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USING <INCLUDE> FOR SMALL CHANGES

The <include> tag is a fantastic way to pull out small portions of your screen that you’d like to tweak and lay out separately. This is the scalpel method. You cut out only the portions you want to render differently, you split them into folder-separated layouts, and you’re finished. Which, in this case, is a perfect way to excise the buttons and have them render differently depending on the screen orientation.

Here’s how to do exactly that.

1. Create a new button_layout.xml file in res/layout-land/. This is the file into which we’ll put the landscape-specific layout.

2. Add a LinearLayout and two Buttons in the new button_layout.xml file, and place them next to each other in the new horizontal linear layout. Here’s the final contents of my /layout-land/button_layout.xml.

ptg7794906

<?xml version=”1.0” encoding=”utf-8”?>

<LinearLayout

xmlns:android=”http://schemas.android.com/apk/res/android”

android:orientation=”horizontal”

android:layout_width=”match_parent”

android:layout_height=”wrap_content”

android:layout_marginBottom=”60dp”

android:layout_alignParentBottom=”true”

>

<Button

android:padding=”15dp”

android:gravity=”center”

android:id=”@+id/yes_button”

android:layout_marginLeft=”20dp”

android:layout_marginRight=”5dp”

android:layout_width=”fill_parent”

android:layout_height=”wrap_content”

android:text=”@string/yes_button_text”

android:layout_weight=”50”

/>

<Button

android:padding=”15dp”

android:gravity=”center”

android:id=”@+id/no_button”

android:layout_marginLeft=”5dp”

android:layout_marginRight=”20dp”

android:layout_width=”fill_parent”

android:layout_height=”wrap_content”

UNCOVERING THE SECRETS OF THE RES/ FOLDER 173

ptg7794906 android:text=”@string/no_button_text”

android:layout_weight=”50”

/>

</LinearLayout>

As you can see, I’ve created a horizontal layout with two buttons to be used in landscape mode.

Don’t forget about the portrait layout. If we’re going to include a layout, it’s got to exist for both the landscape configuration and the default configuration.

3. Create a new button_layout.xml file in /res/layout/ (or you could add it as /res/layout-port/button_layout.xml). I’ve just copied the original buttons’ code and pasted it into a new RelativeLayout:

<?xml version=”1.0” encoding=”utf-8”?>

<RelativeLayout

xmlns:android=”http://schemas.android.com/apk/res/android”

android:layout_marginBottom=”60dp”

android:layout_width=”fill_parent”

android:layout_height=”100dp”

android:layout_alignParentBottom=”true”

>

<Button

android:padding=”15dp”

android:gravity=”center”

android:id=”@+id/yes_button”

android:layout_marginLeft=”30dp”

android:layout_marginRight=”30dp”

android:layout_width=”fill_parent”

android:layout_height=”wrap_content”

ptg7794906 android:layout_above=”@+id/no_button”

android:text=”@string/yes_button_text”

/>

<Button

android:padding=”15dp”

android:gravity=”center”

android:id=”@+id/no_button”

android:layout_marginLeft=”30dp”

android:layout_marginRight=”30dp”

android:layout_width=”fill_parent”

android:layout_height=”wrap_content”

android:text=”@string/no_button_text”

android:layout_alignParentBottom=”true”

/>

</RelativeLayout>

At this point, you’ve created two layouts: one for portrait and one for landscape.

4. You can now modify your original XML with an include, like so:

<RelativeLayout>

<!--Text view and relative layout params omitted-->

<include layout=”@layout/button_layout”

android:id=”@+id/button_holder”

/>

</RelativeLayout>

With the <include> tag in place (instead of a single button definition), Android will grab the button_layout.xml file that corresponds to the screen configura-tion. If it can’t find one, it will default back to what’s in /res/layout.

UNCOVERING THE SECRETS OF THE RES/ FOLDER 175

ptg7794906 Now, with this new code, the landscape mode looks much better (Figure 7.3).

Are there things that could be improved? Sure! Now, however, you know how to specify that parts of your user interface should change as the screen’s hardware configuration changes.

MERGING

You don’t have to wrap your excised views in a new ViewGroup (RelativeLayout in the previous example) for them to be included (as I did here). If you don’t want to add another layout to the mix but would like to bring in a series of views from other XML files, simply wrap them in a <merge> tag.

<merge xmlns:android=”http://schemas.android.com/apk/res/android”>

<!-- views go here -->

</merge>

This will allow you to include views without adding another layout to your view hierarchy.

FIGURE 7.3 No awards for design, but much better.

ptg7794906 WHAT CAN YOU DO BEYOND LANDSCAPE?

Lots. You can add suffixes to layout folders to account for just about everything.

Here are a few I use on a regular basis.

䊏 layout-small, layout-normal, layout-large, layout-xlarge

The size modifier accounts for the physical size of the screen. Devices that would use the small layout folder are typically very old, or very strange pieces of hardware, at least until Android powered watches become popular.

Most modern phones fit the layout-normal category, while many tablets are considered xlarge. Google keeps a great breakdown of all the various screen configurations at http://developer.android.com/resources/dashboard/

screens.html.

䊏 layout-ldpi, layout-mdpi, layout-hdpi, layout-xhdpi

The dpi, or dots per inch, of the device is a measurement of screen density.

Screens with high densities (240 dpi) would pull from the layout folder layout-hdpi.

䊏 layout-large-hdpi-land

You can also mix and match the suffixes. This suffix would be used for phones that have large screens and high resolution and that are in land-scape mode. Get creative, but remember that just because you can get very specific about screen configurations, it doesn’t mean you should.