动态设置actionBar的颜色

  actionBar = activity.actionBar ?: when (activity) {
      is AppCompatActivity -> activity.supportActionBar
      else -> null
    }

//view有默认实现
 private val drawableCallback = object : Drawable.Callback {

    override fun invalidateDrawable(who: Drawable) {
      actionBar?.run {
        if (this is android.app.ActionBar) {
          setBackgroundDrawable(who)
        } else if (this is ActionBar) {
          setBackgroundDrawable(who)
        }
      }
    }

    override fun scheduleDrawable(drawable: Drawable, action: Runnable, time: Long) {
      Handler().postAtTime(action, time)
    }

    override fun unscheduleDrawable(drawable: Drawable, action: Runnable) {
      Handler().removeCallbacks(action)
    }
  }

fun setActionBarColor(@ColorInt color: Int) {
    actionBar?.let { ab ->
      val colorDrawable = ColorDrawable(color)

      oldActionBarBackground?.let { oldBackground ->
        val td = TransitionDrawable(arrayOf(oldBackground, colorDrawable))
        // workaround for broken ActionBarContainer drawable handling on pre-API 17 builds
        // https://github.com/android/platform_frameworks_base/commit/a7cc06d82e45918c37429a59b14545c6a57db4e4
        when {
          Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1 -> td.callback = drawableCallback
          ab is android.app.ActionBar -> ab.setBackgroundDrawable(td)
          ab is ActionBar -> ab.setBackgroundDrawable(td)
        }
        td.startTransition(200)
      } ?: run {
        when {
          Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1 -> {
            val td = TransitionDrawable(arrayOf<Drawable>(colorDrawable, colorDrawable))
            td.callback = drawableCallback
            td.startTransition(200)
          }
          ab is android.app.ActionBar -> ab.setBackgroundDrawable(colorDrawable)
          ab is ActionBar -> ab.setBackgroundDrawable(colorDrawable)
        }
      }

      oldActionBarBackground = colorDrawable

      // http://stackoverflow.com/questions/11002691/actionbar-setbackgrounddrawable-nulling-background-from-thread-handler
      if (ab is android.app.ActionBar) {
        val isDisplayingTitle = ab.displayOptions and android.app.ActionBar.DISPLAY_SHOW_TITLE != 0
        ab.setDisplayShowTitleEnabled(!isDisplayingTitle)
        ab.setDisplayShowTitleEnabled(isDisplayingTitle)
      } else if (ab is ActionBar) {
        val isDisplayingTitle = ab.displayOptions and ActionBar.DISPLAY_SHOW_TITLE != 0
        ab.setDisplayShowTitleEnabled(!isDisplayingTitle)
        ab.setDisplayShowTitleEnabled(isDisplayingTitle)
      }
    }
  }