将实际值传递给 Matlab 中的回调函数 [英] Passing actual values to callback function in Matlab

问题描述

让我们假设以下简单的例子:

let's assume the following easy example:

f = figure;
plot(-10:10, (-10:10).^3, '*-r');
x = 1;
y = 1;
set(f, 'ResizeFcn', {@resizeCallback2, x, y});

while 1
    [x, y, button] = ginput(1);
    if(button ~= 1)
        break;
    end

    set(f, 'ResizeFcn', {@resizeCallback2, x, y});
end

%%--------------------------
function resizeCallback2(hFig, ~, foo, bar)    
    foo
    bar
end

有没有更简单的方法可以始终将 x 和 y 的 ACTUAL* 值传递给回调函数，而不必总是在循环中更新它?谢谢！

Is there any easier way to always pass the ACTUAL* values for x and y to the callback function instead of having to always update it in the loop? Thanks!

推荐答案

看起来您正在尝试存储鼠标单击位置的值，然后将这些值用作调整大小函数的一部分(这将被称为晚些时候).我会做出一些改变.

It looks like you are trying to store the value of a mouse click position, and then use those values as a part of the resize function (which would be called at a later time). There are a few changes that I would make.

首先，代替 while 循环，使用另一个回调来捕获鼠标点击.例如，您可以使用图形 ButtonDownFcn 回调来触发一个函数，该函数旨在将鼠标位置捕获到某个位置.

First, instead of the while loop, use another callback to capture the mouse click. For example, you could use the figure ButtonDownFcn call back to trigger a function which was designed to capture the mouse position into some location.

其次，有更好的方法来存储鼠标位置，正确的方法将取决于您的技能水平和您的程序需求.其中一些存储数据的方法是:

Second, there are better ways to store the mouse position, and the right way will depend on your skill level and the needs of your program. Some of these methods of storing data are:

1. 在另一个回调的参数中，就像你现在所做的那样.这很痛苦，但它可能有效.因此，如果它足以满足您的需要，您可以保留它.

1. In the arguments to another callback, like you are doing now. This is pretty painful, but it probably works. So you could keep it if it is good enough for your needs.

大多数 Matlab 对象中的userdata"字段.一些人提出了这个问题，它会工作得很好.我不喜欢依赖这个，因为我总是担心其他一些工具也会想要使用 userdata 字段，而这些工具会覆盖数据.

The 'userdata' field in most Matlab objects. A few people have brought this up, and it will work fine. I don't like to rely on this because I'm always afraid that some other tool will also want to use the userdata field, and the tools will overwrite data.

全局 变量值.我也不喜欢使用全局变量，原因与我不喜欢使用 userdata 字段的原因相同.但无论如何，globals 有时是最好的解决方案.如果您一次只有一个数字，这可能是解决问题的最简单、最省力的解决方案.(多个数字会促使您采用 userdata 解决方案作为最简单的解决方案.)

A global variable value. I don't like to use globals either, for the same reason I don;t like to use the userdata field. But globals are sometimes the best solution anyway. This is probably the easiest, lowest effort solution to your problem if you only have one figure at a time. (Multiple figures would drive you towards the userdata solution as the easiest solution.)

提供一个 handle 类来存储一些数据(即 x 和 y)，并将该类的副本提供给两个回调(ButtonDownFcn 和ResizeFcn).这允许两个函数传递数据，而不会污染任何其他人的命名空间.这是我最喜欢的此类问题的解决方案，因此我将在下面对其进行更详细的描述.

Provide a handle class to store some data (i.e. x and y) and give a copy of that class to each of the two callbacks (ButtonDownFcn and ResizeFcn). This allows the two functions to pass data, without polluting anyone else's namespace. This is my favorite solution to this sort of problem, so I'll give it a more detailed description below.

<小时>

要执行上面的选项 (4) 需要一个类来存储看起来像这样的数据:

---

To execute option (4) above would need a class to store the data that looks something like this:

    classdef ApplicationData < handle
        properties (SetAccess = public, GetAccess = public)
            x = [];
            y = [];
        end
    end

注意，由于ApplicationData扩展了handle，Matlab把它当作一个pass-by-reference对象，这对我们很有用.

Note that since ApplicationData extends handle, Matlab treats it as a pass-by-reference object, which is useful to us.

然后你可以创建这个类的一个实例，并把它交给每个回调函数.

Then you can create an instance of this class, and give it to each callback function.

    dataPassing = ApplicationData;
    set(f, 'ButtonDownFcn', @(x,y) mouseClickCapture(x,y,dataPassing));
    set(f, 'ResizeFcn',     @(x,y) resizeCallback2(x,y, dataPassing));

其中 mouseClickCapture 看起来像这样:

Where mouseClickCapture looks something like this:

    function mouseClickCapture(hAxis, ignored, dataPassingClass)
    mousePositionData = get(hAxis,'CurrentPoint');
    dataPassingClass.x = mousePositionData(1,1);
    dataPassingClass.y = mousePositionData(1,2);

你的 resizeCallback2 看起来像这样:

And your resizeCallback2 looks something like this:

    function resizeCallback2(h, ignored, dataPassingClass)
    %Do something here using 
    %dataPassingClass.x
    %and
    %dataPassingClass.y

这篇关于将实际值传递给 Matlab 中的回调函数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！