Anko：适用的内部范围，混淆财产决议(Anko: inner scope of apply, confusing property resolution)

系统教程行业动态更新时间:2024-06-14 16:57:17

我正在使用Anko DSL编写Android布局。当定义一个TextView ，我想让它中心对齐，所以我这样写：

verticalLayout { textView(R.string.txt_greeting).apply { gravity = Gravity.CENTER_HORIZONTAL // <- this should have changed the alignment textSize = 20.0f } //... }

但是队列并没有改变。在调试器中，我看到重力是为TextView的父LinearLayout设置的。

将声明更改为

textView(R.string.txt_greeting).let { it.gravity = Gravity.CENTER_HORIZONTAL }

和

textView(R.string.txt_greeting).apply { this@apply.gravity = Gravity.CENTER_HORIZONTAL }

乃至

textView(R.string.txt_greeting).apply { this.gravity = Gravity.CENTER_HORIZONTAL }

解决了这个问题，因此在原始代码隐含的情况下， this绝对是解决了this@verticalLayout 。

为什么会发生？

我是否误解了Kotlin lambda中的某些内容，或者它是Kotlin还是Anko中的错误？

I'm writing an Android layout using Anko DSL. When defining a TextView, I wanted to make it center-aligned, so I wrote this:

verticalLayout { textView(R.string.txt_greeting).apply { gravity = Gravity.CENTER_HORIZONTAL // <- this should have changed the alignment textSize = 20.0f } //... }

But the alignment didn't change. In debugger I saw that gravity is set for the LinearLayout which is the TextView's parent.

Changing the statement to either

textView(R.string.txt_greeting).let { it.gravity = Gravity.CENTER_HORIZONTAL }

and

textView(R.string.txt_greeting).apply { this@apply.gravity = Gravity.CENTER_HORIZONTAL }

and even

textView(R.string.txt_greeting).apply { this.gravity = Gravity.CENTER_HORIZONTAL }

solves the problem, thus in the original code implicit this is definitely resolved to this@verticalLayout.

Why does this happen?

Do I misunderstand something in Kotlin lambdas or is it a bug in Kotlin or Anko?