Chapter 18. On-Screen Text Fields
Because Flash is fundamentally a visual environment, movies often present on-screen information to users. Similarly, because Flash is an interactive environment, movies often retrieve information from users through a GUI. To display the value of a variable on screen or to allow a user to type data into a Flash movie, we use text fields.
Text fields provide a means of both setting and retrieving the values of variables that have a visual representation. Text fields come in two varieties -- dynamic text fields, which we use to display information to the user, and user-input text fields, which we use to retrieve information from the user.
18.1. Dynamic Text Fields
A dynamic text field is like a variable viewport -- it displays the value of a specified variable as a text string. Dynamic text fields are created using the Text tool in Flash. However, unlike regular static text, the content of a dynamic text field is connected to a variable and can be changed or retrieved via ActionScript.
By retrieving a text field's value, we can capture on-screen information for use in a script. By setting a text field's value, we cause that value to display on screen.
18.1.1. Creating a Dynamic Text Field
After creating a dynamic text field, you'd normally set the new field's options, as described later.
18.1.2. Changing the Content of a Dynamic Text Field
Once a text field is created, we can use it to display a value on the screen. For example, if we create a dynamic text field named myText, we can set the content of that text field using the following statements:
myText = 10; // Display a number in the text field myText myText = "Welcome to my web site"; // Display a string instead var msg = "Please make a selection"; myText = msg; // Display the value of msg in myText
Whenever the value of the variable myText changes, the content of the myText dynamic text field updates to reflect the change. However, before a value is sent to a dynamic text field for display, it is first converted to a string. The actual content is therefore governed by string-conversion rules described in Table 3-2.
Like normal variables, text fields are tied to the movie clip timeline on which they reside. To access a dynamic text field in a remote movie clip timeline, we use the techniques described in Chapter 2, "Variables" under Section 2.5.6, "Accessing Variables on Different Timelines".
18.1.3. Retrieving the Value of a Dynamic Text Field
We can retrieve a dynamic text field's value by simply using its name. For example, if myTextField were a dynamic text field in our movie, we could retrieve and assign its value to another variable like so:
welcomeMessage = myTextField;
Text field assignment and retrieval are often combined in one statement. You can use the += operator to append text to a text field's current contents:
// Set a text field's value myTextField = "Today's Headlines..."; // Create a new message var newText = "Update! The Party Has Been Cancelled!" // Add the new message to the existing text field content myTextField += newText;
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