Category: tips

Many people use the backward and forward browser arrows to navigate apps. It’s a convenient way to go back to the previous screen.

Unless you make special provisions, this will not happen automatically for your app. Starting in AppStudio 6.2.1, we’ve made this easy.
Continue reading “Using Browser Arrows”

AppStudio 6 introduces a new project property called useStrict. It catches a number of previously non fatal errors in your code and gives error messages.

Here’s an example. If you have the following code:

a = "george"

where a has not been defined, you will get an error with useStrict set to True. There is no error if it is False. UseStrict forces you to have better code.

The solution is to declare the variable before use, using Dim for BASIC and var for JavaScript.

Dim a    ' BASIC
var a;   // JavaScript
a = "george"

Caution: If you turn useStrict on with an existing project, you need to do a complete retest of every part of your project. It will throw errors in code which worked before.

Here is a list of issues found by useStrict:

• Disallows global variables. (Catches missing var declarations and typos in variable names)
• Silent failing assignments will throw error in strict mode (assigning NaN = 5;)
• Attempts to delete undeletable properties will throw (delete Object.prototype)
• Requires all property names in an object literal to be unique (var x = {x1: “1”, x1: “2”})
• Function parameter names must be unique (function sum (x, x) {…})
• Forbids octal syntax (var x = 023; some devs assume wrongly that a preceding zero does nothing to change the number.)
• Forbids the with keyword
• eval in strict mode does not introduce new variables
• Forbids deleting plain names (delete x;)
• Forbids binding or assignment of the names eval and arguments in any form
• Strict mode does not alias properties of the arguments object with the formal parameters. (i.e. in function sum (a,b) { return arguments[0] + b;} This works because arguments[0] is bound to a and so on. )
• arguments.callee is not supported
• Keywords are checked, including some new ones: implements, interface, let, package, private, protected, public, static, and yield.

Previously, we looked at serverStorage, which allows you to save data from your app on the Volt server instead of on the device. serverStorage is saved for the user of the app – other users cannot look at it.

appStorage is data which is shared by all the users of the app. Some possible uses are:

• A product list, with the latest prices and availability.
• A message to all users.
• A table with the latest tax rates or exchange rates.

appStorage works just like serverStorage. It has the same functions. The big differences are that all users of the app see the exact same data, and only Dashboard apps can modify it.

Regular users of the app can use getItem() and getAllItems.

The function clear(), removeItem() and setItem() can be used if the following two conditions are met:

1. Dashboard Access in Project Properties is set to true.
2. The name used to sign into the app is the same as the name used to upload the app to Volt.

To use these functions, there is an additional 3rd parameter with the VoltID of the app whose appStorage is to be changed:

appStorage.setItem("SimpleString", "ABCD", "XxXxXx", done);

Dashboard apps include the Dashboard itself, as well as apps which have Volt Dashboard Access project property set to True. You can check NSB.voltDashboardAccess at runtime to see if Dashboard access is enabled.

This is a powerful features, but it should be used wisely. Set Volt Dashboard Access to false for your users so they only read the data in appStorage. If you have an app which creates and changes data for them, do so in a separate app with Volt Dashboard Access set to true.

When you use serverStorage, the data is saved on the Volt Server. The Dashboard is your tool to manage the apps you have saved on Volt. One of its features is that you can examine and change the data in serverStorage.

Here’s how.
Continue reading “Volt: Accessing serverStorage from the Dashboard”

ClipboardData lets you access the data on the Clipboard. You can:

• Use and modify the data cut or copied to the clipboard
• Use and modify data pasted from the clipboard.

It can be used in Input, Textarea and Textbox controls in all frameworks. It controlled by the oncopy, oncut and onpaste events. The information about the clipboard is passed as a parameter to these events.
Continue reading “Using the Clipboard”

In Project Properties, there is a property named ‘manifestFile’. The setting of this property can have a big effect on how your app works, online and offline.

The default setting is appcache. This causes AppStudio to collect the names of the files in your project and put them in a special file called OfflineApp.appcache. When your app is downloaded to a device, this file is checked by the browser. The files named are stored in the browser’s persistent storage on the device. This allows your app to run even without an internet connection, since all the files needed are present.

Each time a cached app is started, the browser checks to see if the OfflineApp.appcache file has been updated on the server: if so, the new version of the app is downloaded. If it can’t reach the server (perhaps because the device is offline), it does nothing and runs normally.

If the OfflineApp.appcache file has been deleted on the server, the app is deleted from the device.

The manifestFile property can also be set to no caching. The OfflineApp.appcache file won’t be created, and the app will not work in offline mode. It’s worth doing if your app will only work if the device is online: for example, if it has a lot of Ajax calls which are necessary for operation. A side benefit is that you won’t get any “Cache Error” messages.

If you change an app from appcache to no caching, be sure to clear your browser’s cache. Otherwise, it will still think it’s a cached app.

The final choice for this setting is manifest. It’s an obsolete setting. When the standard was first set, it specified .manifest as the ending for the file. Microsoft pointed out that it already was using .manifest for something else. Oops. The standard was revised to call it .appcache instead. Some early AppStudio projects were created in the .manifest days – changing the file suffix now could cause cache errors.

In our last post on positioning, we discussed the different ways of arranging controls on a form. This time, we’re going to have a closer look at static positioning and how you can get your controls to the proper place on your form.

You might want to open a new project in AppStudio and play along. Start a new form with position set to static. Add three Bootstrap buttons:

Notice how they position themselves? They automatically go to the left side of the screen, below the previous button. Let’s see what ways we have to put them on the same line.
Continue reading “Positioning Controls (II)”

Adsense is Google’s web ad service. If you agree to display Google’s ads on your site, you’ll collect money each time someone clicks on an add.

To do so, add the AdSense control to your app. Choose the size (320×50 up to 300×250) and position it. AdSense will automatically display ads in the space. You’ll need to set Client number and Adsense slot number.

Get the Client and slot numbers from Google Adsense when you sign up. Follow Google’s instructions for the rest: they are pretty good.

One of the requirements is to list the name of the site your app is hosted on. If you don’t have a site, no problem. You can use Volt. Simply supply the URL to your app on Volt:

Here’s an ad in an app:

And here’s a link you can try yourself: https://adsense-wets-correctly.volt.live/

Now tell people about your app and watch the money roll in!