Android系统UI显示图层控制方法

        做系统层开发，往往会遇到UI显示图层的一些设置，比如一些界面可以直接被其他界面遮挡，有些界面只能被部分界面遮挡，甚至有些界面需要置顶不被任何界面遮挡；每个界面就是一个Window（窗口），是Window就受WindowManager管理，WindowManager中存在对应的LayoutParams（布局属性），通过设置这些属性可以控制Window的类型，Window的类型中自然就包含其显示图层的控制。

        说到这儿我还想谈谈自己对Window的理解，顾名思义它就是一个窗口，这个窗口里面可以包含一些布局，布局中又可以包含一些View控件，整个组成一个可以展示出来供人交互的界面。Android的界面显示是一个三维空间，x,y轴控制需要展示的界面的大小，z轴控制界面显示的图层，这就存在界面显示优先级的说法了。

        下面简单的介绍下Window的优先级的设置方法：

private Window mWindow;

mWindow = getWindow();

mWindow.setType(WindowManager.LayoutParams.TYPE_SYSTEM_DIALOG); // 各种参数的优先级级别请参考下面Android源码

        adb shell进去执行以下指令可以看到Window所在layer：

        dumpsys -l  ：列出所有可以查看的类型

        dumpsys window ：列出所有正在运行的window相关参数，Surface: shown=true layer=161000 alpha=1.0 rect=(0.0,0.0) 1920.0 x 1.0参数有图层的大小

        dumpsys SurfaceFlinger ：界面显示的层叠关系会必现的比较直观

/**
* Start of window types that represent normal application windows.
*/
public static final int FIRST_APPLICATION_WINDOW = 1;

/**
* Window type: an application window that serves as the "base" window
* of the overall application; all other application windows will
* appear on top of it.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_BASE_APPLICATION   = 1;

/**
* Window type: a normal application window.  The {@link #token} must be
* an Activity token identifying who the window belongs to.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_APPLICATION        = 2;

/**
* Window type: special application window that is displayed while the
* application is starting.  Not for use by applications themselves;
* this is used by the system to display something until the
* application can show its own windows.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_APPLICATION_STARTING = 3;

/**
* End of types of application windows.
*/
public static final int LAST_APPLICATION_WINDOW = 99;

/**
* Start of types of sub-windows.  The {@link #token} of these windows
* must be set to the window they are attached to.  These types of
* windows are kept next to their attached window in Z-order, and their
* coordinate space is relative to their attached window.
*/
public static final int FIRST_SUB_WINDOW        = 1000;

/**
* Window type: a panel on top of an application window.  These windows
* appear on top of their attached window.
*/
public static final int TYPE_APPLICATION_PANEL  = FIRST_SUB_WINDOW;

/**
* Window type: window for showing media (such as video).  These windows
* are displayed behind their attached window.
*/
public static final int TYPE_APPLICATION_MEDIA  = FIRST_SUB_WINDOW+1;

/**
* Window type: a sub-panel on top of an application window.  These
* windows are displayed on top their attached window and any
* {@link #TYPE_APPLICATION_PANEL} panels.
*/
public static final int TYPE_APPLICATION_SUB_PANEL = FIRST_SUB_WINDOW+2;

/** Window type: like {@link #TYPE_APPLICATION_PANEL}, but layout
* of the window happens as that of a top-level window, <em>not</em>
* as a child of its container.
*/
public static final int TYPE_APPLICATION_ATTACHED_DIALOG = FIRST_SUB_WINDOW+3;

/**
* Window type: window for showing overlays on top of media windows.
* These windows are displayed between TYPE_APPLICATION_MEDIA and the
* application window.  They should be translucent to be useful.  This
* is a big ugly hack so:
* @hide
*/
public static final int TYPE_APPLICATION_MEDIA_OVERLAY  = FIRST_SUB_WINDOW+4;

/**
* End of types of sub-windows.
*/
public static final int LAST_SUB_WINDOW         = 1999;

/**
* Start of system-specific window types.  These are not normally
* created by applications.
*/
public static final int FIRST_SYSTEM_WINDOW     = 2000;

/**
* Window type: the status bar.  There can be only one status bar
* window; it is placed at the top of the screen, and all other
* windows are shifted down so they are below it.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_STATUS_BAR         = FIRST_SYSTEM_WINDOW;

/**
* Window type: the search bar.  There can be only one search bar
* window; it is placed at the top of the screen.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_SEARCH_BAR         = FIRST_SYSTEM_WINDOW+1;

/**
* Window type: phone.  These are non-application windows providing
* user interaction with the phone (in particular incoming calls).
* These windows are normally placed above all applications, but behind
* the status bar.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_PHONE              = FIRST_SYSTEM_WINDOW+2;

/**
* Window type: system window, such as low power alert. These windows
* are always on top of application windows.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_SYSTEM_ALERT       = FIRST_SYSTEM_WINDOW+3;

/**
* Window type: keyguard window.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_KEYGUARD           = FIRST_SYSTEM_WINDOW+4;

/**
* Window type: transient notifications.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_TOAST              = FIRST_SYSTEM_WINDOW+5;

/**
* Window type: system overlay windows, which need to be displayed
* on top of everything else.  These windows must not take input
* focus, or they will interfere with the keyguard.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_SYSTEM_OVERLAY     = FIRST_SYSTEM_WINDOW+6;

/**
* Window type: priority phone UI, which needs to be displayed even if
* the keyguard is active.  These windows must not take input
* focus, or they will interfere with the keyguard.
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_PRIORITY_PHONE     = FIRST_SYSTEM_WINDOW+7;

/**
* Window type: panel that slides out from the status bar
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_SYSTEM_DIALOG      = FIRST_SYSTEM_WINDOW+8;

/**
* Window type: dialogs that the keyguard shows
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_KEYGUARD_DIALOG    = FIRST_SYSTEM_WINDOW+9;

/**
* Window type: internal system error windows, appear on top of
* everything they can.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_SYSTEM_ERROR       = FIRST_SYSTEM_WINDOW+10;

/**
* Window type: internal input methods windows, which appear above
* the normal UI.  Application windows may be resized or panned to keep
* the input focus visible while this window is displayed.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_INPUT_METHOD       = FIRST_SYSTEM_WINDOW+11;

/**
* Window type: internal input methods dialog windows, which appear above
* the current input method window.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_INPUT_METHOD_DIALOG= FIRST
b279
_SYSTEM_WINDOW+12;

/**
* Window type: wallpaper window, placed behind any window that wants
* to sit on top of the wallpaper.
* In multiuser systems shows only on the owning user's window.
*/
public static final int TYPE_WALLPAPER          = FIRST_SYSTEM_WINDOW+13;

/**
* Window type: panel that slides out from over the status bar
* In multiuser systems shows on all users' windows.
*/
public static final int TYPE_STATUS_BAR_PANEL   = FIRST_SYSTEM_WINDOW+14;

/**
* Window type: secure system overlay windows, which need to be displayed
* on top of everything else.  These windows must not take input
* focus, or they will interfere with the keyguard.
*
* This is exactly like {@link #TYPE_SYSTEM_OVERLAY} except that only the
* system itself is allowed to create these overlays.  Applications cannot
* obtain permission to create secure system overlays.
*
* In multiuser systems shows only on the owning user's window.
* @hide
*/
public static final int TYPE_SECURE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW+15;

/**
* Window type: the drag-and-drop pseudowindow.  There is only one
* drag layer (at most), and it is placed on top of all other windows.
* In multiuser systems shows only on the owning user's window.
* @hide
*/
public static final int TYPE_DRAG               = FIRST_SYSTEM_WINDOW+16;

/**
* Window type: panel that slides out from under the status bar
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_STATUS_BAR_SUB_PANEL = FIRST_SYSTEM_WINDOW+17;

/**
* Window type: (mouse) pointer
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_POINTER = FIRST_SYSTEM_WINDOW+18;

/**
* Window type: Navigation bar (when distinct from status bar)
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_NAVIGATION_BAR = FIRST_SYSTEM_WINDOW+19;

/**
* Window type: The volume level overlay/dialog shown when the user
* changes the system volume.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_VOLUME_OVERLAY = FIRST_SYSTEM_WINDOW+20;

/**
* Window type: The boot progress dialog, goes on top of everything
* in the world.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_BOOT_PROGRESS = FIRST_SYSTEM_WINDOW+21;

/**
* Window type: Fake window to consume touch events when the navigation
* bar is hidden.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_HIDDEN_NAV_CONSUMER = FIRST_SYSTEM_WINDOW+22;

/**
* Window type: Dreams (screen saver) window, just above keyguard.
* In multiuser systems shows only on the owning user's window.
* @hide
*/
public static final int TYPE_DREAM = FIRST_SYSTEM_WINDOW+23;

/**
* Window type: Navigation bar panel (when navigation bar is distinct from status bar)
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_NAVIGATION_BAR_PANEL = FIRST_SYSTEM_WINDOW+24;

/**
* Window type: Behind the universe of the real windows.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_UNIVERSE_BACKGROUND = FIRST_SYSTEM_WINDOW+25;

/**
* Window type: Display overlay window.  Used to simulate secondary display devices.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_DISPLAY_OVERLAY = FIRST_SYSTEM_WINDOW+26;

/**
* Window type: Magnification overlay window. Used to highlight the magnified
* portion of a display when accessibility magnification is enabled.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_MAGNIFICATION_OVERLAY = FIRST_SYSTEM_WINDOW+27;

/**
* Window type: Recents. Same layer as {@link #TYPE_SYSTEM_DIALOG} but only appears on
* one user's screen.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_RECENTS_OVERLAY = FIRST_SYSTEM_WINDOW+28;

/**
* Window type: keyguard scrim window. Shows if keyguard needs to be restarted.
* In multiuser systems shows on all users' windows.
* @hide
*/
public static final int TYPE_KEYGUARD_SCRIM           = FIRST_SYSTEM_WINDOW+29;

/**
* Window type: Window for Presentation on top of private
* virtual display.
*/
public static final int TYPE_PRIVATE_PRESENTATION = FIRST_SYSTEM_WINDOW+30;

/**
* End of types of system windows.
*/
public static final int LAST_SYSTEM_WINDOW      = 2999;