按下按钮后，如何更改 JTextField 的背景颜色？

Question

我为学校项目制作贷款计算器，一旦我按下按钮，我就无法弄清楚如何更改背景颜色和黄色。如果可以的话，作为奖励，您如何更改在文本字段中输入的文本的字体大小。txtMonthlyPaymenttxtTotalPaymentComputePayment

谢谢！;)

import java.awt.*; //enables java GUI

import java.awt.event.*;//enables the user to respond, such as using the mouse and keyboard

import javax.swing.*;//more awt and swing imports to be associated with components / objects

import javax.swing.border.TitledBorder; //title of the JFrame window

import java.awt.event.ActionListener; // used to set actions for certain components / objects

import java.awt.Color; // used to alter colour of components / objects

import java.awt.Font; // used to change font size / style

public class LoanCalculator extends JFrame {

//create text fields for interest rate, years, loan amount, monthly pmt and total pmt

private JTextField txtAnnualInterestRate = new JTextField();//text fields that appear, their names

private JTextField txtNumberOfYears = new JTextField();

private JTextField txtLoanAmount = new JTextField();

private JTextField txtMonthlyPayment = new JTextField();//define the control here, then add to the panel, below

private JTextField txtTotalPayment = new JTextField();

//create a compute payment button

private JButton jbtComputeLoan = new JButton("Compute Payment"); //text appears on the button

public LoanCalculator()

{

    //craft a panel to hold labels and text fields

    JPanel p1 = new JPanel(new GridLayout(5, 2));//dimensions specified

    p1.add(new JLabel("Annual Interest Rate"));

    p1.add(txtAnnualInterestRate);

    p1.add(new JLabel("Number of Years"));

    p1.add(txtNumberOfYears);

    p1.add(new JLabel("Loan Amount"));

    p1.add(txtLoanAmount);

    p1.add(new JLabel("Monthly Payment"));

    p1.add(txtMonthlyPayment);

    p1.add(new JLabel("Total Payment"));

    p1.add(txtTotalPayment);

Answer 1

您需要在 中执行此操作。actionPerformedpublic void actionPerformed(ActionEvent e ){    //get values from the text fields    double interest = Double.parseDouble(txtAnnualInterestRate.getText());    int  year =  Integer.parseInt(txtNumberOfYears.getText());    double loanAmount = Double.parseDouble(txtLoanAmount.getText());    Loan loan = new Loan(interest, year, loanAmount);//see page 376 for source for loan object    //display the monthly total payment and monthly payment    txtMonthlyPayment.setText(String.format("%.2f", loan.getMonthlyPayment()));    txtMonthlyPayment.setBackground(Color.YELLOW);    txtTotalPayment.setText(String.format("%.2f", loan.getTotalPayment()));    txtTotalPayment.setBackground(Color.YELLOW);}//end action performed对于您的第二个问题，您可以使用设置字体。例如java.awt.FonttxtMonthlyPayment.setFont(new Font("font name",font_style(int),size(int));