HTML5 Canvas：如何处理mousedown mouseup mouseclick

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问题描述

我一直在用html5画布玩弄一个问题。

I been playing around with html5 canvas and ran into a problem.

canvas.onmousedown = function(e){
        dragOffset.x = e.x - mainLayer.trans.x;
        dragOffset.y = e.y - mainLayer.trans.y;
        canvas.onmousemove = mouseMove;
}
canvas.onmouseup = function(e){
    canvas.onmousemove = null;
}

canvas.onmouseclick = mouseClick;

function mouseMove(e){
    mainLayer.trans.x = e.x - dragOffset.x;
    mainLayer.trans.y = e.y - dragOffset.y;
    return false;
}

function mouseClick(e){
    // click action
}

在这段代码中，我通过拖动偏移进行鼠标单击+拖动平移画布视图。但我也有一个点击事件。现在，每当我拖动鼠标，放开，它会同时运行onmouseup和onclick。

In this code, I make my mouse click+drag pan the canvas view by translating by the drag offset. But I also have a click event. Right now, whenever I drag my mouse and let go, it runs both onmouseup AND onclick.

有什么技巧使它们独一无二吗？

Are there any techniques to make them unique?

推荐答案

在 mousedown 和 mouseup 成功后，元素。在鼠标事件之上，您是否有任何特定的原因使用点击？您应该可以使用 mousedown / mouseup ，是一个方便的事件，节省了一些编码。

A click event happens after a successful mousedown and mouseup on an element. Is there any particular reason you are using click on top of the mouse events? You should be fine with just mousedown/mouseup, click is a convenience event that saves you a little bit of coding.

我通常这样做：

var mouseIsDown = false;

canvas.onmousedown = function(e){
    dragOffset.x = e.x - mainLayer.trans.x;
    dragOffset.y = e.y - mainLayer.trans.y;

    mouseIsDown = true;
}
canvas.onmouseup = function(e){
    if(mouseIsDown) mouseClick(e);

    mouseIsDown = false;
}

canvas.onmousemove = function(e){
    if(!mouseIsDown) return;

    mainLayer.trans.x = e.x - dragOffset.x;
    mainLayer.trans.y = e.y - dragOffset.y;
    return false;
}

function mouseClick(e){
    // click action
}

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