Android：startActivityForResult始終爲空並強制關閉我的應用程序

Question

我有以下情況，這是相當拉我的頭髮：我正在寫一個類來管理Android相機，它擴展了活動。在那個類裏面我有下面的代碼。什麼情況是，我總是得到零點異常--with其強制關閉小friend--在這行：

startActivityForResult(intent, 0); 

但是我得到的System.out.println（「故意不爲空」）;印在logcat中確定...

的logcat的說：

03-08 22:46:38.584: ERROR/AndroidRuntime(1079): java.lang.NullPointerException 
03-08 22:46:38.584: ERROR/AndroidRuntime(1079):  at android.app.Activity.startActivityForResult(Activity.java:2749) 
03-08 22:46:38.584: ERROR/AndroidRuntime(1079):  at com.test.cameratest.startCameraActivity(cameratest.java:39) 

在清單中，我有：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
<uses-permission android:name="android.permission.CAMERA" /> 
<uses-feature android:name="android.hardware.camera"/> 
<activity android:name=".cameratest" /> 

所以，我在做什麼錯？爲什麼startActivityForResult總是拋出null！？

@Override 
public void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
} 

/** As per suggestion tried to change the method from protected to private or public 
but still have the same problem */ 
protected void startCameraActivity() 
{ 
    String path = (new StringBuilder()).append(Environment.getExternalStorageDirectory()).append("/images/test.jpg").toString(); 

    System.out.println("started"); 

    File file = new File(path); 

    System.out.println(path); 

    Uri outputFileUri = Uri.fromFile(file); 

    Intent intent = new Intent("android.media.action.IMAGE_CAPTURE"); 

    intent.putExtra("output", outputFileUri); 
    /** Removed as per suggestion 
    if (intent!=null) 
    { 
     System.out.println("intent not null"); 
      **startActivityForResult(intent, 0);** 
    } 
    */  

    **startActivityForResult(intent, 0);** <== null pointer exception 
} 

編輯：

按照建議，我接過來一看從Android 2.1r2框架上Activity.java線2749和這裏是代碼：

public void startActivityForResult(Intent intent, int requestCode) { 
     if (mParent == null) { 

       **** Line 2749 is the folowing     
       Instrumentation.ActivityResult ar = 
       mInstrumentation.execStartActivity(
        this, mMainThread.getApplicationThread(), mToken, this, 
        intent, requestCode); 
       **** 

      if (ar != null) { 
       mMainThread.sendActivityResult(
        mToken, mEmbeddedID, requestCode, ar.getResultCode(), 
        ar.getResultData()); 
      } 
      if (requestCode >= 0) { 
       // If this start is requesting a result, we can avoid making 
       // the activity visible until the result is received. Setting 
       // this code during onCreate(Bundle savedInstanceState) or onResume() will keep the 
       // activity hidden during this time, to avoid flickering. 
       // This can only be done when a result is requested because 
       // that guarantees we will get information back when the 
       // activity is finished, no matter what happens to it. 
       mStartedActivity = true; 
      } 
     } else { 
      mParent.startActivityFromChild(this, intent, requestCode); 
     } 
    } 

線2749標有雙**但是，我沒有看到該代碼的問題

EDITED

忘了解釋我是如何把這種：

cameratest cam = new cameratest(); 
cam.startCameraActivity(); 

Answer 1

嘗試Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

我不認爲這些常量字符串的引用時，他們的價值必然相等。

Answer 2

下面的文章提供瞭解決這個問題，不僅爲三星設備（我對HTC Desire Z的相同的問題，運行Android的改裝2.3.7）：

http://kevinpotgieter.wordpress.com/2011/03/30/null-intent-passed-back-on-samsung-galaxy-tab/

我意識到這是相當尷尬，但它的作品。總而言之，它建議放棄嘗試獲得原始意圖，並只告訴如何獲取拍攝照片的句柄。