Question

正如标题所说，我得到NullPointerException，我不明白为什么。我已经多次通过代码并在输入之前将数据打印到logcat并且看起来很好。在我输入代码之前，我只想告诉您我使用的是RecyclerView，如果它不明显的话。

// Implement OnLongClick listener. Long Clicked items is removed from list.
@Override
public boolean onLongClick(View view) {
    ViewHolder holder = (ViewHolder) view.getTag();
    if (view.getId() == holder.mNameTextView.getId()) {

        mDataset.remove(holder.getPosition());

        Log.i("NULL POINTER", (holder.mNameTextView.getText().toString()));
        String temp = sqLiteDBadapter.getRowid(holder.mNameTextView.getText().toString()); // --- It fails on this line
        Long temp2 = Long.parseLong(temp);

        sqLiteDBadapter.deleteScore(temp2);

        // Call this method to refresh the list and display the "updated" list
        notifyDataSetChanged();

        Toast.makeText(sContext, "Item " + holder.mNameTextView.getText() + " has been removed from list",
                Toast.LENGTH_SHORT).show();

    }
    return false;
}

以下是SQLiteDBadapter的一部分：

public String getRowid(String date) {
    mDbHelper = new DatabaseHelper(mCtx);
    SQLiteDatabase db=mDbHelper.getReadableDatabase();

    Cursor c = db.rawQuery("SELECT * from " + DATABASE_TABLE + " WHERE date = ?" , new String[] { date });
    if (c.moveToFirst()){
        long temp;
        temp = c.getLong(c.getColumnIndex(KEY_ROWID));
        rowID = String.valueOf(temp);
        Log.i("----_ROW ID = ", rowID);
    }else  if (!c.moveToFirst())
        Log.i("CURSOR ERROR", " CURSOR INDEX MOST LIKELY 0");
    else
        c.moveToFirst();

    return rowID;
}

我在代码

中将rowID声明为String rowID;更早

正如您在此处所见：Database SQLite Fiddle获取行的代码完全正常。

同样，Log.i NULL POINTER在崩溃前打印输出：I/NULL POINTER﹕ Nov 2, 2014 11:51:14 AM，这是根据Fiddle

的正确格式

11-02 12:29:30.917      419-419/com.archeryscoresmaterialdesign W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4160f620)
11-02 12:29:30.927      419-419/com.archeryscoresmaterialdesign E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.archeryscoresmaterialdesign, PID: 419
java.lang.NullPointerException
        at com.archeryscoresmaterialdesign.RecyclerViewAdapter.onLongClick(RecyclerViewAdapter.java:90)
        at android.view.View.performLongClick(View.java:4476)
        at android.widget.TextView.performLongClick(TextView.java:8362)
        at android.view.View$CheckForLongPress.run(View.java:18451)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5171)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:837)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:653)
        at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

在此代码中

if (c.moveToFirst()){
    long temp;
    temp = c.getLong(c.getColumnIndex(KEY_ROWID));
    rowID = String.valueOf(temp);
    Log.i("----_ROW ID = ", rowID);
}else  if (!c.moveToFirst())
    Log.i("CURSOR ERROR", " CURSOR INDEX MOST LIKELY 0");
else
    c.moveToFirst();

你最终可能永远不会为rowID分配任何东西，如果你简单地声明它 String rowID; 不字符串rowID = new String（）;它保持为空。这有可能吗？

Answer 2

您是否正在创建sqLiteDBadapter？

我想你已经创建了SQLiteOpenHelper的子类。您正在尝试在Object上调用方法，该方法为null。试试这个：

SQLiteDBadapter db = new SQLiteDBadapter(ApplicationContext);

现在你应该可以调用任何方法了。完成阅读，写作，技术后...别忘了关闭数据库连接。

db.close();

获取SQLite rowID的NullPointerException

2 个答案: