Databding的使用

Posted 2023-01-13 呼啸

1.在app的build.gradle文件里开启配置：

android 
  ...
    buildFeatures 
        dataBinding true
    

2.布局代码：

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <data>
        <variable
            name="student"
            type="com.example.myapplication.data.Student" />
        <variable
            name="like"
            type="com.example.myapplication.data.Like" />
    </data>
   <androidx.constraintlayout.widget.ConstraintLayout
       android:layout_width="match_parent"
       android:layout_height="match_parent">
       <EditText
           android:id="@+id/tv_my"
           app:layout_constraintStart_toStartOf="parent"
           app:layout_constraintEnd_toEndOf="parent"
           app:layout_constraintTop_toTopOf="parent"
           app:layout_constraintBottom_toBottomOf="parent"
           android:text="@(student.like.likeName == null) ? student.name : student.like.likeName"
           android:layout_width="200dp"
           android:layout_height="100dp"
           android:background="@color/purple_200"/>

       <Button
           android:id="@+id/btn_my"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           app:layout_constraintTop_toBottomOf="@id/tv_my"
           app:layout_constraintStart_toStartOf="@id/tv_my"
           android:text="show"
           />

   </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

3.相关实体类：

package com.example.myapplication.data

import androidx.databinding.BaseObservable
import androidx.databinding.Bindable
import com.example.myapplication.BR

class Student
   
    var name:String? = "name"
       
   
    var like:Like? = null
        

class Like 
    var likeName:String? = null

4.Activity的使用代码：

class MainActivity : AppCompatActivity() 
    private lateinit var recycler: RecyclerView
    private lateinit var ctb: CollapsingToolbarLayout
    private lateinit var appBarLayout: AppBarLayout
    private lateinit var mToolbar:Toolbar
    private var student:Student ?= null
    lateinit var binding:ActivityMain4Binding

    override fun onCreate(savedInstanceState: Bundle?) 
        super.onCreate(savedInstanceState)
        binding = ActivityMain4Binding.inflate(layoutInflater)
        setContentView(binding.root)
        binding.btnMy.setOnClickListener 
            student?.like = Like().apply 
                likeName = "likename"
            
            student?.name = "name2"
        
        student = Student().apply 
            name = "name"
        
        testBinding()
    

    private fun testBinding()
        binding.student = this.student

    

但是这个时候我们会发现，只有第一次新建的时候，起作用，我们点击按钮的时候是没反应的。所以我们要实现BaseObervable。

class Student : BaseObservable()
    @get:Bindable
    var name:String? = "name"
        set(value) 
            field = value
            notifyPropertyChanged(BR.name)
        
    @get:Bindable
    var like:Like? = null
        set(value) 
            field = value
            notifyPropertyChanged(BR.like)
        

这个时候就可以动态更改xml里的数据了。我们来看下界面：

这个时候我们点击按钮：

 

 it works!