java不能引用非final变量

Question

下面的代码继续给我:

Cannot refer to a non-final variable textBoxPassword inside an inner class defined in a different method Login.java /ChurchWebLogin/src/com/gwt/churchweb/churchweblogin/client line 61

package com.gwt.churchweb.churchweblogin.client;

import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.FlexTable;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.HasHorizontalAlignment;
import com.google.gwt.user.client.ui.CheckBox;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.user.client.Window;

public class Login extends Composite {

    public Login() {

        VerticalPanel verticalPanel = new VerticalPanel();
        initWidget(verticalPanel);
        verticalPanel.setSize("329px", "186px");

        Label lblNewLabel = new Label("Sign into your account");
        lblNewLabel.setStyleName("gwt-Login-SigninLabel");
        verticalPanel.add(lblNewLabel);

        FlexTable flexTable = new FlexTable();
        verticalPanel.add(flexTable);
        flexTable.setWidth("308px");

        Label lblNewLabel_1 = new Label("Username:");
        lblNewLabel_1.setStyleName("gwt-Label-Login");
        flexTable.setWidget(0, 0, lblNewLabel_1);
        lblNewLabel_1.setWidth("72px");

        TextBox textboxUsername = new TextBox();
        textboxUsername.setStyleName("gwt-LoginTextBox");
        flexTable.setWidget(0, 1, textboxUsername);
        textboxUsername.setWidth("204px");

        Label lblNewLabel_2 = new Label("Password:");
        lblNewLabel_2.setStyleName("gwt-Label-Login");
        flexTable.setWidget(1, 0, lblNewLabel_2);
        lblNewLabel_2.setWidth("66px");

        TextBox textBoxPassword = new TextBox();
        textBoxPassword.setStyleName("gwt-LoginTextBox");
        flexTable.setWidget(1, 1, textBoxPassword);
        textBoxPassword.setWidth("204px");
        flexTable.getCellFormatter().setHorizontalAlignment(0, 0, HasHorizontalAlignment.ALIGN_LEFT);
        flexTable.getCellFormatter().setHorizontalAlignment(1, 0, HasHorizontalAlignment.ALIGN_LEFT);

        CheckBox chckbxRememberMeOn = new CheckBox("Remember me on this computer");
        chckbxRememberMeOn.setStyleName("gwt-Checkbox-Login");
        flexTable.setWidget(2, 1, chckbxRememberMeOn);

        Button btnSignIn = new Button("Sign In");
        btnSignIn.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                if (textboxUsername.getText().length() == 0
                        || textBoxPassword.getText().length() == 0) {
                        Window.alert("Username or password is empty."); 
                    }
            }
        });

        btnSignIn.setStyleName("gwt-Login-SigninButton");
        flexTable.setWidget(3, 1, btnSignIn);



    }


}

Answer 1

final TextBox textboxUsername = new TextBox();

和

final TextBox textBoxPassword = new TextBox();

应该修复它。

Java 要求对来自内部类的变量的引用是 final 变量(我想是出于并发管理的原因)。