android data binding jetpack V

来实现一个recyclerview绑定。

看了例子理一下思路。

第一个关系：

item 与itemview 数据与展示绑定。

recyclerview 更新数据和UI过程是：获取holder类型->产生holder->获取holder（）->holder+data->展示。

代码在adapter中执行。

1.获取某个位置的holder类型。

 @Override
    public int getItemViewType(int position) {
        return super.getItemViewType(position);
    }

2.创建holder

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {   return viewHolder;
    }

3.绑定数据并展示出来。

@Override
    public void onBindViewHolder(ViewHolder holder, int position) {
       
    }

现在使mvvm 那么

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第一步：在createholder的时候要确定 binding 与xml的绑定关系。

第二步：在onBindViewHolder中让关系实现并展示。

看示例代码怎么实现第一步

  @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
　　　　　//读取xml对内存
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        //建立绑定关系
　　　　　ViewDataBinding binding = DataBindingUtil.inflate(inflater, layoutId, parent, false);
        //建立一下holder
　　　　 ViewHolder viewHolder = new ViewHolder(binding.getRoot());
        //把绑定关系记录在holder的变量里。
　　　　　viewHolder.setBinding(binding);
        return viewHolder;
    }

 @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
　　　　　//执行绑定，给绑定关系设置数据。
        holder.getBinding().setVariable(brId,mDatas.get(position));
　　　　　//让绑定生效。
        holder.getBinding().executePendingBindings();
    }

<?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">

    <data>

        <import type="com.ht.jetpack.model.Student" />

        <variable
            name="student"
            type="Student" />
    </data>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <ImageView
            android:layout_width="280dp"
            android:layout_height="210dp"
            android:layout_margin="10dp"
            android:scaleType="centerCrop"
            app:studentAvatar="@{student.resId}" />

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="40dp"
            android:gravity="center"
            android:text="@{student.name}"
            android:textSize="18sp" />

    </LinearLayout>
</layout>

xml是绑定关系。

整个过程：加xml->产生绑定关->滚动到某个位置->获取绑定关系，给绑定加入数据->展示

声明的变量：

给变量赋值：

brId是

就是xml里声明的模型变量。

难点：

这个之前没有见过。自定义了一个属性，进行了绑定。

具定实现在这儿：

这个需要求单独一下块内容去学习。

看一下运行效果：

以下是实例代码：要运行请自己找几张图加到drawable里命名一致就可以了。

package com.ht.jetpack.adapter;


import android.databinding.BindingAdapter;
import android.widget.ImageView;

public class BindingUtil {

    @BindingAdapter("bind:studentAvatar")
    public static void showImageByUrl(final ImageView imageView, int resId) {
        imageView.setImageResource(resId);
    }
}

package com.ht.jetpack.adapter;


import android.content.Context;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;

public class InitRecyclerView {

    public static void initLinearLayoutVERTICAL(Context context, RecyclerView recyclerView) {
        LinearLayoutManager layoutManager = new LinearLayoutManager(context);
        layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
    }

    public static void initLinearLayoutWithoutDivid(Context context, RecyclerView recyclerView) {
        LinearLayoutManager layoutManager = new LinearLayoutManager(context);
        layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
    }

    public static void initLinearLayoutHorizontal(Context context, RecyclerView recyclerView) {
        LinearLayoutManager layoutManager = new LinearLayoutManager(context);
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
    }

    public static void initStaggered(Context context, RecyclerView recyclerView) {
        StaggeredGridLayoutManager sgm = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(sgm);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
    }
}

package com.ht.jetpack.adapter;


import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.ViewGroup;


import java.util.List;

/**
 * Created by hongtao
 */
public class MySimpleAdapter<T> extends RecyclerView.Adapter<ViewHolder>{

    private List<T> mDatas;

    private int layoutId;

    private int brId;

    public MySimpleAdapter(List<T> mDatas, int layoutId, int brId) {
        this.mDatas = mDatas;
        this.layoutId = layoutId;
        this.brId = brId;
    }

    @Override
    public int getItemViewType(int position) {
        return super.getItemViewType(position);
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        ViewDataBinding binding = DataBindingUtil.inflate(inflater, layoutId, parent, false);
        ViewHolder viewHolder = new ViewHolder(binding.getRoot());
        viewHolder.setBinding(binding);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.getBinding().setVariable(brId,mDatas.get(position));
        holder.getBinding().executePendingBindings();
    }

    @Override
    public int getItemCount() {
        return mDatas == null ? 0 : mDatas.size();
    }
}

package com.ht.jetpack.adapter;

import android.databinding.ViewDataBinding;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Created by hongtao .
 */
public class ViewHolder extends RecyclerView.ViewHolder {

    private ViewDataBinding binding;

    public ViewDataBinding getBinding() {
        return binding;
    }

    public void setBinding(ViewDataBinding binding) {
        this.binding = binding;
    }

    public ViewHolder(View itemView) {
        super(itemView);
    }
}

   RecyclerView recyclerView = (RecyclerView) findViewById(R.id.show_list);

        InitRecyclerView.initLinearLayoutWithoutDivid(this, recyclerView);
        List<Student> students = new ArrayList<>();
        Student student = new Student(R.drawable.tx2, "Kate");
        students.add(student);
        student = new Student(R.drawable.tx3, "tom");
        students.add(student);
        student = new Student(R.drawable.tx4, "Johnson");
        students.add(student);
        student = new Student(R.drawable.tx5, "Make");
        students.add(student);

        MySimpleAdapter<Student> adapter = new MySimpleAdapter<>(students, R.layout.student_item, BR.student);
        recyclerView.setAdapter(adapter);

在main layout里声明   
 <android.support.v7.widget.RecyclerView
            android:id="@+id/show_list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_above="@+id/navigation"
            android:layout_below="@id/tv"
            android:scrollbars="vertical" />

android data binding jetpack V

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