我正在尝试使用 SQLite 设置数据库来存储用户名和密码,但每当我在模拟器上注册帐户时,都会出错。另外,如果我只是尝试登录而不注册,则会出错。这只是我的第二篇文章,所以如果我在发帖时有什么可以做得更好的地方,请告诉我!
public class DbHelper extends SQLiteOpenHelper {
private static String DbName = "SimpleDatabase";
private static int DbVersion = 1;
//Table Names
private static final String TABLE_USER = "User";
//Column Names
private static final String USER_NAME = "UserName";
private static final String PASSWORD = "Password";
//Create statements
// Todo table create statement
private static final String CREATE_TABLE_USER = "CREATE TABLE "
+ TABLE_USER + "(" + USER_NAME + "TEXT PRIMARY KEY,"
+ PASSWORD + "TEXT)" ;
public DbHelper(Context context) {
super(context, DbName, null, DbVersion);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE_USER);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXIST "+TABLE_USER);
onCreate(db);
}
public Boolean InsertUser(String userName,String password){
SQLiteDatabase db = this.getWritableDatabase();
String query = "SELECT * FROM "+TABLE_USER+" WHERE "+USER_NAME+" == '"+userName+"';";
Cursor c = db.rawQuery(query,null);
if(c != null && c.moveToFirst()) {
c.close();
return false ;
}else{
ContentValues values = new ContentValues();
values.put(USER_NAME, userName);
values.put(PASSWORD, password);
db.insert(TABLE_USER, null, values);
return true;
}
}
public Boolean loginUser(String userName,String password){
SQLiteDatabase db = this.getWritableDatabase();
String query = "SELECT * FROM "+TABLE_USER+" WHERE "+USER_NAME+" == '"+userName+"' AND "+PASSWORD+" == '"+password+"';";
Cursor c = db.rawQuery(query,null);
if(c != null && c.moveToFirst()) {
c.close();
return true;
}
return false;
}
}
这是与 DbHelper 一起使用的 LOGIN 类
public class Login extends Fragment {
TextInputLayout usernamelayout, passwordLayout;
EditText userName,password;
Button login, goToRegister;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.content_login,container,false);
}
@Override
public void onViewCreated(final View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
usernamelayout = (TextInputLayout)view.findViewById(R.id.user_name_layout);
passwordLayout = (TextInputLayout)view.findViewById(R.id.password_layout);
userName = (EditText)view.findViewById(R.id.user_name);
password = (EditText)view.findViewById(R.id.password);
login = (Button)view.findViewById(R.id.login_button);
login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String userText = userName.getText().toString().trim();
String passwordText = password.getText().toString().trim();
if (userText.isEmpty()) {
usernamelayout.setErrorEnabled(true);
usernamelayout.setError("Please Enter User Name");
} else if (passwordText.isEmpty()) {
passwordLayout.setErrorEnabled(true);
passwordLayout.setError("Please Enter Password");
} else {
DbHelper helper = new DbHelper(getActivity());
if (helper.loginUser(userText, passwordText)) {
startActivity(new Intent(getActivity(), MainActivity.class));
} else {
Toast.makeText(getActivity(), "User Name or Password is incorrect", Toast.LENGTH_SHORT).show();
}
}
}
});
goToRegister = (Button)view.findViewById(R.id.go_to_register_button);
goToRegister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Register fragment = new Register();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP){
setSharedElementReturnTransition(TransitionInflater.from(getActivity()).inflateTransition(R.transition.change_image_trans));
setExitTransition(TransitionInflater.from(getActivity()).inflateTransition(android.R.transition.fade) );
fragment.setSharedElementEnterTransition(TransitionInflater.from(getActivity()).inflateTransition(R.transition.change_image_trans));
fragment.setEnterTransition(TransitionInflater.from(getActivity()).inflateTransition(android.R.transition.fade));
}
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.addSharedElement(view.findViewById(R.id.logo),"LOGO");
transaction.replace(R.id.main_container, fragment);
transaction.commit();
}
});
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
getActivity().setTitle("Uhvents Login");
}
}
这是 REGISTER 类。
public class Register extends Fragment {
TextInputLayout usernamelayout, passwordLayout;
EditText userName,password;
Button register, goToLogin;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.content_register,container,false);
}
@Override
public void onViewCreated(final View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
usernamelayout = (TextInputLayout) view.findViewById(R.id.user_name_layout);
passwordLayout = (TextInputLayout) view.findViewById(R.id.password_layout);
userName = (EditText) view.findViewById(R.id.user_name);
password = (EditText) view.findViewById(R.id.password);
register = (Button) view.findViewById(R.id.register_button);
register.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String userText = userName.getText().toString().trim();
String passwordText = password.getText().toString().trim();
if(userText.isEmpty()) {
usernamelayout.setErrorEnabled(true);
usernamelayout.setError("Please Enter User Name");
}
else if (passwordText.isEmpty()){
passwordLayout.setErrorEnabled(true);
passwordLayout.setError("Please Enter Password");
}
else {
DbHelper helper = new DbHelper(getActivity());
if (helper.InsertUser(userText,passwordText)){
Toast.makeText(getActivity(), "Registration Success", Toast.LENGTH_SHORT).show();
if (getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
{
goToLogin.performClick();
}
}else {
Toast.makeText(getActivity(), "User Name already in use.",Toast.LENGTH_SHORT).show();
}
}
}
});
goToLogin = (Button)view.findViewById(R.id.go_to_login);
goToLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Login fragment = new Login();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP){
setSharedElementReturnTransition(TransitionInflater.from(getActivity()).inflateTransition(R.transition.change_image_trans));
setExitTransition(TransitionInflater.from(getActivity()).inflateTransition(android.R.transition.fade) );
fragment.setSharedElementEnterTransition(TransitionInflater.from(getActivity()).inflateTransition(R.transition.change_image_trans));
fragment.setEnterTransition(TransitionInflater.from(getActivity()).inflateTransition(android.R.transition.fade));
}
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.addSharedElement(view.findViewById(R.id.logo),"LOGO");
transaction.replace(R.id.main_container, fragment);
transaction.commit();
}
});
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
getActivity().setTitle("Register for Uhvents");
}
}
这是每当我运行上述场景时收到的错误日志。
致命异常:主进程:com.uhdapt.tutorial4,PID:4807 android.database.sqlite.SQLiteException:没有这样的列:UserName(代码1):,编译时:SELECT * FROM User WHERE UserName == 'alex' AND Password == '1234' 在 android.database.sqlite.SQLiteConnection.nativePrepareStatement( native 方法) 在 android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:887) 在 android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:498) 在 android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588) 在 android.database.sqlite.SQLiteProgram.(SQLiteProgram.java:58) 在 android.database.sqlite.SQLiteQuery.(SQLiteQuery.java:37) 在 android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44) 在 android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1316) 在 android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1255) 在 com.uhdapt.tutorial4.database.DbHelper.loginUser(DbHelper.java:68) 在 com.uhdapt.tutorial4.fragments.Login$1.onClick(Login.java:63) 在 android.view.View.performClick(View.java:5198) 在 android.view.View$PerformClick.run(View.java:21147) 在 android.os.Handler.handleCallback(Handler.java:739) 在 android.os.Handler.dispatchMessage(Handler.java:95) 在 android.os.Looper.loop(Looper.java:148) 在 android.app.ActivityThread.main(ActivityThread.java:5417) 在 java.lang.reflect.Method.invoke( native 方法) 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
最佳答案
您需要在串联中添加空格。
这部分没有空间
" + USER_NAME + "TEXT PRIMARY KEY,"
还有这个
+ PASSWORD + "TEXT)";
所以将其更改为
private static final String CREATE_TABLE_USER = "CREATE TABLE "
+ TABLE_USER + "(" + USER_NAME + " TEXT PRIMARY KEY,"
+ PASSWORD + " TEXT)";
关于java - 无法使用 Android Studio 2.1 从 SQLite 数据库获取值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38089780/