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106 lines
4.1 KiB
Markdown
106 lines
4.1 KiB
Markdown
<!--docs:
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title: "Badge"
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layout: detail
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section: components
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excerpt: "Badges can contain dynamic information, such as a number of pending requests."
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iconId: badge
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path: /catalog/badging/
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-->
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# `BadgeDrawable`
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## Using badges
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Badge | Badge with number | Badge with a maximum character count
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--------------------------------------------- | ---------------------------------------------------- | ------------------------------------
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 |  | 
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**Note:** This component is still under development and may not support the full
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range of customization Material Android components generally support, for
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instance, themed attributes.
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A `BadgeDrawable` represents dynamic information such as a number of pending
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requests in a [`BottomNavigationView`](BottomNavigation.md) or
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[`TabLayout`](Tabs.md).
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## Design & API Documentation
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- [Material Design guidelines: Bottom Navigation](https://material.io/design/components/bottom-navigation.html#behavior)
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- [Class definition](https://github.com/material-components/material-components-android/tree/master/lib/java/com/google/android/material/badge/BadgeDrawable.java)
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- [Class overview](https://developer.android.com/reference/com/google/android/material/badge/BadgeDrawable)
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## Usage
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Create an instance of `BadgeDrawable` by calling `create(Context)` or
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`createFromAttributes(Context, AttributeSet, int, int)}`.
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The approach used to add and display a `BadgeDrawable` on top of its anchor view
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depends on the API level:
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In API 18+ (APIs supported by
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[ViewOverlay](https://developer.android.com/reference/android/view/ViewOverlay))
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1. Add `BadgeDrawable` as a
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[ViewOverlay](https://developer.android.com/reference/android/view/ViewOverlay)
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to the desired anchor view.
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2. Update the `BadgeDrawable`'s coordinates (center and bounds) based on its
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anchor view using `#updateBadgeCoordinates(View)`.
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Both steps have been encapsulated in a util method:
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```java
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BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor);
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```
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In Pre API-18
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1. Set `BadgeDrawable` as the foreground of the anchor view's `FrameLayout`
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ancestor.
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2. Update the `BadgeDrawable`'s coordinates (center and bounds) based on its
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anchor view, relative to its `FrameLayout` ancestor's coordinate space.
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Option 1: `BadgeDrawable` will dynamically create and wrap the anchor view in a
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`FrameLayout`, then insert the `FrameLayout` into the original anchor view
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position in the view hierarchy. Same syntax as API 18+
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```java
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BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor);
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```
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Option 2: If you do not want `BadgeDrawable` to modify your view hierarchy, you
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can specify a `FrameLayout` to display the badge instead.
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```java
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* BadgeUtils.attachBadgeDrawable(badgeDrawable, anchor, anchorFrameLayoutParent);
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```
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### `BadgeDrawable` Gravity Modes
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`BadgeDrawable` provides four pre-packaged gravity modes that control how the
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badge aligns with its anchor view. By default (`TOP_END`) badge aligns with the
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top and end edges of the anchor (with some offsets). The other options are
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`TOP_START`, `BOTTOM_START` and `BOTTOM_END`.
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### `BadgeDrawable` center offsets
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By default, `BadgeDrawable` is aligned with the top and end edges of its anchor
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view (with some offsets). Call `setBadgeGravity(int)` to change it to one of the
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other supported modes. To adjust the badge's offsets relative to the anchor's
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center, use `setHoriziontalOffset(int)` or `setVerticalOffset(int)`
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### `BadgeDrawable` Attributes
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Feature | Relevant attributes
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------------- | -----------------------------------------------
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Color | `app:backgroundColor` <br> `app:badgeTextColor`
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Label | `app:number`
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Label Length | `app:maxCharacterCount`
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Badge Gravity | `app:badgeGravity`
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### Talkback Support
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`BadgeDrawable` provides a getter for its content description, which is based on
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the number (if any) displayed. Users should specify content description:
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`setContentDescriptionNumberless(CharSequence)`
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`setContentDescriptionQuantityStringsResource(@StringRes)`
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