沉浸式状态栏的探讨
1. 常规theme
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<!-- 下面这句是默认情况 -->
<!--<item name="android:windowTranslucentStatus">false</item>-->
</style>
default.png
2. windowTranslucentStatus true
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="android:windowTranslucentStatus">true</item>
</style>
可以看出状态栏已经是半透明了
windowTranslucentStatus.png
3. android:statusBarColor = @android:color/transparent
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<!--<item name="android:windowTranslucentStatus">true</item>-->
<item name="android:windowTranslucentStatus">false</item>
<item name="android:statusBarColor">@android:color/transparent</item>
</style>
在2的基础上设置状态栏为全透明，注意：这里图片和网页背景冲突，实际上状态栏变成了全白色
statusBarTransparent.png
4. 3的解决方案，windowTranslucentNavigation = true
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="android:windowTranslucentStatus">false</item>
<item name="android:statusBarColor">@android:color/transparent</item>
<item name="android:windowTranslucentNavigation">true</item>
</style>
可以看出状态栏已经变成了全透明色，不过也可以看见navigation bar变成了半透明色
excellent.png
5. 不过设置全透明的navigation bar
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="android:windowTranslucentStatus">false</item>
<item name="android:statusBarColor">@android:color/transparent</item>
<item name="android:windowTranslucentNavigation">true</item>
<item name="android:navigationBarColor">@android:color/transparent</item>
</style>
并没有任何变化
transparentNavigation.png
6. 那尝试设置其他颜色呢？
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="android:windowTranslucentStatus">false</item>
<item name="android:statusBarColor">@android:color/transparent</item>
<item name="android:windowTranslucentNavigation">true</item>
<item name="android:navigationBarColor">@android:color/holo_blue_bright</item>
</style>
并没有效果，猜测，设置了透明操作栏之后，并不允许再设置操作栏的颜色
blueNavigation.png
7. 那回到原点，设置状态栏颜色和操作栏颜色呢
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="android:statusBarColor">@android:color/holo_blue_dark</item>
<item name="android:navigationBarColor">@android:color/holo_blue_dark</item>
</style>
colorPrimaryDark没有效果了，直接设置状态栏的颜色即可
blueAll.png
8. 全屏theme, 这个最简单
<style name="FlagTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:windowFullscreen">true</item>
</style>
但是还是有操作栏
fullscreen.png
9. 隐藏操作栏
使用theme是无法实现这个效果的，只有通过代码
Window window = getWindow();
window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_FULLSCREEN | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
根据google的说明，navigation非常重要，只是一个临时的flag, 只要用户有任何操作，都会被清除。
/**
* Flag for {@link #setSystemUiVisibility(int)}: View has requested that the
* system navigation be temporarily hidden.
*
* <p>This is an even less obtrusive state than that called for by
* {@link #SYSTEM_UI_FLAG_LOW_PROFILE}; on devices that draw essential navigation controls
* (Home, Back, and the like) on screen, <code>SYSTEM_UI_FLAG_HIDE_NAVIGATION</code> will cause
* those to disappear. This is useful (in conjunction with the
* {@link android.view.WindowManager.LayoutParams#FLAG_FULLSCREEN FLAG_FULLSCREEN} and
* {@link android.view.WindowManager.LayoutParams#FLAG_LAYOUT_IN_SCREEN FLAG_LAYOUT_IN_SCREEN}
* window flags) for displaying content using every last pixel on the display.
*
* <p>There is a limitation: because navigation controls are so important, the least user
* interaction will cause them to reappear immediately. When this happens, both
* this flag and {@link #SYSTEM_UI_FLAG_FULLSCREEN} will be cleared automatically,
* so that both elements reappear at the same time.
*
* @see #setSystemUiVisibility(int)
*/
public static final int SYSTEM_UI_FLAG_HIDE_NAVIGATION = 0x00000002;
There is a limitation: because navigation controls are so important, the least user
interaction will cause them to reappear immediately. When this happens, both
this flag and {@link #SYSTEM_UI_FLAG_FULLSCREEN} will be cleared automatically,
so that both elements reappear at the same time.
翻译：
这存在一个限制，因为操作栏的控制非常重要，所以用户的任何操作都会让它显示出来。
在这种情况下，当操作栏显示出来之后，这个flag和`SYSTEM_UI_FLAG_FULLSCREEN`将会被自动清除。
所以，所有的元素将同时出现
