Android之MVVM开发模式和DataBinding的简单用法

最新推荐文章于 2024-08-23 22:53:32 发布

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本文通过示例介绍了 Android Data Binding 的使用方法，包括基本属性绑定、图片加载及 ListView 中的数据绑定技术。

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http://blog.youkuaiyun.com/u012702547/article/details/52077515

以下代码拷贝出来可直接运行看效果：Demo1和Demo2的效果写在一起了。。。。。

1.activity_main.xml

<?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>

        <variable
            name="user"
            type="com.haiyangyin.mytest.been.UserEntity"/>
    </data>

    <LinearLayout
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="com.haiyangyin.mytest.MainActivity">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.username}"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.nickname}"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{`username is:`+user.username}"/><!--字符串拼接-->
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(user.age)}"/><!--int类型转换-->

        <ImageView
            android:id="@+id/iv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:userface="@{user.userface}"/>
    </LinearLayout>
</layout>

2.UserEntity实体类：

package com.haiyangyin.mytest.been;

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

import com.squareup.picasso.Picasso;

/**
 * Created by YinHaiYang on 2017/2/21.
 */

public class UserEntity {
    private String username;
    private String nickname;
    private String userface;
    private int age;

    public UserEntity() {
    }

    public UserEntity(int age, String nickname, String username) {
        this.age = age;
        this.nickname = nickname;
        this.username = username;
    }

    public UserEntity(String userface, String nickname) {
        this.nickname = nickname;
        this.userface = userface;
    }

    @BindingAdapter("bind:userface")
    public static void getInternetImage(ImageView iv, String userface) {
        Picasso.with(iv.getContext()).load(userface).into(iv);
    }

    public int getAge() {
        return age;
    }

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

    public String getNickname() {
        return nickname;
    }

    public void setNickname(String nickname) {
        this.nickname = nickname;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUserface() {
        return userface;
    }

    public void setUserface(String userface) {
        this.userface = userface;
    }

}

3.MainActivity类：

package com.haiyangyin.mytest;

import android.databinding.DataBindingUtil;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;

import com.haiyangyin.mytest.been.UserEntity;
import com.haiyangyin.mytest.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMainBinding activityMainBinding= DataBindingUtil.setContentView(this, R.layout.activity_main);
       // activityMainBinding.setUser(new UserEntity(34,"zhangsan","张三"));
        activityMainBinding.setUser(new UserEntity("http://img2.cache.netease.com/auto/2016/7/28/201607282215432cd8a.jpg","lisi"));

    }
    
}

注意：访问图片的时候AndroidManifest中加网路权限<uses-permission android:name="android.permission.INTERNET" />

Demo3:

acvitivty_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.haiyangyin.mytest.MainActivity">

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

listview_item.xml

<?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>

        <variable
            name="food"
            type="com.haiyangyin.mytest.been.Food" />
    </data>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="96dp">

        <ImageView
            android:id="@+id/iv"
            android:layout_width="96dp"
            android:layout_height="96dp"
            android:padding="6dp"
            app:img="@{food.img}" />

        <TextView
            android:id="@+id/description"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="8dp"
            android:layout_toRightOf="@id/iv"
            android:ellipsize="end"
            android:maxLines="3"
            android:text="@{food.description}" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_marginBottom="2dp"
            android:layout_marginLeft="8dp"
            android:layout_toRightOf="@id/iv"
            android:text="@{food.keywords}"
            android:textStyle="bold" />

    </RelativeLayout>

</layout>

Food.java

package com.haiyangyin.mytest.been;

import android.databinding.BindingAdapter;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

import com.squareup.picasso.Picasso;

/**
 * Created by YinHaiYang on 2017/2/20.
 */

public class Food {
    private String description;
    private String img;
    private String keywords;
    private String summary;

    private Food(){

    }

    public Food(String description, String img, String keywords, String summary) {
        this.description = description;
        this.img = img;
        this.keywords = keywords;
        this.summary = summary;
    }
    @BindingAdapter("bind:img")
    public static void loadInternetImage(ImageView iv,String img){
        Picasso.with(iv.getContext()).load(img).into(iv);
    }

    public void onItemClick(View view){
        Toast.makeText(view.getContext(),getDescription(),Toast.LENGTH_SHORT).show();
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getImg() {
        return img;
    }

    public void setImg(String img) {
        this.img = img;
    }

    public String getKeywords() {
        return keywords;
    }

    public void setKeywords(String keywords) {
        this.keywords = keywords;
    }

    public String getSummary() {
        return summary;
    }

    public void setSummary(String summary) {
        this.summary = summary;
    }
}

FoodAdapter.java

package com.haiyangyin.mytest;

import android.content.Context;
import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import java.util.List;

/**
 * Created by YinHaiYang on 2017/2/20.
 */

public class FoodAdapter<T> extends BaseAdapter {
    private Context context;
    private LayoutInflater inflater;
    private int layoutId;//layoutId这个表示item布局的资源id
    private int variableId;//variableId是系统自动生成的，根据我们的实体类，直接从外部传入即可
    private List<T> lists;

    public FoodAdapter(Context context, int layoutId, int resId, List<T> lists) {
        this.context = context;
        this.layoutId = layoutId;
        this.lists = lists;
        this.variableId = resId;
        inflater=LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return lists.size() > 0 ? lists.size() : 0;
    }

    @Override
    public Object getItem(int position) {
        return lists.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewDataBinding dataBinding;
        if (convertView == null) {
            dataBinding = DataBindingUtil.inflate(inflater, layoutId, parent, false);
        } else {
            dataBinding = DataBindingUtil.getBinding(convertView);
        }
        dataBinding.setVariable(variableId, lists.get(position));
        return dataBinding.getRoot();
    }
}

MainActivity.java

package com.haiyangyin.mytest;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import com.haiyangyin.mytest.been.Food;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            FoodAdapter<Food> adapter = new FoodAdapter<>(MainActivity.this, R.layout.listview_item, com.haiyangyin.mytest.BR.food, foods);
            lv.setAdapter(adapter);
        }
    };
    private List<Food> foods;
    private ListView lv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = ((ListView) findViewById(R.id.listview));
        initData();
    }

    private void initData() {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url("http://www.tngou.net/api/food/list?id=1").build();
        client.newCall(request).enqueue(new Callback() {

            @Override
            public void onFailure(Request request, IOException e) {

            }

            @Override
            public void onResponse(Response response) throws IOException {
                if (response.isSuccessful()) {
                    parseJson(response.body().string());
                }
            }
        });
    }

    private void parseJson(String jsonStr) {
        foods = new ArrayList<>();
        try {
            JSONObject jo = new JSONObject(jsonStr);
            JSONArray tngou = jo.getJSONArray("tngou");
            for (int i = 0; i < tngou.length(); i++) {
                JSONObject item = tngou.getJSONObject(i);
                String description = item.getString("description");
                String img = "http://tnfs.tngou.net/image" + item.getString("img");
                String keywords = "【关键词】 " + item.getString("keywords");
                String summary = item.getString("summary");
                foods.add(new Food(description, img, keywords, summary));
            }
            mHandler.sendEmptyMessage(0);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        foods.get(position).onItemClick(view);
    }
}

运行结果：