LstView findViewByID返回null

Question

我有幾個在XML中定義的對象，當我嘗試獲取句柄時返回null。我看到有幾個職位說要清理這個項目，但這並沒有幫助。當我瀏覽ListView對象時，所有的孩子都是空的？所以我對我做錯了什麼有點不知所措。以下是我認爲相關的代碼，但如果您需要查看其他內容，請通知我，我會將其發佈。

TIA JB

<Button 
    android:id="@+id/btn_NextLift" 
    android:layout_width="100dp" 
    android:layout_height="50dp" 
    android:layout_alignParentBottom="true" 
    android:layout_alignParentRight="true" 
    android:layout_marginRight="30dp" 
    android:layout_marginBottom="40dp" 
    android:text="@string/str_BtnNxtTxt" 
    android:onClick="btn_NextLiftClick" 
    android:longClickable="true" /> 

在活動：

public void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.liftinterface); 
     ...//More code.... 
     ...//Still in the OnCreate.... 
     lstvw_LiftData = (ListView)findViewById(R.id.lstvw_LiftData); 
     ...//Image below of this object..... 
     //Get a handle on our button 
     Button btn_Nxt = (Button)this.findViewById(R.id.btn_NextLift); 
     btn_Nxt.setOnLongClickListener(new OnLongClickListener() 
     { 
     public boolean onLongClick(View v) 
     { 
     SaveAdvance(); 

     return true; 
      } 
     }); 

這僅僅是我的logcat錯誤：

11-13 22:04:57.798: E/AndroidRuntime(787): FATAL EXCEPTION: main 
11-13 22:04:57.798: E/AndroidRuntime(787): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.gpgvm.ironmike/org.gpgvm.ironmike.IcyArmActivity}: java.lang.NullPointerException 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.os.Handler.dispatchMessage(Handler.java:99) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.os.Looper.loop(Looper.java:123) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread.main(ActivityThread.java:3683) 
11-13 22:04:57.798: E/AndroidRuntime(787): at java.lang.reflect.Method.invokeNative(Native Method) 
11-13 22:04:57.798: E/AndroidRuntime(787): at java.lang.reflect.Method.invoke(Method.java:507) 
11-13 22:04:57.798: E/AndroidRuntime(787): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
11-13 22:04:57.798: E/AndroidRuntime(787): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
11-13 22:04:57.798: E/AndroidRuntime(787): at dalvik.system.NativeStart.main(Native Method) 
11-13 22:04:57.798: E/AndroidRuntime(787): Caused by: java.lang.NullPointerException 
11-13 22:04:57.798: E/AndroidRuntime(787): at org.gpgvm.ironmike.IcyArmActivity.onCreate(IcyArmActivity.java:83) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
11-13 22:04:57.798: E/AndroidRuntime(787): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611) 
11-13 22:04:57.798: E/AndroidRuntime(787): ... 11 more 

Answer 1

當我瀏覽ListView對象時，所有的孩子都是空的？

視圖不會畫，直到完成後onResume()。所以ListView將不會有onCreate()中的任何子項。

這個Button在哪裏？如果它在ListView中，則需要編寫一個自定義適配器來覆蓋它的偵聽器。

---

加成

它是在ListView佈局。

您需要擴展您當前的適配器並覆蓋getView()以給每行這樣的唯一偵聽器。請觀看Android的Romain Guy討論這exact topic在多個Google Talk事件的神話般的細節。