Startup Tasks and Input Arguments in App Designer

App Designer allows you to create a special function that executes when the app starts up, but before the user interacts with the UI. This function is called thestartupFcncallback, and it is useful for setting default values, initializing variables, or executing commands that affect initial state of the app. For example, you might use thestartupFcncallback to display a default plot or a show a list of default values in a table.

创建一个`startupFcn`Callback

To create astartupFcncallback, right-click the app node from the top of theComponent Browserhierarchy, and selectCallbacks>Add StartupFcn callback. The app node has the same name as your MLAPP file.

应用节点Comp内容菜单onent browser.

App designer creates the function and places the cursor in the body of the function. Add commands to this function as you would do for any callback function. Then save and run your app.

Function definition for the startupFcn. The function is in a private methods block, and has one input argument, named app.

SeeApp with Auto-Reflow That Updates Plot Based on User Selectionsfor an example of an app that has astartupFcncallback.

Define Input App Arguments

ThestartupFcn回调也可以定义的函数input arguments for your app. Input arguments are useful for letting the user (or another app) specify initial values when the app starts up.

To add input arguments to an app, open the app in App Designer and clickCode View. Then clickApp Input Argumentsin theEditortab.

App Input Arguments dialog. The dialog contains an edit field for entering arguments for the startupFcn callback.

TheApp Input Argumentsdialog box allows you to add or remove input arguments in the function signature of thestartupFcncallback. Theappargument is always first, so you cannot change that part of the signature. Enter a comma-separated list of variable names for your input arguments. You can also entervararginto make any of the arguments optional. Then clickOK.

After you clickOK, App Designer creates astartupFcncallback that has the function signature you defined in the dialog box. If your app already has astartupFcncallback, then the function signature is updated to include the new input arguments.

After you have created the input arguments and coded thestartupFcn, you can test the app. Expand the drop-down list from theRunbutton in the toolstrip. In the second menu item, specify comma-separated values for each input argument. The app runs after you enter the values and pressEnter.

Run button menu options. The options are to run the app with no arguments, to run the app by specifying input arguments, and to edit app input arguments.

Note

MATLAB^®might return an error if you click theRunbutton without entering input arguments in the drop-down list. The error occurs because the app has required input arguments that you did not specify.

After successfully running the app with a set of input arguments, theRunbutton icon contains a blue circle.

Run button with a blue circle.

The blue circle indicates that your last set of input values are available for re-running your app without having to type them again. Up to seven sets of input values are available to choose from. Click the top half of theRunbutton to re-run the app with the last set of values. Or, click the bottom half of theRunbutton and select one of the previous sets of values.

TheRunbutton also allows you to change the list of arguments in the function signature. SelectEdit App Input Arguments...from the drop-down list in the bottom half of theRunbutton.

Run button menu options.

Alternatively, you can open the sameApp Input Argumentsdialog box by clickingApp Input Argumentsin the toolstrip, or by right-clicking thestartupFcncallback in theCode Browser.

SeeCreate Multiwindow Apps in App Designerfor an example of an app that uses input arguments.