安卓开发控件使用（DataBinding、ViewModel、LiveData、recyclerview）

android下加这个

 compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    dataBinding {
        enabled = true
    }

把项目的 theme 的 parent 指向 QMUI.Compat，至此，QMUI 可以正常工作。

依赖

 def lifecycle_version = "2.2.0"
    def arch_version = "2.1.0"

    // ViewModel
    implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
    // LiveData
    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
    // Lifecycles only (without ViewModel or LiveData)
    implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version"

    implementation 'com.github.JiJiBo:BugUtils:1.0.8'
    // Saved state module for ViewModel
    implementation "androidx.lifecycle:lifecycle-viewmodel-savedstate:$lifecycle_version"


    // alternately - if using Java8, use the following instead of lifecycle-compiler
    implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"

    // optional - helpers for implementing LifecycleOwner in a Service
    implementation "androidx.lifecycle:lifecycle-service:$lifecycle_version"

    // optional - ProcessLifecycleOwner provides a lifecycle for the whole application process
    implementation "androidx.lifecycle:lifecycle-process:$lifecycle_version"

    // optional - ReactiveStreams support for LiveData
    implementation "androidx.lifecycle:lifecycle-reactivestreams-ktx:$lifecycle_version"

 implementation 'com.github.JiJiBo:BugUtils:1.0.8'
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
    implementation 'com.qmuiteam:qmui:2.0.0-alpha10'
    implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
    implementation 'io.reactivex.rxjava3:rxjava:3.0.0'
    implementation 'com.squareup.okhttp3:okhttp:3.10.0'
    implementation 'com.google.code.gson:gson:2.8.6'
    implementation 'com.github.bumptech.glide:glide:4.11.0'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'

allprojects {
    repositories {
        google()
        jcenter()
        maven { url 'https://jitpack.io' }
        maven {
            url "https://maven.google.com"
        }
        maven { url "https://oss.jfrog.org/libs-snapshot" }
    }
}

这是在安卓中使用jectpack,来实现recyclerview，所以就是把数据用条目展示出来

首先实现item所依存的bean，也就是传给adapter的arraylist<Bean> 那个Bean

 public class Student {
    private int age;
    private String name;

    public Student() {
    }

    public Student(int age, String name) {
        this.age = age;
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
} 

然后再写item的布局文件

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>

        <variable
            name="student"
            type="com.zcf.myshujubangding.Student" />

        <import
            alias="deal"
            type="com.zcf.myshujubangding.DealUtils" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_1"
            android:layout_width="100dp"
            android:layout_height="match_parent"
            android:text="@{student.name}" />

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="#000" />

        <TextView
            android:id="@+id/tv_2"
            android:layout_width="100dp"
            android:layout_height="match_parent"
            android:text="@{deal.toString(student.age)}" />

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="#000" />
    </LinearLayout>
</layout>

这里引进一个东西没有说，就是

DealUtils

他长这样

package com.zcf.myshujubangding;

public class DealUtils {
 
    public static String toString(int age) {
       return  age+"";
    }
} 

就是把数字转为字符串这个工具类可以被引进xml

下面展示适配器怎么写

public class AccountDetailAdapter extends Adapter<AccountDetailAdapter.FenLeiViewHolder> {

    private ArrayList<Student> datas;

    public AccountDetailAdapter(ArrayList<Student> datas) {
        this.datas = datas;
    }

    @NonNull
    @Override
    public FenLeiViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

        //这里注意
        ItemAccountDetailBinding inflate = DataBindingUtil.inflate(LayoutInflater.from(BugApp.getContext()), R.layout.item_account_detail, parent, false);

        return new FenLeiViewHolder(inflate.getRoot());
    }

    @Override
    public void onBindViewHolder(@NonNull FenLeiViewHolder holder, final int position) {
        //这里注意
        ItemAccountDetailBinding bind = DataBindingUtil.bind(holder.itemView);
        bind.setStudent(datas.get(position));
        bind.executePendingBindings();
    }

    @Override
    public int getItemCount() {
        return datas.size();
    }

    protected class FenLeiViewHolder extends RecyclerView.ViewHolder {
        public FenLeiViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }


} 

下面的工作就是从网络获取数据，存入recycleview

数据用在ViewModel中获取，里面有个获取假数据的方法

public class MainViewModel extends ViewModel {
    private MutableLiveData<ArrayList<Student>> students;

    public MainViewModel() {
    }

    public MutableLiveData<ArrayList<Student>> getStudents() {
        if (students == null) {
            students = new MutableLiveData<>();
            students.setValue(new ArrayList<Student>());
        }
        return students;
    }

    public void getFalseData() {
        ArrayList<Student> ss = new ArrayList<>();

        ss.add(new Student(12, "f"));
        ss.add(new Student(32, "d"));
        ss.add(new Student(12, "e3"));
        ss.add(new Student(322, "fde"));
        students.getValue().addAll(ss);
    }

}

还没把主页面的布局文件拿出来

现在拿出来

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".MainActivity">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/rv"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:bindData="@{rvData}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />


    </LinearLayout>

    <data>

        <import
            alias="student"
            type="com.zcf.myshujubangding.Student" />

        <variable
            name="rvData"
            type="java.util.ArrayList&lt;student>"
 />
    </data>
</layout>

里面引入了两个数据，recycleview里有个属性，把引入的数据放在里面，这个属性会在恰当的时刻做什么呢

public class RvAdapter {
    @BindingAdapter("bindData")
    public static void bindAdapter(RecyclerView rv, ArrayList<Student> datas) {
        rv.setAdapter(new AccountDetailAdapter(datas));
        rv.setLayoutManager(new LinearLayoutManager(rv.getContext()));
        rv.addItemDecoration(new DividerItemDecoration(rv.getContext(), DividerItemDecoration.VERTICAL));
    }
} 

你看，他会把传入的数据和recycleview绑定在一起

重要的看看主页面

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        //得到viewmodel
        val get = ViewModelProviders.of(this).get(MainViewModel::class.java)
        //得到布局Binding
        val contentView =
            DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
        //初始化recycleview
        contentView.rvData = get.students.value
        //recycleview数据更新的监听
        get.students.observe(this, object : Observer<ArrayList<Student>> {
            override fun onChanged(t: ArrayList<Student>?) {
                if (contentView.rv.adapter != null) {
                    contentView.rv.adapter!!.notifyDataSetChanged()
                }
            }
        })
        //一个获取数据的方法
        get.getFalseData()


    }
}

本文地址：https://blog.csdn.net/sinat_40387150/article/details/108164111