Within SAP Fiori, we distinguish between tree tables and trees. Both usually allow the user to display and work with a hierarchical set of items. While tree tables are usually used for more complex data, trees are generally used for rather basic data. Trees are mostly used in the master list for a master-detail scenario using the flexible column layout and in popovers or dialogs. In certain use cases, they can also be used in the dynamic page layout.
In the case of tree tables and trees, items that contain additional items are called nodes, while items that do not contain any other items are called leaves. If available, a single topmost node is called a root node. Apart from the hierarchical structure of its nodes and leaves, a tree is quite similar to a list.
Use the tree if:
- You need to display the key identifier of hierarchically structured items (for example in the first column of the flexible column layout).
- Selecting one or more items out of a set of hierarchically structured items is a main use case.
- The hierarchy has a restricted number of levels (up to about 12, depending on the content) and items (around 200).
- You want to have only one implementation for all devices.
Do not use the tree if:
- The main use case is to select one item from a very small number of non-hierarchical items, without viewing additional details. In this case, a select or combo box might be more appropriate.
- Items are not structured hierarchically. Use a list instead.
- The hierarchy turns out to have only two levels. In this case, use a grouped list.
- The hierarchy turns out to be just a categorization based on several details of the item. In this case, an analytical table provides multi-level grouping. Note that the analytical table is not fully responsive. It is only available for desktops and tablets, so you will need to take an adaptive approach by offering an additional UI for smartphones.
- You need to display very deep hierarchies with additional data per item. In this case, use a tree table. Note that the tree table is not fully responsive. It is only available for desktops and tablets, so you will need to take an adaptive approach by offering an additional UI for smartphones.
- The structure contains more than 200 items. In this case, use the tree table. It is optimized for large item sets and provides better performance. Note that the tree table is not fully responsive. It is only available for desktops and tablets, so you will need to take an adaptive approach by offering an additional UI for smartphones.
- You need an overview of a large amount of data. In this case, use a chart.
Check out the table overview to decide which SAP Fiori table is most suitable for your needs.
Responsiveness and Adaptiveness
The tree is like a list containing hierarchical data. It acts as a container for items, with the possibility to expand and collapse nodes. When reducing the width, item texts wrap to ensure that the tree adapts to the new size.
In addition, the tree changes the indentation per level dynamically when the user expands a node, based on number of levels currently showing.
The title bar (optional) contains the title of the tree. In addition, an item counter and toolbar items can be placed on the title bar.
The collection of hierarchical items occupies the main part of the tree.
The standard tree item consists of:
- A highlight indicator (optional)
- An expand/collapse button for nodes
- A selector in form of a checkbox or a radio button (optional)
- An icon (optional)
- A text
- A counter (optional)
- Additional buttons with actions such as Edit, Navigate, or Delete (optional)
If additional controls are needed, use a custom tree item. The custom tree item allows you to use any combination of controls inside the tree.
Behavior and Interaction (incl. Gestures)
The height of the tree is defined by the numbers of items it contains. It does not have a scroll container on its own, but is scrolled together with the page or its parent.
A tree can have one of the following selection modes (sap.m.Tree / sap.m.ListBase, property: mode):
None: Items cannot be selected (sap.m.ListMode.None).
Beware: Items can, nevertheless, use the sap.m.ListType “navigation” which allows click-handling on specific items. This should only be used when the click triggers a navigation to a corresponding item details page.
Single select master: One item of the tree can be selected. To select an item, click anywhere on the item. Single select master does not add any visual indication to the tree and therefore cannot be differentiated from trees without selection if no item is selected. Therefore, always keep one item selected. For single selection, this is the preferred mode. (sap.m.ListMode.SingleSelectMaster)
Single select left: One item of the tree can be selected. For this, the tree provides radio buttons on the left side of each line item. Use this selection mode only if clicking on the item triggers something else, such as a navigation. Ideally, always keep one item selected, even in initial state (sap.m.ListMode.SingleSelectLeft).
Multiple selection: Allows the selection of one or more items. For this, the tree provides checkboxes on the left side of each line item. Each item is selected independently of the others (sap.m.ListMode.MultiSelect).
To delete single items, use the tree in “delete” mode (sap.m.Tree / sap.m.ListBase, property: mode, value: sap.m.ListMode.Delete). This adds a Delete button to each item. Clicking or tapping this button triggers the deletion of the corresponding item. Do not use this mode if deleting multiple items at once is the preferred use case. Delete is a mode of the tree and therefore cannot be used together with single selection or multi selection.
Line Item Level
Expandable and Collapsible Nodes
To allow navigation from an item, set type to “navigation” within the corresponding item (sap.m.StandardTreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Navigation). This will create an indicator at the end of the line (“>”) and the entire item will become selectable. Clicking or tapping the line triggers the navigation event. However, clicking or tapping a selectable area or an expandable/collapse node does not. Use the navigation event to navigate to a new page containing item details.
If no navigation is possible, set type to “inactive”.
Navigation is an item type and therefore cannot be used together with “edit” or in combination with click events for the entire item (“active”).
To allow the user to edit an item, set type to “detail” within the corresponding item (sap.m.StandardTreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Detail or sap.m.ListType.DetailAndActive). This will create an edit button at the end of the line. Clicking the button triggers the edit event. Use this event to either open a dialog or a details page where the item can be edited.
Edit is an item type and therefore cannot be used together with “navigation” or in combination with click events for the entire item (“active”).
Clicking an Item
Items as a whole can be clickable. An event is fired by clicking on the item (anywhere except when triggering a selection or when expanding/collapsing a node). Apps can react to the event, such as by opening a dialog (sap.m.StandardTreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Active or sap.m.ListType.DetailAndActive).
Active elements do not have a visual indication and therefore cannot be differentiated from non-active elements.
“Active” is an item type and therefore cannot be used together with “navigation” or “edit”. In addition, “active” uses the entire item as a clickable area and thus cannot be used together with single select master.
The context menu can be triggered for the tree or per item.
Context menus are opened by right-clicking (desktop), long press (mobile), the context menu key, or SHIFT+F10.
Be aware that using the context menu overrides the browser context menu, which can no longer be opened.
If a control inside a tree is the “click target”, and the control also provides a context menu, the control context menu “wins”.
Drag and Drop
One or several items can be repositioned within a tree or moved to other UI elements using drag and drop operations (sap.m.ListBase, aggregation: dragDropConfig). While being dragged, the items are shown as ghost elements on the mouse cursor.
Drop targets can be on items, between items, or both (sap.ui.core.dnd.DropPosition). On a drop target, the mouse cursor changes to either a “copy”, “link”, “move”, or “none” cursor. “None” indicates that the dragged item cannot be dropped in the current position (sap.ui.core.dnd.DropEffect).
Drag and drop is only available on supporting browsers.
Tree vs. List
Trees are more complex than lists due to their hierarchical view. Users tend to have more problems finding items in hierarchical views than in flat lists, except where the hierarchical view is natural. By natural we mean that every child node should be part of only one parent, and this relationship between the child and parent is clear and well known.
Broad vs. Deep Hierarchies
When you use trees, you should choose broad hierarchies over deep hierarchies. Deep hierarchies make finding items more complicated. So try to reduce hierarchical levels where possible, especially if the hierarchy is not natural. Ideally, a tree should have a maximum of four levels, the first two of which should contain the most important items.
You can use the following methods to reduce hierarchy levels:
- Avoid a single root node. It is usually not needed.
- Container nodes at the top level can usually be replaced by tabs or value pickers.
- Eliminate unnecessary mid-level containers, for example, by combining redundant ones.
- Exercise care when using a tree due to its overall complexity. The hierarchical structure of the data does not necessarily mean that a tree control is required.
The tree can be used to display hierarchical data. Unfortunately, trees convey an immediate feeling of complexity. Ideally, show trees only if there is no other option. You should instead try the following:
- Flatten the data. A list is still complex, but less so than a tree. A combo box might also fit in some use cases.
- When only two levels are needed, a grouped list control can be used. This works well, where group nodes are used for categorizing their children and where the group nodes themselves do not need to be selectable.
- Break down the data into manageable chunks. Allow the user to navigate or drill down between them.
- Use charts with drilldown functionality until the amount of data is more manageable.
If needed, implement the title text by adding a title to a toolbar. Place the toolbar above the tree.
Use a title text if it is not already provided by the surrounding area. Do not use a title text if it would just repeat text that is already in the context above the tree.
Use a title if you need a toolbar. To avoid repeating text, feel free to use generic text as a title, such as Items.
If you use a title, be sure to include the following:
- A title text for the tree.
- An (optional) item count using the following format: Title (Number of Items). For example, Items (17). Depending on the use case, either count all items or leaves only (for example, if nodes are mainly used for categorization).
To indicate that the tree is currently loading items, use the busy state (sap.m.Tree, property: busy). Do not show any items or text. As soon as the data is loaded, remove the busy state and show all items.
Think of the initial expandable/collapsible state of a tree. If your structure contains many items on the root level, it might make sense to collapse the whole tree in its initial state.
In contrast, if the most important items are displayed on a deeper level (if, for example, the parent nodes are simply a kind of categorization), the tree should be expanded up to the first level where the most important items immediately appear.
The standard tree item allows you to set one text per item. The text wraps, which can lead to items of different heights depending on the length of the text. An icon can be shown before the text. Try not to use the icons, and only use them if the meaning of the icons is clear and unambiguous. In addition, a counter can be placed on the right side of the item (sap.m.StandardTreeItem / sap.m.ListItemBase, property: counter).
The custom tree item allows you to use any combination of controls inside a tree, including editable controls (selection controls, Expand/Collapse buttons, navigation indicators, counters).
When designing a custom tree item, consider the responsive behavior. Take into account that all the controls you can add to a tree require additional width. Their position cannot be changed.
To display object names with an ID, show the ID in brackets after the corresponding object name.
Try not to display an empty tree. If there is no way around this, provide instructions on how to fill the tree with data (sap.m.Tree / sap.m.ListBase, properties: showNoData, noDataText).
- If a tree is initially empty, provide at least a basic text:
No items available.
Overwrite this whenever a hint can be provided on how to fill the tree with data.
- If a tree is used together with a filter bar (as in the list report), and is initially empty, use the following text:
No filters set. To start, enter your search and filter settings and run the search.
- If a tree is used together with a filter bar and the filter does not return results, use the following text:
No items found. Check the search and filter settings.
Adapt the texts above if:
- The text is not precise enough for your use case (for example, no search is offered, only the search is offered).
- You are using the live search (no Go button in the filter bar). In this case, leave out “run the search”.
- The standard text is misleading (for example, if the data is filled based on a master-detail pattern instead of search and filter settings).
To show that an item needs attention, a highlight indicator can be shown in front of the item. The highlight indicator can be used to show:
- A semantic state (for example, red or orange if the item contains an error or warning)
- A neutral state (for example, blue to highlight newly added items)
(sap.m.StandardTreeItem / sap.m.ListIemBase, property: highlight)
To show that an item is locked, add the string (Locked by [name]) to the text of the item.
To show that an item is in a draft state, add the string (Draft) to the text of the item.
Show only one state at any one time.
To trigger actions on items, show the actions on a toolbar above the tree. Do not offer action triggering on multiple items if the tree is expected to have fewer than 10 items in most cases.
The following actions on single items must always be in-line:
Delete: Use “Delete” mode (sap.m.Tree / sap.m.ListBase, property: mode, value: sap.m.ListMode.Delete). This places a delete button at the end of each item.
Navigation: Use the “Navigation” item type (sap.m.StandardTreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Navigation). This places a navigation indicator at the end of the corresponding items. Use this to navigate to a new page containing item details.
Edit: Use the “Detail” item type (sap.m.TreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Detail). This places an edit icon at the end of the corresponding items.
From these three actions (delete, navigation, and edit), you can combine delete and edit, or delete and navigation. Edit and navigation cannot be combined.
To trigger actions that are independent of the selection, show the actions on a toolbar above the tree. For example: Add, Collapse All, Expand All, …
To trigger a default action on the entire item, use the “Active” or “DetailAndActive” item type (sap.m.TreeItem / sap.m.ListItemBase, property: type, value: sap.m.ListType.Active). Active items trigger an event when clicked, which can be handled by apps, for example, to open a dialog. Selection and expanding/collapsing a node does not trigger the event, but are handled by the tree. Do not use this for navigation, to switch the line item to an edit state, or to delete the item.
Active can be combined with edit and delete, but not with navigation. Do not combine active with single selection master.
When you add an item, add the new item as the first item of the corresponding node.
For mass editing:
- Provide multiselection (sap.m.Tree/ sap.m.ListBase, property: mode, value: sap.m.ListMode.MultiSelect).
- Provide an Edit button on the toolbar above the tree.
- If several items are selected, triggering the Edit button opens a dialog in which the user edits the corresponding fields for all selected items.
For more details, see mass editing.
Use the context menu only to give users a quick way of accessing functions that are already available elsewhere (for example, as buttons in the toolbar).
Don’t just offer actions in the context menu itself, as users might not realize that these actions are available at all.
Drag and Drop
Drag and drop is “invisible” on the UI: users can’t see where dragging is available and where it isn’t. In addition, it is not accessible, since there is no generic keyboard interaction. Drag and drop is also not available on all browsers. For these reasons, provide it only in addition to existing (and visible) UI elements that fulfill the same purpose. For example, offer (toolbar) buttons for moving or for copying and pasting items.
If you offer drag and drop for rearranging items within a tree, use the following options:
- For dropping items as a child, use whole nodes as drop targets (sap.ui.core.dnd.DropPosition.On).
- For dropping items on the same level, use the space between items as drop targets (sap.ui.core.dnd.DropPosition.Between).
- If you want to allow users to drop items as a child or sibling, offer both drop targets (sap.ui.core.dnd.DropPosition.OnOrBetween).
This provides better feedback on where the item will be inserted. Show the “move” mouse cursor (sap.ui.core.dnd.DropEffect.Move).
Do not combine rearranging items within one level and sorting. If you really need to do so, make sure that there is a dedicated sort criterion for the user-defined sort order, and only offer options for rearranging items if this sort order is set.
Moving items from one node to another can be combined with sorting without any issues.
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