Android：startActivityForResult始终为空并强制关闭我的应用程序

• Z时代
• 2024-01-10
• 分类：问答

我有以下情况，这是相当拉我的头发：我正在写一个类来管理Android相机，它扩展了活动。在那个类里面我有下面的代码。什么情况是，我总是得到零点异常--with其强制关闭小friend--在这行：Android：startActivityForResult始终为空并强制关闭我的应用程序

startActivityForResult(intent, 0); 

但是我得到的System.out.println（“故意不为空”）;印在logcat中确定...

的logcat的说：

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) 

在清单中，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，我在做什么错？为什么startActivityForResult总是抛出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 
} 

编辑：

按照建议，我接过来一看从Android 2.1r2框架上Activity.java线2749和这里是代码：

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); 
     } 
    } 

线2749标有双**但是，我没有看到该代码的问题

EDITED

忘了解释我是如何把这种：

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

回答：

回答：

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