Use tags to reuse layout code

Http://www.chengyunfeng.com/2010/01/android-layout-optimization-of-the-two-use-include-and-merge
If you need to use the same layout design in a project, you can use the <include/> label to reuse the layout code. This label is not described in the android development documentation. This tag is used in the android main screen program:

<com.android.launcher.Workspace
  android:id="@+id/workspace"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  launcher:defaultScreen="1">
  <include android:id="@+id/cell1" layout="@layout/workspace_screen" />
  <include android:id="@+id/cell2" layout="@layout/workspace_screen" />
  <include android:id="@+id/cell3" layout="@layout/workspace_screen" />

</com.android.launcher.Workspace>

You can reference a layout multiple times without copying or pasting it repeatedly. You can use the include tag to override the values of some attributes. For example, the preceding example overwrites the id value in the referenced layout. The following is another example:

<Include android: layout_width = "fill_parent" layout = "@ layout/image_holder"/>
<Include android: layout_width = "256dip" layout = "@ layout/image_holder"/>

Use the <merge/> label to reduce the view hierarchy

In the Android layout file, a top-level container is required to accommodate other components, but multiple components cannot be placed directly. For example, the following code
:

<FrameLayout xmlns: android = "http://schemas.android.com/apk/res/android"

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent">

<ImageView

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent"

Android: scaleType = "center"

Android: src = "@ drawable/golden_gate"/>

<TextView

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "Golden Gate"/>

</FrameLayout>

The code above shows an image and a title on the top of the image. The result is as follows:

The default layout of the android activity is FrameLayout, so that the layout code above has two layers of FrameLayout, through HierarchyViewer
The structure of the tool is as follows:

If you can remove the FrameLayout statement from the layout file, you can further optimize the layout code. However, because the layout code needs to be accommodated by the outer container, if
If you delete FrameLayout directly, this file is not a legal layout file. In this case, you can use the <merge/> label.
Modify the Code as follows to eliminate unnecessary FrameLayout:

<Merge xmlns: android = "http://schemas.android.com/apk/res/android">

<ImageView

Android: layout_width = "fill_parent"

Android: layout_height = "fill_parent"

Android: scaleType = "center"

Android: src = "@ drawable/golden_gate"/>

<TextView

Android: layout_width = "wrap_content"

Android: layout_height = "wrap_content"

Android: text = "Golden Gate"/>

</Merge>

The HierarchyViewer tool shows the following structure:

Merge also has some restrictions: it can only be used for the root element of the xml layout file; inflate a merge-based root element in the code
When layout a file, you must specify a ViewGroup as its container and set attachToRoot to true. For more information, see
The inflate () function doc.

Sample project code above:
Http://progx.org/users/Gfx/android/MergeLayout.zip