如何使用 JNA 在 java 中获取 chrome 进程的句柄

Question

I am new to JNA, and I need to take a screenshot of a chrome window using java and JNA, I already have the function for taking screenshots of a given window using this code:

  public BufferedImage capture(WinDef.HWND hWnd) {

    WinDef.HDC hdcWindow = User32.INSTANCE.GetDC(hWnd);
    WinDef.HDC hdcMemDC = GDI32.INSTANCE.CreateCompatibleDC(hdcWindow);



    WinDef.RECT bounds = new WinDef.RECT();
    User32Extra.INSTANCE.GetClientRect(hWnd, bounds);

    int width = bounds.right - bounds.left;
    int height = bounds.bottom - bounds.top;

    WinDef.HBITMAP hBitmap = GDI32.INSTANCE.CreateCompatibleBitmap(hdcWindow, width, height);

    WinNT.HANDLE hOld = GDI32.INSTANCE.SelectObject(hdcMemDC, hBitmap);
    GDI32Extra.INSTANCE.BitBlt(hdcMemDC, 0, 0, width, height, hdcWindow, 0, 0, WinGDIExtra.SRCCOPY);

    GDI32.INSTANCE.SelectObject(hdcMemDC, hOld);
    GDI32.INSTANCE.DeleteDC(hdcMemDC);

    WinGDI.BITMAPINFO bmi = new WinGDI.BITMAPINFO();
    bmi.bmiHeader.biWidth = width;
    bmi.bmiHeader.biHeight = -height;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = WinGDI.BI_RGB;

    Memory buffer = new Memory(width * height * 4);
    GDI32.INSTANCE.GetDIBits(hdcWindow, hBitmap, 0, height, buffer, bmi, WinGDI.DIB_RGB_COLORS);

    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    image.setRGB(0, 0, width, height, buffer.getIntArray(0, width * height), 0, width);

    GDI32.INSTANCE.DeleteObject(hBitmap);
    User32.INSTANCE.ReleaseDC(hWnd, hdcWindow);

    return image;

}

然后我使用以下代码保存缓冲图像：

     BufferedImage image;

     WinDef.HWND hWnd = User32.INSTANCE.FindWindow(null, "notepad - untitled");
                image = capture(hWnd);
                File outputfile = new File("image.jpg");
                try {
                    ImageIO.write(image, "jpg", outputfile);
                } catch (IOException e) {
                    e.printStackTrace();
                }

这适用于某些应用程序，例如记事本，但不适用于 chrome，对于 chrome，它只会引发非法参数异常，因为程序正在尝试捕获宽度和高度基本上为 0 的屏幕截图，因为找不到该进程，完整例外是：

Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: Allocation size must be greater than zero
at com.sun.jna.Memory.<init>(Memory.java:111)
at de.xliquid.stadiarpc.Main.capture(Main.java:103)
at de.xliquid.stadiarpc.Main$1.run(Main.java:56)
at com.sun.javafx.scene.KeyboardShortcutsHandler.processAccelerators(KeyboardShortcutsHandler.java:347)
at com.sun.javafx.scene.KeyboardShortcutsHandler.dispatchBubblingEvent(KeyboardShortcutsHandler.java:163)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$KeyHandler.process(Scene.java:3964)
at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3910)
at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2501)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:217)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:149)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$357(GlassViewEventHandler.java:248)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:247)
at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
at com.sun.glass.ui.View.notifyKey(View.java:966)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)

我尝试使用当前的 chrome 标题，但这不起作用，我认为最好的解决方案是获取 chrome 的第一个选项卡的句柄。 可悲的是，我真的不知道从哪里开始。 谁能告诉我我能做什么？ 提前致谢。

Answer 1

JNA 的WindowUtils class 在这里可以提供帮助。 getAllWindows()方法将返回一个List<DesktopWindow> ，其中每个DesktopWindow实例都包含一个标题（与您的 Chrome 进程匹配）和该 window 的HWND句柄。

DesktopWindow也有一个带有位置和大小尺寸的Rectangle ，因此您可以从桌面本身复制适当的尺寸，例如这个简单的单行：

BufferedImage screenShot = new Robot().createScreenCapture(rectangle);

此 StackOverlow 问题的答案确定了用于截取整个 window 的多个其他选项； 只需适当地替换您从DesktopWindow class 派生的Rectangle （或使用您自己的代码上面的矩形尺寸）。

或者，如果您不需要来自WindowUtils class 的所有信息，您可以更直接地使用 WinAPI 的EnumWindows function 来直接迭代 Z0F4137ED1502B5045D6083AA28 只需要您的信息。5C428 这是WindowUtils内部使用的 function，因此它的源代码将是一个很好的简化起点。