預期浮動，但其值是一個java.lang.Double中

Question

Activity_A：

Intent intent = new Intent(Activity_A.this, 
          Activity_B.class); 
intent.putExtra("user_lat", 
        getSharedPreferences(
        Activity_C.USER_PREFS, 0).getFloat(
        "lat", 0)); 
Log.d("lat from prefs = ", 
      getSharedPreferences(Activity_C.USER_PREFS, 0) 
      .getFloat("lat", 0)); 
intent.putExtra("lng", 
        getSharedPreferences(
        Activity_C.USER_PREFS, 0).getFloat(
        "user_lng", 0)); 
Log.d("lng from prefs = ", 
      getSharedPreferences(Activity_C.USER_PREFS, 0) 
      .getFloat("lng", 0)"); 

的logcat的顯示：

12月12日至1日：36：53.409：從首選項=（554）d/LAT ：18.599348

12月12日至1日：36：53.409：d /從首選項=（554）LNG：73.7625

和Activity_B：

try { 

     MyLat = this.getIntent().getDoubleExtra("user_lat", 0); 
     MyLng = this.getIntent().getDoubleExtra("user_lng", 0); 
    } catch (Exception e) { 

     Log.e("Exception in getting user lat and lng as Double", 
       e.toString()); 
    } 
    if (MyLat == 0.0 || MyLng == 0.0) { 

     try { 

      MyLat = this.getIntent().getFloatExtra("user_lat", 0); 
      MyLng = this.getIntent().getFloatExtra("user_lng", 0); 
     } catch (Exception e) { 

      Log.e("Exception in getting user lat and lng as Float", 
        e.toString()); 
     } 
    } 

    Log.d("MyLat and MyLng", MyLat + "+" + MyLng); 

和logcat的：

12月12日至1日：36：57.168：d/MyLat和MyLng（554）：18.599348068237305 + 0.0

和logcat的錯誤：

12-01 12:36:57.138: W/Bundle(554): Key user_lat expected Double but value was a java.lang.Float. The default value 0.0 was returned. 
12-01 12:36:57.159: W/Bundle(554): Attempt to cast generated internal exception: 
12-01 12:36:57.159: W/Bundle(554): java.lang.ClassCastException: java.lang.Float 
12-01 12:36:57.159: W/Bundle(554): at android.os.Bundle.getDouble(Bundle.java:1017) 
12-01 12:36:57.159: W/Bundle(554): at android.content.Intent.getDoubleExtra(Intent.java:3377) 
12-01 12:36:57.159: W/Bundle(554): at com.wicfy.mobileapp.MapMarkerActivity.onCreate(MapMarkerActivity.java:60) 
12-01 12:36:57.159: W/Bundle(554): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
12-01 12:36:57.159: W/Bundle(554): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
12-01 12:36:57.159: W/Bundle(554): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
12-01 12:36:57.159: W/Bundle(554): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
12-01 12:36:57.159: W/Bundle(554): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
12-01 12:36:57.159: W/Bundle(554): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-01 12:36:57.159: W/Bundle(554): at android.os.Looper.loop(Looper.java:130) 
12-01 12:36:57.159: W/Bundle(554): at android.app.ActivityThread.main(ActivityThread.java:3683) 
12-01 12:36:57.159: W/Bundle(554): at java.lang.reflect.Method.invokeNative(Native Method) 
12-01 12:36:57.159: W/Bundle(554): at java.lang.reflect.Method.invoke(Method.java:507) 
12-01 12:36:57.159: W/Bundle(554): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
12-01 12:36:57.159: W/Bundle(554): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
12-01 12:36:57.159: W/Bundle(554): at dalvik.system.NativeStart.main(Native Method) 

我想，因爲我將user_lat作爲Activity_B中的雙精度值，所以我必須將它轉換爲雙期間intent.putExtra

但然後我得到這個在logcat中：

12月12日至1日：36：57.168：d/MyLat和MyLng（554）：0.0 + 0.0

12-01 12:07:50.218: W/Bundle(498): Key user_lat expected Float but value was a java.lang.Double. The default value 0.0 was returned. 
12-01 12:07:50.249: W/Bundle(498): Attempt to cast generated internal exception: 
12-01 12:07:50.249: W/Bundle(498): java.lang.ClassCastException: java.lang.Double 
12-01 12:07:50.249: W/Bundle(498): at android.os.Bundle.getFloat(Bundle.java:984) 
12-01 12:07:50.249: W/Bundle(498): at android.content.Intent.getFloatExtra(Intent.java:3360) 
12-01 12:07:50.249: W/Bundle(498): at com.wicfy.mobileapp.MapMarkerActivity.onCreate(MapMarkerActivity.java:71) 
12-01 12:07:50.249: W/Bundle(498): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
12-01 12:07:50.249: W/Bundle(498): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
12-01 12:07:50.249: W/Bundle(498): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
12-01 12:07:50.249: W/Bundle(498): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
12-01 12:07:50.249: W/Bundle(498): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
12-01 12:07:50.249: W/Bundle(498): at android.os.Handler.dispatchMessage(Handler.java:99) 
12-01 12:07:50.249: W/Bundle(498): at android.os.Looper.loop(Looper.java:130) 
12-01 12:07:50.249: W/Bundle(498): at android.app.ActivityThread.main(ActivityThread.java:3683) 
12-01 12:07:50.249: W/Bundle(498): at java.lang.reflect.Method.invokeNative(Native Method) 
12-01 12:07:50.249: W/Bundle(498): at java.lang.reflect.Method.invoke(Method.java:507) 
12-01 12:07:50.249: W/Bundle(498): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
12-01 12:07:50.249: W/Bundle(498): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
12-01 12:07:50.249: W/Bundle(498): at dalvik.system.NativeStart.main(Native Method) 

我沒有得到Log.e消息。可能是因爲它的內部異常並不會導致崩潰。

所以，我怎樣才能得到它我是從在Activity_B發送throught意圖Activity_A實際值

謝謝

Answer 1

由於該值已存儲在SharedPreferences文件中，因此似乎最簡單的答案是不使用Intent。

在活動B使用：

float myLat = getSharedPreferences(Activity_C.USER_PREFS, 0).getFloat("lat", 0); 
// Read the Longitude in the same way 

---

您是試圖從一個位置對象（我認爲），但SharedPreferences不雙打工作，雙打的工作。你可能會更安全地將雙打轉換成絃樂，然後再回來。這樣你就不會獲得或失去進入和來自Floats的精確度。

Answer 2

雖然原語，你可以投double到float（有損失的精度）和float到double（沒有警告），在Float和Double的情況下，這將不起作用。因此，每當您將Float放入Bundle時，您都必須確定它是Float而不是Double。希望這可以幫助。