Activity Indicators

Activity indicators are used to present an indeterminate progress state. They inform the user that a background task is in progress, but that the length of the task is not known. For example, an application might use an activity indicator to reflect network activity, a file load operation, or a long-running CPU operation. They are often animated to simulate the appearance of progress and to let the user know that the UI is still responsive.

In Pivot, activity indicators are represented by instances of the ActivityIndicator component, shown below:

The BXML for the example is shown below:

            
            <progress:ActivityIndicators title="Activity Indicators" maximized="true"
                xmlns:bxml="http://pivot.apache.org/bxml"
                xmlns:progress="org.apache.pivot.tutorials.progress"
                xmlns="org.apache.pivot.wtk">
                <TablePane>
                    <columns>
                        <TablePane.Column width="1*"/>
                    </columns>

                    <TablePane.Row height="1*">
                        <Border styles="{padding:2}">
                            <BoxPane styles="{horizontalAlignment:'center', verticalAlignment:'center'}">
                                <ActivityIndicator bxml:id="activityIndicator1"
                                    preferredWidth="24" preferredHeight="24"/>
                                <ActivityIndicator bxml:id="activityIndicator2" styles="{color:'#aa0000'}"
                                    preferredWidth="48" preferredHeight="48"/>
                                <ActivityIndicator bxml:id="activityIndicator3" styles="{color:16}"
                                    preferredWidth="96" preferredHeight="96"/>
                            </BoxPane>
                        </Border>
                    </TablePane.Row>

                    <TablePane.Row height="-1">
                        <BoxPane styles="{horizontalAlignment:'center', padding:6}">
                            <PushButton bxml:id="activityButton" styles="{minimumAspectRatio:3}"/>
                        </BoxPane>
                    </TablePane.Row>
                </TablePane>
            </progress:ActivityIndicators>
            
        

Clicking the "Start" button activates the three sample indicators; clicking the button again de-activates them. The button press handler simply toggles the "active" property of the indicators:

            
            package org.apache.pivot.tutorials.progress;

            import java.net.URL;

            import org.apache.pivot.beans.Bindable;
            import org.apache.pivot.collections.Map;
            import org.apache.pivot.util.Resources;
            import org.apache.pivot.wtk.ActivityIndicator;
            import org.apache.pivot.wtk.Button;
            import org.apache.pivot.wtk.ButtonPressListener;
            import org.apache.pivot.wtk.PushButton;
            import org.apache.pivot.wtk.Window;

            public class ActivityIndicators extends Window implements Bindable {
                private ActivityIndicator activityIndicator1 = null;
                private ActivityIndicator activityIndicator2 = null;
                private ActivityIndicator activityIndicator3 = null;
                private PushButton activityButton = null;

                @Override
                public void initialize(Map<String, Object> namespace, URL location, Resources resources) {
                    activityIndicator1 = (ActivityIndicator)namespace.get("activityIndicator1");
                    activityIndicator2 = (ActivityIndicator)namespace.get("activityIndicator2");
                    activityIndicator3 = (ActivityIndicator)namespace.get("activityIndicator3");
                    activityButton = (PushButton)namespace.get("activityButton");

                    activityButton.getButtonPressListeners().add(new ButtonPressListener() {
                        @Override
                        public void buttonPressed(Button button) {
                            activityIndicator1.setActive(!activityIndicator1.isActive());
                            activityIndicator2.setActive(!activityIndicator2.isActive());
                            activityIndicator3.setActive(!activityIndicator3.isActive());
                            updateButtonData();
                        }
                    });

                    updateButtonData();
                }

                private void updateButtonData() {
                    activityButton.setButtonData(activityIndicator1.isActive() ? "Stop" : "Start");
                }
            }
            
        

Note that activity indicators are scalable. They are drawn using the Java 2D API and can be presented at different sizes without losing resolution. Also note that the default activity indicator skin supports "color" and "backgroundColor" styles to allow further customization of their appearance.