Kotlin addTextChangeListener 람다?

Kotlin addTextChangeListener 람다?

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Kotlin에서 EditText addTextChangeListener에 대한 람다 표현식을 어떻게 빌드하나요? 아래는 오류를 제공합니다.

passwordEditText.addTextChangedListener { charSequence  ->
    try {
        password = charSequence.toString()
    } catch (error: Throwable) {
        raise(error)
    }
}

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addTextChangedListener()얻어 TextWatcher3 방법에 대한 인터페이스를이다. 당신이 쓴 것은 TextWatcher오직 하나의 방법 만있는 경우에만 작동합니다 . 나는 당신이 얻는 오류가 다른 두 가지 방법을 구현하지 않는 람다와 관련이 있다고 추측 할 것입니다. 앞으로 두 가지 옵션이 있습니다.

1) 람다를 버리고 익명의 내부 클래스를 사용하십시오.

editText.addTextChangedListener(object : TextWatcher {
  override fun afterTextChanged(p0: Editable?) {
  }

  override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
  }

  override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
  }
})

2) 람다 식을 사용할 수 있도록 확장 메서드를 만듭니다.

fun EditText.afterTextChanged(afterTextChanged: (String) -> Unit) {
    this.addTextChangedListener(object : TextWatcher {
      override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
      }

      override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
      }

      override fun afterTextChanged(editable: Editable?) {
        afterTextChanged.invoke(editable.toString())
      }
    })
}

그런 다음 확장을 다음과 같이 사용하십시오.

editText.afterTextChanged { doSomethingWithText(it) }

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이 Kotlin샘플 이 이를 명확히하는 데 도움 이되기를 바랍니다 .

class MainFragment : Fragment() {

    private lateinit var viewModel: MainViewModel

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View {
    val view = inflater.inflate(R.layout.main_fragment, container, false)

    view.user.addTextChangedListener(object : TextWatcher {
        override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {

        }

        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {

        }

        override fun afterTextChanged(s: Editable) {
                userLayout.error =
                        if (s.length > userLayout.counterMaxLength) {
                            "Max character length is: ${userLayout.counterMaxLength}"
                        } else null
        }
    })
    return view
}

override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
    // TODO: Use the ViewModel
   }
}

이 XML레이아웃으로 :

<android.support.design.widget.TextInputLayout
    android:id="@+id/userLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:counterMaxLength="5"
    app:counterEnabled="true"
    android:hint="user_name">

    <android.support.design.widget.TextInputEditText
        android:id="@+id/user"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</android.support.design.widget.TextInputLayout>

그리고 이것은 Gradle:

android {
    compileSdkVersion 'android-P'
...
}
    api 'com.android.support:design:28.0.0-alpha1'

    implementation 'com.android.support:appcompat-v7:28.0.0-alpha1' // appcompat library

---

조금 오래되었지만 Kotlin Android 확장 프로그램을 사용하면 다음과 같이 할 수 있습니다.

editTextRequest.textChangedListener {
            afterTextChanged {
                // Do something here...
            }
}

추가 코드가 필요하지 않으며 다음을 추가하십시오.

implementation 'androidx.core:core-ktx:1.0.0'

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if you use implementation 'androidx.core:core-ktx:1.1.0-alpha05' you can use

For android.widget.TextView
TextWatcher 
TextView.doBeforeTextChanged(crossinline action: (text: CharSequence?, start: Int, count: Int, after: Int) -> Unit)
Add an action which will be invoked before the text changed.

TextWatcher 
TextView.doOnTextChanged(crossinline action: (text: CharSequence?, start: Int, count: Int, after: Int) -> Unit)
Add an action which will be invoked when the text is changing.

TextWatcher 
TextView.doAfterTextChanged(crossinline action: (text: Editable?) -> Unit)

https://developer.android.com/reference/kotlin/androidx/core/widget/package-summary#extension-functions

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Test it :

passwordEditText.addTextChangedListener(object:TextWatcher{override fun afterTextChanged(s: Editable?) {

    }

    override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
    }

    override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {

    }

})

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Another alternative is the KAndroid library -

implementation 'com.pawegio.kandroid:kandroid:0.8.7@aar'

Then you could do something like this...

editText.textWatcher { afterTextChanged { doSomething() } }

Obviously it is excessive to use an entire library to solve your problem, but it also comes with a range of other useful extensions that eliminate boilerplate code in the Android SDK.

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You can make use of kotlin's named parameters:

private val beforeTextChangedStub: (CharSequence, Int, Int, Int) -> Unit = { _, _, _, _ -> }
private val onTextChangedStub: (CharSequence, Int, Int, Int) -> Unit = { _, _, _, _ -> }
private val afterTextChangedStub: (Editable) -> Unit = {}

fun EditText.addChangedListener(
        beforeTextChanged: (CharSequence, Int, Int, Int) -> Unit = beforeTextChangedStub,
        onTextChanged: (CharSequence, Int, Int, Int) -> Unit = onTextChangedStub,
        afterTextChanged: (Editable) -> Unit = afterTextChangedStub
) = addTextChangedListener(object : TextWatcher {
    override fun beforeTextChanged(charSequence: CharSequence, i: Int, i1: Int, i2: Int) {
        beforeTextChanged(charSequence, i, i1, i2)
    }

    override fun onTextChanged(charSequence: CharSequence, i: Int, i1: Int, i2: Int) {
        onTextChanged(charSequence, i, i1, i2)
    }

    override fun afterTextChanged(editable: Editable) {
        afterTextChanged(editable)
    }
})

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You simply have to do

passwordEditText.doAfterTextChanged{ }

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This looks neat:

passwordEditText.setOnEditorActionListener { 
    textView, keyCode, keyEvent ->
    val DONE = 6

    if (keyCode == DONE) {                       
         // your code here
    }
    false
}

참고URL : https://stackoverflow.com/questions/40569436/kotlin-addtextchangelistener-lambda