java java将图像添加到画布
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java add image to canvas
提问by Remmy
I'm trying to add a image to a java canvas. I'm using the "ImageIO.read" to get the image source. The problem i'm facing is that i don't know how to display it on the canvas after reading the image location. Also later i will need to load a different image(e.g. after a button pressed) how can i do this. The update (canvas.update) method needs a "Graphics" parameter instead of an image. Below you'll find my code simplified (i left out all code that's not relevant to the canvas issue.)
我正在尝试将图像添加到 Java 画布。我正在使用“ImageIO.read”来获取图像源。我面临的问题是我不知道如何在读取图像位置后在画布上显示它。稍后我将需要加载不同的图像（例如按下按钮后）我该怎么做。update (canvas.update) 方法需要“Graphics”参数而不是图像。下面你会发现我的代码被简化了（我省略了所有与画布问题无关的代码。）
public class MainWindow {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
window = new MainWindow();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public MainWindow() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
Canvas csStatusImage = new Canvas();
csStatusImage.setBounds(393, 36, 200, 200);
frame.getContentPane().add(csStatusImage);
Image iMg;
try {
iMg = ImageIO.read(new File("Images/Error_status_1.png"));
csStatusImage.imageUpdate(iMg, 10, 2, 2, 9, 10);
csStatusImage.checkImage(iMg, (ImageObserver) this);
csStatusImage.createImage((ImageProducer) iMg);
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
回答by MadProgrammer
First of all, you going to need some way to paint the image. To achieve this, you can override the paintmethod of the java.awt.Canvasclass
首先，您需要某种方法来绘制图像。为此，您可以覆盖类的paint方法java.awt.Canvas
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
Frame frame = new Frame("Testing");
frame.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
frame.add(new ImageCanvas());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public class ImageCanvas extends Canvas {
private BufferedImage img;
public ImageCanvas() {
try {
img = ImageIO.read(new File("Images/Error_status_1.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
@Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
}
@Override
public void paint(Graphics g) {
super.paint(g);
if (img != null) {
int x = (getWidth() - img.getWidth()) / 2;
int y = (getHeight() - img.getHeight()) / 2;
g.drawImage(img, x, y, this);
}
}
}
}
I have to tell you, AWT is out-of-date by some 15+ years, replaced by Swing. You may find it hard to get additional support with this API. If you can, you'd better of using Swing or JavaFX
我必须告诉你，AWT 已经过时了大约 15 年以上，取而代之的是 Swing。您可能会发现很难获得此 API 的额外支持。如果可以，最好使用 Swing 或 JavaFX
