從意圖調用數據庫類

Question

我想知道如何從我創建的意圖調用我的數據庫類。當我在intent類中進行調用時，我得到一個空指針異常，就像意圖無法看到外部類......任何想法都非常感謝或指向鏈接？

呼籲意圖從郵件類

Intent showContent = new Intent(context, IntentResults.class); 
Log.d(LOG_TAG, "About to launch sub-activity"); 

// Set the request code to any code you like, you can identify the 
// callback via this code 
startActivityForResult(showContent, 0); 
Log.d(LOG_TAG, "launched sub-activity"); 

然後我打電話的意圖類將包括DB類。 AABDatabaseManager db = new AABDatabaseManager（this）; 公共類IntentResults延伸活動{

private static final String LOG_TAG = "IntentResultsClass"; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.intentayanlsisdatapage); 

    Log.d(LOG_TAG, "in sub-activity"); 




    Log.d(LOG_TAG, "finish should have run"); 

    int NumOfEntries = db.countNumberOfEntries(); 

    String numberOfEntries = ""+NumOfEntries; 

我得到一個空指針在這裏

int NumOfEntries = db.countNumberOfEntries() 

爲doesent DB類似乎得到貫徹。我一直在尋找：

External AsyncTask class with ProgressDialog [Update: and returning back?]

但figureing爲什麼當我從意圖調用DB類是不想要工作對我來說沒有快樂，任何幫助非常appriceated。

只是爲了增加更多的細節：

11-30 12:42:09.199: WARN/dalvikvm(31304): threadid=1: thread exiting with uncaught exception (group=0x4001d800) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304): FATAL EXCEPTION: main 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{test3.patrickrice.net/test3.patrickrice.net.IntentResults}: java.lang.NullPointerException 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.os.Handler.dispatchMessage(Handler.java:99) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.os.Looper.loop(Looper.java:123) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at java.lang.reflect.Method.invoke(Method.java:521) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at dalvik.system.NativeStart.main(Native Method) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304): Caused by: java.lang.NullPointerException 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at test3.patrickrice.net.AABDatabaseManager.<init>(AABDatabaseManager.java:65) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at test3.patrickrice.net.IntentResults.<init>(IntentResults.java:17) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at java.lang.Class.newInstanceImpl(Native Method) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at java.lang.Class.newInstance(Class.java:1429) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 
11-30 12:42:09.311: ERROR/AndroidRuntime(31304):  ... 11 more 
11-30 12:42:09.389: WARN/ActivityManager(59): Force finishing activity test3.patrickrice.net/.IntentResults 
11-30 12:42:09.889: WARN/ActivityManager(59): Activity pause timeout for HistoryRecord{45147568 test3.patrickrice.net/.IntentResults} 
11-30 12:42:19.395: WARN/ActivityManager(59): Launch timeout has expired, giving up wake lock! 

感謝 帕特

Answer 1

你有一個空指針，因爲你不初始化AABDatabaseManager db。在onCreate你應該有類似db = new AABDatabaseManage()。

user370305是正確的壽，你爲什麼完成onCreate()？ finish()，完成當前活動，以便它下面的代碼可能不會被達到。