Fragment ViewBinding

Fragment viewbinding步驟

建立xml

先在 res/layout/ 目錄下，建立一個fragment_my.xml

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<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/name_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

自動產生

app下的build.gradle設置以下內容

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android {
    ...

    buildFeatures {
        viewBinding = true
    }
}

Build > CleanProject

接著會自動產生 FragmentMyBinding

這個類是根據你的 XML 佈局檔案名稱自動生成的：

你的 XML 檔案 自動生成的 Binding 類
fragment_my.xml FragmentMyBinding
fragment_home.xml FragmentHomeBinding
fragment_profile.xml FragmentProfileBinding

命名規則：

移除底線 _

每個單字首字母大寫

結尾加上 Binding

Fragment View Binding

會自動產生 FragmentMyBinding

import com.example.coroutine.databinding.FragmentMyBinding

使用延遲初始化

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private lateinit var binding: FragmentMyBinding

初始化binding。
傳回binding的xml第一個元素root。

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    binding = FragmentMyBinding.inflate(layoutInflater)
    return binding.root

Binding程式碼

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import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import com.example.coroutine.databinding.FragmentMyBinding

class FragA: Fragment() {
  private lateinit var binding: FragmentMyBinding
  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View? {
    binding = FragmentMyBinding.inflate(layoutInflater)
    return binding.root
  }
}

onViewCreated()使用Binding。

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class FragA: Fragment() {
  private lateinit var binding: FragmentMyBinding
  override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
  ): View? {
    binding = FragmentMyBinding.inflate(layoutInflater)
    return binding.root
  }

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    binding.nameTv.text = "Hello world"
  }
}

Activity使用Fragment

使用FragmentContainerView
img

activity_main2.xml

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<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.52"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView3"
        android:name="com.example.coroutine.fragment.FragA"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />
</androidx.constraintlayout.widget.ConstraintLayout>

binding 檔案

activity_main2.xml會產生 ActivityMain2Binding 類別

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import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.example.coroutine.databinding.ActivityMain2Binding

class MainActivity14 : AppCompatActivity() {
  private lateinit var binding : ActivityMain2Binding
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = ActivityMain2Binding.inflate(layoutInflater)
    setContentView(binding.root)
    val textv = binding.textView2

  }
}

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