Android沉浸式通知栏开源库SystemBarTint源码解

前一段时间我写了一篇关于沉浸式的文章：Android实现沉浸式状态栏的那些坑
当时只是知道SystemBarTint的存在，并没有去了解它的实现效果和原理，因为搜Android沉浸式时好多都提到这个开源库，还以为很强大、很深奥，就没敢仓促的去看源码。今天把SystemBarTint拉下来一看，发现这个库仅仅只有一个类：SystemBarTintManager，全篇通读下来发现原理也是相当简单：就是在状态栏填充一个指定颜色、与状态栏等高的view

    private void setupStatusBarView(Activity activity) {
        Window win = activity.getWindow();
        ViewGroup decorViewGroup = (ViewGroup) win.getDecorView();//拿到decorview
        
        mStatusBarTintView = new View(context);
        LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT, mConfig.getStatusBarHeight());
        params.gravity = Gravity.TOP;
        if (mNavBarAvailable && !mConfig.isNavigationAtBottom()) {
            params.rightMargin = mConfig.getNavigationBarWidth();
        }
        mStatusBarTintView.setLayoutParams(params);
        mStatusBarTintView.setBackgroundColor(DEFAULT_TINT_COLOR);
        mStatusBarTintView.setVisibility(View.GONE);
        // 将纯色的StatusBarTintView添加到decorview
        decorViewGroup.addView(mStatusBarTintView);
    }

稍微修改了一点源码，便于理解。导航栏的实现也是一样的。

这样看来，这个库仅仅是用view填充状态栏，虽然可以设置颜色、drawable，但是跟有些需求还是有出入的，所以还是可以看看另一种方案：让view延伸到状态栏，然后设置状态栏等高的padding。
可以参考http://blog.csdn.net/brian512/article/details/52096445

SystemBarTint里面对于状态栏和导航栏高度的获取方法还是可以学习一下的，那么多人用过没问题，应该算是适配不错的：

        private static final String STATUS_BAR_HEIGHT_RES_NAME = "status_bar_height";
        private static final String NAV_BAR_HEIGHT_RES_NAME = "navigation_bar_height";
        private static final String NAV_BAR_HEIGHT_LANDSCAPE_RES_NAME = "navigation_bar_height_landscape";
        private static final String NAV_BAR_WIDTH_RES_NAME = "navigation_bar_width";
        private static final String SHOW_NAV_BAR_RES_NAME = "config_showNavigationBar";
        
   
        private int getStatusBarHeightHeight(Context context) {
            return getInternalDimensionSize(context.getResources(), STATUS_BAR_HEIGHT_RES_NAME);
        }
        @TargetApi(14)
        private int getActionBarHeight(Context context) {
            int result = 0;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
                TypedValue tv = new TypedValue();
                context.getTheme().resolveAttribute(android.R.attr.actionBarSize, tv, true);
                result = TypedValue.complexToDimensionPixelSize(tv.data, context.getResources().getDisplayMetrics());
            }
            return result;
        }

        @TargetApi(14)
        private int getNavigationBarHeight(Context context) {
            Resources res = context.getResources();
            int result = 0;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
                if (hasNavBar(context)) {
                    String key;
                    if (mInPortrait) {
                        key = NAV_BAR_HEIGHT_RES_NAME;
                    } else {
                        key = NAV_BAR_HEIGHT_LANDSCAPE_RES_NAME;
                    }
                    return getInternalDimensionSize(res, key);
                }
            }
            return result;
        }

        @TargetApi(14)
        private int getNavigationBarWidth(Context context) {
            Resources res = context.getResources();
            int result = 0;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
                if (hasNavBar(context)) {
                    return getInternalDimensionSize(res, NAV_BAR_WIDTH_RES_NAME);
                }
            }
            return result;
        }

        @TargetApi(14)
        private boolean hasNavBar(Context context) {
            Resources res = context.getResources();
            int resourceId = res.getIdentifier(SHOW_NAV_BAR_RES_NAME, "bool", "android");
            if (resourceId != 0) {
                boolean hasNav = res.getBoolean(resourceId);
                // check override flag (see static block)
                if ("1".equals(sNavBarOverride)) {
                    hasNav = false;
                } else if ("0".equals(sNavBarOverride)) {
                    hasNav = true;
                }
                return hasNav;
            } else { // fallback
                return !ViewConfiguration.get(context).hasPermanentMenuKey();
            }
        }

        private int getInternalDimensionSize(Resources res, String key) {
            int result = 0;
            int resourceId = res.getIdentifier(key, "dimen", "android");
            if (resourceId > 0) {
                result = res.getDimensionPixelSize(resourceId);
            }
            return result;
        }

        @SuppressLint("NewApi")
        private float getSmallestWidthDp(Activity activity) {
            DisplayMetrics metrics = new DisplayMetrics();
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                activity.getWindowManager().getDefaultDisplay().getRealMetrics(metrics);
            } else {
                // TODO this is not correct, but we don't really care pre-kitkat
                activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);
            }
            float widthDp = metrics.widthPixels / metrics.density;
            float heightDp = metrics.heightPixels / metrics.density;
            return Math.min(widthDp, heightDp);
        }