当在android中按下后退按钮时，白屏会显示一段时间

Question

我在我的Android应用程序中使用了黑色主题，我不明白为什么我按下后退按钮时会出现白屏。谁能告诉我为什么会这样？

 <application
    android:name="com.sample.ApplicationClass"
    android:allowBackup="false"
    android:debuggable="true"
    android:hardwareAccelerated="true"
    android:icon="@drawable/appicon"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >

以下是我的风格定义                    

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">

    <!-- All customizations that are NOT specific to a particular API-level can go here. -->
    <item name="android:progressBarStyleHorizontal">@style/ProgressBarAppTheme</item>
    <item name="android:seekBarStyle">@style/SeekBarAppTheme</item>
</style>

  <!--
    Base application theme, dependent on API level. This theme is replaced
    by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
-->
<style name="AppBaseTheme" parent="@android:style/Theme.Black">
    <!--
        Theme customizations available in newer API levels can go in
        res/values-vXX/styles.xml, while customizations related to
        backward-compatibility can go here.
    -->
</style>
<!-- CUSTOM SEEK BAR THEME -->
<style name="SeekBarAppTheme" parent="android:Widget.SeekBar">
    <item name="android:progressDrawable">@drawable/apptheme_scrubber_progress_horizontal_holo_light</item>
    <item name="android:indeterminateDrawable">@drawable/apptheme_scrubber_progress_horizontal_holo_light</item>
    <item name="android:minHeight">13dip</item>
    <item name="android:maxHeight">13dip</item>
    <item name="android:thumb">@drawable/apptheme_scrubber_control_selector_holo_light</item>
    <item name="android:thumbOffset">16dip</item>
    <item name="android:paddingLeft">16dip</item>
    <item name="android:paddingRight">16dip</item>
</style>

<!-- CUSTOM PROGRESS BAR THEME -->
<style name="ProgressBarAppTheme" parent="android:Widget.ProgressBar.Horizontal">
    <item name="android:progressDrawable">@drawable/apptheme_progress_horizontal_holo_light</item>
    <item name="android:indeterminateDrawable">@drawable/apptheme_progress_indeterminate_horizontal_holo_light</item>
    <item name="android:minHeight">16dip</item>
    <item name="android:maxHeight">16dip</item>
</style>

以下是我的应用截图