一行代码实现沉浸式状态栏

参考了StatusBarUtil这个库，使用里面StatusBarUtil.setColor(Activity activity,int color),发现状态栏颜色改变 但透明度存在一定差异

于是用其StatusBarUtil.setTransparent(Activity activity)，状态栏变为透明，但颜色却变为白色，于是看了其源码，整理出一个方法，一行代码实现沉浸式状态栏效果；

效果图：

	StatusBarUtil.setColor(this,0xc30d23,0);

import android.app.Activity;
import android.content.Context;
import android.os.Build;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.LinearLayout;

/**
 * Created by Administrator on 2016/12/26.
 */

public class StatusBarUtil {

    /**
     * 设置状态栏颜色
     *
     * @param activity       需要设置的activity
     * @param color          状态栏颜色值
     * @param statusBarAlpha 状态栏透明度
     */
    public static void setColor(Activity activity, int color, int statusBarAlpha) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            activity.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
            activity.getWindow().setStatusBarColor(calculateStatusColor(color, statusBarAlpha));
        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            activity.getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
            // 生成一个状态栏大小的矩形
            View statusView = createStatusBarView(activity, color, statusBarAlpha);
            // 添加 statusView 到布局中
            ViewGroup decorView = (ViewGroup) activity.getWindow().getDecorView();
            decorView.addView(statusView);
            setRootView(activity);
        }
    }

    /**
     * 计算状态栏颜色
     *
     * @param color color值
     * @param alpha alpha值
     * @return 最终的状态栏颜色
     */
    private static int calculateStatusColor(int color, int alpha) {
        float a = 1 - alpha / 255f;
        int red = color >> 16 & 0xff;
        int green = color >> 8 & 0xff;
        int blue = color & 0xff;
        red = (int) (red * a + 0.5);
        green = (int) (green * a + 0.5);
        blue = (int) (blue * a + 0.5);
        return 0xff << 24 | red << 16 | green << 8 | blue;
    }

    /**
     * 设置根布局参数
     */
    private static void setRootView(Activity activity) {
        ViewGroup rootView = (ViewGroup) ((ViewGroup) activity.findViewById(android.R.id.content)).getChildAt(0);
        rootView.setFitsSystemWindows(true);
        rootView.setClipToPadding(true);
    }

    /**
     * 生成一个和状态栏大小相同的半透明矩形条
     *
     * @param activity 需要设置的activity
     * @param color    状态栏颜色值
     * @param alpha    透明值
     * @return 状态栏矩形条
     */
    private static View createStatusBarView(Activity activity, int color, int alpha) {
        // 绘制一个和状态栏一样高的矩形
        View statusBarView = new View(activity);
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                getStatusBarHeight(activity));
        statusBarView.setLayoutParams(params);
        statusBarView.setBackgroundColor(calculateStatusColor(color, alpha));
        return statusBarView;
    }

    /**
     * 获取状态栏高度
     *
     * @param context context
     * @return 状态栏高度
     */
    private static int getStatusBarHeight(Context context) {
        // 获得状态栏高度
        int resourceId = context.getResources().getIdentifier("status_bar_height", "dimen", "android");
        return context.getResources().getDimensionPixelSize(resourceId);
    }


}