Question

我有一个结构,没有像原来的C那样充分描述。

    public class DISPLAY_DEVICE extends Structure {
        public char DeviceName[] = new char[32];
        public int StateFlags;
    }

Whereas it actually needs, way, more variables. However it will take me a long time to port them all over. Now I create the struct and pass the pointer to a dll function, and try to use device.read(); to regain the variables. However, the variables return empty. So my question is, do I need to fill out the whole struct? Or is there something else wrong?

    DISPLAY_DEVICE displayDevice = new DISPLAY_DEVICE();
    int i = 0;
    while((CLibrary.INSTANCE.EnumDisplayDevicesA(Pointer.NULL, i, displayDevice.getPointer(), 0))) {
        System.out.println("screen" + i);
        displayDevice.read();
        System.out.println(displayDevice.StateFlags);
        System.out.println(displayDevice.DeviceName);

Answer 1

至少,你必须确定结构的大小与其本土对口单位相同(如果你可以用一个旁边的田子来pad你不 care。)

For example:

public class MyStruct extends Structure {
   public char[] DeviceName = new char[32];
   public char StateFlags;
   public byte[] dontcare = new char[128];
}

如果在JNA的平台无法提供定义,你也可以利用JNAerator从C负责人那里自动进行基因制图。

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