firka/flutter
firka/flutter
4
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Add doc for transparent image inside Opacity (#22278)

Browse Source
This commit is contained in:
liyuqian 2018-09-26 13:03:26 -07:00 committed by GitHub
parent 960d669897
commit 84c61ad640
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 16 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
packages/flutter/lib/src/widgets/basic.dart
View File

@ -143,12 +143,25 @@ class Directionality extends InheritedWidget {
/// This is more efficient than adding and removing the child widget from the
/// tree on demand.
///
/// ## Opacity Animation
/// ## Opacity animation
///
/// Animating an [Opacity] widget directly causes the widget (and possibly its
/// subtree) to rebuild each frame, which is not very efficient. Consider using
/// an [AnimatedOpacity] instead.
///
/// ## Transparent image
///
/// If only a single [Image] needs to be composited with an opacity between 0.0
/// and 1.0, it's much faster to directly use [Image] as following:
///
/// ```dart
/// Image(
/// image: image,
/// color: Color.fromRGBO(255, 255, 255, opacity),
/// colorBlendMode: BlendMode.modulate
/// )
/// ```
///
/// See also:
///
/// * [Visibility], which can hide a child more efficiently (albeit less
@ -161,6 +174,8 @@ class Directionality extends InheritedWidget {
/// animate opacity.
/// * [FadeTransition], which uses a provided animation to efficiently animate
/// opacity.
/// * [Image], which can directly provide a partially transparent image with
/// much less performance hit.
class Opacity extends SingleChildRenderObjectWidget {
/// Creates a widget that makes its child partially transparent.
///