一个案例 用异步的方式获取内容和图片

Mainactivity

package com.example.lixin.zonghe;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.EditText;
import android.widget.ExpandableListView;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.lixin.zonghe.Bean.FoodInfo;
import com.example.lixin.zonghe.utils.LoadImageAsyncTask;
import com.example.lixin.zonghe.utils.StreamTools;
import com.google.gson.Gson;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private int index = 0;
    private ViewPager vp;
    private List<String> imgeAddress = new ArrayList<String>();
    private List<FoodInfo.ResultBean.DataBean.StepsBean> steps;
    private ExpandableListView exp;
    private EditText et;
    private FoodInfo foodInfo;
    private String name;


    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            //UI操作

            switch (msg.what){
                case 1:
                {
                    //界面切换
                    vp.setCurrentItem(index);
                }
                break;
            }

        }
    };



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

        imgeAddress.add("http://imgs.juheapi.com/health_knowledge/37f66a49e340be76df98199e29a312ff.jpg");
        imgeAddress.add("http://imgs.juheapi.com/health_knowledge/7ee98f9699ff2384376a002ac0a8bdb6.jpg");
        imgeAddress.add("http://imgs.juheapi.com/health_knowledge/3594118459d3a894739d7f41d5e3e732.jpg");
        imgeAddress.add("http://imgs.juheapi.com/health_knowledge/8dd7c5be67a19f8f7da73dbf2cc78025.jpg");

        vp = (ViewPager) findViewById(R.id.viewpager);
        et = (EditText) findViewById(R.id.et_text);
        exp = (ExpandableListView) findViewById(R.id.exp_list_view);

        //设置适配器
        vp.setAdapter(new MyPageAdapter());
        //开始轮播
        autoPlay();
    }

    class MyPageAdapter extends PagerAdapter {


        @Override
        public int getCount() {
            return Integer.MAX_VALUE;//2的31次方减1
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            //super.destroyItem(container, position, object);
            container.removeView((View) object);
        }


        @Override
        public Object instantiateItem(ViewGroup container, int position) {

            //产生一个条目，添加到显示容器里
            final ImageView imageView = new ImageView(MainActivity.this);


            new LoadImageAsyncTask(new LoadImageAsyncTask.ImageCallBackListener() {
                @Override
                public void imageCallBack(Bitmap bitmap) {
                    if(bitmap != null){
                        imageView.setImageBitmap(bitmap);
                    }else{
                        imageView.setImageResource(R.mipmap.ic_launcher);
                    }

                }//position % imgeAddress.size() 这个是取模，//position ++ 2的31 减一次方为止  0,1,2
            }).execute(imgeAddress.get(position % imgeAddress.size()));

            //添加到container
            container.addView(imageView);
            return imageView;
        }
    }
    private void autoPlay(){
        new Thread(){
            @Override
            public void run() {
                super.run();

                while (true){

                    index++;//index++ 1  ++index  1-> 2
                    int index1 = index % imgeAddress.size();
                    try { Thread.sleep(3000);} catch (InterruptedException e) { e.printStackTrace(); }//sleep 睡觉 UI不工作了

                    //发送消息

                    handler.sendEmptyMessage(1);
                }
            }
        }.start();
    }
    public void btn(View view){
        name = et.getText().toString().trim();
        System.out.println(name);
        getMenuInfo("http://apis.juhe.cn/cook/query?key=ff196b6ac0c60459952b35982c752568&menu="+name);

    }
    private void getMenuInfo(String path){

        new AsyncTask<String,Void,String>(){




            @Override
            protected void onPostExecute(String s) {
                super.onPostExecute(s);
                if (s!=null){

                    Gson gson = new Gson();
                    foodInfo = gson.fromJson(s, FoodInfo.class);
                    exp.setAdapter(new MyExpandAdapter());
                }else {
                    System.out.println("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
                }
            }

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

                try {
                    String path = params[0];
                    URL url = new URL(path);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(5000);
                    connection.setReadTimeout(5000);

                    int code = connection.getResponseCode();
                    if (code == 200){
                        InputStream is = connection.getInputStream();
                        String json = StreamTools.readFrom(is);
                        System.out.println("aaaa"+json);
                        return json;
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }
                return null;
            }
        }.execute(path);


    }
    public void loadImage(String path, final ImageView iv_image){


            new AsyncTask<String,Void,Bitmap>(){

                @Override
                protected void onPostExecute(Bitmap bitmap) {
                    super.onPostExecute(bitmap);
                    if (bitmap!=null){

                        iv_image.setImageBitmap(bitmap);

                    }else{

                        iv_image.setImageResource(R.mipmap.ic_launcher);

                    }

                }

                @Override
                protected Bitmap doInBackground(String... params) {

                    try {
                        String path = params[0];
                        URL url = new URL(path);
                        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                        connection.setRequestMethod("GET");
                        connection.setConnectTimeout(5000);
                        connection.setReadTimeout(5000);

                        int code = connection.getResponseCode();

                        if (code == 200){
                            InputStream is = connection.getInputStream();
                            return BitmapFactory.decodeStream(is);
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }

                    return null;
                }
            }.execute(path);

        }
    private class MyExpandAdapter extends BaseExpandableListAdapter{


        @Override
        public int getGroupCount() {
            return foodInfo.getResult().getData().size();
        }

        @Override
        public int getChildrenCount(int groupPosition) {
            return foodInfo.getResult().getData().get(groupPosition).getSteps().size();
        }

        @Override
        public Object getGroup(int groupPosition) {
            return foodInfo.getResult().getData().get(groupPosition);
        }

        @Override
        public Object getChild(int groupPosition, int childPosition) {
            return foodInfo.getResult().getData().get(groupPosition).getSteps().get(childPosition);
        }

        @Override
        public long getGroupId(int groupPosition) {
            return groupPosition;
        }

        @Override
        public long getChildId(int groupPosition, int childPosition) {
            return childPosition;
        }

        @Override
        public boolean hasStableIds() {
            return false;
        }

        @Override
        public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {

        if (convertView==null){
            convertView = View.inflate(MainActivity.this,R.layout.group_item,null);
        }
        ImageView iv = (ImageView) convertView.findViewById(R.id.groupIcon);
            TextView tv = (TextView) convertView.findViewById(R.id.groupTvTitle);

            tv.setText(foodInfo.getResult().getData().get(groupPosition).getTitle());
            loadImage(foodInfo.getResult().getData().get(groupPosition).getAlbums().get(0),iv);

            return convertView;
        }

        @Override
        public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
           if (convertView==null){
               convertView = View.inflate(MainActivity.this,R.layout.child_item,null);
           }
            ImageView iv1 = (ImageView) convertView.findViewById(R.id.childIcon);
            TextView tv1 = (TextView) convertView.findViewById(R.id.childTvTitle);

            tv1.setText(foodInfo.getResult().getData().get(groupPosition).getSteps().get(childPosition).getStep());
            loadImage(foodInfo.getResult().getData().get(groupPosition).getSteps().get(childPosition).getImg(),iv1);

            return convertView;
        }

        @Override
        public boolean isChildSelectable(int groupPosition, int childPosition) {
            return false;
        }
    }

}

LoadImageAsyncTask 获取图片

package com.example.lixin.zonghe.utils;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;

import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * Created by hua on 2017/7/12.
 */

public class LoadImageAsyncTask extends AsyncTask<String,Void,Bitmap> {


    public interface ImageCallBackListener{
        void imageCallBack(Bitmap bitmap);
    }
    public LoadImageAsyncTask(ImageCallBackListener imageCallBackListener){
        this.imageCallBackListener = imageCallBackListener;
    }
    private ImageCallBackListener imageCallBackListener;


    @Override
    protected void onPostExecute(Bitmap bitmap) {
        super.onPostExecute(bitmap);
        imageCallBackListener.imageCallBack(bitmap);
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        try {

            String path = params[0];
            URL url = new URL(path);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);

            int code = connection.getResponseCode();

            if (code == 200){

                InputStream is = connection.getInputStream();
               return BitmapFactory.decodeStream(is);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
}

工具类 StreamTools

package com.example.lixin.zonghe.utils;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;

/**
 * Created by hua on 2017/7/13.
 */

public class StreamTools {
    public static String readFrom(InputStream is)throws Exception{

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len = 0;
        while((len = is.read(buffer))!=-1){
            baos.write(buffer,0,len);
        }
        is.close();
        baos.close();
        return baos.toString();
    }
}