在我的应用程序中，我想根据谁登录到应用程序来调出模块。
如果我使用测试数据(例如简单数据，例如 1 作为用户名和 1 作为密码)，这将非常有效，但是当我使用实际测试数据(例如 C343)时，它会抛出错误，指出没有这样的列，即使尽管在 logcat 中它显示在数据库中。
下面是我如何从数据库中选择信息:
在DB.java
public class DB extends SQLiteOpenHelper {
public static final int db_version = 1;
//Student Table
public static final String Table = "Students";
public static final String Student_ID = "Student_ID";
public static final String Student_Name = "Student_Name";
public static final String Student_Password = "Student_Password";
public static final String Student_Gender = "gender";
public static final String Student_Age = "age";
public static final String Student_Course = "course";
public static final String Modules1 = "modules1";
public static final String Modules2 = "modules2";
public static final String Modules = "modules";
public static final String CNumber = "CNumber";
//Modules Table
public static final String Table2 = "Modules";
public static final String Module_ID = "moduleid";
public static final String Module_Name = "modulename";
public static final String Module_Lectureroom = "modulelectureroom";
public static final String Module_Seminarroom = "moduleseminarroom";
public static final String Module_Lecturer = "modulelecturer";
public static final String Module_Group = "modulegroup";
public static final String Module_Lecturetime = "modulelecturetime";
public static final String Module_Seminartime = "moduleseminartime";
public static final String Module_Lecturedate = "modulelecturedate";
public static final String Module_Seminardate = "moduleseminardate";
public boolean checker = false;
public DB(Context context) {
super(context, tableColumns.Database, null, db_version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("DROP TABLE IF EXISTS " + Table);
Log.d("DB", "Creating table...");
//Students Table
db.execSQL("CREATE TABLE " + Table + "(" +
Student_ID + " INTEGER PRIMARY KEY, " +
Student_Name + " TEXT, " +
Student_Password + " TEXT, " +
Student_Age + " TEXT, " +
Student_Gender + " TEXT, " +
Student_Course + " TEXT, " +
Modules1 + " TEXT, " +
Modules2 + " TEXT, " +
Modules + " TEXT, " +
CNumber + " TEXT)");
Log.d("DB", "Student Table Created");
//Modules Table
db.execSQL("DROP TABLE IF EXISTS " + Table2);
db.execSQL("CREATE TABLE " + Table2 + "(" +
Module_ID + " INTEGER PRIMARY KEY, " +
Module_Name + " TEXT, " +
Module_Lectureroom + " TEXT, " +
Module_Seminarroom + " TEXT, " +
Module_Lecturer + " TEXT, " +
Module_Group + " TEXT, " +
Module_Lecturetime + " TEXT, " +
Module_Seminartime + " TEXT, " +
Module_Lecturedate + " TEXT, " +
Module_Seminardate + " TEXT)");
Log.d("DB", "Module Table Created");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + Table);
db.execSQL("DROP TABLE IF EXISTS " + Table2);
onCreate(db);
}
public boolean Login(String username, String password) throws SQLException
{
SQLiteDatabase db = this.getWritableDatabase();
Cursor mCursor = db.rawQuery("SELECT * FROM " + Table + " WHERE CNumber=? AND Student_Password=?", new String[]{username,password});
if (mCursor != null) {
if(mCursor.getCount() > 0)
{
checker = true;
return true;
}
}
return false;
}
public void createstudents()
{
insertStudent("Matt", "123", 22, "Male", "Computing", "Digital Security", "Mod2", "Mod3", "C3438525");
insertStudent("Charlie", "Test", 19, "Male", "Sport Science", "Biomech Analysis", "Meas & Eval for Phsio", "Prof Dev", "C33429960");
insertStudent("Amber", "Test", 20, "Female", "Travel & Tourism", "Work based learning", "Sustainable Tourism", "Tourism Operations", "C3399607");
insertStudent("1", "1", 1, "1", "1", "1", "1", "3", "2");
insertStudent("Test", "Test", 2, "Test", "Test", "Test", "Test", "Test", "C343Test");
Log.d("Students", "Created");
}
public void createmodules()
{
insertModules("Digital Security", "CAG05", "JG202", "Michael Kemp", "A", "15:00PM", "11:00AM", "Tuesday", "Tuesday");
Log.d("Modules", "Created");
}
public void reset(SQLiteDatabase db)
{
db.execSQL("DROP TABLE IF EXISTS " + Table);
onCreate(db);
}
public List<tableStudents> getData() {
List<tableStudents> studentList = new ArrayList<tableStudents>();
// Select All Query
String selectQuery = "SELECT * FROM " + Table;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
tableStudents student = new tableStudents();
student.name = cursor.getString(1);
student.password = cursor.getString(2);
student.age = Integer.parseInt(cursor.getString(3));
student.gender = cursor.getString(4);
student.course = cursor.getString(5);
student.modules = cursor.getString(6);
student.modules1 = cursor.getString(7);
student.modules2 = cursor.getString(8);
student.cnumber = cursor.getString(9);
studentList.add(student);
} while (cursor.moveToNext());
}
// return contact list
return studentList;
}
public List<tableStudents> getStudentsModules(String username) {
List<tableStudents> studentModules = new ArrayList<tableStudents>();
// Select All Query depending on who is logged in.
String selectQuery = "SELECT " + Modules1 + ", " + Modules2 + ", " + Modules + " FROM " + Table + " WHERE " + CNumber + " = " + username;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
tableStudents student = new tableStudents();
student.modules = cursor.getString(0);
student.modules1 = cursor.getString(1);
student.modules2 = cursor.getString(2);
studentModules.add(student);
} while (cursor.moveToNext());
}
// return contact list
return studentModules;
}
public List<tableModules> getModules() {
List<tableModules> moduleList = new ArrayList<tableModules>();
// Select All Query
String selectQuery = "SELECT * FROM " + Table2;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
tableModules module = new tableModules();
module.modulename = cursor.getString(1);
module.modulelectureroom = cursor.getString(2);
module.moduleseminarroom = cursor.getString(3);
module.modulelecturer = cursor.getString(4);
module.modulegroup = cursor.getString(5);
module.modulelecturetime = cursor.getString(6);
module.moduleseminartime = cursor.getString(7);
module.modulelecturedate = cursor.getString(8);
module.moduleseminardate = cursor.getString(9);
moduleList.add(module);
} while (cursor.moveToNext());
}
// return contact list
return moduleList;
}
public boolean insertStudent(String name, String password, int age, String gender, String course, String modules, String modules1, String modules2, String CNumb) {
SQLiteDatabase db = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(Student_Name, name);
contentValues.put(Student_Gender, gender);
contentValues.put(Student_Age, age);
contentValues.put(Student_Password, password);
contentValues.put(Student_Course, course);
contentValues.put(Modules, modules);
contentValues.put(Modules1, modules1);
contentValues.put(Modules2, modules2);
contentValues.put(CNumber, CNumb);
db.insert(Table, null, contentValues);
Log.d("DB", "Students Inserted Successfully");
return true;
}
public boolean insertModules(String modulename, String modulelectureroom, String moduleseminarroom, String modulelecturer, String modulegroup, String modulelecturetime, String moduleseminartime, String modulelecturedate, String moduleseminardate) {
SQLiteDatabase db = getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(Module_Name, modulename);
contentValues.put(Module_Lectureroom, modulelectureroom);
contentValues.put(Module_Seminarroom, moduleseminarroom);
contentValues.put(Module_Lecturer, modulelecturer);
contentValues.put(Module_Group, modulegroup);
contentValues.put(Module_Lecturetime, modulelecturetime);
contentValues.put(Module_Seminartime, moduleseminartime);
contentValues.put(Module_Lecturedate, modulelecturedate);
contentValues.put(Module_Seminardate, moduleseminardate);
db.insert(Table2, null, contentValues);
Log.d("DB", "Modules Inserted Successfully");
return true;
}
}
然后在 MainActivity.java 中调用它，将模块保存为字符串。
List<tableStudents> studentModules = db.getStudentsModules(sessionName);
for (tableStudents session: studentModules)
{
//Save modules to string
String module1 = session.modules.toString();
String module2 = session.modules1.toString();
String module3 = session.modules2.toString();
}
这是当我使用 C343Test 作为用户名和 Test 作为密码登录时的 Logcat:
02-22 00:24:15.214: D/Username+PW Combos(2593): Username: C343Test Password: Test
02-22 00:24:15.214: D/Digital Security(2593): Michael Kemp
02-22 00:24:15.302: E/SQLiteLog(2593): (1) no such column: C343Test
02-22 00:24:15.322: D/AndroidRuntime(2593): Shutting down VM
02-22 00:24:15.333: E/AndroidRuntime(2593): FATAL EXCEPTION: main
02-22 00:24:15.333: E/AndroidRuntime(2593): Process: com.example.project, PID: 2593
02-22 00:24:15.333: E/AndroidRuntime(2593): java.lang.RuntimeException: Unable to resume activity {com.example.project/com.example.project.MainActivity}: android.database.sqlite.SQLiteException: no such column: C343Test (code 1): , while compiling: SELECT modules1, modules2, modules FROM Students WHERE CNumber = C343Test
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2989)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3020)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2395)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.access$800(ActivityThread.java:151)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.os.Handler.dispatchMessage(Handler.java:102)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.os.Looper.loop(Looper.java:135)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.main(ActivityThread.java:5257)
02-22 00:24:15.333: E/AndroidRuntime(2593): at java.lang.reflect.Method.invoke(Native Method)
02-22 00:24:15.333: E/AndroidRuntime(2593): at java.lang.reflect.Method.invoke(Method.java:372)
02-22 00:24:15.333: E/AndroidRuntime(2593): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
02-22 00:24:15.333: E/AndroidRuntime(2593): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
02-22 00:24:15.333: E/AndroidRuntime(2593): Caused by: android.database.sqlite.SQLiteException: no such column: C343Test (code 1): , while compiling: SELECT modules1, modules2, modules FROM Students WHERE CNumber = C343Test
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255)
02-22 00:24:15.333: E/AndroidRuntime(2593): at com.example.project.DB.getStudentsModules(DB.java:160)
02-22 00:24:15.333: E/AndroidRuntime(2593): at com.example.project.MainActivity.onResume(MainActivity.java:79)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1257)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.Activity.performResume(Activity.java:6076)
02-22 00:24:15.333: E/AndroidRuntime(2593): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2978)
02-22 00:24:15.333: E/AndroidRuntime(2593): ... 11 more
最佳答案
如果您以任何方式修改了表，则必须增加数据库版本，否则不会调用 onUpdate。如果要进行字符串比较，则必须使用引号:
String selectQuery = "SELECT " + Modules1 + ", " + Modules2 + ", " + Modules + " FROM " + Table + " WHERE " + CNumber + " = \"" + username + "\"";
关于java - 使用 SQLite 从数据库中选择 - 'No such column'，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35543948/