如何截断文本的开头而不是在MATLAB uilabel中结束

Question

我正在使用MATLAB（2019b）中的App Designer构建GUI。这样的一个方面是允许用户加载文件，然后显示已加载文件的名称。当要显示的文本长于uilabel大小时，默认行为是截断结尾并附加省略号（“ ...”）。我想从front截断并在其中放置省略号，因为对于用户而言，查看文件名和文件路径更为重要。这是我希望它看起来像的一个示例。

实现此目的的最佳方法是什么？现在，我有一个方法可以测量uilabel的宽度，然后估算出可以容纳多少个字符并以此为基础截断文本。但是，这似乎并不一致，可能是按比例间距而不是单间距。另外，由于uilabel的宽度是以像素为单位测量的，所以我担心在其他显示器分辨率和显示环境下它的表现将不一致。有没有比我目前正在做的更好的方法，或者有一种改进我的方法使其更可靠的方法？

示例代码：

classdef sampleApp < matlab.apps.AppBase

% Properties that correspond to app components
properties (Access = public)
    UIFigure               matlab.ui.Figure
    SelectaFileButton      matlab.ui.control.Button
    defaultFilename        matlab.ui.control.Label
    DefaultBehaviorLabel   matlab.ui.control.Label
    ModifiedBehaviorLabel  matlab.ui.control.Label
    modifiedFilename       matlab.ui.control.Label
end

% Callbacks that handle component events
methods (Access = private)

    % Button pushed function: SelectaFileButton
    function SelectaFileButtonPushed(app, event)
        [filename,pathname] = uigetfile('Select a filename to display');
        filestr = fullfile(pathname,filename);

        % This sets the text the normal way
        app.defaultFilename.Text = filestr;
        app.defaultFilename.Tooltip = filestr;

        % This measures the width of the text field and attempts to fit
        % the text to the field
        pos = app.modifiedFilename.Position;
        nchars = floor(0.165*pos(3))-3; % The 0.165 was found through trial and error
        if(length(filestr)>nchars+3)
            shortText = ['...' filestr(end-nchars+1:end)];
        else
            shortText = filestr;
        end   
        app.modifiedFilename.Text = shortText;
        app.modifiedFilename.Tooltip = filestr;
    end
end

% Component initialization
methods (Access = private)

    % Create UIFigure and components
    function createComponents(app)

        % Create UIFigure and hide until all components are created
        app.UIFigure = uifigure('Visible', 'off');
        app.UIFigure.Position = [100 100 297 111];
        app.UIFigure.Name = 'UI Figure';

        % Create SelectaFileButton
        app.SelectaFileButton = uibutton(app.UIFigure, 'push');
        app.SelectaFileButton.ButtonPushedFcn = createCallbackFcn(app, @SelectaFileButtonPushed, true);
        app.SelectaFileButton.Position = [13 68 160 22];
        app.SelectaFileButton.Text = 'Select a File';

        % Create defaultFilename
        app.defaultFilename = uilabel(app.UIFigure);
        app.defaultFilename.Position = [118 39 133 22];
        app.defaultFilename.Text = 'Filename';

        % Create modifiedFilename
        app.modifiedFilename = uilabel(app.UIFigure);
        app.modifiedFilename.Position = [118 19 143 22];
        app.modifiedFilename.Text = 'Filename';

        % Create DefaultBehaviorLabel
        app.DefaultBehaviorLabel = uilabel(app.UIFigure);
        app.DefaultBehaviorLabel.HorizontalAlignment = 'right';
        app.DefaultBehaviorLabel.Position = [-2 40 110 22];
        app.DefaultBehaviorLabel.Text = 'Default Behavior:';

        % Create ModifiedBehaviorLabel
        app.ModifiedBehaviorLabel = uilabel(app.UIFigure);
        app.ModifiedBehaviorLabel.HorizontalAlignment = 'right';
        app.ModifiedBehaviorLabel.Position = [-2 20 110 22];
        app.ModifiedBehaviorLabel.Text = 'Modified Behavior:';

        % Show the figure after all components are created
        app.UIFigure.Visible = 'on';
    end
end

% App creation and deletion
methods (Access = public)

    % Construct app
    function app = sampleApp

        % Create UIFigure and components
        createComponents(app)

        % Register the app with App Designer
        registerApp(app, app.UIFigure)

        if nargout == 0
            clear app
        end
    end

    % Code that executes before app deletion
    function delete(app)

        % Delete UIFigure when app is deleted
        delete(app.UIFigure)
    end
end
end

Answer 1

省略号可能是在系统API（Java）中添加的，matlab不一定可以访问。建议您仅在标签中显示文件名，并使用fileparts提取路径，并将其显示为标签的TooltipString（在R2018中受支持）。