在Java中模拟触摸滚动

Question

我正在寻找一种方法来创建一个触摸应用程序在Java (不是为移动设备)与触摸滚动支持。到目前为止，我一直在搜索，我正在调查如何做到这一点-我找到的是MT4J (http://www.mt4j.org/)，但它似乎不支持它(如果我错了，请纠正我)。所以我的问题是，我如何在水平触摸/滑动上模拟滚动事件？

感谢您的帮助！亲切的问候，亚历克斯

Answer 1

您可以使用JavaFX's touch event framework。

以下是链接教程中有关处理滚动事件的一些示例代码：

rect.setOnScroll(new EventHandler<ScrollEvent>() {
        @Override public void handle(ScrollEvent event) {
            if (!event.isInertia()) {
                rect.setTranslateX(rect.getTranslateX() + event.getDeltaX());
                rect.setTranslateY(rect.getTranslateY() + event.getDeltaY());
            }
            log("Rectangle: Scroll event" +
                ", inertia: " + event.isInertia() + 
                ", direct: " + event.isDirect());
            event.consume();
        }
});

rect.setOnScrollStarted(new EventHandler<ScrollEvent>() {
        @Override public void handle(ScrollEvent event) {
            inc(rect);
            log("Rectangle: Scroll started event");
            event.consume();
        }
});

rect.setOnScrollFinished(new EventHandler<ScrollEvent>() {
        @Override public void handle(ScrollEvent event) {
            dec(rect);
            log("Rectangle: Scroll finished event");
            event.consume();
        }
});

Answer 2

这通过将JScrollPane子类化来实现触摸和拖动滚动条。

因为触摸和拖动本身是不够的，所以我增加了动量，这样当鼠标按键释放时，它就会“抛出”滚动。

在卷轴的末尾没有“弹跳”，因为我负担不起对“弹跳”所有者的诉讼。

它不是完全封装的，因为尽管如果视图是jlist，它可以很好地工作，但如果面板当时正在被拖动，视图上的组件可能需要修改它们的响应。还有一些组件，例如JRadioButton，JCheckBox等，不会将鼠标点击传递给容器，所以你需要向它们添加TouchScroll的MouseListener和MouseMotionListener。

import java.awt.Component;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import javax.swing.JScrollBar;
import javax.swing.JScrollPane;

public class TouchScroll extends JScrollPane implements MouseListener,   MouseMotionListener {
private JScrollBar vbar = this.getVerticalScrollBar();

public TouchScroll(Component view){ // 1-arity CONSTRUCTOR
    super(view);
    view.addMouseListener(this);
    view.addMouseMotionListener(this);
}
public TouchScroll() {  super();    }   // 0-arity CONSTRUCTOR

public void setViewportView(Component view) {
    super.setViewportView(view);
    view.addMouseListener(this);
    view.addMouseMotionListener(this);
}

private static boolean wasdragged = false;  // other MouseListeners may need to know this ...
public boolean wasDragged() {       return wasdragged;  }   // ... this gives them safe access

static int lastY = 0, distY = 0;
double momentum = 0;    // not really physical momentum but it will be used to 'throw' the scroll when the mouse button is released
static boolean lbdown = false;
@Override
public void mouseDragged(MouseEvent e) {
    wasdragged = true;      
    distY = 0;
    int currentY = e.getYOnScreen();
    if(lbdown) {
        distY =  lastY - currentY;
        vbar.setValue(distY + vbar.getValue());
        if(Math.abs(distY) > 1)
            momentum = distY + distY;   // magnify and log the momentum for later use
    }
    lastY = currentY;
}

@Override
public void mousePressed(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1) {
        lastY = e.getYOnScreen();
        lbdown = true;
    }
}

@Override
public void mouseReleased(MouseEvent e) {
    if (e.getButton() == MouseEvent.BUTTON1)
        lbdown = false;
    if(wasdragged)
        wasdragged = false;

    if(Math.abs(momentum) <= 4.0)   // then assume that the mouse wasn't moving (much) when the button was released
        return;
    // otherwise 'throw' the scroll
    int max = vbar.getMaximum();
    int count;
    double brakingforce = 1.04;     // set an initial braking force
    for(count = 1000; count > 0; count--){  // don't allow it to accidentally go on forever
        momentum = momentum / brakingforce; // apply the brake
        if(Math.abs(momentum) < 1.5)
            brakingforce = 1.02;    // ease off the brake towards the end (gives a slight overrun ala iOS)
        if(Math.abs(momentum) < 1.0)    // bring it to a halt
            break;
        int val = vbar.getValue();
        if(val < 0 || val > max)    // prevent overrun
            break;
        vbar.setValue((int) momentum + val);    // increment the scroll bar
        try {
            Thread.sleep(10);       // slow the loop down so the user can see the scroll
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
    }
}

public void mouseMoved(MouseEvent e) {}
public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}

}

下面是一个如何应用它的“基本”示例：

panel = new JPanel();
jlist = new JList(list);
scroller = new TouchScroll(jlist);
panel.add(scroller);

响应鼠标释放的任何组件可能需要执行以下操作：

public void mouseReleased(MouseEvent e) {   
    if(scroller.wasDragged())
        return;
    actionENTER();
}

最后，如前所述，使用鼠标事件的组件需要像这样通知滚动条：

JCheckBox checkbox = new JCheckBox(text);
checkbox.addMouseMotionListener(scroller);
checkbox.addMouseListener(scroller);