popupwindo translate animation 从底部弹出 动画设置

先看一下 translate 用法解析

http://developer.android.com/intl/zh-cn/guide/topics/resources/animation-resource.html

A vertical and/or horizontal motion. Supports the following attributes in any of the following three formats: values from -100 to 100 ending with "%", indicating a percentage relative to itself; values from -100 to 100 ending in "%p", indicating a percentage relative to its parent; a float value with no suffix, indicating an absolute value. Represents a TranslateAnimation.

attributes:

android:fromXDelta

Float or percentage. Starting X offset. Expressed either: in pixels relative to the normal position (such as  "5"), in percentage relative to the element width (such as  "5%"), or in percentage relative to the parent width (such as  "5%p").

注意一句话：

Starting X offset......in pixels relative to the normal position

相对于 normal 位置。。。重点是怎么理解这个normal 

直白点就是popup最后显示的位置。。。。。。以这个点做基准点进行offset(偏移)的设置

比如如上图片的popupwindow 如果想希望他从底部慢慢弹出。。

先确定基准点A 其他相对位置的计算都是以A作为参照点

水平向右为x方向 垂直向下为y方向

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="500"
        android:fromYDelta="100%"
        android:toYDelta="0"/>
</set>

另外需要注意一下 popupWindow 动画的设置方法

 /**
     * <p>Change the animation style resource for this popup.</p>
     *
     * <p>If the popup is showing, calling this method will take effect only
     * the next time the popup is shown or through a manual call to one of
     * the {@link #update()} methods.</p>
     *
     * @param animationStyle animation style to use when the popup appears
     *      and disappears.  Set to -1 for the default animation, 0 for no
     *      animation, or a resource identifier for an explicit animation.
     *      
     * @see #update()
     */
    public void setAnimationStyle(int animationStyle) {
        mAnimationStyle = animationStyle;
    }

这个需要定义在style.xml里 而不是直接饮用anim文件

   <style name="popup_window_bottombar">
        <item name="android:windowEnterAnimation">@anim/....</item>
        <item name="android:windowExitAnimation">@anim/....</item>
    </style>