This is my code:
这是我的代码:
public int getIdMotChuDe(String tenChuDe) {
int IDChuDe = 0;
try
{
Cursor c = null;
c = database.rawQuery(
"SELECT ChuDeID FROM DanhSachChuDe WHERE TenChuDe = ?"
, new String[] {tenChuDe});
c.moveToFirst();
IDChuDe = c.getInt(c.getColumnIndex("ChuDeID"));
c.close();
}
catch(Exception e)
{
e.printStackTrace();
}
return IDChuDe;
}
I'm trying to get ChuDeID from DanhSachChuDe table with condition in WHERE clause. But i don't know why this function always return 0. Help me please. Thanks! Sorry because my english.
我试图从DanhSachChuDe表中获取具有WHERE子句条件的ChuDeID。但我不知道为什么这个功能总是返回0.请帮帮我。谢谢!抱歉,因为我的英文。
1 个解决方案
#1
0
This could be because an Exception is being thrown. The code you are using is not correctly checking the state of your Cursor - it attempts to moveToFirst() before any checking too see if the object is not null.
这可能是因为抛出异常。您正在使用的代码未正确检查Cursor的状态 - 它会在任何检查之前尝试moveToFirst(),同时查看该对象是否为null。
Your code also assumes a result is always returned. This is bad practise, and should be avoided. A much safer and more common solution is the following:
您的代码还假定始终返回结果。这是不好的做法,应该避免。更安全,更常见的解决方案如下:
if (cursor != null) {
// If the cursor has results, move the cursor to first row
if (cursor.moveToFirst()) {
do {
// YOUR METHODS HERE
// then move to next row
} while (cursor.moveToNext());
}
}
#1
0
This could be because an Exception is being thrown. The code you are using is not correctly checking the state of your Cursor - it attempts to moveToFirst() before any checking too see if the object is not null.
这可能是因为抛出异常。您正在使用的代码未正确检查Cursor的状态 - 它会在任何检查之前尝试moveToFirst(),同时查看该对象是否为null。
Your code also assumes a result is always returned. This is bad practise, and should be avoided. A much safer and more common solution is the following:
您的代码还假定始终返回结果。这是不好的做法,应该避免。更安全,更常见的解决方案如下:
if (cursor != null) {
// If the cursor has results, move the cursor to first row
if (cursor.moveToFirst()) {
do {
// YOUR METHODS HERE
// then move to next row
} while (cursor.moveToNext());
}
}