这是 MainApplication,它创建一个 Frame 并保存实现 Graphics 的类。
MainApplication.java
import java.awt.*;
public class MainApplication
{
public MainApplication()
{
Frame frame= new Frame("Test App");
frame.add(new KeyTest());
frame.setBackground(Color.RED);
frame.setLayout(null);
frame.setSize(700,750);
frame.setVisible(true);
}
public static void main(String args[])
{
new MainApplication();
}
}
此类创建所有图形形状并也实现 KeyListener。
KeyTest.java
import java.awt.BasicStroke;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.Stroke;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.RoundRectangle2D;
public class KeyTest extends Canvas {
/**
*
*/
private static final long serialVersionUID = 3L;
Graphics2D graphics2D;
Color color = Color.BLACK;
private static float borderThickness = 5;
Shape firstShape = new RoundRectangle2D.Double(20,40,300,50,10,10);
Shape secondShape = new RoundRectangle2D.Double(20,150,300,50,10,10);
public KeyTest()
{
setBackground(Color.RED);
setSize(700,750);
}
public void paint(Graphics graphics)
{
graphics2D = (Graphics2D)graphics; //TypeCasting to 2D
System.out.println("I am inside paint");
// Smoothening the corners
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// Apple border color
Stroke oldStroke = graphics2D.getStroke();
graphics2D.setStroke(new BasicStroke(borderThickness));
graphics2D.setColor(Color.WHITE);
// Drawing a RoundedRectangle for Apple
graphics2D.draw(firstShape);
graphics2D.setStroke(oldStroke);
// Setting the Background Color
graphics2D.setColor(Color.BLACK);
graphics2D.fill(firstShape);
// Setting the font inside the shape
Font firstFont = new Font("Serif", Font.BOLD,35);
graphics2D.setFont(firstFont);
graphics2D.setColor(Color.WHITE);
graphics2D.drawString("Apple",30,80);
// Pineapple border color
graphics2D.setStroke(new BasicStroke(borderThickness));
graphics2D.setColor(Color.WHITE);
// Drawing a RoundedRectangle for Pineapple
graphics2D.draw(secondShape);
graphics2D.setStroke(oldStroke);
// Setting the Background Color
graphics2D.setColor(Color.BLACK);
graphics2D.fill(secondShape);
// Setting the font inside the shape
Font secondFont = new Font("Serif", Font.BOLD,35);
graphics2D.setFont(secondFont);
graphics2D.setColor(Color.WHITE);
graphics2D.drawString("Pineapple",30,190);
addKeyListener(new KeyListener(){
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
System.out.println(keyCode);
System.out.println(KeyEvent.VK_UP);
if(keyCode==KeyEvent.VK_UP){
System.out.println("Going to move up");
move(firstShape);
}
if(keyCode==KeyEvent.VK_DOWN){
System.out.println("Going to move down");
move(secondShape);
}
}
@Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}});
}
public void move(Shape s){
System.out.println("Check:"+s.getBounds2D());
graphics2D.setColor(Color.GREEN);
graphics2D.fill(s);
System.out.println("moving out");
}
}
我的控制台输出清楚地表明我的 key 监听器可以工作,但它没有执行我打算执行的任务。
控制台输出
block 引用>I am inside paint Going to move up
Check:java.awt.geom.Rectangle2D$Double[x=20.0,y=40.0,w=300.0,h=50.0]
moving out Going to move down
Check:java.awt.geom.Rectangle2D$Double[x=20.0,y=150.0,w=300.0,h=50.0]
moving out
输出:
现在得到的输出..(图像1)
按下向下箭头按钮时我期望的输出(图 2)
按下向上箭头按钮时我期望的输出(图 3)
最佳答案
首先,您不应该添加 KeyListener
从里面paint
方法,因为它每次都会额外注册一个 paint
被调用。
然后,不要依赖存储 Graphics
Component
的对象并在其上绘制内容,因为它可能会发生许多超出您控制范围的事情(例如,它可能会被其他发生的 AWT UI 操作清除)。
唯一相关Graphics
object 是您在 paint
中收到的实例,并且仅在 paint
的范围内方法。
所以在下面的代码中:
-
addKeyListener
已移至paint
之外。 - 关键听众
来电
move
索引为Shape
移动。 move
方法 现在只注册Shape
根据收到的索引突出显示,并调用repaint
。- 该
Graphics2D
object 设置为局部变量paint
,自从它 与外界无关。 -
paintHighlightedShape
负责绘制突出显示的Shape
,在Graphics2D
上作为参数接收的对象 paint
方法现在调用paintHighlightedShape
及其Graphics2D
作为参数传递的对象。
请注意 main
方法已添加到 KeyTest
出于测试目的,其内容应该放在您的主类中。
此外,如果您计划突出显示更多形状,则可以使用 Shape
数组,索引传递到 move
可能是 Shape
的数组索引突出显示。
最后,为了优化事情,如果它是突出显示的形状,我们不应该绘制常规形状,因为无论如何它都会被绿色形状隐藏。
考虑创建一个 drawShape(Graphics2D, Shape)
方法将绘制规则形状或绿色形状,具体取决于是否突出显示形状。
您可以从 paint
调用此方法方法,在所有形状上循环。
import java.awt.BasicStroke;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.Stroke;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.RoundRectangle2D;
public class KeyTest extends Canvas {
/**
*
*/
private static final long serialVersionUID = 3L;
Color color = Color.BLACK;
private static float borderThickness = 5;
Shape firstShape = new RoundRectangle2D.Double(20, 40, 300, 50, 10, 10);
Shape secondShape = new RoundRectangle2D.Double(20, 150, 300, 50, 10, 10);
Shape highlightedShape;
public KeyTest() {
setBackground(Color.RED);
setSize(700, 750);
}
public static void main(final String[] args) {
Frame frame = new Frame("Test App");
final KeyTest keyTest = new KeyTest();
keyTest.addKeyListener(new KeyListener() {
@Override
public void keyTyped(final KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyPressed(final KeyEvent e) {
int keyCode = e.getKeyCode();
System.out.println(keyCode);
System.out.println(KeyEvent.VK_UP);
if (keyCode == KeyEvent.VK_UP) {
System.out.println("Going to move up");
keyTest.move(1);
}
if (keyCode == KeyEvent.VK_DOWN) {
System.out.println("Going to move down");
keyTest.move(2);
}
}
@Override
public void keyReleased(final KeyEvent e) {
// TODO Auto-generated method stub
}
});
frame.add(keyTest);
frame.setBackground(Color.RED);
frame.setLayout(null);
frame.setSize(700, 750);
frame.setVisible(true);
}
public void paint(final Graphics graphics) {
Graphics2D graphics2D = (Graphics2D) graphics; //TypeCasting to 2D
System.out.println("I am inside paint");
// Smoothening the corners
graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
// Apple border color
Stroke oldStroke = graphics2D.getStroke();
graphics2D.setStroke(new BasicStroke(borderThickness));
graphics2D.setColor(Color.WHITE);
// Drawing a RoundedRectangle for Apple
graphics2D.draw(firstShape);
graphics2D.setStroke(oldStroke);
// Setting the Background Color
graphics2D.setColor(Color.BLACK);
graphics2D.fill(firstShape);
// Setting the font inside the shape
Font firstFont = new Font("Serif", Font.BOLD, 35);
graphics2D.setFont(firstFont);
graphics2D.setColor(Color.WHITE);
graphics2D.drawString("Apple", 30, 80);
// Pineapple border color
graphics2D.setStroke(new BasicStroke(borderThickness));
graphics2D.setColor(Color.WHITE);
// Drawing a RoundedRectangle for Pineapple
graphics2D.draw(secondShape);
graphics2D.setStroke(oldStroke);
// Setting the Background Color
graphics2D.setColor(Color.BLACK);
graphics2D.fill(secondShape);
// Setting the font inside the shape
Font secondFont = new Font("Serif", Font.BOLD, 35);
graphics2D.setFont(secondFont);
graphics2D.setColor(Color.WHITE);
graphics2D.drawString("Pineapple", 30, 190);
paintHighlightedShape(graphics2D);
}
private void paintHighlightedShape(final Graphics2D graphics2D) {
if (highlightedShape != null) {
graphics2D.setColor(Color.GREEN);
graphics2D.fill(highlightedShape);
}
}
public void move(final int shapeNumber) {
switch (shapeNumber) {
case 1:
highlightedShape = firstShape;
break;
case 2:
highlightedShape = secondShape;
break;
default:
}
System.out.println("Check:" + highlightedShape.getBounds2D());
System.out.println("Moving shape : " + highlightedShape);
repaint();
System.out.println("moving out");
}
}
关于java - Keylistener 可以工作,但没有执行预期的操作。为什么?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41608971/