如何使用JNA在java中获得chrome进程的句柄

Question

我是JNA的新手，我需要使用java和JNA截屏一个chrome窗口，我已经有了使用以下代码截屏给定窗口的功能：

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区图像：

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();
}

这适用于一些应用程序，例如记事本，但不适用于chrome，对于chrome，它只是抛出一个非法参数异常，因为该程序试图捕获一个宽度和高度基本为0的屏幕截图，因为没有找到该进程，完全的异常是：

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)

我试着使用chrome的当前标题，但没有成功，我认为最好的解决方案是只处理chrome的第一个选项卡。遗憾的是，我真的不知道从哪里开始。有人能告诉我我能做什么吗？提前谢谢。

Answer 1

JNA的WindowUtils类在这里会有所帮助。getAllWindows()方法将返回一个List<DesktopWindow>，其中每个DesktopWindow实例都包括一个标题(与您的Chrome进程相匹配(和该窗口的HWND句柄。

DesktopWindow还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，例如这个简单的一行：

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

这个StackOverlow问题的答案确定了拍摄整个窗口截图的多个其他选项；只需适当地替换从DesktopWindow类派生的Rectangle(或者使用上面自己的代码和矩形的尺寸(。

或者，如果不需要WindowUtils类中的所有信息，可以更直接地使用WinAPI的EnumWindows函数直接迭代窗口，只捕获所需的信息。这是WindowUtils内部使用的函数，因此它的源代码将是简化的一个很好的起点。