Android 中framework层替换系统progressbar

    在framework层，系统定义的progressbar位于frameworks\base\core\res\res\values\styles.xml文件中定义:

 <style name="Widget.ProgressBar">
        <item name="android:indeterminateOnly">true</item>
        <item name="android:indeterminateDrawable">@android:drawable/progress_medium_white</item>
        <item name="android:indeterminateBehavior">repeat</item>
        <item name="android:indeterminateDuration">3500</item>
        <item name="android:minWidth">48dip</item>
        <item name="android:maxWidth">48dip</item>
        <item name="android:minHeight">48dip</item>
        <item name="android:maxHeight">48dip</item>
        <item name="android:mirrorForRtl">false</item>
    </style>

    <style name="Widget.ProgressBar.Large">
        <item name="android:indeterminateDrawable">@android:drawable/progress_large_white</item>
        <item name="android:minWidth">76dip</item>
        <item name="android:maxWidth">76dip</item>
        <item name="android:minHeight">76dip</item>
        <item name="android:maxHeight">76dip</item>
    </style>
    
    <style name="Widget.ProgressBar.Small">
        <item name="android:indeterminateDrawable">@android:drawable/progress_small_white</item>
        <item name="android:minWidth">16dip</item>
        <item name="android:maxWidth">16dip</item>
        <item name="android:minHeight">16dip</item>
        <item name="android:maxHeight">16dip</item>
    </style>

     其中"android:indeterminateDrawable"属性定义了progressbar的动画效果，progress_small_white定义在frameworks\base\core\res\res\drawable\下，自定义动画其实就是在drawable文件夹下自定义新的动画文件。

    <?xml version="1.0" encoding="utf-8"?>
<!--
/*
**
** Copyright 2009, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0 **
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
-->
<animated-rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/spinner_black_48"
android:pivotX="50%"
android:pivotY="50%"
android:framesCount="12"
android:frameDuration="100" />

    系统定义的为属性动画，我们可以自己更换一张图片就行旋转，或者定义其他动画，包括帧动画来实现更复杂的动画效果。注意在新建帧动画时，要把帧动画的每一张图片在public.xml下进行注册，不能直接模仿系统的定义方法。