ContentResolver.quer返回null-android

我編寫一個提供程序並創建一個數據庫。當我調用ContentResolver.insert是好的，但ContentResolver.query失敗並返回null。ContentResolver.quer返回null-android

c=mContentResolver.query(uri, DatabaseContants.COLUMNS_FAVORITEPOI,null, null,DatabaseContants.PLACEID_FAVORITE+" DESC");

日誌是

06-02 03:31:34.235: E/AndroidRuntime(23134): FATAL EXCEPTION: main 
06-02 03:31:34.235: E/AndroidRuntime(23134): java.lang.RuntimeException: Unable to   start activity ComponentInfo {com.example.providerdatabase/com.example.providerdatabase.PrivoterDatabaseActivity}:   java.lang.NullPointerException 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2082) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2107) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread.access$600(ActivityThread.java:139) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1207) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.os.Looper.loop(Looper.java:137) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread.main(ActivityThread.java:4812) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at java.lang.reflect.Method.invokeNative(Native Method) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at java.lang.reflect.Method.invoke(Method.java:511) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at dalvik.system.NativeStart.main(Native Method) 
06-02 03:31:34.235: E/AndroidRuntime(23134): Caused by: java.lang.NullPointerException 
06-02 03:31:34.235: E/AndroidRuntime(23134): at com.example.providerdatabase.DatabaseController.getCount(DatabaseController.java:47) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at com.example.providerdatabase.PrivoterDatabaseActivity.onCreate(PrivoterDatabaseActivity.java:62) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.Activity.performCreate(Activity.java:5008) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
06-02 03:31:34.235: E/AndroidRuntime(23134): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2046) 
06-02 03:31:34.235: E/AndroidRuntime(23134): ... 11 more

你能幫助我嗎？

來源

2012-12-12 Hilda

異常來自'47'行的'DatabaseController'類中的'getCount（）'方法。 – Luksprog

是的，getCount（）中的查詢函數。 c = mContentResolver.query（uri，DatabaseContants.COLUMNS_FAVORITEPOI，null，null，DatabaseContants.PLACEID_FAVORITE +「DESC」）;它返回null – Hilda

如果這是'DatabaseController'中的行'47'，那麼再檢查'mContentResolver'是否爲'null'。 – Luksprog

這是我的錯誤。我不記得在ContentProvider的query方法的switch聲明中添加break。如果你有這個錯誤，請檢查你的ContentProvider的代碼。

來源

2012-12-13 09:24:47 Hilda

ContentResolver.quer返回null-android

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