Part 3 - Alternative Layout Views

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last updated: 2017-03

Part 3 explains how layouts can be versioned by using resource qualifiers. For example, there can be a version of a layout that is only used when the device is in landscape mode and a layout version that is only for portrait mode.

Creating Alternative Layouts

When you click the Alternative Layout View icon (to the left of Device), a preview pane opens to list the alternative layouts available in your project. If there are no alternative layouts, the Default view is presented:

Alternate layout view pane

Alternate layout view pane

When you click the green plus sign next to New Version, the Create Layout Variation dialog opens so that you can select the resource qualifiers for this layout variation:

Create layout variation

Create layout variation

In the following example, the resource qualifier for Screen Orientation is set to Landscape, and the Screen Size is changed to Large. This creates a new layout version named large-land:

Large-land variation

Large-land variation

Note that the preview pane on the left displays the effects of the resource qualifier selections. Clicking Add creates the alternative layout and switches the Designer to that layout. The Alternative Layout View preview pane indicates which layout is loaded into the Designer via a small right pointer as indicated in the following screenshot:

Loaded layout indicator

Loaded layout indicator

Editing Alternative Layouts

When you create alternative layouts, it is often desirable to make a single change that applies to all forked versions of a layout. For example, you may want to change the button text to yellow in all layouts. If you have a large number of layouts, maintenance can quickly become cumbersome and error-prone if you need to propagate a single change to all versions.

To simplify the maintenance of multiple layout versions, the Designer provides a Multi-edit mode that propagates your changes across one or more layouts. When more than one layout is present, the Multi-edit icon is displayed:

Multi-edit icon

Multi-edit icon

When you click the Multi-edit icon, lines appear that indicate that the layouts are linked (as shown below); that is, when you make a change to one layout, that change is propagated to any linked layouts. You can unlink all layouts by clicking the circled icon indicated in the following screenshot:

Unlink all layouts

Unlink all layouts

If you have more than two layouts, you can selectively toggle the edit button to the left of each layout preview to determine which layouts are linked together. For example, if you want to make a single change that propagates to the first and last of three layouts, you would first unlink the middle layout as shown here:

Unlink middle layout

Unlink middle layout

In this example, a change made to either the Default or long layout will be propagated to other layout but not to the large-land layout.

Multi-Edit Example

In general, when you make a change to one layout, that same change is propagated to all other linked layouts. For example, adding a new TextView widget to the Default layout and changing its text string to Portrait will cause the same change to be made to all linked layouts. Here is how it looks in the Default layout:

Add TextView

Add TextView

The TextView is also added to the large-land layout view because it is linked to the Default layout:

Landscape TextView

Landscape TextView

But what if you want to make a change that is local to only one layout (that is, you don't want the change to be propagated to any of the other layouts)? To do this, you must unlink the layout that you want to change before you modify it, as explained next.

Making Local Changes

Suppose we want both layouts to have the added TextView, but we also want to change the text string in the large-land layout to Landscape rather than Portrait. If we make this change to large-land while both layouts are linked, the change will propagate back to the Default layout. Therefore, we must first unlink the two layouts before we make the change. When we modify the text in large-land to Landscape, the Designer marks this change with a red frame to indicate that the change is local to the large-land layout and is not propagated back to the Default layout:

Local change

Local change

When you click the Default layout to view it, the TextView text string is still set to Portrait.

Handling Conflicts

If you decide to change the color of the text in the Default layout to green, you'll see a warning icon appear on the linked layout. Clicking that layout opens the layout to reveal the conflict. The widget that caused the conflict is highlighted with a red frame and the following message is displayed: Recent changes have caused conflicts in this alternative layout.

Conflicting change

Conflicting change

A conflict box is displayed on the right of the widget to explain the conflict:

Conflict warning

The conflict box shows the list of properties that have changed and it lists their values. Clicking Ignore Conflict applies the property change only to this widget. Clicking Apply applies the property change to this widget as well as to the counterpart widget in the linked Default layout. If all property changes are applied, the conflict is automatically discarded.

View Group Conflicts

Property changes are not the only source of conflicts. Conflicts can be detected when inserting or removing widgets. For example, when the large-land layout is unlinked from the Default layout, and the TextView in the large-land layout is dragged and dropped above the Button, the Designer marks the moved widget to indicate the conflict:

View group conflict

View group conflict

However, there is no marker on the Button. Although the position of the Button has changed, the Button shows no applied changes that are specific to the large-land configuration.

If a CheckBox is added to the Default layout, another conflict is generated, and a warning icon is displayed over the large-land layout:

Checkbox conflict

Checkbox conflict

Clicking the large-land layout reveals the conflict. The following message is displayed: Recent changes have caused conflicts in this alternative layout.

Alt layout conflict

Alt layout conflict

In addition, the conflict box displays the following message:

Conflict message

Adding the CheckBox causes a conflict because the large-land layout has changes in the LinearLayout that contains it. However, in this case the conflict box displays the widget that was just inserted into the Default layout (the CheckBox).

If you click Ignore Conflict, the Designer resolves the conflict, allowing the widget displayed in the conflict box to be dragged and dropped into the layout where the widget is missing (in this case, the large-land layout):

Resolved group conflict

Resolved group conflict

As seen in the previous example with the Button, the CheckBox does not have a red change marker because only the LinearLayout has changes that were applied in the large-land layout.

Conflict Persistence

Conflicts are persisted in the layout file as XML comments, as shown here:

<!-- Widget Inserted Conflict | id:__root__ | @+id/checkBox1 -->

Therefore, when a project is closed and reopened, all the conflicts will still be there – even the ones that have been ignored.

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