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Creating Tasks
This article gives a fairly in-depth overview of working with Tasks and adding them to GanttChart and GridView widgets. If you read one gwt-gantt wiki article, I recommend you read this one ...
The GanttChart and GridView widgets both take in items of type Task, which is a simple interface that defines all the required fields to render a set of Tasks.
Task task1 = new Task();
task1.setUID(1);
task1.setName(...);
task1.setLevel(0);
task1.setOrder(1);
task1.setPercentComplete(50);
task1.setStart(...);
task1.setFinish(...);
gantt.addItem(task1);
The Unique Id, or UID field, is probably the most important field for a Task. It is used by gwt-gantt to uniquely identify a Task and match it to its predecessors (in order to join Tasks with connectors.
This UID heavily used internally, so make sure to give each Task its own unique id.
task1.setUID(1);
The Over attribute specifies aTasks order in the Gantt chart. gwt-gannt does not automatically calculate a Tasks order. It is up to the developer to explicitly set this property in order for the gantt chart to render correctly.
gwt-gannt will sort all Tasks based on the Order property prior to rendering the Gantt Chart.
The Level attribute, along with the Order attribute, defines the Task hierarchy in the tree. A level of 0 means that the task is a root-level Task. A Task with a level of 2 is two levels deep in the tree structure, meaning the Task is a child of a child.
gwt-gannt relies on the developer to correctly set the Level attribute. It will not automatically calculate the hierarchy of a list of Tasks.
In the following example task5 is considered a parent of task6, based on the Order and Level attributes:
task5.setSummary(true);
task5.setOrder(5);
task5.setLevel(0);
task6.setOrder(6)
task6.setLevel(1);
The Summary boolean attribute defines if a Task has children and is collapsible. Summary tasks are rendered differently than regular tasks.
The Milestone boolean attribute defines a task as a milestone, meaning it will be rendered as lasting only one day (regardless of Start and Finish date), and will be displayed as a Diamond shape.
The Collapsed boolean attribute defines if a summary Task should be collapsed, hiding all of its child tasks. The TaskGrid widget will set this property when a user clicks the expand / collapse buttons. This is one of the only times a gwt-gantt widget will update a Task's attribute.
Note: this attribute is only taken into account for Summary tasks (ie isSummary() == true).
Predecessors can be used to define a relationship between two Tasks. Visually this is represented by drawing a line connecting two Tasks.
In the below example, we are adding a Predecessor to task6. It's Predecessor is defined as task5 (we pass in task5's UID). We also define the PredecessorType.
task5.setSummary(true);
task5.setOrder(5);
task5.setLevel(0);
task6.setOrder(6)
task6.setLevel(1);
task6.getPredecessors().add(new Predecessor(5, PredecessorType.SS));
There are four different PredecessorTypes, each of which is rendered differently on a GanttChart:
- Start to Start (SS)
- Start to Finish (SF)
- Finish to Finish (FF)
- Finish to Start (FS)
If you make changes to a Task, and would like the changes reflected in the GanttChart or TaskGrid, you will need to manually instruct the widget to refresh its layout. This is done by invoking the ListDataProvider's refresh() method:
dataProvider.refresh();
In order to manually select or deselect a Task, you can use the SelectionModel:
selectionModel.setSelected(task, true);
The selection model will handle updating and refreshing the GanttChart to reflect the selection changes.