kotlin 学习记录1

  // 1、?声明，说明这个对象可以为null
  private var alphaAnimation: AlphaAnimation= null

   override fun attachLayoutRes(): Int {
      return R.layout.activity_splash
   }
    // 2、简化版  重写了attachLayoutRes方法，返回值是R.layout.activity_splash，所以下面的是简写
   override fun attachLayoutRes(): Int = R.layout.activity_splash

    // 3、alphaAnimation?.run  当alphaAnimation为null的时候，
    alphaAnimation?.run {

            // 4、object是匿名对象关键字
            setAnimationListener(object : Animation.AnimationListener {
                override fun onAnimationRepeat(p0: Animation?) {
                }

                override fun onAnimationEnd(p0: Animation?) {
                    jumpToMain()
                }

                override fun onAnimationStart(p0: Animation?) {
                }
            })

        // 5、MainActivity::class.java  等价于  MainActivity.this
        val intent = Intent(this, MainActivity::class.java)

        val splash:ConstraintLayout =  findViewById(R.id.layout_splash);
        splash.startAnimation(alphaAnimation)
        // 6、等价于
        layout_splash.startAnimation(alphaAnimation)