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Android：如何使用共享首选项从SQLite检查有效登录？

[英]Android: How to check for valid login from SQLite with Shared Preferences?

 原文  2013-11-12 04:53:01  7   3    java/ android/ database/ sqlite/ shared

问题描述

我正在尝试与我的sqlite数据库实现会话（共享首选项）。

我有要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执行此操作。

如果是有效的登录名，请登录用户（转到指定的下一个活动）并将其保存在共享首选项中。 这是我的目标； 但是，我在执行此操作时遇到了麻烦。

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

3 个解决方案

解决方案1
 1  2013-11-12 05:36:42

您没有将文本字段的用户名和密码存储到SharedPreferences，但是您的代码将空值存储到sharedPreferences。 试试这个代码 

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;
    SharedPreferences sp;
    SharedPreferences.Editor editor;

    @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);




        btnLogin.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                String userName = inputUserName.getText().toString();
                String userPass = inputUserPass.getText().toString();

                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{
                    boolean validLogin = validateLogin(userName, userPass, MainActivity.this);
                    if(validLogin){ 

                        //SharedPreferences
                        SharedPreferences settings = getSharedPreferences("MYPREFS", 0);
                        inputUserName.setText(settings.getString("username", ""));
                        inputUserPass.setText(settings.getString("password", ""));

                        SharedPreferences.Editor editor = settings.edit();
                        editor.putString("username", userName);
                        editor.putString("password", userPass);
                        editor.commit();

                        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();
                        }
                        //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

解决方案2
 0  2013-11-12 06:09:14

而不是存储的UserName和Password的数据库，你可以使用SharedPreferences存储它像这样

解决方案3
 0  2013-11-12 06:21:17

在ValidateLogin（）中，您正在关闭游标，在关闭游标之后，您正在调用cursor.getCount（）。 这是错误的。 检查我编辑的代码。 

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);

                if(validLogin){

                    //SharedPreferences
                    SharedPreferences settings = getSharedPreferences("MYPREFS", 0);
                    SharedPreferences.Editor editor = settings.edit();
                    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();

        int i = c.getCount();
c.close();        
if(i <= 0){
            Toast.makeText(getApplicationContext(), "Incorrect Login..\nTry Again", Toast.LENGTH_SHORT).show();
            return false;
            }

        return true;
        }catch(Exception e){
            e.printStackTrace();
return false;
        }
    }//validate Login

}//Mainactivity

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