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theField.onSetFocus(oldFocus)

Arguments

oldFocus

The TextField, MovieClip, or Button object that previously had focus, or null if no object was previously focused.

Description

The onSetFocus( ) event is triggered when theField gains focus. A text field is said to have focus when it contains the text insertion point or when characters within it are selected. A field gains focus when:

• The user clicks it with the mouse or navigates to it with the Tab key.

• Selection.setFocus( ) assigns focus programmatically.

When a text field's selectable property is false, the field cannot be focused by the user, but it can be focused programmatically with Selection.setFocus( ).

The following code registers a callback function that responds to onSetFocus( ):

// Create a text field that accepts user input
this.createTextField("theField_txt", 1, 0, 0, 200, 20);
theField_txt.type = "input";
theField_txt.border = true;
// Assign the onSetFocus() callback using a function literal
theField_txt.onSetFocus = function (newFocus) {
  trace(this + " now has focus. Old focus was " + newFocus);
};

Notice that from the body of the callback we can refer to theField_txt using the this keyword. To stop a callback from handling the onSetFocus( ) event, use the delete operator, as in:

// Make sure to omit the () operator after the function name!
delete theField_txt.onSetFocus;

To capture all focus events centrally, rather than for a single instance, use Selection.onSetFocus( ).

Example

The following code uses onSetFocus( ) and onKillFocus( ) to highlight a field with color when it is focused, providing a nice interface cue for the user:

this.createTextField("userName_txt", 1, 0, 0, 200, 20);
userName_txt.type = "input";
userName_txt.border = true;
userName_txt.background = true;
userName_txt.backgroundColor = 0xA4660B;
userName_txt.onSetFocus = function (oldFocus) {
  this.backgroundColor = 0xF5BF70;
}
userName_txt.onKillFocus = function (newFocus) {
  this.backgroundColor = 0xA4660B;
}

To apply this effect to all text fields in a movie, use:

TextField.prototype.onSetFocus = function (oldFocus) {
  this.backgroundColor = 0xF5BF70;
}
TextField.prototype.onKillFocus = function (newFocus) {
  this.backgroundColor = 0xA4660B;
}

See Also

Selection.onSetFocus( ), Selection.setFocus( ), TextField.background, TextField.backgroundColor, TextField.onKillFocus( ), TextField.selectable, TextField.tabEnabled, TextField.tabIndex, TextField.type; Chapter 10

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