The document discusses styles and themes in Android development. It defines styles as collections of properties that specify a view's look and format, and themes as styles applied to an entire activity or application. It provides examples of using styles at different levels from inline to styles to themes. It also discusses replacing PNG files with shapes to reduce file sizes and improve performance. Finally, it addresses some questions around when styles cannot help and provides references for further information.

1. Android: Styles
What's not New, but is Undiscovered for many
Praha, Nov 16th
2010
Pavel Petřek
CTO

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Who is who
Pavel Petřek
Developer, speaker,
smartphones enthusiast
Inmite co-founder
Inmite
Smartphone developers (Android: Corkbin, OnTheRoad,
Lokola, SMS ticket, DMS and more)
Smart-web-apps based on Google APIs

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Agenda
Styles and themes
Life without PNGs
Q&A

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Let's start with Definitions
Style
A collection of properties that specify the look and format for a
View or window
Theme
A style applied to an entire Activity or application, rather than
an individual View

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Inline vs. Style vs. Theme
Stage 0: inline
Stage 1: style
Stage 2: theme
<TextView
android:id="@+id/row_validity_tv"
android:layout_width="wrap_content"
android:layout_height="?android:attr/listPreferredItemHeight"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textStyle="bold"
android:gravity="center_vertical"
android:layout_marginLeft="3dip"
android:text="@string/l_invalid"
android:textColor="@color/orange" />
<TextView
android:id="@+id/row_valid_to_hint_tv"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/l_valid_to_long"
android:layout_gravity="center_vertical"
android:gravity="right"
android:layout_weight="1" /> layout.xml

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Inline vs. Style vs. Theme
Stage 0: inline
Stage 1: style
Stage 2: theme
<EditText
android:id="@+id/login_email_et"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0"
android:hint="E-mail"
android:inputType="textEmailAddress"
android:textAppearance="@style/TextAppearance.Medium.Inverse"
/>
<EditText
android:id="@+id/login_password_et"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0"
android:hint="Password"
android:inputType="textPassword"
android:textAppearance="@style/TextAppearance.Medium.Inverse"
android:imeOptions="actionGo"
/>
<style name="TextAppearance">
<item name="android:typeface">serif</item>
<item name="android:textSize">16.0sp</item>
<item name="android:textStyle">normal</item>
<item name="android:textColor">@color/black</item>
<item name="android:textColorHighlight">#ffff9200</item>
<item name="android:textColorHint">@color/gray</item>
<item name="android:textColorLink">#ff5c5cff</item>
</style>
<style name="TextAppearance.Medium">
<item name="android:textSize">14.0sp</item>
</style>
<style name="TextAppearance.Medium.Inverse">
<item name="android:textColor">@color/white</item>
<item name="android:textColorHint">@color/gray</item>
</style> styles.xml
layout.xml

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Inline vs. Style vs. Theme
Stage 0: inline
Stage 1: style
Stage 2: theme
<Button
android:id="@+id/login_forget_bt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.5"
android:text="@string/l_forget_password"
/>
<Button
android:id="@+id/login_login_bt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="@string/l_login"
/>
<style name="Button" parent="@android:style/Widget.Button">
<item name="android:background">@drawable/button</item>
<item name="android:textAppearance">@style/TextAppearance.Small</item>
<item name="android:padding">15dip</item>
<item name="android:textColor">@color/button_text_color</item>
</style>
<style name="MyTheme" parent="@android:style/Theme.NoTitleBar">
<item name="android:buttonStyle">@style/Button</item>
</style>
layout.xml
themes.xml

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Key benefits
Saves your time
Makes the code DRY (Do not Repeat Yourself)
→Separates the Look from UI structure is replacable

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Real world example (Corkbin)
Only one ImageView (and it's even shared)
4 widgets + window defined in theme
Benefit:
100 View definitions automatically styled
15 windows automatically styled

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Styles and inheritance
Explicit vs. Implicit (by name)
Plus
Saves a lot of copy-paste even for styling
Preserves much of the original
Minus
Various vendors provides various built-in resources
<style name="TextView" parent="@android:style/Widget.TextView">
<item name="android:textAppearance">@style/TextAppearance.Small</item>
</style>
<style name="TextView.shadow">
<item name="android:shadowColor">@color/black</item>
<item name="android:shadowDy">-1.0</item>
<item name="android:shadowRadius">1.0</item>
</style>
styles.xml

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When styles cannot help
Multiple inheritance
<style name="MyTextView" parent="@style/SomeTextView.Small" parent="@style/SomeTextView.Bold">
<item name="android:someOption">myOptionValue</item>
</style>

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When styles cannot help
Multiple inheritance
AlertDialog / ProgressDialog
loginDialog = new ProgressDialog(this);
loginDialog.setMessage(getString(R.string.l_logging));
loginDialog.setCancelable(false);
loginDialog.setIndeterminate(true);
loginDialog.setProgressStyle(R.style.my_color_progress);
loginDialog.setLabelStyle(R.style.my_progress_text_appearance);

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When styles cannot help
Multiple inheritance
AlertDialog / ProgressDialog
Dialog from Builder
AlertDialog f = new AlertDialog.Builder(this, R.drawable.my_supadupa_theme)
.setTitle(getText(R.string.l_error))
.setMessage(getText(R.string.msg_login_failed))
.setCancelable(true)
.setIcon(android.R.drawable.ic_dialog_alert)
.setPositiveButton(getText(R.string.l_ok), new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
})
.create();

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Agenda
Styles and themes
Life without PNGs
Q&A

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Where we use PNGs in app UI
app icons
action icons
window backgrounds
View component backgrounds (Button, EditText, ...)

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Where we use PNGs in app UI
app icons
action icons
window backgrounds
View component backgrounds (Button, EditText, …)
→Typical activity: 2 layouts x 3 DPIs a lot of PNGs

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Where we use PNGs in app UI
app icons
action icons
window backgrounds
View component backgrounds (Button, EditText, …)
→Typical activity: 2 layouts x 3 DPIs a lot of PNGs

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Shapes on the stage
Replace PNG with shape
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<stroke android:color="#88ffffff"
android:width="1px" />
<gradient android:startColor="#77111188"
android:centerColor="#88111155"
android:endColor="#99000000"
android:angle="-90" />
<corners android:radius="10dip" />
</shape>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<stroke android:color="#88000000"
android:width="1px" />
<solid android:color="#77555555" />
</shape>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#ff9999ee"
android:centerColor="#ffddddee"
android:endColor="#ffffffff"
android:angle="-90" />
</shape>

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What shapes do we have?
Rectange
Oval
Line
Ring

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9-patch vs. Shape
9-patch:
Round corners
Gradients
General stretchable areas
Built-in padding areas
Can explicitly use dither
Better support by SDK
Shape
Round corners
Gradients
Memory efficient
CPU efficient

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Real world example
c:geo – Geo-caching tool (by carnero_cc)

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Real world example
<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<stroke android:color="#66000000" android:width="1px" />
<solid android:color="#11000000" />
</shape>
Skin purely based on Shapes
Two skins – light & dark
All DPIs covered
Plenty of time saved
my_drawable.xml

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Key messages
Styles
save your time and get you more flexibility
Themes
save more of your time and get you even more flexibility
Shapes (if smartly used)
saves your time and your phone's battery

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Agenda
Styles and themes
Life without PNGs
Q&A

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Q & A

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References
http://developer.android.com/guide/topics/ui/themes.html
http://developer.android.com/guide/topics/resources/drawab
le-resource.html#Shape
https://github.com/carnero/c-geo/tree/master/res/
http://groups.google.com/
http://www.google.com/
http://www.stackoverflow.com/

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Thanks for your attention
Pavel Petřek
pavel@inmite.eu http://www.inmite.eu/ http://twitter.com/pavelpetrek