android 数据绑定(4)实用特性及疑惑：使用控件、格式化@string/xxx、对象传递、双向数据绑定

1.在布局内使用其它控件 

1.1 效果

　　箭头所指3个控件的内容随输入框内容而变化。

1.2 示例代码

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <import type="android.view.View" />
        <import type="com.example.databind.Exts" />
    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:clickable="true"
        android:background="#ffffff"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/features_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="binding features"
            android:textAllCaps="false"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />


        <TextView
            android:id="@+id/features_txt1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="48dp"
            android:background="#f8f8f8"
            android:textSize="12sp"
            android:text='@{featureEdt.text.toString(),default="取 feature_edt 的值"}'
            app:layout_constraintEnd_toStartOf="@+id/features_txt2"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/feature_edt" />

        <TextView
            android:id="@+id/features_txt2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="#f8f8f8"
            android:textSize="12sp"
            android:text='@{featureEdt.text.toString(),default="取 feature_edt 的值"}'
            app:layout_constraintBottom_toBottomOf="@+id/features_txt1"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/features_txt1"
            app:layout_constraintTop_toTopOf="@+id/features_txt1" />
        <!--android:textColor="@{featureEdt.text.hasCharX('e') ? @color/colorAccent : @color/colorPrimaryDark }"-->

        <EditText
            android:id="@+id/feature_edt"
            android:layout_width="0dp"
            android:layout_height="64dp"
            android:layout_marginStart="16dp"
            android:layout_marginLeft="16dp"
            android:layout_marginTop="32dp"
            android:layout_marginEnd="16dp"
            android:layout_marginRight="16dp"
            android:background="@drawable/edt_bg"
            android:ems="10"
            android:textColor='@{featureEdt.text.toString().length() > 8 ? @color/colorAccent : @color/colorPrimaryDark }'
            android:inputType="textPersonName"
            android:paddingLeft="8dp"
            android:text="Name"
            android:maxLength="16"
            android:maxLines="1"
            android:textAllCaps="false"
            android:textSize="12sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/features_title" />

        <TextView
            android:id="@+id/toast"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="9sp"
            android:textColor='@{featureEdt.text.toString().length() &lt; 1 ? @color/colorAccent : @color/colorPrimaryDark,default=@color/colorPrimary}'
            android:text='@{featureEdt.text.toString().length() &lt; 1 ? "不能为空" :"1-16个字符",default = "1-16个字符"}'
            app:layout_constraintStart_toStartOf="@+id/feature_edt"
            app:layout_constraintTop_toBottomOf="@+id/feature_edt" />

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

1.3 特性描述

• 控件按驼峰式命名法命名,如 :   feature_edt   ->   featureEdt
• 其它控件可以在布局内访问这个控件以及它的成员，第34、45、81行。
• 不可以调用控件的扩展成员。第50行。
• 控件自己可以调用自己,第63行。

2. 可以使用格式化字符串

• 示例，@string/xxx 可以和 “字符串” 相加 ，如下

      <TextView
              android:id="@+id/tvFormat"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_marginTop="24dp"
              android:text='@{@string/format("李4",0x20,33.333333f) + " string/xxx 可以和 字符串相加 ",default=@string/format}'
              app:layout_constraintStart_toStartOf="@+id/feature_edt"
              app:layout_constraintTop_toBottomOf="@+id/features_txt1" />

• string.xml

  <resources>
      <string name="app_name">DataBind</string>
      <string name="format">format : name=%1$s,age=%2$1d,value=%3$32f </string>
      //...
  </resources>

  　

3.对象传递到include布局中

3.1 示例

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:bind="http://schemas.android.com/apk/res-auto">
    <data>
        <variable name="data" type="com.example.databind.Data" />
        <variable name="click" type="com.example.databind.Click" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clickable="true"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:onClick="@{click::onStartClicked}">

        //...

        <include
            android:id="@+id/include"
            layout="@layout/include"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            app:layout_constraintEnd_toEndOf="@+id/frgmt2"
            app:layout_constraintStart_toStartOf="@+id/frgmt2"
            app:layout_constraintTop_toBottomOf="@+id/frgmt2"
            bind:data="@{data}"
            bind:title='@{"标题"}'
            />
...

　　代码中把 data 传递给 @layout/include ，要求这个布局也使用数据绑定布局，且也声明data和title变量。

如下：

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
        <variable name="data" type="com.example.databind.Data" />
        <variable name="title" type="String" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#7ff77ff7"
        >
    
        //...

        <TextView
            android:id="@+id/value"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="32dp"
            android:layout_marginLeft="32dp"
            android:text="@{String.valueOf(data.value),default = value}"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/key"
            app:layout_constraintTop_toTopOf="@+id/key" />

      

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

3.2 不支持 merge 为直接子元素

数据绑定不支持 include 作为 merge 元素的直接子元素

    <?xml version="1.0" encoding="utf-8"?>
    <layout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:bind="http://schemas.android.com/apk/res-auto">
       <data>
           <variable name="user" type="com.example.User"/>
       </data>
       <merge><!-- Doesn't work -->
           <include layout="@layout/name"
               bind:user="@{user}"/>
           <include layout="@layout/contact"
               bind:user="@{user}"/>
       </merge>
    </layout>
    

#.后台线程的疑惑

#.1 问题

英文原版

中文版　

#.2 疑惑?

　　Collection<T> 实现类 里存放的数据，不能在后台线程中修改？

#.3 测试代码

　　在后台线程中对list 操作，并没有发现问题

package com.example.databind

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.ObservableField
import androidx.fragment.app.Fragment
import com.example.databind.databinding.MapCollectionBinding
import kotlin.concurrent.thread

class MapCollectionFrgmt : Fragment() {

    lateinit var binding : MapCollectionBinding

    val list    = ArrayList<String>()
    val map     = HashMap<String,ObservableField<String>>()
    val data    = Data()

    init {
        data.key = "data key"
        data.key = "data value"

        map.put("key1",ObservableField("value1"))
        map.put("key2",ObservableField("value2"))
        map.put("key3",ObservableField("value3"))
        map.put("key4",ObservableField("value4"))

        list.add("value0")
        list.add("value1")
        list.add("value2")
        list.add("value3")
    }


    fun onDataThreadMainClicked(view: View){
        val random = (Math.random() * 1000).toInt()
        data.key = "新Main key$random"
        data.value = random
        binding.data = data
    }

    fun onDataThreadOtherClicked(view: View){
        thread {
            val random = (Math.random() * 1000).toInt()
            data.key = "新other key$random"
            data.value = random
            binding.data = data
        }
    }

    fun onMap1ThreadMain(v : View){
        val random = (Math.random() * 1000).toInt()
        val ob = ObservableField<String>()
        ob.set("新Main value$random")
        map.put("key1",ob)
        binding.map = map
    }
    fun onMap1ThreadOther(v : View){
        thread {
            val random = (Math.random() * 1000).toInt()
            val ob = ObservableField<String>()
            ob.set("新Main value$random")
            map.put("key1",ob)
            binding.map = map
        }
    }
    fun onList0ThreadMain(v : View){
        val random = (Math.random() * 1000).toInt()
        list[0] = "新Main value$random"
        binding.list = list
    }
    fun onList0ThreadOther(v : View){
        thread {
            val random = (Math.random() * 1000).toInt()
            list[0] = "新Main value$random"
            binding.list = list
        }
    }
    fun initBinding(){
        binding.list = list
        binding.data = data
        binding.map = map

        binding.threadMainData.setOnClickListener(this::onDataThreadMainClicked)
        binding.threadOtherData.setOnClickListener(this::onDataThreadOtherClicked)
        binding.threadMainMap1.setOnClickListener(this::onMap1ThreadMain)
        binding.threadOtherMap1.setOnClickListener(this::onMap1ThreadOther)
        binding.threadMainList0.setOnClickListener(this::onList0ThreadMain)
        binding.threadOtherList0.setOnClickListener(this::onList0ThreadOther)
        /*if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            val text: String = getString(R.string.map_title, map.size)
            val styledText: Spanned = Html.fromHtml(text, FROM_HTML_OPTION_USE_CSS_COLORS)
            binding.mapTitle.text = styledText
        }*/
    }


    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        binding = MapCollectionBinding.inflate(inflater,container,false)
        initBinding()
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    }

    override fun onDetach() {
        super.onDetach()
    }

}

布局

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <data >
        <import type="androidx.databinding.ObservableField" />
        <variable name="data" type="com.example.databind.Data" />
        <variable name="map" type="java.util.HashMap&lt;String,ObservableField&lt;String>>" />
        <variable name="list" type="java.util.List&lt;String>" />
    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:clickable="true"
        android:background="#ffffff"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/data_title"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:background="#f6f6f6"
            android:paddingLeft="16dp"
            android:text="data "
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/map_title"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:background="#f8f8f8"
            android:paddingLeft="16dp"
            android:text="@{@string/map_title(map.size()) ,default=@string/map_title}"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/data_key" />


        <TextView
            android:id="@+id/data_key"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="32dp"
            android:layout_marginLeft="32dp"
            android:layout_marginTop="16dp"
            android:text='@{data.key}'
            app:layout_constraintStart_toStartOf="@+id/data_title"
            app:layout_constraintTop_toBottomOf="@+id/data_title" />

        <TextView
            android:id="@+id/data_value"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginLeft="16dp"
            android:text='@{String.valueOf(data.value)}'
            app:layout_constraintStart_toEndOf="@+id/data_key"
            app:layout_constraintTop_toTopOf="@+id/data_key" />

        <TextView
            android:id="@+id/map_key1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="24dp"
            android:layout_marginLeft="24dp"
            android:layout_marginTop="16dp"
            android:text='@{@string/map_key_value("key1",map["key1"]),default=@string/map_key_value}'
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/map_title" />

        <TextView
            android:id="@+id/map_key3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text='@{@string/map_key_value("key1",map["key3"]),default=@string/map_key_value}'
            app:layout_constraintStart_toStartOf="@+id/map_key1"
            app:layout_constraintTop_toBottomOf="@+id/map_key2" />

        <TextView
            android:id="@+id/map_key4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text='@{@string/map_key_value("无效key",map["无效key"]),default=@string/map_key_value}'
            app:layout_constraintStart_toStartOf="@+id/map_key2"
            app:layout_constraintTop_toBottomOf="@+id/map_key3" />

        <TextView
            android:id="@+id/map_key2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text='@{@string/map_key_value("key2",map["key2"]),default=@string/map_key_value}'
            app:layout_constraintStart_toStartOf="@+id/map_key1"
            app:layout_constraintTop_toBottomOf="@+id/map_key1" />


        <TextView
            android:id="@+id/list_title"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="24dp"
            android:background="#f8f8f8"
            android:paddingLeft="16dp"
            android:text="@{@string/list_title(list.size()) ,default=@string/list_title}"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/map_key4" />


        <TextView
            android:id="@+id/list_0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="24dp"
            android:layout_marginLeft="24dp"
            android:layout_marginTop="16dp"
            android:text='@{@string/list_index(0,list[0]),default=@string/list_index}'
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/list_title" />

        <TextView
            android:id="@+id/list_1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text='@{@string/list_index(1,list[1]),default=@string/list_index}'
            app:layout_constraintStart_toStartOf="@+id/list_0"
            app:layout_constraintTop_toBottomOf="@+id/list_0" />

        <TextView
            android:id="@+id/list_2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text='@{@string/list_index(2,list[2]),default=@string/list_index}'
            app:layout_constraintStart_toStartOf="@+id/list_1"
            app:layout_constraintTop_toBottomOf="@+id/list_1" />

        <TextView
            android:id="@+id/list_3"
            android:layout_width="104dp"
            android:layout_height="15dp"
            android:layout_marginTop="8dp"
            android:text='@{@string/list_index(-1,list[-1]) ,default=@string/list_index}'
            app:layout_constraintStart_toStartOf="@+id/list_2"
            app:layout_constraintTop_toBottomOf="@+id/list_2" />

        <TextView
            android:id="@+id/thread_title"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="32dp"
            android:background="#f8f8f8"
            android:paddingLeft="16dp"
            android:text="在线程中修改数据"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/list_3" />

        <Button
            android:id="@+id/thread_main_data"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="主线程修改data"
            android:textAllCaps="false"
            app:layout_constraintEnd_toStartOf="@+id/thread_other_data"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/thread_title" />

        <Button
            android:id="@+id/thread_other_data"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="非主线程修改data"
            android:textAllCaps="false"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/thread_main_data"
            app:layout_constraintTop_toBottomOf="@+id/thread_title" />

        <Button
            android:id="@+id/thread_main_list0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="主线程修改list[0]"
            android:textAllCaps="false"
            app:layout_constraintEnd_toStartOf="@+id/thread_other_list0"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/thread_main_data" />

        <Button
            android:id="@+id/thread_other_list0"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="非主线程修改list[0]"
            android:textAllCaps="false"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/thread_main_list0"
            app:layout_constraintTop_toBottomOf="@+id/thread_main_data" />

        <Button
            android:id="@+id/thread_main_map1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="主线程修改map[key1]"
            android:textAllCaps="false"
            app:layout_constraintEnd_toStartOf="@+id/thread_other_map1"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/thread_main_list0" />

        <Button
            android:id="@+id/thread_other_map1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="非主线程修改map[key1]"
            android:textAllCaps="false"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/thread_main_map1"
            app:layout_constraintTop_toBottomOf="@+id/thread_main_list0" />

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

 

#.4 viewModel 放在集合里？

　　布局文件中通过viewModel访问数据，然后viewModel放在集合里？还会这么用？不解。