Using styles and themes without going crazy

Presented at Droidcon NYC 2015.

1. Using styles and themes without going crazy Dan Lew
2. • No style <View android:background=“#FF0000” /> • Style <!--- some_layout.xml --> <View style="@style/MyStyle" /> <!--- styles.xml -->
 <style name="MyStyle">
 <item name="android:background">#FF0000</item>
 </style>
3. When to style • Semantically identical Views • All styled Views should change at once
4. When NOT to style • Single-use styles • Coincidentally using the same attributes <TextView
 android:id="@+id/title"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
 
 <TextView
 android:id="@+id/body"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
5. When NOT to style • Single-use styles • Coincidentally using the same attributes <TextView
 android:id="@+id/title"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
 
 <TextView
 android:id="@+id/body"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
6. When NOT to style • Single-use styles • Coincidentally using the same attributes <TextView
 android:id="@+id/title"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
 
 <TextView
 android:id="@+id/body"
 android:textColor="@color/blue_200"
 android:textColorHint=“@color/grey_500" />
7. static final int NUM_COLUMNS = 3;
 
 static final int NUM_RETRIES = 3; static final int NUM_THREE = 3;
8. // static final int NUM_COLUMNS = 3;
 
 // static final int NUM_RETRIES = 3;
 static final int NUM_THREE = 3;
9. No style? <ImageView
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:scaleType="centerCrop"
 android:src="@drawable/image"
 /> No problem!
12. Inheritance
13. • Parent <style name="Parent" /> • Explicit child <style name="Child" parent="Parent" /> • Implicit child <style name="Parent.Child" />
14. Custody Battle <style name="Implicit" />
 
 <style name="Explicit" /> <style name="Implicit.Child" parent="Explicit" /> • Who gets the child? • Choices: • Both • Implicit • Explicit
16. Avoid mixing implicit and explicit parenting
17. <Button
 style="@style/Widget.Button.Calculator"
 /> <style name="Widget.Button.Calculator"
 parent="Widget.AppCompat.Button.Borderless" />
18. <Button
 style="@style/Widget.Button.Calculator"
 /> <style name="Widget.Button.Calculator"
 parent="Widget.HahaFooledYou.Sucker" />
19. • Explicit parent -> dotless child <style name="BorderlessButton"
 parent="Widget.AppCompat.Button.Borderless" /> • Fake it! <style name="Widget.Button"
 parent="Widget.AppCompat.Button" />
 
 <style name="Widget.Button.Borderless"
 parent="Widget.AppCompat.Button.Borderless" />
20. Multiple Styles
21. IMPOSSIBLE …except for TextAppearance! Image source: https://goo.gl/meSNFL
22. TextAppearance Attributes • textColor • textColorHighlight • textColorHint • textColorLink • textSize • textStyle • fontFamily • typeface • textAllCaps • shadowColor • shadowDx • shadowDy • shadowRadius • elegantTextHeight • letterSpacing • fontFeatureSettings
23. TextAppearance • In action <TextView
 style="@style/MyStyle"
 android:textAppearance="@style/MyText"
 /> • Always inherit TextAppearance! <style name="MyText" parent="TextAppearance.AppCompat">
 <item name="android:textColor">#F00</item>
 </style>
24. Themes! • Write a whole lot of UX code at once! • Setup defaults for everything! • Activity-level theming! • Configure system-created Views! • Theme swapping!
25. Themes vs. Styles • Same thing! <style name="Style">
 <item name="android:background">#FF0000</item>
 </style> <style name="Theme">
 <item name="android:statusBarColor">@color/blue_200</item>
 </style> • Different scope • Different attributes
26. Do not mix up styles and themes
27. Themes in Manifest • Application <application
 android:theme="@style/Theme.AppCompat"> • Activity <activity
 android:theme="@style/Theme.AppCompat.Light">
28. Applying to View <Toolbar
 android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
 app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
 />
30. Use AppCompat
31. Use AppCompat • Material on all devices • Baseline themes/styles • Enables View theming pre-Lollipop • …And more!
32. Window Attributes <style name="AppTheme" parent="Theme.AppCompat">
 <item name="android:windowBackground">@color/background</item>
 <item name="android:statusBarColor">@color/blue_200</item>
 <item name="android:windowFullscreen">true</item>
 </style>
33. Color Attributes <style name="ColorTheme" parent="Theme.AppCompat">
 <item name="colorPrimary">#F00</item>
 <item name="colorPrimaryDark">#0F0</item>
 <item name="colorControlNormal">#00F</item>
 </style>
34. Default Styles <style name="AppTheme" parent="Theme.AppCompat">
 <item name="buttonStyle">@style/MyButton</item>
 <item name="android:spinnerItemStyle">@style/MySpinnerItem</item>
 
 <item name="android:textAppearance">@style/MyText</item>
 <item name="android:textAppearanceInverse">@style/MyTextInverse</item>
 </style>
35. Resource Attributes <style name="AttrTheme" parent="Theme.AppCompat">
 <item name="selectableItemBackground">@drawable/bg</item>
 </style> <!-- some_layout.xml -->
 <Button android:background="?attr/selectableItemBackground" />
36. Resource Attributes <style name="AttrTheme" parent="Theme.AppCompat">
 <item name="selectableItemBackground">@drawable/bg</item>
 </style> <!-- some_layout.xml -->
 <Button android:background="?attr/selectableItemBackground" />
37. Namespacing • Official attributes <style name="MyTheme">
 <item name="android:colorPrimary">#000</item>
 </style> • Custom attributes <style name="MyTheme" parent="Theme.AppCompat">
 <item name="colorPrimary">#000</item>
 </style> v21 only appcompat magic
38. Finding Attributes • Most difficult part of themes • Anyone can create attributes • Anything can use attributes
39. Attributes in XML • Look for ?attr or ?android:attr <Button android:background="?attr/selectableItemBackground" />
40. Individual Attributes • Look for resolveAttribute() context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true); attribute
41. View Style Attributes • Look for obtainStyledAttributes() TypedArray a = context.obtainStyledAttributes(attrs,
 com.android.internal.R.styleable.ImageView, defStyleAttr, defStyleRes); • Investigate TypedArray usage int alpha = a.getInt(com.android.internal.R.styleable.ImageView_drawableAlpha, 255); attribute default
42. What color is what?
43. Debug Color Theme
44. Color By Numbers https://goo.gl/BPNhp1
45. HierarchyViewer
46. Dump Theme
47. Recipe for Sanity • Use AppCompat • Modify theme first • Reference theme attributes • Apply themes to Views when necessary • Use styles wisely
48. Resource Qualifiers
49. <style name="MyTheme" parent="Theme.AppCompat">
 <item name="android:windowBackground">@color/bg_window</item>
 </style> <!-- values/colors.xml -->
 <color name="bg_window">#FF0000</color>
 
 <!-- values-v21/colors.xml -->
 <color name="bg_window">#0000FF</color>
50. <!-- values/styles.xml -->
 <style name="BaseToolbar" />
 
 <!-- values-v21/styles.xml -->
 <style name="BaseToolbar">
 <item name="android:elevation">4dp</item>
 </style> <!-- values/styles.xml -->
 <style name="Toolbar" parent="BaseToolbar" /> <!-- values/styles.xml -->
 <style name="BaseToolbar" />
 
 <!-- values-v21/styles.xml -->
 <style name="BaseToolbar">
 <item name="android:elevation">4dp</item>
 </style>
51. Qualifier Triangle values/Theme values-v21/Theme Theme.Used qualifier modifications what is actually used
52. Qualifier Diamond values/Theme.Platform values-v21/Theme.Platform Theme.Platform.Used values/Theme attributes for everyone what is actually used qualifier modifications
53. Custom Attributes <!-- values/attrs.xml -->
 <attr name="myAttribute" format="dimension" />
 
 <!-- values/themes.xml -->
 <style name="MyTheme" parent="Theme.AppCompat">
 <item name="myAttribute">4dp</item>
 </style>
 
 <!-- values/styles.xml -->
 <style name="MyStyle">
 <item name="android:padding">?attr/myAttribute</item>
 </style>
54. Custom Attributes <!-- values/attrs.xml -->
 <attr name="myAttribute" format="dimension" />
 
 <!-- values/themes.xml -->
 <style name="MyTheme" parent="Theme.AppCompat">
 <item name="myAttribute">4dp</item>
 </style>
 
 <!-- values/styles.xml -->
 <style name="MyStyle">
 <item name="android:padding">?attr/myAttribute</item>
 </style>
55. Custom Attributes <!-- values/attrs.xml -->
 <attr name="myAttribute" format="dimension" />
 
 <!-- values/themes.xml -->
 <style name="MyTheme" parent="Theme.AppCompat">
 <item name="myAttribute">4dp</item>
 </style>
 
 <!-- values/styles.xml -->
 <style name="MyStyle">
 <item name="android:padding">?attr/myAttribute</item>
 </style>
56. Dynamic Text Appearance myTextView.setTextAppearance(context, R.style.TextAppearance_AppCompat);
57. Dynamic Styles public View(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) themed context layout attributes default style (v21+) default style attribute (from theme, e.g. buttonStyle)
58. Dynamic Styles • Context carries theme • ContextThemeWrapper replaces parts of theme Context themedContext = new ContextThemeWrapper(baseContext, R.style.MyTheme);
 
 // Use in LayoutInflater
 View view = LayoutInflater.from(themedContext) .inflate(R.layout.my_layout, null);
 
 // Use in View constructor
 View view = new View(themedContext);
59. Dynamic Theming • setTheme() • Call before setContentView() • Otherwise, restart Activity
60. Thank You! • @danlew42 • +DanielLew • http://danlew.net • Color debug theme: https://goo.gl/BPNhp1