如何滚动时使像谷歌播放淡入在动作条 [英] How to make a ActionBar like Google Play that fades in when scrolling

问题描述

如何制作透明或半透明的动作条，如谷歌播放淡入或缩小使用滚动时 windowActionBarOverlay ？

How to make transparent or translucent ActionBar like Google Play that fades in or out when scrolling using windowActionBarOverlay?

查看下面的截图

推荐答案

以下是code我用的app我的工作

The following is the code I used in the app I am working

您必须使用 OnScrollChanged 功能在滚动型。 动作条不会让你设置不透明度，所以设置在动作条背景绘制，你可以根据滚动的滚动视图量改变其不透明度。我给一个工作流程示例

You will have to use the OnScrollChanged function in your ScrollView. ActionBar doesn't let you set the opacity , so set a background drawable on the actionbar and you can change its opacity based on the amount of scroll in the scrollview. I have given an example workflow

该函数集给出了适当的字母的观点locationImage基于其位置WRT窗口。

The function sets gives the appropriate alpha for the view locationImage based on its position WRT window .

this.getScrollY（）给你多少滚动视图已滚动

public void OnScrollChanged(int l, int t, int oldl, int oldt) {
    // Code ...
    locationImage.setAlpha(getAlphaForView(locationImageInitialLocation- this.getScrollY()));
}


private float getAlphaForView(int position) {
    int diff = 0;
    float minAlpha = 0.4f, maxAlpha = 1.f;
    float alpha = minAlpha; // min alpha
    if (position > screenHeight)
        alpha = minAlpha;
    else if (position + locationImageHeight < screenHeight)
        alpha = maxAlpha;
    else {
        diff = screenHeight - position;
        alpha += ((diff * 1f) / locationImageHeight)* (maxAlpha - minAlpha); // 1f and 0.4f are maximum and min
                                            // alpha
        // this will return a number betn 0f and 0.6f
    }
    // System.out.println(alpha+" "+screenHeight +" "+locationImageInitialLocation+" "+position+" "+diff);
    return alpha;
}

编辑：我已经添加了一个例子工作的样品在 https://github.com/ramanadv/fadingActionBar ，你可以有看看吧。

EDIT : I have added an example working sample at https://github.com/ramanadv/fadingActionBar , you can have a look at it.

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