從另一種方法的方法中獲取變量

Question

/* 
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* To change this template file, choose Tools | Templates 
* and open the template in the editor. 
*/ 

package controle_financeiro; 

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

/** 
* 
* @author IAGO 
*/ 

public class TelaCadastroCategoria extends javax.swing.JFrame { 

    /** 
    * Creates new form TelaCadastroCategoria 
    */ 
    public TelaCadastroCategoria() { 
     initComponents(); 
    } 


    @SuppressWarnings("unchecked") 
    // <editor-fold defaultstate="collapsed" desc="Generated Code">       
    private void initComponents() { 

     jLabel1 = new javax.swing.JLabel(); 
     nomeCategoria = new javax.swing.JTextField(); 
     botao_cadastra_tela_cadastro_categorias = new javax.swing.JButton(); 
     botao_voltar_tela_cadastro_categorias = new javax.swing.JButton(); 

     setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 

     jLabel1.setFont(new java.awt.Font("Tahoma", 0, 18)); // NOI18N 
     jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER); 
     jLabel1.setText("Nome da Categoria"); 

     nomeCategoria.addMouseListener(new java.awt.event.MouseAdapter() { 
      public void mouseClicked(java.awt.event.MouseEvent evt) { 
       nomeCategoriaMouseClicked(evt); 
      } 
     }); 

     botao_cadastra_tela_cadastro_categorias.setText("Cadastrar"); 
     botao_cadastra_tela_cadastro_categorias.addMouseListener(new java.awt.event.MouseAdapter() { 
      public void mouseClicked(java.awt.event.MouseEvent evt) { 
       botao_cadastra_tela_cadastro_categoriasMouseClicked(evt); 
      } 
     }); 

     botao_voltar_tela_cadastro_categorias.setText("Voltar"); 
     botao_voltar_tela_cadastro_categorias.addMouseListener(new java.awt.event.MouseAdapter() { 
      public void mouseClicked(java.awt.event.MouseEvent evt) { 
       botao_voltar_tela_cadastro_categoriasMouseClicked(evt); 
      } 
     }); 
     botao_voltar_tela_cadastro_categorias.addActionListener(new java.awt.event.ActionListener() { 
      public void actionPerformed(java.awt.event.ActionEvent evt) { 
       botao_voltar_tela_cadastro_categoriasActionPerformed(evt); 
      } 
     }); 

     javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); 
     getContentPane().setLayout(layout); 
     layout.setHorizontalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addGroup(layout.createSequentialGroup() 
       .addGap(98, 98, 98) 
       .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 191, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)) 
      .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup() 
       .addContainerGap(76, Short.MAX_VALUE) 
       .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false) 
        .addGroup(layout.createSequentialGroup() 
         .addComponent(botao_voltar_tela_cadastro_categorias, javax.swing.GroupLayout.PREFERRED_SIZE, 87, javax.swing.GroupLayout.PREFERRED_SIZE) 
         .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
         .addComponent(botao_cadastra_tela_cadastro_categorias, javax.swing.GroupLayout.PREFERRED_SIZE, 110, javax.swing.GroupLayout.PREFERRED_SIZE)) 
        .addComponent(nomeCategoria, javax.swing.GroupLayout.PREFERRED_SIZE, 250, javax.swing.GroupLayout.PREFERRED_SIZE)) 
       .addGap(74, 74, 74)) 
     ); 
     layout.setVerticalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addGroup(layout.createSequentialGroup() 
       .addGap(50, 50, 50) 
       .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 45, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addGap(40, 40, 40) 
       .addComponent(nomeCategoria, javax.swing.GroupLayout.PREFERRED_SIZE, 45, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 52, Short.MAX_VALUE) 
       .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) 
        .addComponent(botao_cadastra_tela_cadastro_categorias, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE) 
        .addComponent(botao_voltar_tela_cadastro_categorias, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)) 
       .addGap(25, 25, 25)) 
     ); 

     pack(); 
    }// </editor-fold>       

    int var_id=1; 

    private void botao_cadastra_tela_cadastro_categoriasMouseClicked(java.awt.event.MouseEvent evt) {                  
    try { 

      String url = "jdbc:postgresql://localhost:5432/db_controle_financeiro"; 
      String usuario = "us_iago"; 
      String senha = "123"; 

      Class.forName("org.postgresql.Driver"); 

      Connection con; 

      con = DriverManager.getConnection(url, usuario, senha); 
      System.out.println("Conexão realizada com sucesso."); 
      Statement stm = con.createStatement(); 
      stm.executeUpdate("INSERT INTO categoria (id,nome) VALUES ('" + var_id + "','" + nome_categoria + "'"); 
      var_id++; 


      con.close(); 
     } catch (ClassNotFoundException | SQLException e) { 
      System.out.println("Problemas ao conectar ao banco."); 
     }  
     TelaInicial tela_inicial_ccategoria = new TelaInicial(); 
     tela_inicial_ccategoria.setVisible(true); 
     dispose(); 
    }                  


    private void nomeCategoriaMouseClicked(java.awt.event.MouseEvent evt) {           
     String nome_categoria = (nomeCategoria.getText()); 
    }           



    public static void main(String args[]) { 


     java.awt.EventQueue.invokeLater(new Runnable() { 
      public void run() { 
       new TelaCadastroCategoria().setVisible(true); 
      } 
     }); 
    } 

    // Variables declaration - do not modify      
    private javax.swing.JButton botao_cadastra_tela_cadastro_categorias; 
    private javax.swing.JButton botao_voltar_tela_cadastro_categorias; 
    private javax.swing.JLabel jLabel1; 
    public javax.swing.JTextField nomeCategoria; 
    // End of variables declaration     
} 

我在java中製作財務控制程序，但是我遇到了從另一個方法中訪問方法中的變量的問題。我如何從方法botao_cadastra_tela_cadastro_categoriasMouseClicked中的方法nomeCategoriaMouseClicked訪問變量nome_categoria？

Answer 1

您可以使變量成爲實例變量。不要用任何方法聲明它，而應將聲明/分配置於頂部。然後你可以在該課程的任何地方訪問它。

public class TelaCadastroCategoria extends javax.swing.JFrame { 
    String nome_categoria; 
    // All the other code goes here 
} 

您將能夠在該類的任何方法中使用它。