[英]How do I use a separate method to call the paint component method and draw a rectangle?
I am using Swing to create a GUI which would draw a new rectangle every time a method runs.我正在使用 Swing 创建一个 GUI,它会在每次运行方法时绘制一个新的矩形。 I want to use variables that would get incremented and continue making new rectangles in a series.我想使用会增加的变量并继续在一系列中制作新的矩形。 My goal is to give a visual representation of a linked list and to emphasize on the concept that a linked list has a head which points to the next item which points to the next and so on.我的目标是给出链表的可视化表示,并强调链表有一个指向下一个项目的头的概念,该头指向下一个项目,依此类推。
I am a beginner with basic knowledge of Java, and I'm just getting started with Swing and creating User interfaces.我是一名具备 Java 基础知识的初学者,我刚刚开始使用 Swing 并创建用户界面。
void insert(int i, int j) {
//some code which would create a new rectangle and add to my GUI.
}
// this is my panel class
public class MyPanel extends JPanel{
MyPanel() {
this.setPreferredSize(new Dimension(500, 500));
}
public void paint(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
g2D.setPaint(Color.blue);
g2D.setStroke(new BasicStroke(5));
g2D.drawRect(i, j, 100, 50);
}
}
What you can do:你可以做什么:
insert(int,int)
method创建一个列表来存储传递给insert(int,int)
方法的参数insert(int,int)
method在insert(int,int)
方法中填充该列表paintComponents()
-method can loop over the saved values and display them paintComponents()
- 方法可以遍历保存的值并显示它们// records are fairly new to Java. See (*) for what it does
private record Tuple(int i, int j) {}
// this list contains values added by the `insert(int, int)` method
private final List<Tuple> tuples = new ArrayList<>();
private void insert(final int i, final int j) {
// do some stuff
// ...
// save passed values to a list using the helper class "Tuple"
this.tuples.add(new Tuple(i, j));
// repaint UI
this.repaint();
}
@Override
public void paintComponents(final Graphics g) {
super.paintComponents(g);
// loop over saved values and do something with their values
for (final Tuple tuple : this.tuples) {
// draw rect for saved tuple
g.drawRect(tuple.i * 10, tuple.j * 10, 20, 20);
}
}
(*) records were introduced in Java 14 and they can be used to create data classes in a short way. (*) 记录是在 Java 14 中引入的,它们可用于在短时间内创建数据类。
They automatically generate Getters, the equals()
, hashCode()
and toString()
-method.它们会自动生成 Getter、 equals()
、 hashCode()
和toString()
方法。
For this example, the record could be be rewritten to:对于此示例,记录可以重写为:
private class Tuple {
private final int i;
private final int j;
public Tuple(final int i, final int j) {
this.i = i;
this.j = j;
}
}
(we don't need equals()
, hashCode()
and toString()
) (我们不需要equals()
、 hashCode()
和toString()
)
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