按下键时调用方法

Question

我正在使用opencv和视频捕获，我想调用一个基于按键获取该帧的方法。我不确定我做错了什么，但当我按下空格键运行程序时，图像没有被捕获。这是我的代码：

public class VideoCap implements KeyListener{

GetContours takeFrame = new GetContours();
static{
    System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
}

VideoCapture cap;
Mat2Image mat2Img = new Mat2Image();
Mat copy = new Mat();
VideoCap(){
    cap = new VideoCapture();
    cap.open(0);
} 

int frames = 0;
/*int savedCount = 0; //keep track of saved frames
String[] photos = {"first.png","second.png","third.png","forth.png",
"fifth.png","sixth.png","seventh.png","eigth.png","ninth.png"};
*/
boolean captured = false;
BufferedImage getOneFrame() {

    frames++;

    cap.read(mat2Img.mat);

    mat2Img.mat = takeFrame.captureFrame(mat2Img.mat);

    if(captured == true){
        mat2Img.mat = takeFrame.captureFrame(mat2Img.mat);
        System.out.println("WRITTEN!!!");
        Imgcodecs.imwrite("first.png", mat2Img.mat);
        System.exit(0);
    }
    return mat2Img.getImage(mat2Img.mat);
}
@Override
public void keyPressed(KeyEvent e) {
    if(e.getKeyCode() == KeyEvent.VK_SPACE){
        captured = true;
    }   
}