Android开源框架——Retrofit入门（二）

        在明白和清楚了Retrofit的基本用法和获取百度主界面之后，下一步尝试获取知乎日报的最新文章标题。

        知乎日报的开放API: http://news-at.zhihu.com/api/4/news/latest

这个API返回的是json字符串，我们可以通过一些方式将json字符串转化为Java实体类。

         1、推荐使用网上的一个服务 http://www.bejson.com/json2javapojo/

         2、AndroidStudio也提供了一个插件GsonFormat，大家可以自行查询，将Json转化为实体Java类。

                                             例子：   通过使用Retrofit来获取知乎日报

               添加依赖

                

compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4'//Retrofit2所需要的包compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'//ConverterFactory的Gson依赖包

             添加网络许可

<uses-permission android:name="android.permission.INTERNET" />

         1>通过知乎日报API返回的数据来获取一个实体类ZhihuEntity，相关代码如下：

package com.example.app_retrofit;import java.util.List;/** * Created by 尽途 on 2017/7/21. */public class ZhihuEntity {    /**     * date : 20170721     * stories : [{"images":["https://pic4.zhimg.com/v2-81bcb9402f5de2bc332792815d891feb.jpg"],"type":0,"id":9535059,"ga_prefix":"072112","title":"大误 · 光绪 20 年，我的左臂没了"},{"images":["https://pic4.zhimg.com/v2-331fddc6b65a7c1010201a94bfa4f95b.jpg"],"type":0,"id":9527991,"ga_prefix":"072111","title":"近几年受追捧的日式建筑风格，其实也不完美"},{"images":["https://pic3.zhimg.com/v2-691cddd7bc8293d4ffb5af3d306c687a.jpg"],"type":0,"id":9533795,"ga_prefix":"072111","title":"不要长篇大论，就推荐 3 个最实用的 Excel 函数"},{"images":["https://pic3.zhimg.com/v2-abd6e944219c5722ec319bd40fc206a2.jpg"],"type":0,"id":9532340,"ga_prefix":"072109","title":"火过之后，VR 为何没成为像 iPhone 一样的时尚流行品？"},{"images":["https://pic1.zhimg.com/v2-1a7914acd259139728d77562f37e1bf4.jpg"],"type":0,"id":9534199,"ga_prefix":"072108","title":"家长帮助孩子的方法，就像是建筑用的「脚手架」"},{"title":"买房时说得多好，入住以后绿化没了，电梯坏了，遍地垃圾","ga_prefix":"072107","images":["https://pic3.zhimg.com/v2-f04ae40601d33409e15c1b8725d6814e.jpg"],"multipic":true,"type":0,"id":9531776},{"images":["https://pic4.zhimg.com/v2-ee46569b08751e54cd37a632e68128bf.jpg"],"type":0,"id":9533680,"ga_prefix":"072107","title":"比统计局早半个月预测出经济趋势，真是厉害"},{"images":["https://pic2.zhimg.com/v2-3dbcf22093c7ef491c4420d106064c25.jpg"],"type":0,"id":9534297,"ga_prefix":"072107","title":"怎么成为老司机？来一条一条对照着练吧"},{"images":["https://pic2.zhimg.com/v2-acb5bec97d166312b220b684b6f0d689.jpg"],"type":0,"id":9532612,"ga_prefix":"072106","title":"瞎扯 · 如何正确地吐槽"},{"images":["https://pic2.zhimg.com/v2-0b63ecae67fb62a9ac8728acd36acc0d.jpg"],"type":0,"id":9533500,"ga_prefix":"072106","title":"这里是广告 · 一包未来定制牛奶里能有多少高科技？"}]     * top_stories : [{"image":"https://pic4.zhimg.com/v2-91e5099dc6a7ebb7e865221a050e3eaf.jpg","type":0,"id":9534297,"ga_prefix":"072107","title":"怎么成为老司机？来一条一条对照着练吧"},{"image":"https://pic1.zhimg.com/v2-74230046934f7defbe40aa04f11078e4.jpg","type":0,"id":9533680,"ga_prefix":"072107","title":"比统计局早半个月预测出经济趋势，真是厉害"},{"image":"https://pic3.zhimg.com/v2-0a1983daeb6b6b4fe1c8b8ce79f266b6.jpg","type":0,"id":9531776,"ga_prefix":"072107","title":"买房时说得多好，入住以后绿化没了，电梯坏了，遍地垃圾"},{"image":"https://pic4.zhimg.com/v2-3f3cdb304fa86088fb31a01dbc940013.jpg","type":0,"id":9533191,"ga_prefix":"072019","title":"是不是觉得自己拍的照片挺美，就是看起来不高级？"},{"image":"https://pic4.zhimg.com/v2-614dffa0ed36c5e13f8e34a486922f3f.jpg","type":0,"id":9526772,"ga_prefix":"072016","title":"一届奥斯卡，三部片子剧情撞车：动画史上最大的抄袭悬案"}]     */    private String date;    private List<StoriesBean> stories;    private List<TopStoriesBean> top_stories;    public String getDate() {        return date;    }    public void setDate(String date) {        this.date = date;    }    public List<StoriesBean> getStories() {        return stories;    }    public void setStories(List<StoriesBean> stories) {        this.stories = stories;    }    public List<TopStoriesBean> getTop_stories() {        return top_stories;    }    public void setTop_stories(List<TopStoriesBean> top_stories) {        this.top_stories = top_stories;    }    public static class StoriesBean {        /**         * images : ["https://pic4.zhimg.com/v2-81bcb9402f5de2bc332792815d891feb.jpg"]         * type : 0         * id : 9535059         * ga_prefix : 072112         * title : 大误 · 光绪 20 年，我的左臂没了         * multipic : true         */        private int type;        private int id;        private String ga_prefix;        private String title;        private boolean multipic;        private List<String> images;        public int getType() {            return type;        }        public void setType(int type) {            this.type = type;        }        public int getId() {            return id;        }        public void setId(int id) {            this.id = id;        }        public String getGa_prefix() {            return ga_prefix;        }        public void setGa_prefix(String ga_prefix) {            this.ga_prefix = ga_prefix;        }        public String getTitle() {            return title;        }        public void setTitle(String title) {            this.title = title;        }        public boolean isMultipic() {            return multipic;        }        public void setMultipic(boolean multipic) {            this.multipic = multipic;        }        public List<String> getImages() {            return images;        }        public void setImages(List<String> images) {            this.images = images;        }    }    public static class TopStoriesBean {        /**         * image : https://pic4.zhimg.com/v2-91e5099dc6a7ebb7e865221a050e3eaf.jpg         * type : 0         * id : 9534297         * ga_prefix : 072107         * title : 怎么成为老司机？来一条一条对照着练吧         */        private String image;        private int type;        private int id;        private String ga_prefix;        private String title;        public String getImage() {            return image;        }        public void setImage(String image) {            this.image = image;        }        public int getType() {            return type;        }        public void setType(int type) {            this.type = type;        }        public int getId() {            return id;        }        public void setId(int id) {            this.id = id;        }        public String getGa_prefix() {            return ga_prefix;        }        public void setGa_prefix(String ga_prefix) {            this.ga_prefix = ga_prefix;        }        public String getTitle() {            return title;        }        public void setTitle(String title) {            this.title = title;        }    }}

       2>接口定义（以知乎日报API为例）

接口名定义为GetZhihu1,具体如下：

public interface GetZhihu1 {    @GET("/api/4/news/latest")    Call<ZhihuEntity>getZhihuNews();

         3>创建Retrofit并引用

    Retrofit retrofit=new Retrofit                .Builder()                .baseUrl(baseUrl)                .addConverterFactory(GsonConverterFactory.create())//涉及到json到实体的转变，                .build();        GetZhihu1 getZhihu1=retrofit.create(GetZhihu1.class);        Call<ZhihuEntity>call=getZhihu1.getZhihuNews();        call.enqueue(new Callback<ZhihuEntity>() {            @Override            public void onResponse(Call<ZhihuEntity> call, Response<ZhihuEntity> response) {                List<ZhihuEntity.StoriesBean> storiesBeen=response.body().getStories();//获取                text_zhihu_get.setText(storiesBeen.get(1).getTitle());//x显示一部分            }            @Override            public void onFailure(Call<ZhihuEntity> call, Throwable t) {            }        });

为了显示结果，我选取了返回数据的一部分数据显示在TextView中。
       具体代码如下：

1、XML代码：

<?xml version="1.0" encoding="utf-8"?><LinearLayout android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    xmlns:android="http://schemas.android.com/apk/res/android" >    <Button        android:id="@+id/button_zhihu1_get"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="获取"/>    <TextView        android:id="@+id/text_zhihu1_get"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="hello world"/></LinearLayout>

2、Java代码：

package com.example.app_retrofit;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.Button;import android.widget.TextView;import java.util.List;import butterknife.Bind;import butterknife.ButterKnife;import butterknife.OnClick;import retrofit2.Call;import retrofit2.Callback;import retrofit2.Response;import retrofit2.Retrofit;import retrofit2.converter.gson.GsonConverterFactory;public class Zhihu1Activity extends AppCompatActivity {    @Bind(R.id.button_zhihu1_get)    Button button_zhihu1_get;    @Bind(R.id.text_zhihu1_get)    TextView text_zhihu_get;    private String baseUrl="http://news-at.zhihu.com";    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_zhihu1);        ButterKnife.bind(this);    }    @OnClick(R.id.button_zhihu1_get)    public void onclickButton_zhihi1_get(){        Retrofit retrofit=new Retrofit                .Builder()                .baseUrl(baseUrl)                .addConverterFactory(GsonConverterFactory.create())//涉及到json到实体的转变，                .build();        GetZhihu1 getZhihu1=retrofit.create(GetZhihu1.class);        Call<ZhihuEntity>call=getZhihu1.getZhihuNews();        call.enqueue(new Callback<ZhihuEntity>() {            @Override            public void onResponse(Call<ZhihuEntity> call, Response<ZhihuEntity> response) {                List<ZhihuEntity.StoriesBean> storiesBeen=response.body().getStories();                text_zhihu_get.setText(storiesBeen.get(1).getTitle());            }            @Override            public void onFailure(Call<ZhihuEntity> call, Throwable t) {            }        });    }}

3、接口代码：

package com.example.app_retrofit;import retrofit2.Call;import retrofit2.http.GET;/** * Created by 尽途 on 2017/7/29. */public interface GetZhihu1 {    @GET("/api/4/news/latest")    Call<ZhihuEntity>getZhihuNews();}

       4、实现结果与问题：

代码片段中的ButterKnife为一个挺好用的view注入框架，在此不再赘述。