java - 在 Java 中模拟触摸滚动

Question

我正在寻找一种方法来创建具有触摸滚动支持的 Java 触摸应用程序（不适用于移动设备）。到目前为止，我一直在搜索，我正在调查如何做到这一点 - 我发现的是 MT4J（http://www.mt4j.org/），但它似乎不支持这一点（如果我错了，请纠正我）。所以我的问题是，我如何在水平触摸/滑动时模拟滚动事件？

感谢帮助！亲切的问候，亚历克斯

Answer 1

这通过子类化 JScrollPane 实现了触摸和拖动滚动条。

因为触摸和拖动本身是不够的，所以我增加了动力，以便在释放鼠标按钮时“抛出”滚动。

卷轴的末端没有“反弹”，因为我无力为“反弹”的所有者打官司。

它没有完全封装，因为虽然视图是 jlist 时它可以正常工作，但如果当时正在拖动面板，视图上可能存在需要修改其响应的组件。还有一些组件，例如 JRadioButton、JCheckBox 等，会消耗鼠标点击而不将它们传递给容器，因此您需要向它们添加 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) {}

}

这是一个“基本”示例，说明如何应用它：

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

任何响应鼠标释放的组件都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);

Answer 2

您可以使用JavaFX 的触摸事件框架。

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();
        }
});