What is the difference between textView.setText(string) and textView.text = $string

问题

Hi I am making a app with Kotlin and I found that I can both use

textView.setText(str)

and

textView.text = $str

I wanna know what I should use and the differences between them. Thank you.

回答1:

They're the same in most cases, basically Kotlin generates a synthetic property for the class attributes based on their getter, which you can use to assign values to and get values from.

//So, for most cases
textView.setText("some value");
//Is the same as
textView.text = "some value"
//The second is simply shorter and is the 'kotlin way' of assigning values

Now, here's the catch -

In most cases, this works fine. But, as mentioned, the synthetic property is generated from the getter, if there is a setter as well, then issues arise. The reason is that the getter and the setter may have different types. For example, EditText has Editable getter, now, kotlin creates a synthetic property text of the type Editable.

editText.setText("some value"); //Works
editText.text = "some value" //Won't work, will show an error stating that expected type is Editable

回答2:

textView.setText(str) and textView.text = $str, does the same job of setting the specified str to TextView. The only difference I can come up with is,

textView.setText(str) // old Java way of setting Text where method setText(str) was being called.

textView.text = $str //new Kotlin way of setting Text where instead of a method, a synthetic property is being called.

回答3:

As in the Kotlin, you are not using findViewById

so to access your textView, import statement must be like this

import kotlinx.android.synthetic.main.<layout>.*

And textView.text = $str is the Synthetic Property access provided by Kotlin Plugin for android

You can use both, not much difference in the usability, but for the easier code writing this would be better

For more information, read this https://kotlinlang.org/docs/tutorials/android-plugin.html

回答4:

Both works the same way.

Java Convention

textView.setText(“…”)

Kotlin Convention

textView.text=”…”

“Methods that follow the Java conventions for getters and setters (no-argument methods with names starting with get and single-argument methods with names starting with set) are represented as properties in Kotlin.”- documentation

thus textView.text=”…” instead of textView.setText(“…”) if you are using Kotlin to follow Kotlin Conventions.

Ref - Begin Kotlin; from an Activity, a Button and a TextView

回答5:

The method setText() and getText() are called setters and getters, they are automatically generated in kotlin.

class ClassName{
    var name: String= "some_value"
}

You can use the name property directly with the object of the class or you can also use the auto-generated setter method.

class Another{
    var c = ClassName()

    c.name = "value"
    c.setName("value")
}

But if a property starts with a val instead of var then it is immutable and does not allow a setter.
In case you want to read further:- Setters and getters in kotlin

来源：https://stackoverflow.com/questions/57056445/what-is-the-difference-between-textview-settextstring-and-textview-text-str

标签

android

kotlin