MACROMEDIA FLEX-CREATING ADVANCED COMPONENTS, Manual

Page 1: ...Creating Advanced Components...

Page 2: ...y website mentioned in this guide then you do so at your own risk Macromedia provides these links only as a convenience and the inclusion of the link does not imply that Macromedia endorses or accepts...

Page 3: ...ateChildren method 9 Implementing the commitProperties method 10 Implementing the measure method 10 Implementing the layoutChildren method 12 Implementing the draw method 12 Defining getters and sette...

Page 4: ...4 Contents...

Page 5: ...About creating components Most new controls extend an existing class If you want to create a component that is based on the Button control for example you can subclass the mx controls Button class How...

Page 6: ...d defines events and event handlers for the component When you extend an existing component class you can inherit from only one class ActionScript 2 0 does not allow multiple inheritance To edit Actio...

Page 7: ...lasses broadcast their events just before drawing If you are familiar with Flash this event is analogous to the enterFrame MovieClip event The UIObject class posts events to its listeners just before...

Page 8: ...ify a Button s behavior it is simpler to extend the Button class as a custom MXML component For more information see Developing Flex Applications About the component instantiation life cycle When you...

Page 9: ...ct method to instantiate a subobject of your component The createClassObject method has the following signature createClassObject className instanceName depth initObject The following table describes...

Page 10: ...e ViewStack selectedIndex property the ViewStack container does not display a new page right away Instead it privately stores a pendingSelectedIndex property When it is time for Flash Player to update...

Page 11: ...s how wide its label is in order to compute the value of the _measuredPreferredWidth property Note Although you can let Flex determine these values for you your application startup time will decrease...

Page 12: ...accordingly function layoutChildren Void text_mc setSize layoutWidth mode_mc width layoutHeight if labelPlacement left mode_mc move layoutWidth mode_mc width 0 text_mc move 0 0 else mode_mc move 0 0 t...

Page 13: ...edia recommends that you use initial capital letters for the second word and each word that follows For example public function get initialColorStyle Number The variable that stores the property s val...

Page 14: ...geProp1 when the property is modified ChangeEvent changeProp1 var prop1 Number You can also instruct your component to generate an event when a getter or setter method is called as the following examp...

Page 15: ...the architecture mx core UIObject and mx core UIComponent These classes define low level component events such as draw resize move load and others that are fundamental to all components Subclasses of...

Page 16: ...a subobject you use the createClassObject method as the following example shows function createChildren Void createClassObject TextInput text_mc 0 preferredWidth 80 editable false text_mc addEventLis...

Page 17: ...alls the commitProperties method You should call the invalidateSize method infrequently because it measures and redraws everything on the screen and this can be a computationally expensive action Some...

Page 18: ...lity When developers add the MyButton component to an application they can use the Accessibility panel to make it available to screen readers Adding versioning When releasing components you should def...

Page 19: ...xt example The following code example implements the class definition for the ModalText component The ModalText component is a text input whose default is the noneditable mode but you can switch to ed...

Page 20: ...SkinName falseDownSkin modeDownSkinName mode_mc addEventListener click this e Implement the measure method The default width is the size of the text plus the button The height is dictated by the butto...

Page 21: ...tchEvent type placementChanged function get labelPlacement String return __labelPlacement private var __text String ModalText ChangeEvent textChanged Inspectable defaultValue ModalText function set te...

Page 22: ...ML Ensure that the attribute is spelled correctly Also be sure that it is not private I don t get any errors but nothing shows up Verify that the component was instantiated One way to do this is to pu...

Page 23: ...ck the values of the preferredWidth and preferredHeight properties Other code might have set those values to zero If so set a breakpoint in the setters for the width height preferredWidth and preferre...

Page 24: ...24 Creating Advanced Components...