数据库已成功创建，但无论用户提供的电子邮件地址或密码是否正确，用户都会自动登录。我不确定我在hasObject方法中使用的rawQuery是否正确。
我在下面包含了RegistrationDatabaseHelper.java类，其中hasObject方法是最终方法：
public class RegistrationDatabaseHelper extends SQLiteOpenHelper {
//declaring variable so we can find the name of our database
public static final String DATABASE_NAME = "belfast.db";
public static final String TABLE_NAME = "reg_details_table";
public static final String COL_1 ="ID";
public static final String COL_2 ="EMAIL";
public static final String COL_3 ="USERNAME";
public static final String COL_4 ="PASSWORD";
public static final String COL_5 ="DOB";
public static final String COL_6 ="MOBILE";
//default constructor below
public RegistrationDatabaseHelper(Context context) {
//when the constructor is called it will create your database
super(context, DATABASE_NAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
//creating the table WITHIN the database below
db.execSQL(" create table " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT,EMAIL TEXT,USERNAME TEXT,PASSWORD STRING,DOB TEXT,MOBILE LONG) ");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
//creating a method below to insert data
public boolean insertData(String emailAddress, String userName, String password, String dob, Long mobileNumber){
//we will use this SQLDatabase instance to insert our data
SQLiteDatabase db = this.getWritableDatabase();
//now we need to create an instance of the class ContentValue
ContentValues contentValues = new ContentValues();
//we will now take this contentValues instance and insert it into the data columns
//the first arg is the column name itself, the second is the data itself.
contentValues.put(COL_2, emailAddress);
contentValues.put(COL_3, userName);
contentValues.put(COL_4, password);
contentValues.put(COL_5, dob);
contentValues.put(COL_6, mobileNumber);
//we then insert our data using the db instance created above
//this takes three arguments. The first is the table name, The second is null and the third
//is the contentValues which we have created.
long result = db.insert(TABLE_NAME,null,contentValues);
if (result==-1){
return false;
} else {
return true;
}
}
//creating a method that will show all data that has been entered into the database, using
//elements from the Cursor class. The Cursor interface allows read-write access to the result
public Cursor getAllData(){
//creating an instance of the database class firstly to allow us to get all the data
SQLiteDatabase db = this.getWritableDatabase();
//now we will create an instance of the Cursor class called result and use the
//rawQuery method. Basically creates a SQL query.
Cursor result = db.rawQuery("select * from "+ TABLE_NAME,null);
//we will now return the instance of this cursor, which is "result"
return result;
}
//creating a method that will update all data in our database, using 4 args all of which are
//string, they are id, name, surname and marks
public boolean updateData(String emailAddress, String userName, String password, String dob, Long mobileNumber){
//creating an instance of the database class firstly to allow us to get all the data
SQLiteDatabase db = this.getWritableDatabase();
//now we need to create an instance of the class ContentValue
ContentValues contentValues = new ContentValues();
//we will now take this contentValues instance and insert it into the data columns
//the first arg is the column name itself, the second is the data itself.
contentValues.put(COL_2, emailAddress);
contentValues.put(COL_3, userName);
contentValues.put(COL_4, password);
contentValues.put(COL_5, dob);
contentValues.put(COL_6, mobileNumber);
//the below update method will update any args you pass through here
//the first argument is the table name itself, the second is the contentValues, the third
//is the condition you want to impose, such as "ID = ?" where the ? is the ID provided. The
//fourth arg is the String[] array
db.update(TABLE_NAME, contentValues, "EMAIL = ?", new String[] {emailAddress});
//we will return true to see if the data is really updated or not
return true;
}
public Integer deleteData(String emailAddress){
//creating an instance of the database class firstly to allow us to get all the data
SQLiteDatabase db = this.getWritableDatabase();
//calling the delete function on our db instance. It takes 3 args, 1st is the name of the
//table, the second is the ID number represented by "ID = ?" and the third arg is the String
//Array[] of the argument type id. The return below returns the integer of the ID
return db.delete(TABLE_NAME, "EMAIL = ?", new String[] {emailAddress});
}
public boolean hasObject(String emai){
SQLiteDatabase db = this.getWritableDatabase();
String selectString = "SELECT * FROM " + TABLE_NAME + " WHERE " + COL_2 + "= ?";
Cursor cursor = db.rawQuery(selectString,null);
boolean exist;
if(cursor.getCount()>0){
exist=true;
} else {
exist=false;
}
db.close();
cursor.close();
return exist;
}
}
下面还列出了SignInActivity.java类，signIn方法确定用户是否成功登录：
public class SignInActivity extends Activity {
//creating an instance of the RegistrationDatabaseHelper class
RegistrationDatabaseHelper myDb;
EditText userName;
EditText password;
Button emailSignIn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sign_in_screen);
myDb = new RegistrationDatabaseHelper(this);
userName = (EditText) findViewById(R.id.etUserName);
password = (EditText) findViewById(R.id.etPass);
emailSignIn = (Button) findViewById(R.id.btnSignIn);
signIn();
}
public void signIn(){
emailSignIn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
boolean recordExists = myDb.hasObject(userName.getText().toString());
if(recordExists=true){
Intent intentSignIn = new Intent(getApplicationContext(), HomePageActivity.class);
Toast.makeText(getApplicationContext(), "Login successful, redirecting to Home Page.", Toast.LENGTH_LONG).show();
startActivity(intentSignIn);
} else {
Toast.makeText(getApplicationContext(), "Invalid credentials, please try again.", Toast.LENGTH_LONG).show();
}
}
});
}
}
有谁知道用户登录的原因，无论输入如何？正如我所说，我对Android开发相对较新，并且不确定我哪里出错了，所以任何建议都会非常感激。非常感谢提前！
答案 0 :(得分：0)
I am not sure if the rawQuery I am using in the hasObject method is correct.不，这是不：
Cursor cursor = db.rawQuery(selectString,null);
您没有传递要在?子句中使用的参数（WHERE）。
相反，您传递 null 。
正确实施：
Cursor cursor = db.rawQuery(selectString, new String[]{"Your search string here"});
不要担心单引号（SQL字符串分隔符）：它们将根据需要自动添加。