facebook/fresco

Overlay drawable alpha value not respected

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#1,905 建立於 2017年9月18日

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 (1 留言) (2 反應) (1 負責人)Java (17,072 star) (3,750 fork)batch import
buggood first issuehelp wanted

描述

Description

Reported via StackOverflow: https://stackoverflow.com/questions/45971482/translucent-image-overlay-drawable-loses-alpha

If you set an overlay drawable, the alpha value will always be set to 255, no matter what the actual alpha value is.

Reproduction

Drawable drawable = ...;
drawable.setAlpha(50);
draweeView.getHierarchy().setOverlayImage(drawable);

The alpha value of the drawable will be 255 instead of 50.

Solution

The reason for this is that a FadeDrawable holds all drawables of the drawee hierarchy and fades between them as needed - but does not respect initial alpha values.

Additional Information

  • Fresco version: 1.5.0
  • Platform version: All platforms

貢獻者指南

技術棧
javaandroid
領域
mobile
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
mostly clear
前置要求
JavaAndroid drawablesFresco library basics
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
60
研究方向
Investigate the FadeDrawable class in Fresco's source code to understand how it handles drawable alpha values. The issue points out that FadeDrawable resets alpha to 255 when setting overlay images. Look at the setAlpha and fade methods in FadeDrawable.java to see how initial alpha values are ignored. Consider modifying the constructor or adding a method to preserve the drawable's original alpha.