Java 中未处理的异常错误，即使使用 try-catch
Unhandled Exception Error in Java even with try-catch
我对 Java 很陌生，开始在 YouTube 上学习。为了练习 GUI 程序，我决定制作自己的程序，现在我正在尝试调整图像的大小以添加到我的应用程序中的按钮。我搜索了如何调整图像大小并在网上找到了一些源代码，我决定对其进行测试并将其放入我自己的程序中，但是当我调用该方法时出现 unreported exception java.io.IOException; must be caught or declared to be thrown 错误并且 IntelliJ IDE 显示 Unhandled exception: java.io.IOException。我的代码中有 try-catch 块，但这仍然出现。我怎样才能解决这个问题？这是我的一些代码：
Images.java（class用网上找到的resizer方法）try-catch我自己放的
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class Images {
//Image resizer method for scaling images
void resizeImage(String inputImagePath, String outputImagePath, int scaledWidth, int scaledHeight) throws IOException {
//reads input image
File inputFile = new File(inputImagePath);
BufferedImage inputImage = ImageIO.read(inputFile);
//creates output image
BufferedImage outputImage = new BufferedImagee(scaledWidth, scaledHeight, inputImage.getType());
//scales the inputImage to the output image
Graphics2D g2d = outputImage.createGraphics();
g2d.drawImage(inputImage, 0, 0, scaledWidth, scaledHeight, null);
g2d.dispose();
// extracts extension of output file
String formatName = outputImagePath.substring(outputImagePath.lastIndexOf(".") + 1);
//writes to output file
ImageIO.write(outputImage, formatName, new File(outputImagePath));
try {
inputFile = null;
inputImage = ImageIO.read(inputFile);
}
catch(IOException e){
e.printStackTrace();
System.out.println("image file path is null");
}
}
}
GUI.java（当我尝试调用该方法时出现错误的地方）。错误出现在 plus.resizeImage.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import com.company.Images;
public class GUI extends JFrame {
//This will be used for dimensions of the window
private int height, width;
GUI(int w, int h) {
super("OS Control");
setWidth(w);
setHeight(h);
setSize(getWidth(), getHeight());
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setContent();
setVisible(true);
}
//Gets and sets for height and width of window
public void setHeight(int height) {
this.height = height;
}
public int getHeight() {
return height;
}
public void setWidth(int width) {
this.width = width;
}
public int getWidth() {
return width;
}
////////////////////////////////////////////////
/*Method with the actual contents of the aplication
i.e buttons, text fields, etc.
*/
void setContent() {
//variables used in the methods for ease of changing if needed
int buttonWidth, buttonHeight;
int searchBarWidth, searchBarHeight;
buttonWidth = 200;
buttonHeight = 100;
searchBarWidth = 350;
searchBarHeight = 25;
//Panel for the two center buttons
JPanel buttons = new JPanel();
//flow layout to center horizontally
buttons.setLayout(new FlowLayout());
buttons.setBackground(Color.decode("#9E9E9E"));
JButton mechanicButton = new JButton("Mecanicos");
mechanicButton.setPreferredSize(new Dimension(buttonWidth, buttonHeight));
mechanicButton.setFocusable(false);
mechanicButton.addActionListener(new MechanicButtonEventHandling());
buttons.add(mechanicButton);
JButton osButton = new JButton("Ordens de Servico");
osButton.setPreferredSize(new Dimension(buttonWidth, buttonHeight));
osButton.setFocusable(false);
osButton.addActionListener(new OSButtonEventHandling());
buttons.add(osButton);
JPanel center = new JPanel();
//gridbag layout to center vertically
center.setLayout(new GridBagLayout());
center.setBackground(Color.decode("#9E9E9E"));
//combine the two to center horizontally and vertically
center.add(buttons);
JPanel search = new JPanel();
search.setLayout(new FlowLayout());
search.setBackground(Color.decode("#9E9E9E"));
search.setSize(new Dimension(getWidth(), searchBarHeight));
JTextField searchBar = new JTextField("Pesquisar: ");
searchBar.setPreferredSize(new Dimension(searchBarWidth, searchBarHeight));
searchBar.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 10));
search.add(searchBar);
JPanel plusPanel = new JPanel();
plusPanel.setLayout(new BorderLayout());
plusPanel.setSize(new Dimension(10, 10));
Images plus = new Images();
plus.resizeImage("plus.png","plusButton.png", 10, 10);
ImageIcon plusButtonImage = new ImageIcon("plusButton.png");
JButton plusButton = new JButton(plusButtonImage);
plusButton.setSize(new Dimension(10, 10));
plusPanel.add(plusButton, BorderLayout.SOUTH);
//add to jframe
add(search);
add(center);
add(plusPanel);
}
private class MechanicButtonEventHandling implements ActionListener {
public void actionPerformed(ActionEvent e) {
JFrame mechanicList = new JFrame("Lista de Mecanicos");
mechanicList.setSize(getWidth(), getHeight());
mechanicList.setLocation(100, 100);
mechanicList.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
mechanicList.setVisible(true);
}
}
private class OSButtonEventHandling implements ActionListener {
public void actionPerformed(ActionEvent e) {
JFrame osList = new JFrame("Lista de ordens de servico");
osList.setSize(getWidth(), getHeight());
osList.setLocation(700, 100);
osList.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
osList.setVisible(true);
}
}
}
您需要更好地了解 Java 如何处理异常。
您的 Images#resizeImage 方法包含一些抛出 IOException this being 的操作，ImageIO#read 和 ImageIO#write 调用。
在方法主体的底部执行此操作：
try {
inputFile = null;
inputImage = ImageIO.read(inputFile);
} catch(IOException e){
e.printStackTrace();
System.out.println("image file path is null");
}
在此代码位中，您使用 try-catch 子句处理抛出的 IOException。这
但是对于这些调用不能说相同：
BufferedImage inputImage = ImageIO.read(inputFile);
ImageIO.write(outputImage, formatName, new File(outputImagePath));
因为这两个都抛出了一个不在方法范围内处理的异常（即使用 try-catch 子句），你强制方法的签名有一个 throws 声明 IOException 被这两个抛出。由于 IOException 是一个已检查的异常，编译器希望找到一个 try-catch 子句来包装对 Images#resizeImage 方法的调用。
要修复您的代码，您有两种可能的解决方案：
从方法体中删除 try-catch 子句，仅保留 throws 声明，强制调用者在调用点处理异常。
包装几乎所有的方法体或在 try-catch 子句中抛出 IOException 的地方，从而在方法体中处理异常（这不是一个好主意，因为这样你就不会知道调整大小的操作是否失败）。
看来您对异常如何工作以及需要如何处理它们的理解有点有限，所以在做任何其他事情之前，我建议先绕道检查一下。
https://docs.oracle.com/javase/tutorial/essential/exceptions/index.html
我对 Java 很陌生，开始在 YouTube 上学习。为了练习 GUI 程序，我决定制作自己的程序，现在我正在尝试调整图像的大小以添加到我的应用程序中的按钮。我搜索了如何调整图像大小并在网上找到了一些源代码，我决定对其进行测试并将其放入我自己的程序中，但是当我调用该方法时出现 unreported exception java.io.IOException; must be caught or declared to be thrown 错误并且 IntelliJ IDE 显示 Unhandled exception: java.io.IOException。我的代码中有 try-catch 块，但这仍然出现。我怎样才能解决这个问题？这是我的一些代码：
Images.java（class用网上找到的resizer方法）try-catch我自己放的
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class Images {
//Image resizer method for scaling images
void resizeImage(String inputImagePath, String outputImagePath, int scaledWidth, int scaledHeight) throws IOException {
//reads input image
File inputFile = new File(inputImagePath);
BufferedImage inputImage = ImageIO.read(inputFile);
//creates output image
BufferedImage outputImage = new BufferedImagee(scaledWidth, scaledHeight, inputImage.getType());
//scales the inputImage to the output image
Graphics2D g2d = outputImage.createGraphics();
g2d.drawImage(inputImage, 0, 0, scaledWidth, scaledHeight, null);
g2d.dispose();
// extracts extension of output file
String formatName = outputImagePath.substring(outputImagePath.lastIndexOf(".") + 1);
//writes to output file
ImageIO.write(outputImage, formatName, new File(outputImagePath));
try {
inputFile = null;
inputImage = ImageIO.read(inputFile);
}
catch(IOException e){
e.printStackTrace();
System.out.println("image file path is null");
}
}
}
GUI.java（当我尝试调用该方法时出现错误的地方）。错误出现在 plus.resizeImage.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import com.company.Images;
public class GUI extends JFrame {
//This will be used for dimensions of the window
private int height, width;
GUI(int w, int h) {
super("OS Control");
setWidth(w);
setHeight(h);
setSize(getWidth(), getHeight());
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setContent();
setVisible(true);
}
//Gets and sets for height and width of window
public void setHeight(int height) {
this.height = height;
}
public int getHeight() {
return height;
}
public void setWidth(int width) {
this.width = width;
}
public int getWidth() {
return width;
}
////////////////////////////////////////////////
/*Method with the actual contents of the aplication
i.e buttons, text fields, etc.
*/
void setContent() {
//variables used in the methods for ease of changing if needed
int buttonWidth, buttonHeight;
int searchBarWidth, searchBarHeight;
buttonWidth = 200;
buttonHeight = 100;
searchBarWidth = 350;
searchBarHeight = 25;
//Panel for the two center buttons
JPanel buttons = new JPanel();
//flow layout to center horizontally
buttons.setLayout(new FlowLayout());
buttons.setBackground(Color.decode("#9E9E9E"));
JButton mechanicButton = new JButton("Mecanicos");
mechanicButton.setPreferredSize(new Dimension(buttonWidth, buttonHeight));
mechanicButton.setFocusable(false);
mechanicButton.addActionListener(new MechanicButtonEventHandling());
buttons.add(mechanicButton);
JButton osButton = new JButton("Ordens de Servico");
osButton.setPreferredSize(new Dimension(buttonWidth, buttonHeight));
osButton.setFocusable(false);
osButton.addActionListener(new OSButtonEventHandling());
buttons.add(osButton);
JPanel center = new JPanel();
//gridbag layout to center vertically
center.setLayout(new GridBagLayout());
center.setBackground(Color.decode("#9E9E9E"));
//combine the two to center horizontally and vertically
center.add(buttons);
JPanel search = new JPanel();
search.setLayout(new FlowLayout());
search.setBackground(Color.decode("#9E9E9E"));
search.setSize(new Dimension(getWidth(), searchBarHeight));
JTextField searchBar = new JTextField("Pesquisar: ");
searchBar.setPreferredSize(new Dimension(searchBarWidth, searchBarHeight));
searchBar.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 10));
search.add(searchBar);
JPanel plusPanel = new JPanel();
plusPanel.setLayout(new BorderLayout());
plusPanel.setSize(new Dimension(10, 10));
Images plus = new Images();
plus.resizeImage("plus.png","plusButton.png", 10, 10);
ImageIcon plusButtonImage = new ImageIcon("plusButton.png");
JButton plusButton = new JButton(plusButtonImage);
plusButton.setSize(new Dimension(10, 10));
plusPanel.add(plusButton, BorderLayout.SOUTH);
//add to jframe
add(search);
add(center);
add(plusPanel);
}
private class MechanicButtonEventHandling implements ActionListener {
public void actionPerformed(ActionEvent e) {
JFrame mechanicList = new JFrame("Lista de Mecanicos");
mechanicList.setSize(getWidth(), getHeight());
mechanicList.setLocation(100, 100);
mechanicList.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
mechanicList.setVisible(true);
}
}
private class OSButtonEventHandling implements ActionListener {
public void actionPerformed(ActionEvent e) {
JFrame osList = new JFrame("Lista de ordens de servico");
osList.setSize(getWidth(), getHeight());
osList.setLocation(700, 100);
osList.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
osList.setVisible(true);
}
}
}
您需要更好地了解 Java 如何处理异常。
您的 Images#resizeImage 方法包含一些抛出 IOException this being 的操作，ImageIO#read 和 ImageIO#write 调用。
在方法主体的底部执行此操作：
try {
inputFile = null;
inputImage = ImageIO.read(inputFile);
} catch(IOException e){
e.printStackTrace();
System.out.println("image file path is null");
}
在此代码位中，您使用 try-catch 子句处理抛出的 IOException。这
但是对于这些调用不能说相同：
BufferedImage inputImage = ImageIO.read(inputFile);
ImageIO.write(outputImage, formatName, new File(outputImagePath));
因为这两个都抛出了一个不在方法范围内处理的异常（即使用 try-catch 子句），你强制方法的签名有一个 throws 声明 IOException 被这两个抛出。由于 IOException 是一个已检查的异常，编译器希望找到一个 try-catch 子句来包装对 Images#resizeImage 方法的调用。
要修复您的代码，您有两种可能的解决方案：
从方法体中删除 try-catch 子句，仅保留 throws 声明，强制调用者在调用点处理异常。
包装几乎所有的方法体或在 try-catch 子句中抛出 IOException 的地方，从而在方法体中处理异常（这不是一个好主意，因为这样你就不会知道调整大小的操作是否失败）。
看来您对异常如何工作以及需要如何处理它们的理解有点有限，所以在做任何其他事情之前，我建议先绕道检查一下。
https://docs.oracle.com/javase/tutorial/essential/exceptions/index.html