SharedPreferences itemQuantitySP = getApplicationContext().getSharedPreferences("bifrostPrefs", android.content.Context.MODE_PRIVATE); 
    SharedPreferences.Editor editor = itemQuantitySP.edit(); 
    editor.putString(key, value); 
    editor.commit(); 
} 

保存sharedpreferences：

if (Integer.parseInt(quantityEditText.getText().toString()) == 250) 
{ 
    cb4.setText("Elaborate Totem (" + item1 + "/250)"); 
    saveItemQuantity("cb4", cb4.getText().toString()); 
    cb4.setChecked(true); 
} 
... //REST OF THE CODE 

獲取sharedpreferences：

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_bifrost); 

    getItemQuantity("cb4"); 
... //REST OF THE CODE 

第二個問題是，我有很多的複選框，並設置默認值來爲他們的每一個將是非常耗時的。那麼有沒有辦法簡單地從XML讀取默認值？正如你所看到的，現在，我創建了一個名爲sp1的新變量並將其設置爲默認值，但是當然我想擺脫它。

logcat的文件：代碼

06-27 16:31:44.782: E/AndroidRuntime(13139): FATAL EXCEPTION: main 
06-27 16:31:44.782: E/AndroidRuntime(13139): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.matthewstudios.gw2legendary/com.example.gw2legendary.Bifrost}: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread.access$600(ActivityThread.java:141) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.os.Looper.loop(Looper.java:137) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread.main(ActivityThread.java:5041) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at java.lang.reflect.Method.invokeNative(Native Method) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at java.lang.reflect.Method.invoke(Method.java:511) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at dalvik.system.NativeStart.main(Native Method) 
06-27 16:31:44.782: E/AndroidRuntime(13139): Caused by: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:224) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at com.example.gw2legendary.Bifrost.getItemQuantity(Bifrost.java:849) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at com.example.gw2legendary.Bifrost.onCreate(Bifrost.java:152) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.Activity.performCreate(Activity.java:5104) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
06-27 16:31:44.782: E/AndroidRuntime(13139): ... 11 more 
06-27 16:31:49.391: E/fb4a(:<default>):MmsConfig(13225): MmsConfig.loadMmsSettings mms_config.xml missing uaProfUrl setting 

部分：

public void submitQuantityButton (View v){ 
    final Spinner sItems = (Spinner)findViewById(R.id.spinner1); 
    final Context context = this; 
    final CheckBox cb4 = (CheckBox) findViewById(R.id.checkBox4); 
    final CheckBox cb5 = (CheckBox) findViewById(R.id.checkBox5); 
    final CheckBox cb6 = (CheckBox) findViewById(R.id.checkBox6); 
    final CheckBox cb7 = (CheckBox) findViewById(R.id.checkBox7); 
    final CheckBox cb9 = (CheckBox) findViewById(R.id.checkBox9); 
    final CheckBox cb10 = (CheckBox) findViewById(R.id.checkBox10); 
    final CheckBox cb11 = (CheckBox) findViewById(R.id.checkBox11); 
    final CheckBox cb12 = (CheckBox) findViewById(R.id.checkBox12); 
    final CheckBox cb13 = (CheckBox) findViewById(R.id.checkBox13); 
    final CheckBox cb15 = (CheckBox) findViewById(R.id.checkBox15); 
    final CheckBox cb16 = (CheckBox) findViewById(R.id.checkBox16); 
    final CheckBox cb17 = (CheckBox) findViewById(R.id.checkBox17); 
    final CheckBox cb18 = (CheckBox) findViewById(R.id.checkBox18); 
    final CheckBox cb25 = (CheckBox) findViewById(R.id.checkBox25); 
    final CheckBox cb27 = (CheckBox) findViewById(R.id.checkBox27); 
    final CheckBox cb28 = (CheckBox) findViewById(R.id.checkBox28); 
    final CheckBox cb29 = (CheckBox) findViewById(R.id.checkBox29); 
    final CheckBox cb30 = (CheckBox) findViewById(R.id.checkBox30); 
    final CheckBox cb31 = (CheckBox) findViewById(R.id.checkBox31); 
    final CheckBox cb33 = (CheckBox) findViewById(R.id.checkBox33); 
    final CheckBox cb34 = (CheckBox) findViewById(R.id.checkBox34); 
    final CheckBox cb35 = (CheckBox) findViewById(R.id.checkBox35); 
    final CheckBox cb36 = (CheckBox) findViewById(R.id.checkBox36); 
    final CheckBox cb37 = (CheckBox) findViewById(R.id.checkBox37); 

    //WRONG VALUE ERROR 
    final AlertDialog.Builder wrongValueBuilder = new AlertDialog.Builder(context); 
    wrongValueBuilder.setTitle("Warning"); 
    wrongValueBuilder.setMessage("The value you entered is too high!"); 
    wrongValueBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 

     @Override 
     public void onClick(DialogInterface dialog, int which) { 
      dialog.cancel(); 
     } 
    }); 

    //EMPTY TEXT ERROR 
    final AlertDialog.Builder emptyETextErrorBuilder = new AlertDialog.Builder(context); 
    emptyETextErrorBuilder.setTitle("Warning"); 
    emptyETextErrorBuilder.setMessage("Please enter a value before pressing this button"); 
    emptyETextErrorBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 

     @Override 
     public void onClick(DialogInterface dialog, int which) { 
      dialog.cancel(); 
     } 
    }); 

      final int position = sItems.getSelectedItemPosition(); 
      EditText quantityEditText = (EditText)findViewById(R.id.editText1); 

      switch (position){ 
      case 0: 
       AlertDialog.Builder spinnerErrorBuilder = new AlertDialog.Builder(context); 
       spinnerErrorBuilder.setTitle("Warning"); 
       spinnerErrorBuilder.setMessage("Please choose an item from the list above and then enter a certain value"); 
       spinnerErrorBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 

        @Override 
        public void onClick(DialogInterface dialog, int id) { 
         dialog.cancel(); 
        } 
       }); 
       AlertDialog spinnerError = spinnerErrorBuilder.create(); 
       spinnerError.show(); 
       break; 
      case 1: 
       String item1 = quantityEditText.getText().toString(); 
       if (item1.matches("")) 
       { 
        AlertDialog emptyETextError = emptyETextErrorBuilder.create(); 
        emptyETextError.show(); 
       } 
       else 
       { 
        if (Integer.parseInt(quantityEditText.getText().toString()) <= 250) 
        { 
         if (Integer.parseInt(quantityEditText.getText().toString()) == 250) 
         { 
          cb4.setText("Elaborate Totem (" + item1 + "/250)"); 
          saveItemQuantity("cb4", cb4.getText().toString()); 
          cb4.setChecked(true); 
         } 
         else 
         { 
          cb4.setText("Elaborate Totem (" + item1 + "/250)"); 
          saveItemQuantity("cb4", cb4.getText().toString()); 
          cb4.setChecked(false); 
         } 
        } 

Answer 1

堆棧跟蹤，3個以下行，說明問題出在哪裏：

06-27 16:31:44.782: E/AndroidRuntime(13139): Caused by: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String 
06-27 16:31:44.782: E/AndroidRuntime(13139): at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:224) 
06-27 16:31:44.782: E/AndroidRuntime(13139): at com.example.gw2legendary.Bifrost.getItemQuantity(Bifrost.java:849) 

所以，你必須在文件Bifrost中存在的問題.java，在849行，在getItemQuantity()方法中。它對應於getString()方法的調用。看看這3行很有趣，並試圖瞭解如何獲取所有這些信息，因爲每次在代碼中出現異常時都必須執行相同的操作。

我可以假設你試圖從SharedPreferences得到的值已經被保存爲Boolean，並且你試圖將它作爲String，所以你有這個ClassCastException。只需使用該密鑰修改您在SharedPreferences中保存的值即可。

要獲得更多信息，請嘗試學習如何調試應用程序，並使用斷點檢查執行時的變量值。斷點允許您準確停止執行，並查找所有變量的狀態和值。使用Eclipse或NetBeans等IDE進行調試非常簡單，並且可以在很多情況下爲您提供幫助。

Answer 2

很明顯的錯誤是從閱讀堆棧跟蹤什麼：

java.lang.ClassCastException：JAVA .lang.Boolean不能轉換爲java.lang.String

是的，你可以閱讀預設從XML文件牛逼的價值觀，瞭解arrays.xml和http://developer.android.com/guide/topics/resources/more-resources.html#TypedArray這裏