CODEWITHSUNDEEP
javaandroidandroid-annotations
Grisgram
Grisgram

Reputation: 3253

Android Support Annotation "should have @Retention(RetentionPolicy.SOURCE)"

I am using the @Retention and @StringDef annotations for some of my methods in a library and I face a strange warning, I want to understand.

In a static class, SIP, I use this annotation:

public static final String CODEC_SPEEX_16K  = "speex/16000/1";
public static final String CODEC_SPEEX_8K   = "speex/8000/1";
public static final String CODEC_SPEEX_32K  = "speex/32000/1";
public static final String CODEC_ILBC_8K    = "iLBC/8000/1";
public static final String CODEC_GSM_8K     = "GSM/8000/1";
public static final String CODEC_PCMU_8K    = "PCMU/8000/1";
public static final String CODEC_PCMA_8K    = "PCMA/8000/1";
public static final String CODEC_G722_16K   = "G722/16000/1";

@Retention(RetentionPolicy.CLASS)
@StringDef({
    CODEC_SPEEX_16K,
    CODEC_SPEEX_8K,
    CODEC_SPEEX_32K,
    CODEC_ILBC_8K,
    CODEC_GSM_8K,
    CODEC_PCMU_8K,
    CODEC_PCMA_8K,
    CODEC_G722_16K
    })
public @interface CodecName {}

which compiles fine, without any warnings.

In the static class Tools I use this annotation:

public static final String RES_TYPE_STRING = "string";
public static final String RES_TYPE_DRAWABLE = "drawable";
public static final String RES_TYPE_LAYOUT = "layout";
public static final String RES_TYPE_VIEW = "id";
public static final String RES_TYPE_DIMEN = "dimen";
public static final String RES_TYPE_COLOR = "color";
public static final String RES_TYPE_ANIM = "anim";
public static final String RES_TYPE_MIPMAP = "mipmap";

@Retention(RetentionPolicy.CLASS)
@StringDef({
    RES_TYPE_STRING,
    RES_TYPE_DRAWABLE,
    RES_TYPE_LAYOUT,
    RES_TYPE_DIMEN,
    RES_TYPE_COLOR,
    RES_TYPE_ANIM,
    RES_TYPE_VIEW,
    RES_TYPE_MIPMAP
})
public @interface ResourceType {
}

and I get the warning:

The typedef annotation ....toolbox.Tools.ResourceType should have @Retention(RetentionPolicy.SOURCE)

It seems to be uncritical, everything works fine. But can someone please explain me, why

Annotation#1 does not get a warning ;

Annotation#2 gets a warning;

Both are built identical, both only used in static context. From my point of view, both are the same.

Upvotes: 22

Views: 3173

Answers (1)

Mohammad Misbah
Mohammad Misbah

Reputation: 1084

Typedef annotations Typedef annotations check whether a particular parameter, return value, or field references a specific set of constants. They also enable code completion to automatically offer the allowed constants.

Use the @IntDef and @StringDef annotations to create enumerated annotations of integer and string sets to validate other types of code references.

Typedef annotations use @interface to declare the new enumerated annotation type. The @IntDef and @StringDef annotations, along with @Retention, annotate the new annotation and are necessary to define the enumerated type. The @Retention(RetentionPolicy.SOURCE) annotation tells the compiler not to store the enumerated annotation data in the .class file.

The following example shows the steps to create an annotation that checks whether a value passed as a method parameter references one of the defined constants:

import androidx.annotation.IntDef
//...
// Define the list of accepted constants and declare the NavigationMode annotation.
@Retention(AnnotationRetention.SOURCE)
@IntDef(NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, NAVIGATION_MODE_TABS)
annotation class NavigationMode

// Declare the constants.
const val NAVIGATION_MODE_STANDARD = 0
const val NAVIGATION_MODE_LIST = 1
const val NAVIGATION_MODE_TABS = 2

abstract class ActionBar {

    // Decorate the target methods with the annotation.
    // Attach the annotation.
    @get:NavigationMode
    @setparam:NavigationMode
    abstract var navigationMode: Int

}

When you build this code, a warning is generated if the mode parameter doesn't reference one of the defined constants (NAVIGATION_MODE_STANDARD, NAVIGATION_MODE_LIST, or NAVIGATION_MODE_TABS).

Combine @IntDef and @IntRange to indicate that an integer can be either a given set of constants or a value within a range.

Upvotes: 0

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