为什么即使没有错误，我的Android Studio代码也会随机带红色下划线？

Question

Sometimes my code gets randomly underlined in red even when there is no error

For example, in my Kotlin code (screenshot above):

    nameTextView=findViewById(R.id.nameDashboardTextView)
    ageTextView=findViewById(R.id.ageDashboardTextView)
    emailIDTextView=findViewById(R.id.emailIDTextView)
    genderTextView=findViewById(R.id.genderTextView)
    weightTextView=findViewById(R.id.weightTextView)
    heightTextView=findViewById(R.id.heightTextView)
    progressBar3=findViewById(R.id.progressBar3)

findViewById of any random variables gets underlined in red. When I copy the text, remove it, and paste it back, the "error" is removed. Furthermore, the red line doesn't stop the code from compiling or executing, the application works perfectly, but in Android Studio, some random line like findViewById or other straightforward code will get underlined in red.

The error for the above example reads:

Cannot infer type parameter T in

fun findViewById ( id:Int ) :T! None of the following substitutions ( Int) ( Int) ( Int) can be applied to ( Int)

Any idea why this happens? I'm using Android Studio 3.1.3, 4th June 2018 build

Answer 1

Because Kotlin compiler cannot infer the specific type for your variables. To dismiss this red line you could you 2 ways.

The former:

private lateinit var nameTextView: TextView

nameTextView = findViewById(R.id.nameDashboardTextView)

The latter:

nameTextView = findViewById<TextView>(R.id.nameDashboardTextView)