java.lang.RuntimeException：無法啓動活動ComponentInfo {java.lang.ClassCastException：android.widget.LinearLayout

Question

這個異常是什麼意思？

07-05 12:09:11.788: W/dalvikvm(445): threadid=1: thread exiting with uncaught exception (group=0x40015560) 
07-05 12:09:11.808: E/AndroidRuntime(445): FATAL EXCEPTION: main 
07-05 12:09:11.808: E/AndroidRuntime(445): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.a2zunitconverter.miniproject/com.a2zunitconverter.miniproject.weight}: java.lang.ClassCastException: android.widget.LinearLayout 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.os.Handler.dispatchMessage(Handler.java:99) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.os.Looper.loop(Looper.java:123) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread.main(ActivityThread.java:3683) 
07-05 12:09:11.808: E/AndroidRuntime(445): at java.lang.reflect.Method.invokeNative(Native Method) 
07-05 12:09:11.808: E/AndroidRuntime(445): at java.lang.reflect.Method.invoke(Method.java:507) 
07-05 12:09:11.808: E/AndroidRuntime(445): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
07-05 12:09:11.808: E/AndroidRuntime(445): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
07-05 12:09:11.808: E/AndroidRuntime(445): at dalvik.system.NativeStart.main(Native Method) 
07-05 12:09:11.808: E/AndroidRuntime(445): Caused by: java.lang.ClassCastException: android.widget.LinearLayout 
07-05 12:09:11.808: E/AndroidRuntime(445): at com.a2zunitconverter.miniproject.weight.onCreate(weight.java:31) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
07-05 12:09:11.808: E/AndroidRuntime(445): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
07-05 12:09:11.808: E/AndroidRuntime(445): ... 11 more 
07-05 12:09:15.538: D/dalvikvm(454): GC_EXTERNAL_ALLOC freed 49K, 53% free 2560K/5379K, external 2076K/2137K, paused 56ms 

這裏是我的XML代碼：

<?xml version="1.0" encoding="utf-8"?> 
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/scrollView1" 
    android:layout_width="match_parent" 
    android:layout_height="fill_parent" 
    android:background="@drawable/weight4"> 
    <LinearLayout 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:orientation="vertical" > 

     <TextView 
      android:id="@+id/textView1" 
      android:layout_width="match_parent" 
      android:layout_height="50dp" 
      android:text="@string/weight" 
      android:textAppearance="?android:attr/textAppearanceLarge" 
      android:textColor="#ffffff" /> 

     <EditText 
      android:id="@+id/wquery" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:ems="10" 
      android:inputType="numberDecimal" 
      android:text="@string/value" > 

      <requestFocus /> 
     </EditText> 

     <TextView 
      android:id="@+id/textView2" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:text="@string/label2" 
      android:textAppearance="?android:attr/textAppearanceMedium" 
      android:textColor="#ffffff" /> 

     <LinearLayout 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:orientation="horizontal" > 

      <Spinner 
       android:id="@+id/convertfrom" 
       android:layout_width="126dp" 
       android:layout_height="wrap_content" > 
      </Spinner> 

      <ImageView 
       android:id="@+id/imageView1" 
       android:layout_width="34dp" 
       android:layout_height="61dp" 
       android:background="#cccccc" 
       android:src="@drawable/arrows" /> 

      <Spinner 
       android:id="@+id/convertto" 
       android:layout_width="137dp" 
       android:layout_height="wrap_content" > 
      </Spinner> 
     </LinearLayout> 

     <LinearLayout 
      android:id="@+id/back1" 
      android:layout_width="match_parent" 
      android:layout_height="248dp" 
      android:orientation="vertical" > 

      <TextView 
       android:id="@+id/textView3" 
       android:layout_width="213dp" 
       android:layout_height="wrap_content" 
       android:text="@string/result" 
       android:textAppearance="?android:attr/textAppearanceLarge" 
       android:textColor="#ffffff" /> 

      <TextView 
       android:id="@+id/result" 
       android:layout_width="269dp" 
       android:layout_height="100dp" 
       android:textAppearance="?android:attr/textAppearanceLarge" 
       android:textColor="#66cc00" /> 

      <ImageView 
       android:id="@+id/exit" 
       android:layout_width="74dp" 
       android:layout_height="match_parent" 
       android:src="@drawable/back" /> 
     </LinearLayout> 
    </LinearLayout> 
</ScrollView> 

Answer 1

，你可以從該行看到：07-05 12:09:11.808: E/AndroidRuntime(445): at com.a2zunitconverter.miniproject.weight.onCreate(weight.java:31)

有一個錯誤在你onCreate功能行號31

Answer 2

錯誤ClassCastException意味着您正在嘗試將對象轉換爲特定類與其類型不匹配。

看來你正在試圖將LinearLayout對象轉換爲其他對象。如果你發佈你的java代碼，我們可以更具體。

Answer 3

有時你可能會在修改佈局xml後在Eclipse中出現這個錯誤。嘗試在Eclipse中製作「Clean Project」。這對我有幫助。