实现单一ListView条目样式HttpURLConnection、AsyncTask、Universal-Image-Loade

       使用HttpURLConnection、AsyncTask、Universal-Image-Loade实现访问网络接口获取数据，将数据展示在列表上，使用Universal-Image-Loader展示图片并对图片做全局配置，将图片缓存在SD卡的image目录下，列表图片显示成圆形。

1.在AndroidManifest.xml（清单文件）中进行权限配置：

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

2.在MainActivity中获取接口路径、解析JSon文件
package com.example.dell.a1511q0104;

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;

import com.google.gson.Gson;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView listView;

    String url = "http://api.tianapi.com/tiyu/?key=fe7aac932e1e94f10a4f8d0f2d5fe924&num=10";
    private StringBuilder builder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //找到资源控件的ID
        listView = findViewById(R.id.list_view);
        MyTask myTask = new MyTask();
        myTask.execute(url);
    }

    class MyTask extends AsyncTask<String,Void,String>{

        @Override
        protected String doInBackground(String... strings) {

            try {
                //创建URL路径
                URL url = new URL(strings[0]);
                //打开连接
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                //进行设置
                urlConnection.setRequestMethod("GET");
                urlConnection.setConnectTimeout(5000);
                urlConnection.setReadTimeout(5000);
                //判断响应码
                int responseCode = urlConnection.getResponseCode();
                if(responseCode==200){
                    //获取数据
                    InputStream inputStream = urlConnection.getInputStream();
                    //调取将流转为字符串的方法
                    String s = StreamToString(inputStream);
                    return s;
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            if(s!=null){
                //进行解析
                Gson gson = new Gson();
                RequestData requestData = gson.fromJson(s, RequestData.class);
                List<RequestData.NewslistBean> list = requestData.getNewslist();
                //创建适配器
                MyAdapter myAdapter = new MyAdapter(MainActivity.this, list);
                listView.setAdapter(myAdapter);

            }
        }
    }

    //设置将流转为字符串的方法
    private String StreamToString(InputStream stream){
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
            builder = new StringBuilder();
            String str;
            while ((str=reader.readLine())!=null){
                builder.append(str);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return builder.toString();
    }
}
3.创建一个类，封装Json数据的JavaBean
Alt+s:打开GsonFormat进行需解析的Json数据封装
4.创建一个类，继承Application
package com.example.dell.a1511q0104;

import android.app.Application;
import android.os.Environment;

import com.nostra13.universalimageloader.cache.disc.impl.UnlimitedDiscCache;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;

import java.io.File;

/**
 * Created by dell on 2018/1/4.
 */

public class MyApplication extends Application{
    @Override
    public void onCreate() {
        super.onCreate();
//自定义SD卡缓存目录 1.android默认cache-app被卸载时，缓存的目录一并被删除    2.自定义
        File file = new File(Environment.getExternalStorageDirectory().getPath()+"/images");
        //1.将Application初始化 进行全局配置
        ImageLoaderConfiguration configuration = new ImageLoaderConfiguration.Builder(this)
                .memoryCacheExtraOptions(400,700)//缓存图片的最大的长和高
                .threadPoolSize(3)//线程池的数量
                .threadPriority(4)//
                .memoryCacheSize(20*1024*1024)//设置内存缓存区大小
                .diskCacheSize(80*1024*1024)//设置SD卡缓存区大小
                .diskCache(new UnlimitedDiscCache(file))//自定义SD卡缓存目录
                .writeDebugLogs()//打印日志内容
                .diskCacheFileNameGenerator(new Md5FileNameGenerator())//给缓存的文件名进行MD5加密处理
                .build();
        ImageLoader.getInstance().init(configuration);

    }
}
5.创建适配器，对ListView进行优化
package com.example.dell.a1511q0104;

import android.content.Context;
import android.graphics.Bitmap;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
import com.nostra13.universalimageloader.core.display.RoundedBitmapDisplayer;

import java.util.List;

/**
 * Created by dell on 2018/1/4.
 */

class MyAdapter extends BaseAdapter{
   private Context context;
   private List<RequestData.NewslistBean> list;
   private DisplayImageOptions options;

    public MyAdapter(Context context, List<RequestData.NewslistBean> list) {
        this.context=context;
        this.list=list;
        options = new DisplayImageOptions.Builder()
                .cacheInMemory(true)//使用内存缓存
                .cacheOnDisk(true)//使用磁盘缓存
                .showImageOnLoading(R.mipmap.ic_launcher)//设置正在下载的图片
                .showImageForEmptyUri(R.mipmap.ic_launcher)//url为空或请求的资源不存在时
                .showImageOnFail(R.mipmap.ic_launcher)//下载失败时显示的图片
                .bitmapConfig(Bitmap.Config.RGB_565)//设置图片色彩模式 1px=2字节
                .imageScaleType(ImageScaleType.EXACTLY)//设置图片的缩放模式
                .displayer(new RoundedBitmapDisplayer(100))//设置圆角 30代表半径 自定义
                .build();

    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int i) {
        return list.get(i);
    }

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

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        ViewHolder holder;
        if(view==null){
            view=View.inflate(context,R.layout.listview,null);
            holder = new ViewHolder();
            holder.textView=view.findViewById(R.id.text_view);
            holder.imageView=view.findViewById(R.id.image_view);
            view.setTag(holder);
        }else{
            holder = (ViewHolder) view.getTag();
        }
            holder.textView.setText(list.get(i).getTitle());
        ImageLoader.getInstance().displayImage(list.get(i).getPicUrl(),holder.imageView,options);
        return view;
    }

    class ViewHolder{
        ImageView imageView;
        TextView textView;
    }
}
实现如下图效果：