FiniteWidgetIterator class / dart_web_toolkit_ui Library / API Reference / Dart Web Toolkit

FiniteWidgetIterator class

Iterator over a finite number of widgets, which are stored in a delegate class (usually a widget panel).

In order to use this class, assign each widget in the panel an arbitrary index. For example, {@link HeaderPanel} defines the header as index 0, the content as index 1, and the footer as index 2. Construct a new {@link FiniteWidgetIterator} with a {@link WidgetProvider} that provides the child widgets.

class FiniteWidgetIterator implements Iterator<Widget> {

 int index = -1;
 WidgetProvider provider;
 int widgetCount;

 /**
  * Construct a new {@link FiniteWidgetIterator}.
  *
  * <p>
  * The widget count is the number of child widgets that the panel supports,
  * regardless of whether or not they are set.
  *
  * @param provider the widget provider
  * @param widgetCount the finite number of widgets that can be provided
  */
 FiniteWidgetIterator(WidgetProvider provider, int widgetCount) {
   this.provider = provider;
   this.widgetCount = widgetCount;
 }

 bool moveNext() {
   // Iterate over the remaining widgets until we find one.
   for (int i = index + 1; i < widgetCount; i++) {
     IsWidget w = provider.get(i);
     if (w != null) {
       return true;
     }
   }
   return false;
 }

 Widget get current => _getCurrent();
 
 Widget _getCurrent() {
   // Iterate over the remaining widgets until we find one.
   for (int i = index + 1; i < widgetCount; i++) {
     index = i;
     IsWidget w = provider.get(i);
     if (w != null) {
       return w.asWidget();
     }
   }
   throw new Exception("No Such Element");
 }

 void remove() {
   if (index < 0 || index >= widgetCount) {
     throw new Exception("Illegal State");
   }
   IsWidget w = provider.get(index);
   if (w == null) {
     throw new Exception("Widget was already removed.");
   }
   w.asWidget().removeFromParent();
 }
}

Implements

Iterator<Widget>

Constructors

new FiniteWidgetIterator(WidgetProvider provider, int widgetCount) #

Construct a new {@link FiniteWidgetIterator}.

The widget count is the number of child widgets that the panel supports, regardless of whether or not they are set.

@param provider the widget provider @param widgetCount the finite number of widgets that can be provided

FiniteWidgetIterator(WidgetProvider provider, int widgetCount) {
 this.provider = provider;
 this.widgetCount = widgetCount;
}

Properties

final Widget current #

Returns the current element.

Return null if the iterator has not yet been moved to the first element, or if the iterator has been moved after the last element of the Iterable.

docs inherited from Iterator<Widget>

Widget get current => _getCurrent();

int index #

int index = -1

WidgetProvider provider #

WidgetProvider provider

int widgetCount #

int widgetCount

Methods

bool moveNext() #

Moves to the next element. Returns true if current contains the next element. Returns false, if no element was left.

It is safe to invoke moveNext even when the iterator is already positioned after the last element. In this case moveNext has no effect.

docs inherited from Iterator<Widget>

bool moveNext() {
 // Iterate over the remaining widgets until we find one.
 for (int i = index + 1; i < widgetCount; i++) {
   IsWidget w = provider.get(i);
   if (w != null) {
     return true;
   }
 }
 return false;
}

void remove() #

void remove() {
 if (index < 0 || index >= widgetCount) {
   throw new Exception("Illegal State");
 }
 IsWidget w = provider.get(index);
 if (w == null) {
   throw new Exception("Widget was already removed.");
 }
 w.asWidget().removeFromParent();
}