HttpUrlConnection+图片加载+工具类+接口回调+单例+AsyncTask封装工具类

1.MainActivity页面

package com.example.httpurlconnection;

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

public class MainActivity extends AppCompatActivity {

    private ListView listView;
    private NewsAdaper mAdaper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获取资源id
        listView = findViewById(R.id.listview);
        //创建适配器
        mAdaper = new NewsAdaper(MainActivity.this);
        //给listview赋值
        listView.setAdapter(mAdaper);
        //加载数据的方法
        infoData();
    }
    private String urlStr = "http://api.expoon.com/AppNews/getNewsList/type/1/p/1";
    //加载数据的方法
    private void infoData() {
        NetUtil.getInstance(MainActivity.this).getResult(urlStr, NewsBean.class, new NetUtil.AsyCallBack<NewsBean>() {
            @Override
            public void onSuccess(NewsBean o) {
                mAdaper.setmData(o.getData());
            }
        });
    }
}

2.Bean类

package com.example.httpurlconnection;

import java.util.List;

public class NewsBean {

    private List<DataBean> data;

    public List<DataBean> getData() {
        return data;
    }

    public void setData(List<DataBean> data) {
        this.data = data;
    }

    public static class DataBean {

        private String news_id;
        private String news_title;
        private String news_summary;
        private String pic_url;

        public String getNews_id() {
            return news_id;
        }

        public void setNews_id(String news_id) {
            this.news_id = news_id;
        }

        public String getNews_title() {
            return news_title;
        }

        public void setNews_title(String news_title) {
            this.news_title = news_title;
        }

        public String getNews_summary() {
            return news_summary;
        }

        public void setNews_summary(String news_summary) {
            this.news_summary = news_summary;
        }

        public String getPic_url() {
            return pic_url;
        }

        public void setPic_url(String pic_url) {
            this.pic_url = pic_url;
        }
    }
}

3.适配器类

package com.example.httpurlconnection;

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

import java.util.ArrayList;
import java.util.List;

public class NewsAdaper extends BaseAdapter {
    private List<NewsBean.DataBean> mData;
    private Context mContext;

    public NewsAdaper(Context mContext) {
        this.mContext = mContext;
        //初始化
        mData = new ArrayList<>();
    }
    public void setmData(List<NewsBean.DataBean> datas){
        this.mData = datas;
        notifyDataSetChanged();
    }
    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public NewsBean.DataBean getItem(int position) {
        return mData.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if(convertView == null){
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item,parent,false);
            holder = new ViewHolder(convertView);
        }else{
            holder = (ViewHolder) convertView.getTag();
        }
        holder.bind(getItem(position));
        return convertView;
    }
    //寄存器
    class ViewHolder{
        ImageView image;
        TextView text1;
        TextView text2;
        //获取资源id
        public ViewHolder(View convertView) {
            image = convertView.findViewById(R.id.image);
            text1 = convertView.findViewById(R.id.text1);
            text2 = convertView.findViewById(R.id.text2);
            convertView.setTag(this);
        }
        //赋值
        public void bind(final NewsBean.DataBean item) {
            text1.setText(item.getNews_title());
            text2.setText(item.getNews_summary());
            image.setTag(item.getPic_url());
            NetUtil.getInstance(mContext).loadImage(item.getPic_url(), new NetUtil.imageCallBack() {
                @Override
                public void getImageSuccess(String imageUrl, Bitmap bitmap) {
                    if(image.getTag().equals(item.getPic_url())){
                        image.setImageBitmap(bitmap);
                    }
                }
            });
        }
    }
}

4.工具类+单例

package com.example.httpurlconnection;


import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.LruCache;

import com.google.gson.Gson;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;


public class NetUtil {
    //单例
    private static NetUtil instance;
    //图片内存缓存
    private static LruCache<String,Bitmap> cache;
    private File saveDir;
    //提供方法，获取对象

    public static NetUtil getInstance(Context context) {
        if(instance == null){
            instance = new NetUtil(context);
        }
        return instance;
    }

    //私有构造
    private NetUtil(Context context){
      int size = (int)(Runtime.getRuntime().freeMemory()*0.3);
      cache = new LruCache<>(size);
      //图片文件缓存目录
        saveDir = new File(context.getCacheDir(),"imag_cache");
        //不存在创建
        if(!saveDir.exists()){
            saveDir.mkdirs();
        }
    }
    //httpurlconnection网络请求返回string
    public String getResult(String urlStr){
        String result = "";
        try {
            //定义url地址
            URL url = new URL(urlStr);
            //打开连接
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            //定义请求类型
            urlConnection.setRequestMethod("GET");
            //设置超时
            urlConnection.setReadTimeout(5000);
            urlConnection.setConnectTimeout(5000);
            //获取状态码
            int responseCode = urlConnection.getResponseCode();
            if(responseCode == 200){
                 result = stream2String(urlConnection.getInputStream());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
    //将字节流装换为字符流
    private String stream2String(InputStream inputStream) throws IOException {
        InputStreamReader isr = new InputStreamReader(inputStream);
        BufferedReader br = new BufferedReader(isr);
        StringBuilder builder = new StringBuilder();
        for(String tmp = br.readLine();tmp!=null;tmp = br.readLine()){
            builder.append(tmp);
        }
        return builder.toString();
    }
    //解析gson返回bean
    public  <E> E getResult(String urlStr,Class clazz){
        String result = getResult(urlStr);
       E e = (E) new Gson().fromJson(result,clazz);
        return e;
    }
    //定义接口
    public interface AsyCallBack<E>{
        void onSuccess(E e);
    }
    //执行线程的方法
    @SuppressLint("StaticFieldLeak")
    public  void getResult(String urlStr, final Class clazz, final AsyCallBack asyCallBack){
        new AsyncTask<String,Void,Object>(){
            @Override
            protected Object doInBackground(String... strings) {
                return getResult(strings[0],clazz);
            }

            @Override
            protected void onPostExecute(Object o) {
                asyCallBack.onSuccess(o);
            }
        }.execute(urlStr);
    }
    //加载网络图片 返回Bitmap
    public  Bitmap loadImage(String urlImage){
        Bitmap bitmap = null;
        try {
            //定义url地址
            URL url = new URL(urlImage);
            //打开连接
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            //定义请求类型
            urlConnection.setRequestMethod("GET");
            //设置超时
            urlConnection.setReadTimeout(5000);
            urlConnection.setConnectTimeout(5000);
            //获取状态码
            int responseCode = urlConnection.getResponseCode();
            if(responseCode == 200){
                bitmap = BitmapFactory.decodeStream(urlConnection.getInputStream());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return bitmap;
    }
    //定义接口
    public interface imageCallBack{
        void getImageSuccess(String imageUrl,Bitmap bitmap);
    }
    //获取图片回调接口
    @SuppressLint("StaticFieldLeak")
    public  void loadImage(final String imageUrl, final imageCallBack imageCallBack){
        new AsyncTask<String,Void,Bitmap>(){
            @Override
            protected Bitmap doInBackground(String... strings) {
                return loadImage(strings[0]);
            }

            @Override
            protected void onPostExecute(Bitmap bitmap) {
                imageCallBack.getImageSuccess(imageUrl,bitmap);
            }
        }.execute(imageUrl);
    }
    //获取图片三级缓存
    public Bitmap loadImageWork(String imageUrl){
        Bitmap bitmap = null;
        //从内存中取图片
        bitmap = cache.get(url2Key(imageUrl));
        //内存命中
        if(bitmap!=null){
            return bitmap;
        }
        //从磁盘中取图片
        bitmap = getBitmapForFile(imageUrl);
        //文件命中
        if(bitmap!=null){
            cache.put(url2Key(imageUrl),bitmap);
            return bitmap;
        }
        //从网络申请
        bitmap = loadImage(imageUrl);
       //写文件
        saveBitmap2File(imageUrl,bitmap);
        //存到内存缓存
        cache.put(url2Key(imageUrl),bitmap);
        return bitmap;
    }
    //将图片存到文件
    private void saveBitmap2File(String imageUrl, Bitmap bitmap) {
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(new File(saveDir,url2Key(imageUrl)));
            //图片质量压缩
            bitmap.compress(Bitmap.CompressFormat.JPEG,100,fos);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }finally {
            if(fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    //从文件读取图片
    private Bitmap getBitmapForFile(String imageUrl) {
    //解码文件为bitmap图片
        return BitmapFactory.decodeFile(new File(saveDir,url2Key(imageUrl)).getAbsolutePath());
    }

    //将url装换为key
    private String url2Key(String imageUrl) {

        return String.valueOf(imageUrl.hashCode());
    }
}