Question

好的，让我们从头开始：

在我的Mainactivity中，我有一个连接到MySQL数据库的空白和另一个发送查询并返回用户和密码的空白

我将数据库的名称和密码存储到两个变量中，然后将它们与我在用户的EditText中写入的内容和密码进行比较，问题是如果EdittText中的内容等于我从数据库中带来的东西总是告诉我它们不一样。

这是代码：

package com.example.merli.loginconmysql;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.Connection;

public class MainActivity extends Activity {

    EditText usuario;
    EditText contra;
    Button entrar;
    String usuarioAchequear;
    String contraAChequear;

    String bd_usuario = "android";
    String bd_contra = "123456";
    String bd_url = "jdbc:mysql://192.168.1.13:3306/test" + "?user=" + bd_usuario + "&password=" + bd_contra + "&useUnicode=true&characterEncoding=UTF-8";
    Connection conec;
    Statement estado;
    ResultSet query;
    Context contexto = this;
    int prueba;


    @Override
    protected void onCreate(Bundle savedInstanceState) {

        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        usuario = (EditText) findViewById(R.id.usuario);
        contra = (EditText) findViewById(R.id.contrasena);
        entrar = (Button) findViewById(R.id.entrar);


        conxecionBaseDatos();

        entrar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                entrarxD();
                prueba = usuario.getText().toString().length();
                if (usuario.getText().toString() == usuarioAchequear)
                {
                    AlertDialog.Builder dialogo = new AlertDialog.Builder(contexto);
                    dialogo.setMessage("Bienvenido! " + usuarioAchequear);
                    dialogo.setPositiveButton("Okey", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.cancel();
                        }
                    });

                    dialogo.create();
                    dialogo.show();
                }else
                {
                    AlertDialog.Builder dialogo = new AlertDialog.Builder(contexto);
                    dialogo.setMessage("Usuario o contraseña incorrecta   " + prueba);
                    dialogo.setPositiveButton("Okey", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.cancel();
                        }
                    });

                    dialogo.create();
                    dialogo.show();
                }

            }
        });

    }

    public void conxecionBaseDatos()
    {
        try{

            Class.forName("com.mysql.jdbc.Driver").newInstance();

            conec = DriverManager.getConnection(bd_url);
            estado = conec.createStatement();

        }catch (Exception e)
        {
            AlertDialog.Builder dialogo = new AlertDialog.Builder(contexto);
            dialogo.setMessage(e.getMessage());
            dialogo.setPositiveButton("Okey", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });

            dialogo.create();
            dialogo.show();

        }
    }

    public void entrarxD()
    {
        try {
            query = estado.executeQuery("SELECT * FROM tabla WHERE usuario = '" + usuario.getText().toString() + "'");

            query.first();
            while (query.next())
            {
                usuarioAchequear = query.getString("usuario");
                contraAChequear = query.getString("contra");
            }

            AlertDialog.Builder dialogo = new AlertDialog.Builder(contexto);
            dialogo.setMessage("Usuario:" + usuarioAchequear + "   Contraseña:" + contraAChequear);
            dialogo.setPositiveButton("Okey", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });

            dialogo.create();
            dialogo.show();

        }catch (Exception e)
        {
            AlertDialog.Builder dialogo = new AlertDialog.Builder(contexto);
            dialogo.setMessage(e.getMessage());
            dialogo.setPositiveButton("Okey", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            });

            dialogo.create();
            dialogo.show();
        }



    }
}

Answer 1

请将您的if条件更改为以下内容：

if (usuario.getText().toString().equal(usuarioAchequear)){
   //some code here 
}

Answer 2

使用字符串，您必须使用milliseconds TimeStamp(int mm, int dd, int HH, int MM, int SS, int yyyy) { tm ttm = tm(); ttm.tm_year = yyyy - 1900; // Year since 1900 ttm.tm_mon = mm - 1; // Month since January ttm.tm_mday = dd; // Day of the month [1-31] ttm.tm_hour = HH; // Hour of the day [00-23] ttm.tm_min = MM; ttm.tm_sec = SS; time_t ttime_t = mktime(&ttm); system_clock::time_point time_point_result = std::chrono::system_clock::from_time_t(ttime_t); milliseconds now_ms = std::chrono::time_point_cast<std::chrono::milliseconds>(time_point_result).time_since_epoch(); return now_ms; } milliseconds getRandomTimestamp(int mm_1, int dd_1, int HH_1, int MM_1, int SS_1, int yyyy_1, int mm_2, int dd_2, int HH_2, int MM_2, int SS_2, int yyyy_2, int N) { milliseconds lowerRangeBound = fixedTimeStamp(mm_1, dd_1, HH_1, MM_1, SS_1, yyyy_1); milliseconds upperRangeBound = fixedTimeStamp(mm_2, dd_2, HH_2, MM_2, SS_2, yyyy_2); long lowerRange_ = lowerRangeBound.count(); long upperRange_ = upperRangeBound.count(); //long output = rand() % (upperRange_ - lowerRange_ + 1) + lowerRange_; // rand() replaced after @Jarod42's suggestion. std::default_random_engine generator; std::uniform_int_distribution<int> distribution(lowerRange_, upperRange_); long output = distribution(generator); std::chrono::duration<long> dur(output); return dur; }方法：

equals()

Answer 3

你应该comapare值

if (usuario.getText().toString().equals(usuarioAchequear))
{
    //Some codes
}

而不是比较参考

usuario.getText().toString().equals(usuarioAchequear)

在此处进一步阅读：HERE

我比较了两个相等的值，但结果表明它们是不同的

3 个答案: