WindowManager.LayoutParams的探究

上次在子线程更新UI时用了一下WindowManager.LayoutParams，当时觉得不太顺手。以前都是用空参构造器，这次用了type和flag属性，出现了意想不到的效果。也看看源码吧，多锻炼锻炼。

public static class WindowManager.LayoutParams
extends ViewGroup.LayoutParams implements Parcelable 

 WindowManager.LayoutParams是WindowManager里的静态类，源码两千多行，不过大部分都是一些常量。

/**
         * The general type of window.  There are three main classes of　　　　　　window主要的type分为三种：
         * window types:
         * <ul>
         * <li> <strong>Application windows</strong> (ranging from　　　　　　　　　　应用窗口（从FIRST_APPLICATION_WINDOW到LAST_APPLICATION_WINDOW）是普通的顶层应用窗口，
         * {@link #FIRST_APPLICATION_WINDOW} to　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
         * {@link #LAST_APPLICATION_WINDOW}) are normal top-level application
         * windows.  For these types of windows, the {@link #token} must be　　　　对这类window而言，它们的token必须设置给它们所属的activity的token
         * set to the token of the activity they are a part of (this will
         * normally be done for you if {@link #token} is null).
         * <li> <strong>Sub-windows</strong> (ranging from　　　　　　　　　　　　　　　子窗口从FIRST_SUB_WINDOW到LAST_SUB_WINDOW与另一个顶层的window
         * {@link #FIRST_SUB_WINDOW} to　　　　　　　　　　　　　　　　　　　　　　　　　　　关联。这些window的token必须与它们依附的window的token一致。
         * {@link #LAST_SUB_WINDOW}) are associated with another top-level
         * window.  For these types of windows, the {@link #token} must be
         * the token of the window it is attached to.
         * <li> <strong>System windows</strong> (ranging from　　　　　　　　　　　　　　系统窗口从FIRST_SYSTEM_WINDOW到lAST_SYSTEM_WINDOW是系统出于
         * {@link #FIRST_SYSTEM_WINDOW} to　　　　　　　　　　　　　　　　　　　　　　　　　　特别的目的使用的一类特殊的窗口。它们不应被应用随意使用，而且使用时
         * {@link #LAST_SYSTEM_WINDOW}) are special types of windows for　　　　　　　　需要特殊的权限。

 

         * use by the system for specific purposes.  They should not normally
         * be used by applications, and a special permission is required
         * to use them.
         * </ul>

 实在太多了，留到后面总结吧。

　　周一刚好整理一下。WindowManager是个接口。源码中是这样介绍的：用Context.geSystemService(Context.WINDOW_SERVICE)得到WindowManager的实例，内部类LayoutParams可以通过getWindow.getAttributes()或者new出来。然后是设置参数的一些变量，例如type，flag，format，x，y等。特意对照源码做了一个参照表格，此外，还要说一下源码中的@hide。带有@hide标识的方法或者接口是Android系统不想让开发者使用的功能，是那些当前版本尚未稳定的架构。在下一个API，这些带有@hide的方法属性等可能得到验证删除@hide并予以开发者调用也有可能这些功能不合适被移除掉。因此，这些可以看做是Android下个版本的新功能的趋势，但也可能胎死腹中，而且一般开发人员都不会用到这些。因此，LayoutParams中带有@hide、@Deprecated的变量方法不在本文中予以收录。

接下来是flag：

 

下面是format的说明：

/**
         * The desired bitmap format.  May be one of the constants in
         * {@link android.graphics.PixelFormat}.  Default is OPAQUE.
         */bitmap格式。PixelFormat的一个常量。默认是OPAQUE
        public int format;

说明flag的设置决定了window能否接收键盘输入：

/**
         * Given a particular set of window manager flags, determine whether
         * such a window may be a target for an input method when it has
         * focus.  In particular, this checks the
         * {@link #FLAG_NOT_FOCUSABLE} and {@link #FLAG_ALT_FOCUSABLE_IM}
         * flags and returns true if the combination of the two corresponds
         * to a window that needs to be behind the input method so that the
         * user can type into it.
         *
         * @param flags The current window manager flags.
         *
         * @return Returns true if such a window should be behind/interact
         * with an input method, false if not.
         */
        public static boolean mayUseInputMethod(int flags) {
            switch (flags&(FLAG_NOT_FOCUSABLE|FLAG_ALT_FOCUSABLE_IM)) {
                case 0:
                case FLAG_NOT_FOCUSABLE|FLAG_ALT_FOCUSABLE_IM:
                    return true;
            }
            return false;
        }

softInputMode：输入法模式，也可以在theme的WindowSoftInputMode设置。

 /**
         * Desired operating mode for any soft input area.  May be any combination
         * of:
         *
         * <ul>
         * <li> One of the visibility states
         * {@link #SOFT_INPUT_STATE_UNSPECIFIED}, {@link #SOFT_INPUT_STATE_UNCHANGED},
         * {@link #SOFT_INPUT_STATE_HIDDEN}, {@link #SOFT_INPUT_STATE_ALWAYS_VISIBLE}, or
         * {@link #SOFT_INPUT_STATE_VISIBLE}.
         * <li> One of the adjustment options
         * {@link #SOFT_INPUT_ADJUST_UNSPECIFIED},
         * {@link #SOFT_INPUT_ADJUST_RESIZE}, or
         * {@link #SOFT_INPUT_ADJUST_PAN}.
         * </ul>
         *
         *
         * <p>This flag can be controlled in your theme through the
         * {@link android.R.attr#windowSoftInputMode} attribute.</p>
         */
        public int softInputMode;

Gravity：

/**
         * Placement of window within the screen as per {@link Gravity}.  Both
         * {@link Gravity#apply(int, int, int, android.graphics.Rect, int, int,
         * android.graphics.Rect) Gravity.apply} and
         * {@link Gravity#applyDisplay(int, android.graphics.Rect, android.graphics.Rect)
         * Gravity.applyDisplay} are used during window layout, with this value
         * given as the desired gravity.  For example you can specify
         * {@link Gravity#DISPLAY_CLIP_HORIZONTAL Gravity.DISPLAY_CLIP_HORIZONTAL} and
         * {@link Gravity#DISPLAY_CLIP_VERTICAL Gravity.DISPLAY_CLIP_VERTICAL} here
         * to control the behavior of
         * {@link Gravity#applyDisplay(int, android.graphics.Rect, android.graphics.Rect)
         * Gravity.applyDisplay}.
         *
         * @see Gravity
         */
        public int gravity;

horizontalMargin：

/**
         * The horizontal margin, as a percentage of the container's width,
         * between the container and the widget.  See
         * {@link Gravity#apply(int, int, int, android.graphics.Rect, int, int,
         * android.graphics.Rect) Gravity.apply} for how this is used.  This
         * field is added with {@link #x} to supply the <var>xAdj</var> parameter.
         */
        public float horizontalMargin;

verticalMargin:

/**
         * The vertical margin, as a percentage of the container's height,
         * between the container and the widget.  See
         * {@link Gravity#apply(int, int, int, android.graphics.Rect, int, int,
         * android.graphics.Rect) Gravity.apply} for how this is used.  This
         * field is added with {@link #y} to supply the <var>yAdj</var> parameter.
         */
        public float verticalMargin;

动画：必须使用系统资源，不能使用应用内自定义的动画。

/**
         * A style resource defining the animations to use for this window.
         * This must be a system resource; it can not be an application resource
         * because the window manager does not have access to applications.
         */
        public int windowAnimations;

 

还有一些window属性不再一一列举：

/**
         * An alpha value to apply to this entire window.
         * An alpha of 1.0 means fully opaque and 0.0 means fully transparent
         */
        public float alpha = 1.0f;

        /**
         * When {@link #FLAG_DIM_BEHIND} is set, this is the amount of dimming
         * to apply.  Range is from 1.0 for completely opaque to 0.0 for no
         * dim.
         */
        public float dimAmount = 1.0f;

当然，还发现了一个属性，systemUiVisibility：

/**
         * Control the visibility of the status bar.
         *
         * @see View#STATUS_BAR_VISIBLE
         * @see View#STATUS_BAR_HIDDEN
         */
        public int systemUiVisibility;

源码中介绍这个变量可以控制状态栏的visibility，接着跳到View.STATUS_BAR_HIDDEN看看。

/**
     * @deprecated Use {@link #SYSTEM_UI_FLAG_LOW_PROFILE} instead.
     */
    public static final int STATUS_BAR_HIDDEN = SYSTEM_UI_FLAG_LOW_PROFILE;

发现已经被弃用了，SYSTEM_UI_FLAG_LOW_PROFILE替代了它。

/**
     * Flag for {@link #setSystemUiVisibility(int)}: View has requested the
     * system UI to enter an unobtrusive "low profile" mode.
     *
     * <p>This is for use in games, book readers, video players, or any other
     * "immersive" application where the usual system chrome is deemed too distracting.
     *
     * <p>In low profile mode, the status bar and/or navigation icons may dim.
     *
     * @see #setSystemUiVisibility(int)
     */
    public static final int SYSTEM_UI_FLAG_LOW_PROFILE = 0x00000001;

从这一段介绍看出，这个常量是在setSystemUiVisibility()传入的参数，竟然涉及到了沉浸式模式：用在游戏，电子书阅读或者任何“身临其境”的应用，而在一般的系统浏览器中被认为是太分心的。这个留在下一篇博客细说吧，还打算封一个工具库。

好的，内容非常的多，但不怎么常用。

　　人往高处走，水往低处流。