方法1：

 public void setTransparentForWindow(Activity activity) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            activity.getWindow().setStatusBarColor(Color.TRANSPARENT);
            activity.getWindow()
                    .getDecorView()
                    .setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            activity.getWindow()
                    .setFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS, WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
        }
    }

方法2：

 public void setTransparentForWindow(Activity activity) {
        WindowManager.LayoutParams winParams = activity.getWindow().getAttributes();
        final int bits = WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS;
        winParams.flags |= bits;
        activity.getWindow().setAttributes(winParams);
    }

注意：xml文件中不能出现下列语句

    android:fitsSystemWindows="true"