Question

有没有办法找出Java中鼠标的第一次拖动？

例如：

public void mouseDragged(MouseEvent e)
{
    if (first drag of the mouse)  // what should I write here?
        System.out.println("This is the first drag");
    else System.out.println("This isn't the first drag");
}

如果我拖动鼠标5次，我应该在控制台中看到这个文字：

This is the first drag
This isn't the first drag
This isn't the first drag
This isn't the first drag
This isn't the first drag

Answer 1

boolean first=true;//this should be a instance variable.

先拖动！使用布尔变量首先检测或不检测。比如

public void mouseDragged(MouseEvent e)
{
    if (first) { // this is only true if it's first drag
        System.out.println("This is the first drag");
        first=false;
    }
    else {
        System.out.println("This isn't the first drag");
    }

}

...更新

这是你可以检测到的第一次拖动。但是拖动时通常会触发鼠标拖动事件的问题。为了避免这种情况你可以修改这一点。

声明实例变量

boolean draging = true;
boolean mark = true;
boolean first = true;

仅在拖动开始时打印。当我们打印鼠标拖动时，我们停止打印它，直到鼠标释放并进行重新整理。

public void mouseDragged(java.awt.event.MouseEvent evt) {
        draging = true;
        if (mark) {
            if (first) {
                System.out.println("This is the first drag");
            }else{
                System.out.println("This isn't the first drag");
            }
            mark = false;
        }
}

首先更改为false，因此首先拖动就足够了。并准备好打印新拖动[mark = true]

public void mouseReleased(java.awt.event.MouseEvent evt) {
          if (draging) {
            mark = true;
            first=false;
        }
}

这是第一个和更新的例子的输出。第一个代码存在问题[因为在拖动时连续触发事件拖动，而不是一个]。

第一个例子

This is the first drag
This is the first drag
This is the first drag
.............................//this continues until u finish[released] first drag
This isn't the first drag
This isn't the first drag
This isn't the first drag
................................

更新了一个

This is the first drag //a drag [ click--move--relesed] mark only 1time
This isn't the first drag
This isn't the first drag
This isn't the first drag
...............................

Answer 2

我会稍微修改FastSnails解决方案以解决当按钮关闭时mouseDragged在每个鼠标移动时触发的行为：

boolean first = true;
boolean triggered = false;

public void mouseDragged(MouseEvent e){
    if(!triggered){
        if(first){
            System.out.println("This is the first drag");
            first=false;
        }
        else{
            System.out.println("This isn't the first drag");
        }
        triggered = true;
    }
}

当然，我们必须在mouseReleased事件中重置该标志，这标志着“拖动”的结束：

public void mouseReleased(MouseEvent e){
    triggered = false;
}

使用此方法意味着每次“拖动”只会触发一次消息，而不是每次鼠标移动都会触发。

第一个鼠标拖动动作

2 个答案: