英文:
How to draw image created in try/catch?
问题
I'm learning Java, and I've converted File type into Image using IOException, but how can I use my new Image outside of try/catch?
因为现在 IntelliJ 不识别图像。
英文:
I'm learning Java, and I've converted File type into Image using IOException, but how can I use my new Image outside of try/catch?
try {File obraz = new File("C:\\Users\\ender\\Pictures\\logo.jpg");Image image = ImageIO.read(obraz);} catch (IOException ex) {ex.printStackTrace();}}public void paintComponent(Graphics g){Graphics2D g2 = (Graphics2D) g;g2.drawImage(image);}
Because now IntelliJ does not recognize image.
答案1
得分: 2
在这种情况下，由于paintComponent经常被调用，而您希望只加载一次图像，因此将图像放入字段中。
private Image image;...() {try {File obraz = new File("C:\\Users\\ender\\Pictures\\logo.jpg");image = ImageIO.read(obraz);} catch (IOException ex) {ex.printStackTrace();}}...() throws IOException {File obraz = new File("C:\\Users\\ender\\Pictures\\logo.jpg");image = ImageIO.read(obraz);}@Overridepublic void paintComponent(Graphics g){Graphics2D g2 = (Graphics2D) g;if (image != null) {g2.drawImage(image);}}
我已经展示了两种解决方案：
- 如现在所做的那样捕获异常：但应该执行一些操作，向用户提供文件"logo.jpg"不存在的错误消息。
- 通过
throws传递异常，通常是更好的解决方案。
根据约定，应使用@Override，因为这样可以捕获拼写错误，例如public void paintComponent(Graphics2D g)或public void painComponent(Graphics g)。
英文:
In this case - as paintComponent will be called often, and you want to load the image just once, put the image in a field.
private Image image;...() {try {File obraz = new File("C:\\Users\\ender\\Pictures\\logo.jpg");image = ImageIO.read(obraz);} catch (IOException ex) {ex.printStackTrace();}}...() throws IOException {File obraz = new File("C:\\Users\\ender\\Pictures\\logo.jpg");image = ImageIO.read(obraz);}@Overridepublic void paintComponent(Graphics g){Graphics2D g2 = (Graphics2D) g;if (image != null) {g2.drawImage(image);}}
I have shown two solutions:
- catching the exception as done now: but one should do something, give an error message to the user that file logo.jpg does not exist
- passing the exception on by throws, often the better solution.
The convention is to use @Override as this catches typos like public void paintComponent(Graphics2D g) or public void painComponent(Graphics g).
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