如何在JFrame上显示Graphics2D对象

Question

这是我第一次尝试构建GUI，但我陷入了僵局，似乎找不到解决方案。目前我已经设置了GUI的部分内容，但我想插入我在另一个类上创建的图，但我不确定如何将其与当前的JFrame链接。我可以让它作为一个单独的实体工作，但不能一起工作。

主显示类别：

public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(MainDisplay.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(MainDisplay.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(MainDisplay.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(MainDisplay.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MainDisplay().setVisible(true);
}
});
float LvBTC;
float LvLTC;
float LvETH;
float[] HBTC;
float[] HLTC;
float[] HETH;
float CurETH;
float CurBTC;
float CurLTC;
WebScraper WS1 = new WebScraper();
LvBTC = WS1.LvScrapeBTC();
LvLTC = WS1.LvScrapeLTC();
LvETH = WS1.LvScrapeETH();
HBTC = WS1.HScrapeBTC();
HLTC = WS1.HScrapeLTC();
HETH = WS1.HScrapeETH(); 
System.out.println("Bitcoin's Current Price is: $"+LvBTC);
System.out.println("Litecoin's Current Price is: $"+LvLTC);
System.out.println("Ethereum's Current Price is: $"+LvETH);
Graph G1 = new Graph();
G1.CurrentValues(HBTC);
for (int i = 0; 5 > i;) {
System.out.println("Day " + (i + 1) + ": $" + G1.CurValues[i]);
i++;
}
System.out.println("Index of largest value: " + G1.IndexLarge(G1.CurValues));
System.out.println("Index of smallest value: " + G1.IndexSmall(G1.CurValues));
Graph Graphing = new Graph();

}

图形类：

package comsci_ia;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.util.ArrayList;
import java.util.Arrays;
import javax.swing.JFrame;
public class Graph extends JFrame {
int IndexL;
int IndexS;
int DistanceDay1;
int DistanceDay2;
int DistanceDay3;
int DistanceDay4;
int DistanceDay5;
float[] CurValues = new float[5];
ArrayList<Point> points = new ArrayList<>();
public float[] CurrentValues(float[] array) {
DatabaseBrowser DB1 = new DatabaseBrowser();
WebScraper WS1 = new WebScraper();
float[] HBTC = WS1.HScrapeBTC();
float[] HETH = WS1.HScrapeETH();
float[] HLTC = WS1.HScrapeLTC();
float CurHold = 0;
boolean BTCCheck = false;
BTCCheck = Arrays.equals(HBTC, array);
boolean LTCCheck = false;
LTCCheck = Arrays.equals(HLTC, array);
boolean ETHCheck = false;
ETHCheck = Arrays.equals(HETH, array);
if (BTCCheck == true) {
CurHold = DB1.RetriveBTC();
}
if (LTCCheck == true) {
CurHold = DB1.RetriveLTC();
}
if (ETHCheck == true) {
CurHold = DB1.RetriveETH();
}
float pick;
for (int i = 0; 5 > i;) {
for (int z = 0; z < array.length; z++) {
pick = array[z];
pick = pick * CurHold;
CurValues[i] = pick;
i++;
}
}
return CurValues;
}
public int IndexLarge(float[] array) {
float temp = 0;
for (int i = 0; 5 > i;) { //Cycles through ArrayList and replaces temp with the Largest value
if (array[i] > temp) {
temp = array[i];
}
i++;
}
int IndexCheck = 0; //Searches and records the index of "temp" value (Largest value in array)
for (IndexCheck = 0; 5 > IndexCheck;) {
if (array[IndexCheck] == temp) {
break;
}
IndexCheck++;
}
IndexL = IndexCheck;
return IndexL;
}
public int IndexSmall(float[] array) {
float temp = 1000000;
for (int i = 0; 5 > i;) { //Cycles through ArrayList and replaces temp with the smallest value
if (array[i] < temp) {
temp = array[i];
}
i++;
}
int IndexCheck = 0; //Searches and records the index of "temp" value (smallest value in array)
for (IndexCheck = 0; 5 > IndexCheck;) {
if (array[IndexCheck] == temp) {
break;
}
IndexCheck++;
}
IndexS = IndexCheck;
return IndexS;
}
public void Plotter(float[] array) { 
/*  int DayRefL = IndexL + 1;
int DayRefS = IndexS + 1; */
float ValRange;
float ValPx;
points = null;
ValRange = array[IndexL] - array[IndexS];
ValPx = (300f/ ValRange); //Number is the pixel distance between highest and lowest values
DistanceDay1 = (int) ((int) 50 + ((array[IndexL] - array[0]) * ValPx));
DistanceDay2 = (int) ((int) 50 + ((array[IndexL] - array[1]) * ValPx));
DistanceDay3 = (int) ((int) 50 + ((array[IndexL] - array[2]) * ValPx));
DistanceDay4 = (int) ((int) 50 + ((array[IndexL] - array[3]) * ValPx));
DistanceDay5 = (int) ((int) 50 + ((array[IndexL] - array[4]) * ValPx));
}
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
int DotSize = 10;
int width = g2.getFontMetrics().stringWidth("Today");
int middle = width / 2;
g2.setColor(Color.BLACK);
/* g2.drawLine(10, 10, 10, 410); //Frame Boundaries
g2.drawLine(410, 10, 10, 10); //Frame Boundaries
g2.drawLine(410, 10, 410, 410); //Frame Boundaries
g2.drawLine(410, 410, 10, 410); //Frame Boundaries */
//Axis
g2.drawLine(30, 30, 30, 370);
g2.drawLine(370, 370, 30, 370);
//Points & Connections
PlotPoints(g2, 98, DistanceDay1, DotSize);
g2.drawLine(98, DistanceDay1, 166, DistanceDay2);
PlotPoints(g2, 166, DistanceDay2, DotSize);
g2.drawLine(166, DistanceDay2, 234, DistanceDay3);
PlotPoints(g2, 234, DistanceDay3, DotSize);
g2.drawLine(234, DistanceDay3, 302, DistanceDay4);
PlotPoints(g2, 302, DistanceDay4, DotSize);
g2.drawLine(302, DistanceDay4, 370, DistanceDay5);
PlotPoints(g2, 370, DistanceDay5, DotSize);
//Labels
g2.drawString("Today", 370 - middle, 390);
/*  g2.drawString("Test", 98 - middle, 40);
g2.drawString("Test", 146, 25); */
}
private void PlotPoints(Graphics2D g, int x, int y, int r) {
x = x - (r / 2);
y = y - (r / 2);
g.fillOval(x, y, r, r);
}
}

如果我将Graph类作为一个单独的实体运行，它将导致以下结果：Graph弹出

这是图形代码的一个单独版本，其中会弹出一个显示图形的框架：

package graphing;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Graphing extends JPanel {
@Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
int DotSize = 10;
int width = g2.getFontMetrics().stringWidth("Test");
int middle = width / 2;
g2.setColor(Color.BLACK);
g2.drawLine(10, 10, 10, 390); //Frame Boundaries
g2.drawLine(390, 10, 10, 10); //Frame Boundaries
g2.drawLine(390, 10, 390, 390); //Frame Boundaries
g2.drawLine(390, 390, 10, 390); //Frame Boundaries
//Axis
g2.drawLine(30, 30, 30, 370);
g2.drawLine(370, 370, 30, 370);
//Points & Connections
PlotPoints(g2, 98, 55, DotSize);
g2.drawLine(98, 55, 166, 40);
PlotPoints(g2, 166, 40, DotSize);
g2.drawLine(166, 40, 234, 100);
PlotPoints(g2, 234, 100, DotSize);
g2.drawLine(234, 100, 302, 332);
PlotPoints(g2, 302, 332, DotSize);
g2.drawLine(302, 332, 370, 40);
PlotPoints(g2, 370, 40, DotSize);
//Labels
g2.drawString("Test", 98 - middle, 40);
g2.drawString("Test", 146, 25);
}
private void PlotPoints(Graphics2D g, int x, int y, int r) {
x = x - (r / 2);
y = y - (r / 2);
g.fillOval(x, y, r, r);
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setSize(420, 420);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Graphing app = new Graphing();
frame.setContentPane(app);
frame.setVisible(true);
frame.invalidate();
}
}

Answer 1

因此，我的直接问题是，您正在从JFrame进行扩展，这不是一个好的扩展，因为这将UI锁定在单个用例中(它不容易重复使用(

我的第二个问题是，您在JFrame中创建了一个名为paintComponent的方法，但由于JFrame不使用这种绘画风格，因此它从未被称为

所以，我要做的第一件事是更改Graph，使其从JPanel扩展而来。。。

public class Graph extends JPanel {
//...

然后我会更新你的paintComponent，这样它就可以正确地支持绘画过程。。。

@Overrride
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
//...

现在，下一个问题是，您需要提供一些调整大小的提示，以便添加容器的布局管理器了解如何最好地布局组件。。。

@Override
public Dimension getPreferredSize() {
// I've not been through your code in detail
// so I've not calculated what the actual
// preferred size might be and this is just an
// example you'll have to update
return new Dimension(200, 200);
}

现在，您可以创建Graph的实例，并将其添加到您想要的容器中