BobHanson
commented
6 months ago I suspect this is the issue that JavaScript needs a clock tick to finalize an image loading. I see this in dist/differences.txt:
image loading
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All image loading in SwingJS is synchronous. A MediaTracker call will immediately return "complete". However, it still may take one system clock tick to fully load images. Thus, it is recommended that images be preloaded in the static block of the applet if it is necessary that they be available in init(). This is only an issue if you are trying to access the pixel buffer of the image in JavaScript.
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Applet.getImage(path, name) will return null if the image does not exist.
So the trick here is to load them in a static {...} block and then WAIT until after applet initialization to utilize them. If the problem persists, add a SwingUtilities.invokeLater(()->{....}) runnable that starts your GUI.
hello, i have the following java code and can load and draw image: Graphics2D g2d = (Graphics2D) g; Image image=Toolkit.getDefaultToolkit().getImage(Main.class.getResource("/java2d/images/duke.gif")); g2d.drawImage(image, 9, 9, null);
but the generated js report error: j2sApplet exec testApplet start applet null transpiler was unknown now 5.0.1-v2 for java.lang.Class transpiler was 5.0.1-v2 now 3.3.1-v7 for demo.Main transpiler was 3.3.1-v7 now 5.0.1-v2 for java.util.Hashtable swingjs.api.Interface creating instance of javajs.util.AjaxURLStreamHandlerFactory JSApp get parameter: language = null swingjs.JSUtil initialized;debug=false JSApp get parameter: name = testApplet JSApp get parameter: syncId = 777136185134673 JSApp initialized JSAppletViewer initializing2 JSToolkit initialized JSGraphicsConfiguration initialized swingjs.api.Interface creating instance of swingjs.JSGraphicsEnvironment JSGraphicsEnvironment initialized swingjs.api.Interface creating instance of swingjs.JSScreenDevice JSScreenDevice initialized JSAppletViewer thread run1 mode=0 status=0 JSAppletViewer thread run1 mode=1 status=1 JSAppletViewer runloader JSApp get parameter: main = demo.Main swingjs.api.Interface creating instance of swingjs.JSDummyApplet swingjs.api.Interface creating instance of swingjs.plaf.HTML5LookAndFeel testApplet loaded JSAppletViewer thread run1 mode=1 status=76 testApplet running demo.Main Running main(args) in class demo.Main swingjs.api.Interface creating instance of swingjs.JSGraphicsConfiguration JSGraphicsConfiguration initialized JSGraphics2D pixelRatio is 2.0 JSToolkit.dispatch$I(0): TypeError: Cannot read properties of null (reading '_streamData')
0 function() at Clazz._getStackTrace (http://127.0.0.1:8900/swingjs/swingjs2.js:15972:8)
... at ff (swingjs/j2s/swingjs/JSToolkit.js:207:23) at TypeError.getStackTrace$.ReferenceError.getStackTrace$ (http://127.0.0.1:8900/swingjs/swingjs2.js:21178:106) see Clazz._stack TypeError: Cannot read properties of null (reading '_streamData') at Function.eval [as getAttachedStreamData$java_net_URL$Z] (swingjs/j2s/javajs/util/AjaxURLConnection.js:393:12) at Function.eval [as getURLInputStream$java_net_URL$Z] (swingjs/j2s/swingjs/JSUtil.js:364:17) at clazz.eval [as createImage$java_net_URL] (swingjs/j2s/swingjs/JSToolkit.js:345:14) at clazz.eval [as getImage$java_net_URL] (swingjs/j2s/swingjs/JSToolkit.js:316:13) at Object.eval [as paintComponent$java_awt_Graphics] (swingjs/j2s/demo/Main.js:24:39) at Object.eval (swingjs/j2s/javax/swing/JComponent.js:1450:6) at Object.eval [as paint$java_awt_Graphics] (swingjs/j2s/javax/swing/JComponent.js:190:44) at Object.eval [as 秘paint$java_awt_Graphics] (swingjs/j2s/java/awt/JSComponent.js:290:6) at clazz.eval [as paintChildren$java_awt_Graphics] (swingjs/j2s/javax/swing/JComponent.js:154:4) at clazz.eval [as paint$java_awt_Graphics] (swingjs/j2s/javax/swing/JComponent.js:196:6)