Tools of the Trade (Droidcon NYC 2015)

This talk will tour one of the most understated resources in the Android developer arsenal: the support tools.

Learn how to enrich your methods and classes using annotations, so that Lint and Android Studio will be able to spot errors for you. Or use IntelliJ annotations to define contracts, and let the IDE warn you of potential issues before you even run your code once. Take advantage of the tools namespace to bend even the most cryptic XML resource to your will.
----
Since this deck is quite heavy on the animations side, I've exported a video version of it as well, that you can find here: http://youtu.be/z9zyQwyO8l0
----
The talk video is now available here: https://www.youtube.com/watch?v=AeoeD7K8vKI

Transcript

1. TOOLS
   Sebastiano Poggi
   Novoda, Android GDE
   TRADE
   OF THE
   #toolsOfTrade
   

   View Slide

2. View Slide

3. View Slide

4. View Slide

5. View Slide

6. 1.3
   Android Studio
   

   View Slide

7. “How can this be a NPE?”
   “I wish things were strongly typed,
   all resource IDs look like any other integer!”
   

   View Slide

8. “How can this be a NPE?”
   “I wish things were strongly typed,
   all resource IDs look like any other integer!”
   “Why isn’t this text R.color.red?
   It’s showing as black!”
   

   View Slide

9. “How can this be a NPE?”
   “I wish things were strongly typed,
   all resource IDs look like any other integer!”
   “Why isn’t this text R.color.red?
   It’s showing as black!”
   “I love Eclipse!”
   

   View Slide

10. “How can this be a NPE?”
    “I wish things were strongly typed,
    all resource IDs look like any other integer!”
    “Why isn’t this text R.color.red?
    It’s showing as black!”
    “I love Eclipse!”
    “What? I thought this was on the
    

    View Slide

11. “How can this be a NPE?”
    “I wish things were strongly typed,
    all resource IDs look like any other integer!”
    “Why isn’t this text R.color.red?
    It’s showing as black!”
    “I love Eclipse!”
    “What? I thought this was on the
    UI thread, but it’s crashing”
    

    View Slide

12. Great news!*
    

    View Slide

13. Great news!*
    

    View Slide

14. Great news!*
    Annotations and XML attributes
    will save the day
    

    View Slide

15. SURPRISE
    QUESTION
    Lint
    

    View Slide

16. Lint
    Born in 1979 for C
    

    View Slide

17. Lint
    Born in 1979 for C
    Performs static code analysis
    

    View Slide

18. Lint
    Born in 1979 for C
    Performs static code analysis
    Should be part of your CI builds
    

    View Slide

19. Lint
    Born in 1979 for C
    Performs static code analysis
    Should be part of your CI builds
    

    View Slide

20. tools
    xmlns:
    

    View Slide

21. tools
    xmlns: namespac
    

    View Slide

22. tools
    xmlns: namespace
    Built into the SDK/Android Studio
    

    View Slide

23. tools namespace
    Built into the SDK/Android Studio
    Safe to commit under VCS
    

    View Slide

24. tools namespace
    Built into the SDK/Android Studio
    Safe to commit under VCS
    (Usually)
    

    View Slide

25. tools namespace
    Built into the SDK/Android Studio
    Safe to commit under VCS
    (Usually)
    

    View Slide

26. android:layout_width="wrap_content"

    android:layout_height="wrap_content"
    ...
    Design-time overrides
    Override any android attribute
    /> tools:text="Hello world!"
    

    View Slide

27. Design-time overrides
    Override any android attribute
    />
    tools:text="Hello world!"
    android:layout_width="wrap_content"

    android:layout_height="wrap_content"
    ...
    

    View Slide

28. Tools attributes
    Lint attributes
    

    View Slide

29. Tools attributes
    Lint attributes
    Design attributes
    

    View Slide

30. Tools attributes
    Lint attributes
    Design attributes
    

    View Slide

31. Tools attributes
    Lint attributes
    Design attributes
    

    View Slide

32. android:name=".MyApplication"

    android:label="Babou"
    ...
    />
    Should explicitly set allowBackup…
    Lint attribute: ignore
    Similar to @SuppressWarnings
    

    View Slide

33. />
    android:name=".MyApplication"

    android:label="Babou"
    ...
    Should explicitly set allowBackup…
    Lint attribute: ignore
    Similar to @SuppressWarnings
    tools:ignore="AllowBackup"
    

    View Slide

34. android:name=".MyApplication"

    android:label="Babou"
    ...
    Lint attribute: ignore
    Similar to @SuppressWarnings
    />
    tools:ignore="AllowBackup"
    tools:ignore="AllowBackup"
    

    View Slide

35. <br/>...<br/>Lint attribute: targetApi<br/>Equivalent to @TargetApi<br/>/><br/><item android:elevation="8dp"<br/> tools:targetApi="HONEYCOMB"
    android:elevation requires
    API level 21(current min is 19)
    

    View Slide

36. <br/>...<br/>Lint attribute: targetApi<br/>Equivalent to @TargetApi<br/>/><br/><item android:elevation="8dp"<br/> tools:targetApi="LOLLIPOP" />
    android:elevation requires
    API level 21(current min is 19)
    

    View Slide

37. <br/>...<br/>Lint attribute: targetApi<br/>Equivalent to @TargetApi<br/><item android:elevation="8dp"<br/>
    tools:targetApi="LOLLIPOP" />
    

    View Slide

38. Lint attribute: locale
    Helps spell checking
    Helo, I am a typo.
    
    >
    tools:locale="en">
    

    View Slide

39. Lint attribute: locale
    Helps spell checking
    Helo, I am a typo.
    
    tools:locale="en">
    

    View Slide

40. Tools attributes
    Lint attributes
    Design attributes
    

    View Slide

41. Design attribute: context
    Helps AS tying a layout to an Activity
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    ...
    
    >
    tools:context=".map.MapActivity"
    

    View Slide

42. Design attribute: context
    Helps AS tying a layout to an Activity
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    ...
    
    >
    tools:context=".map.MapActivity"
    

    View Slide

43. Design attribute: context
    Helps AS tying a layout to an Activity
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    tools:context=".map.MapActivity"
    ...
    
    >
    

    View Slide

44. Design attribute: showIn
    Shows a merge in its parent layout’s include
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    ...
    
    >
    tools:showIn="@layout/activity_main"
    

    View Slide

45. android:layout_width="match_parent"

    android:layout_height="match_parent"
    tools:showIn="@layout/activity_main"
    ...
    
    >
    Design attribute: showIn
    Shows a merge in its parent layout’s include
    

    View Slide

46. Design attribute: menu
    Shows a menu in the layout preview
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    ...
    
    >
    tools:menu="map"
    

    View Slide

47. android:layout_width="match_parent"

    android:layout_height="match_parent"
    tools:menu="map"
    ...
    
    >
    Design attribute: menu
    Shows a menu in the layout preview
    

    View Slide

48. Design attribute: actionBarNavMode
    Shows navigation in the action bar
    android:layout_width="match_parent"

    android:layout_height="match_parent"
    ...
    
    >
    tools:actionBarNavMode="tabs"
    

    View Slide

49. android:layout_width="match_parent"

    android:layout_height="match_parent"
    tools:actionBarNavMode="tabs"
    ...
    
    >
    Design attribute: actionBarNavMode
    Shows navigation in the action bar …in theory
    

    View Slide

50. android:layout_width="match_parent"

    android:layout_height="match_parent"
    Design attribute: layout
    Previews a fragment’s layout
    ...
    />
    tools:layout="@layout/fragment_main"
    

    View Slide

51. android:layout_width="match_parent"

    android:layout_height="match_parent"
    tools:layout="@layout/fragment_main"
    ...
    />
    Design attribute: layout
    Previews a fragment’s layout
    

    View Slide

52. Design attributes: list*
    Previews a ListView’s items, header and footer
    android:id="@+id/list"

    ...
    tools:listheader="@layout/list_header"

    tools:listitem="@layout/list_item"

    tools:listfooter="@layout/list_footer"
    />
    

    View Slide

53. android:id="@+id/list"

    ...
    Design attributes: list*
    Previews a ListView’s items, header and footer
    tools:listheader="@layout/list_header"

    tools:listitem="@layout/list_item"

    tools:listfooter="@layout/list_footer"
    />
    

    View Slide

54. Good read
    Tools of the Trade
    by Yours Truly
    https://goo.gl/hZv6S5
    https://goo.gl/sia3ms
    

    View Slide

55. Good read
    Tools attributes
    http://goo.gl/lzd6YP
    

    View Slide

56. Support annotations
    Require support-annotations dependency
    

    View Slide

57. Support annotations
    Require support-annotations dependency
    Design attributes
    support-v4 (and thus v7) depends on it
    

    View Slide

58. Support annotations
    Require support-annotations dependency
    support-v4 (and thus v7) depends on it
    

    View Slide

59. public static String trim(
    return what.trim();
    Nullability annotations
    @Nullable and @NonNull
    String what) {
    @Nullable
    }
    

    View Slide

60. Nullability annotations
    @Nullable and @NonNull
    String what) {
    @Nullable
    public static String trim(
    return what.trim();
    Method invocation may produce
    NullPointerException
    }
    

    View Slide

61. public static String trim(
    if (what == null) {

    return "";

    

    return what.trim();

    Nullability annotations
    @Nullable and @NonNull
    String what) {
    }
    }
    @NonNull
    

    View Slide

62. Nullability annotations
    @Nullable and @NonNull
    String what) {
    @NonNull
    }
    }
    public static String trim(
    if (what == null) {

    return "";

    

    return what.trim();

    Condition 'what == null' is always 'false'
    

    View Slide

63. setMainTextColor(R.color.text_color);

    

    void setMainTextColor(

    textView.setTextColor(getColor(colorId));
    Resource ID annotations
    A lot of @{resType}Res that enforce typing
    @Nullable
    Should pass resolved color instead of resource ID
    }
    int colorId) {
    

    View Slide

64. setMainTextColor(R.color.text_color);

    

    void setMainTextColor(

    textView.setTextColor(getColor(colorId));
    Resource ID annotations
    A lot of @{resType}Res that enforce typing
    @Nullable
    int colorId) {
    }
    @ColorRes
    

    View Slide

65. Resource ID annotations
    @AnimatorRes
    @AnimRes
    @AnyRes
    @ArrayRes
    @AttrRes
    @BoolRes
    @ColorRes
    @DimenRes
    @DrawableRes
    @FractionRes
    @IdRes
    @IntegerRes
    @InterpolatorRes
    @LayoutRes
    @MenuRes
    @PluralsRes
    @RawRes
    @StringRes
    @StyleableRes
    @StyleRes
    @XmlRes
    

    View Slide

66. setTextColor(R.color.text_color);

    

    private void setTextColor(

    ...
    RGB Color annotation
    @ColorInt requires color value, not ID
    }
    int color) {
    @ColorInt
    

    View Slide

67. setTextColor(R.color.text_color);

    

    private void setTextColor(

    ...
    RGB Color annotation
    @ColorInt requires color value, not ID
    }
    @ColorInt int color) {
    Should pass resolved color instead
    of resource id here
    

    View Slide

68. setValue(20);
    

    void setValue(

    // Value must be in [0, 10]
    Range annotations
    @FloatRange and @IntRange
    }
    int value) {
    @IntRange(from=0, to=10)
    

    View Slide

69. setValue(20);
    

    void setValue(

    // Value must be in [0, 10]
    Range annotations
    @FloatRange and @IntRange
    }
    int value) {
    @IntRange(from=0, to=10)
    Value must be ≥ 0 and ≤ 10 (was 20)
    

    View Slide

70. Range annotations
    setCoords(new int[]{42});
    

    void setCoords(

    // Value must be int[2]
    @Size for arrays, collections and strings
    }
    int[] value) {
    @Size(2)
    Value must be ≥ 0 and ≤ 10 (was 20)
    

    View Slide

71. Range annotations
    setCoords(new int[]{42});
    

    void setCoords(

    // Value must be int[2]
    @Size for arrays, collections and strings
    }
    int[] value) {
    @Size(2)
    Value must be ≥ 0 and ≤ 10 (was 20)
    Size must be exactly 2
    

    View Slide

72. int style;
    TypeDef annotations
    The issue with avoiding enums
    @IntRange(from=0, to=10)
    static final int STYLE_MATERIAL = 0;

    static final int STYLE_HOLOYOLO = 1;
    style = 21;
    

    View Slide

73. @IntDef(value={STYLE_MATERIAL, STYLE_HOLOYOLO})

    @Retention(RetentionPolicy.SOURCE)

    @interface Style { }
    TypeDef annotations
    @interface definition: @IntDef and @StringDef
    @IntRange(from=0, to=10)
    static final int STYLE_MATERIAL = 0;

    static final int STYLE_HOLOYOLO = 1;
    

    View Slide

74. style = 21;
    TypeDef annotations
    @interface usage
    @IntRange(from=0, to=10)
    Must be one of: STYLE_MATERIAL, STYLE_HOLOYOLO
    static final int STYLE_MATERIAL = 0;

    static final int STYLE_HOLOYOLO = 1;
    int style;
    @Style
    

    View Slide

75. static final int STYLE_MATERIAL = 0;

    static final int STYLE_HOLOYOLO = 1;
    TypeDef annotations
    @interface usage
    @IntRange(from=0, to=10)
    @Style int style;
    style = 21; Must be one of: STYLE_MATERIAL, STYLE_HOLOYOLO
    

    View Slide

76. Threading annotations
    Specify thread “affinity” for methods
    private void test() {

    textView.setText("Oops!");
    @WorkerThread
    }
    

    View Slide

77. Threading annotations
    Specify thread “affinity” for methods
    private void test() {

    textView.setText("Oops!");
    @WorkerThread
    Method setText must be called from the
    UI thread, currently inferred thread is
    worker
    }
    

    View Slide

78. Threading annotations
    Specify thread “affinity” for methods
    Method setText must be called from the
    UI thread, currently inferred thread is
    worker
    @MainThread
    @BinderThread
    @UiThread
    @WorkerThread
    

    View Slide

79. “Architecture” annotations
    Contracts for methods invocation and overriding
    @CallSuper @CheckResult @VisibleForTesting
    

    View Slide

80. Permissions annotations
    Specifies calling a method requires a permission
    startBluetoothScan();
    @RequiresPermission(Manifest.permission.BLUETOOTH)
    private void startBluetoothScan() { ... }
    

    View Slide

81. Permissions annotations
    Specifies calling a method requires a permission
    @RequiresPermission(Manifest.permission.BLUETOOTH)
    startBluetoothScan();
    private void startBluetoothScan() { ... }
    Missing permissions required by startBluetoothScan:
    android.permission.BLUETOOTH
    

    View Slide

82. Proguard annotation
    Specifies a symbol should be kept by Proguard
    @Keep
    private void myMethod() { ... }
    

    View Slide

83. Good read
    Improving Code Inspection
    with Annotations
    https://goo.gl/QLyf10
    

    View Slide

84. Good read
    Support annotations
    http://goo.gl/3DTImU
    

    View Slide

85. A
    &
    Q
    

    View Slide

86. View debugging
    BONUS
    ROUND
    

    View Slide

87. View debugging
    Built into the SDK since API 1
    

    View Slide

88. View debugging
    Built into the SDK since API 1
    ViewDebug
    

    View Slide

89. View debugging
    Built into the SDK since API 1
    ViewDebug
    

    View Slide

90. public class MyCustomView extends View {

    private int fancyColor;
    Exported view properties
    Use @ExportedProperty
    @Nullable
    public int getFancyColor() {

    return fancyColor;
    }
    @ViewDebug.ExportedProperty
    

    View Slide

91. public class MyCustomView extends View {

    private int fancyColor;
    Exported view properties
    Use @ExportedProperty
    @Nullable
    @ViewDebug.ExportedProperty
    public int getFancyColor() {

    return fancyColor;
    }
    

    View Slide

92. Exported view properties
    Use @ExportedProperty
    @Nullable
    (

    category = "My category"

    )
    public int getFancyColor() {

    return fancyColor;
    }
    @ViewDebug.ExportedProperty
    

    View Slide

93. Good read
    ViewDebug JavaDoc
    http://goo.gl/v54umV
    

    View Slide

94. A
    &
    Q
    (for real this time)
    (also, tweet questions @seebrock3r)
    

    View Slide

95. Thank you!
    @seebrock3r
    +SebastianoPoggi
    rock3r
    Sebastiano Poggi
    Novoda, Android GDE
    #toolsOfTrade
    

    View Slide