我正在尝试使用我的 sqlite 数据库实现会话（共享首选项）。
我有想保存到共享首选项的用户名和密码字段。但是，我只想在登录有效的情况下这样做。
如果是有效登录，请登录用户（按指定转到下一个活动）并将其保存在共享首选项中。这是我的目标；但是，我无法实现这一点。
这是我的代码：
package com.example.votingapp;
import com.example.votingapp.library.DatabaseHandler;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class MainActivity extends Activity {
EditText inputUserName;
EditText inputUserPass;
Button btnLogin;
Button btnRegister;
DatabaseHandler database;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setting default screen to activity_main.xml
setContentView(R.layout.activity_main);
//Importing all assets like buttons, text fields
inputUserName = (EditText) findViewById(R.id.UserName);
inputUserPass = (EditText) findViewById(R.id.UserPass);
btnLogin = (Button) findViewById(R.id.btnLogin);
btnRegister = (Button) findViewById(R.id.btnRegister);
//SharedPreferences
SharedPreferences settings = getSharedPreferences("MYPREFS", 0);
String username = settings.getString("username", null);
String password = settings.getString("password", null);
if(!(username==null) && !(password==null)){
Intent dashboard = new Intent(MainActivity.this, DashboardActivity.class);
startActivity(dashboard);
finish();
}
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String userName = inputUserName.getText().toString();
String userPass = inputUserPass.getText().toString();
boolean validLogin = validateLogin(userName, userPass, MainActivity.this);
//SharedPreferences
SharedPreferences settings = getSharedPreferences("MYPREFS", 0);
SharedPreferences.Editor editor = settings.edit();
if(validLogin){
editor.putString("username", userName);
editor.putString("password", userPass);
editor.commit();
}else{
inputUserName.setText(settings.getString("username", ""));
inputUserPass.setText(settings.getString("password", ""));
}
if(userName.equals("") || userName == null){
Toast.makeText(getApplicationContext(), "Username Empty", Toast.LENGTH_SHORT).show();
}else if(userPass.equals("") || userPass == null){
Toast.makeText(getApplicationContext(), "Password Empty", Toast.LENGTH_SHORT).show();
}else{
if(validLogin){
//Show a dialog of login successful
Toast.makeText(getApplicationContext(), "Login Successful", Toast.LENGTH_SHORT).show();
Intent dashboard = new Intent(MainActivity.this, DashboardActivity.class);
//Close views before starting Dashboard
dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(dashboard);
finish();
}
}
}
});//Login Button On SetListener
btnRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Intent Register = new Intent(MainActivity.this, RegisterActivity.class);
startActivity(Register);
finish();
}
});//Register Button onClickListener
}//On Create
public boolean validateLogin(String userName, String userPass, Context context) {
DatabaseHandler database = new DatabaseHandler(getApplicationContext());
SQLiteDatabase db = database.getReadableDatabase();
//SELECT
String[] columns = {"userId"};
//WHERE clause
String selection = "userName=? AND userPass=?";
//WHERE clause arguments
String[] selectionArgs = {userName, userPass};
Cursor c = null;
try{
//SELECT userId FROM login WHERE username=userName AND password=userPass
c = db.query(DatabaseHandler.TABLE_USERS, columns, selection, selectionArgs, null, null, null);
c.moveToFirst();
c.close();
}catch(Exception e){
e.printStackTrace();
}
int i = c.getCount();
if(i <= 0){
Toast.makeText(getApplicationContext(), "Incorrect Login..\nTry Again", Toast.LENGTH_SHORT).show();
return false;
}
return true;
}//validate Login
}//Mainactivity