Android中WindowManger的层级分析_android windowmanager 指定层

一. Window 分类

•  应用 Window（ApplicationWindow： 对应一个 Acitivity）
• 子 Window    （SubWindow：不能单独存在，需要依附在特定的父 Window 中，比如常见的一些 Dialog 就是一个子 Window）
• 系统 Window （SystemWindow：需要声明权限才能创建的 Window，比如 Toast 和系统状态栏都是系统 Window）

二. Window层级

Window 是分层的，每个 Window 都有对应的 z-ordered，层级大的会覆盖在层级小的 Window 上面，这和 HTML 中的 z-index 概念是完全一致的。

在三种 Window 中，每一种Window的层级范围也是不同的，如下：

应用Window    1~99

子Window        1000~1999

系统Window    2000~2999

这些层级范围对应着 WindowManager.LayoutParams 的 type 参数，如果想要 Window 位于所有 Window 的最顶层，那么采用较大的层级即可，很显然系统 Window 的层级是最大的，当我们采用系统层级时，需要声明权限。

（1）应用程序窗口：

package android.view;
public interface WindowManager
        /**
         * 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;
 
        /**
         * Window type: a variation on TYPE_APPLICATION that ensures the window
         * manager will wait for this window to be drawn before the app is shown.
         * In multiuser systems shows only on the owning user's window.
         */
        public static final int TYPE_DRAWN_APPLICATION = 4;
 
        /**
         * End of types of application windows.
         */
        public static final int LAST_APPLICATION_WINDOW = 99;

 （2）子窗口：

package android.view;
public interface WindowManager
        /**
         * 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
         */
        @UnsupportedAppUsage
        public static final int TYPE_APPLICATION_MEDIA_OVERLAY  = FIRST_SUB_WINDOW + 4;
 
        /**
         * Window type: a above sub-panel on top of an application window and it's
         * sub-panel windows. These windows are displayed on top of their attached window
         * and any {@link #TYPE_APPLICATION_SUB_PANEL} panels.
         * @hide
         */
        public static final int TYPE_APPLICATION_ABOVE_SUB_PANEL = FIRST_SUB_WINDOW + 5;
 
        /**
         * End of types of sub-windows.
         */
        public static final in