| Button.onSetFocus( ) Event Handler | Flash 6 |
| callback invoked when the button gains focus |
The TextField, MovieClip, or Button object that previously had focus, or null if no object was previously focused.
The onSetFocus( ) event handler is executed when theButton gains focus. A button gains focus when:
The user navigates to it with the Tab key.
Selection.setFocus( ) assigns focus programmatically.
When a button's tabEnabled property is false, the button cannot be focused by the user but can be focused programmatically with Selection.setFocus( ). The following code registers a callback function that responds to onSetFocus( ):
// Assign the onSetFocus() callback using a function literal
next_btn.onSetFocus = function (oldFocus) {
trace(this + " now has focus. Old focus was " + oldFocus);
};
Notice that from the body of the callback, we can refer to next_btn 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 next_btn.onSetFocus;
To detect attainment of focus via either the keyboard or mouse, use the onRollOver( ) handler, which executes both when the mouse is over theButton and when theButton gains keyboard focus. To capture all focus events centrally, rather than for a single instance, use Selection.onSetFocus( ).
To activate a keyboard-focused button, the user must press the Enter key or spacebar (which has the same effect as clicking the button and causes the button's onRelease( ) handler to execute).
Button.onKillFocus( ), Button.onRollOver( ), MovieClip.onSetFocus( ), Selection.onSetFocus( ), Selection.setFocus( ), TextField.onSetFocus( ); Chapter 10
