Android使用Retrofit_00_Getting Started

原教程視頻在這裏。

原教程源碼在這裏。

添加Android項目的dependence（注：其他dependence並未列出）

dependencies {
    compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-gson:2.3.0'
}

修改dependencies之後，項目Gradle需要sync一下。

修改Manifest文件，增加一個網絡權限。

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

利用GitHub來進行示例。

創建一個GitHubRepo類，用於表示一個repo。

package com.huyaoyu.retrofitgetstarted;

/**
 * Created by yaoyu on 3/2/18.
 */

public class GitHubRepo {

    private String name;

    public String getName() {
        return name;
    }
}

創建一個GitHubClient Interface，返回一個Call object。

package com.huyaoyu.retrofitgetstarted;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.GET;
import retrofit2.http.Path;

/**
 * Created by yaoyu on 3/2/18.
 */

public interface GitHubClient {

    @GET("/users/{user}/repos")
    Call<List<GitHubRepo>> reposForUser(@Path("user") String user);

}

創建一個GitHubRepoAdapter類，用於生成ListView的各個row。

package com.huyaoyu.retrofitgetstarted;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import java.util.List;

/**
 * Created by yaoyu on 3/2/18.
 */

public class GitHubRepoAdapter extends ArrayAdapter<GitHubRepo> {

    private Context context;
    private List<GitHubRepo> values;

    public GitHubRepoAdapter(Context context, List<GitHubRepo> values) {
        super(context, R.layout.list_item_pagination, values);

        this.context = context;
        this.values  = values;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;

        if ( row == null ) {
            LayoutInflater inflater =
                    (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.list_item_pagination, parent, false);
        }

        TextView textView = (TextView) row.findViewById(R.id.list_item_pagination_text);

        GitHubRepo item = values.get(position);
        String message = item.getName();
        textView.setText(message);

        return row;
    }
}

修改MainActivity類，分別創建Retrofit對象，GitHubClient對象和Call對象。利用Call對象獲得response，從response中利用GitHubRepoAdapter提取出需要的信息填充ListView。

package com.huyaoyu.retrofitgetstarted;

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

import java.util.List;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {

    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listView = (ListView) findViewById(R.id.pagination_list);

        Retrofit.Builder builder = new Retrofit.Builder()
                .baseUrl("https://api.github.com/")
                .addConverterFactory(GsonConverterFactory.create());

        Retrofit retrofit = builder.build();

        GitHubClient client = retrofit.create(GitHubClient.class);

        Call<List<GitHubRepo>> call = client.reposForUser("huyaoyu");

        call.enqueue(new Callback<List<GitHubRepo>>() {
            @Override
            public void onResponse(Call<List<GitHubRepo>> call, Response<List<GitHubRepo>> response) {
                List<GitHubRepo> repos = response.body();

                listView.setAdapter(new GitHubRepoAdapter(MainActivity.this, repos));
            }

            @Override
            public void onFailure(Call<List<GitHubRepo>> call, Throwable t) {
                Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.huyaoyu.retrofitgetstarted.MainActivity">

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

</android.support.constraint.ConstraintLayout>

list_item_pagination.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="wrap_content"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/list_item_pagination_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@+id/label"
        android:textSize="20sp"/>

</LinearLayout>

執行效果如下圖。