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The first block creates two lists (at far right) – one list per person to combine the name and address. This means storing several items for each individual record – in our example, we have two individuals but this could be easily expanded to support more. You’d best be familiar with lists (see volume 1 of my App Inventor 2: Tutorial) before starting on this.įor this example, we want to store a typical name/address combination. Let us now take a look at writing a list – or list of lists to the text file. You should see the Initialize event handler appear in a pop up list – drag that initialize block over to the Blocks editing window.
APP INVENTOR 2 EMULATOR MAC CODE
We can do this by adding the following code to the screen’s Initialize event:įind your screen’s name in the Blocks list and then click the mouse over the screen name. There are several possible ways to handle this but I have chosen to use the mechanism.īut before we get started, let’s add a piece of code to help us during development: let’s always start with a clean data file by deleting the old file (if any) first.
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But writing and reading a series of data elements is a bit more complex. Writing and reading a single line of text is easy. In the example above, the original text is read back from the file and placed in an on screen text box to illustrate success. When the data has actually been read, an event occurs and we need to add an event handler for GotText to process the data that has been read in to the app. But at this point, the data has not yet been read! When our app’s TestFetch button is pressed, the code initiates a read operation by reference ReadFrom and giving it the name of the file to read the data from. The first purple item above, AppendToFile, writes a piece of text to the file indicated at the filename component. Assuming you are implementing this in your own app, you should find the File1 control, probably at the bottom of the list of Blocks, at the left side of the Blocks editor. The new features are those in purple, which reference the File1 control. We will start with a simple example:ītnAddItem.Click is an event handler and you should already be familiar with the concept of event handlers. In the Blocks editor, we will set up some blocks to write text to the file. txtBoxResult1 and txtBoxResult2 – a couple of text boxes that can be used to display the values read from the file.btnTestFetch – when pressed, it starts the process of reading the data from the text file back into the program.btnAddItem – when pressed, it writes some items out to a text file.For this example, we have just a few user interface components: The real work begins over in the Blocks editor. The control is placed below the user interface as it is an invisible control.Īfter dragging the File control, you’ll see something like this at the bottom of the user interface Designer: Drag and drop the File control on to your app. Beneath the Palette heading, find the Storage item.
Let’s start our exploration of the File control in the Designer. But that is beyond the scope of this blog post!)
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(Once data is in a file, you could, hypothetically, email the file to yourself to read it on a computer, or transfer it from an Android to device to another computer using a USB cable and mounting the device as a simulated hard drive. As we will see, the File control is not the easiest thing to use but with some work, the control can be used to store data from our program into a file. App Inventor has introduced a File control that lets us write text data to a file and then read it back, later.
APP INVENTOR 2 EMULATOR MAC HOW TO
The updated tutorial explains where – and why – the files you create may appear to be hidden on the phone – how to find them and how to transfer the files to your PC.Īn earlier blog post described how to store data using TinyDB so that an app’s data can persist between uses of the program, or even to share data between screens in a program.Īnother way to save data is to write the data to a file on your Android device.
APP INVENTOR 2 EMULATOR MAC UPDATE
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