一、概述
传统的Activity与Fragment之间共享数据，Fragment与Fragment之间共享数据，我一般会采用EventBus事件总线来实现。不过现在可以借助另外一种简单的方式LiveData+ViewModel也可以实现这种共享
二、代码示例
示例描述：要求FragmentA发送出数据，FragmentB和Activity都能接收到。FragmentB发送出的数据FragmentA和Activity都能接收到。Activity发送出去的数据FragmentA和FragmentB都能接收到。
上代码：
SharedDataActivity.kt用于承载两个Fragment以及自己数据的Activity
/**
* Activity和Fragment，Fragment和Fragment之间共享数据
*/
class ShareDataActivity :AppCompatActivity(){
private var mModel:UserViewModel?=null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_share_data)
//第一种实现方式
mModel = ViewModelProvider(this,ViewModelProvider.AndroidViewModelFactory.getInstance(com.tony.demo.utils.ContextUtils.getApplicationContext())).get(UserViewModel::class.java)
//第二种实现方式
// mModel = ViewModelProvider(this).get(UserViewModel::class.java)
supportFragmentManager.beginTransaction().replace(R.id.fl_continer1,FragmentA()).commit()
supportFragmentManager.beginTransaction().replace(R.id.fl_continer2, FragmentB()).commit()
btnSendToActivity.setOnClickListener {
mModel?.getAccount()?.postValue(AccountBean("Activity的数据:杨洛峋",5))
}
mModel?.getAccount()?.observe(this){
tvContentActivity.text = "接收到来自${it.name} ${it.age} 岁了！"
}
}
}
activity_shared_data.layout
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="3">
<FrameLayout
android:id="@+id/fl_continer1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1" />
<FrameLayout
android:id="@+id/fl_continer2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1" />
<RelativeLayout
android:id="@+id/fl_continer3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1">
<Button
android:id="@+id/btnSendToActivity"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Activity发送消息" />
<TextView
android:id="@+id/tvContentActivity"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="" />
</RelativeLayout>
</LinearLayout>
FragmentA.kt
/**
* 使用LiveData+ViewModel让A和B进行通信
*/
class FragmentA : Fragment(){
private var mModel: UserViewModel? = null
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_a, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//第一种实现方式
// mModel = ViewModelProvider(requireActivity()).get(UserViewModel::class.java)
//第二种实现方式
mModel = ViewModelProvider(requireActivity(),
ViewModelProvider.AndroidViewModelFactory.getInstance(ContextUtils.getApplicationContext()))
.get(UserViewModel::class.java)
btnSendToB.setOnClickListener {
//A向B发送数据
mModel?.getAccount()?.postValue(AccountBean("FragmentA的消息：杨洛峋",5))
}
//当数据有变化的时候执行此方法
mModel?.getAccount()?.observe(requireActivity()) {
tvContentA.text = "接收到来自${it.name} ${it.age} 岁了!"
}
}
}
fragment_a.layout
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/btnSendToB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="A发送消息"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvContentA"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
FragmentB.kt
/**
* 使用LiveData+ViewModel让A和B进行通信
*/
class FragmentB : Fragment() {
private var mModel: UserViewModel? = null
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_b, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//第一种实现方式
// mModel = ViewModelProvider(requireActivity()).get(UserViewModel::class.java)
//第二种实现方式
mModel = ViewModelProvider(requireActivity(),ViewModelProvider.AndroidViewModelFactory.getInstance(ContextUtils.getApplicationContext())).get(UserViewModel::class.java)
btnSendToA.setOnClickListener {
mModel?.getAccount()?.postValue(AccountBean("FragmentB的消息：杨洛峋小宝宝",5))
}
mModel?.getAccount()?.observe(requireActivity()){
tvContentB.text = "接收到来自${it.name} ${it.age} 岁了！"
}
}
}
framgent_b.layout
<?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"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/btnSendToA"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="B发送消息"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvContentB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
运行测试结果：
标签：Fragment,mModel,ViewModel,ViewModelProvider,Activity,UserViewModel,class From： https://www.cnblogs.com/tony-yang-flutter/p/17622690.html