使用hander让图片发生改变

布局文件：

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent">

    <ImageView

        android:id="@+id/image_view"

        android:scaleType="fitXY"

        android:layout_width="match_parent"

        android:layout_height="200dp" />

</RelativeLayout>

——————————————》activity代码

package news1510a.bawei.com.a17_demo;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.support.v7.app.AppCompatActivity;

import android.widget.ImageView;

import com.google.gson.Gson;

import com.nostra13.universalimageloader.core.ImageLoader;

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import java.util.ArrayList;

import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;

    private List<String> list = new ArrayList<>();

    private int index = 0;

    private Handler handler = new Handler(){

        @Override

        public void handleMessage(Message msg) {

            if (msg.what == 0){

                //街道消息之后,,,切换图片显示

                index ++;

                ImageLoader.getInstance().displayImage(list.get(index %list.size()),imageView,ImageLoaderUtil.getDefaultOption());

                //再次发送

                handler.sendEmptyMessageDelayed(0,3000);

            }

        }

    };

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        imageView = (ImageView) findViewById(R.id.image_view);

        getDataFromNet();

    }

    private void getDataFromNet() {

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

            @Override

            protected String doInBackground(Void... voids) {

                try {

                    URL url = new URL("http://apis.juhe.cn/cook/query?key=65481ae0fb17703c15a794aebaec93c5&menu=%E8%A5%BF%E7%BA%A2%E6%9F%BF&rn=10&pn=3");

                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();

                    connection.setRequestMethod("GET");

                    connection.setReadTimeout(5000);

                    connection.setConnectTimeout(5000);

                    int responseCode = connection.getResponseCode();

                    if (responseCode == 200){

                        InputStream inputStream = connection.getInputStream();

                        String json = StringUtil.streamToString(inputStream,"utf-8");

                        return json;

                    }

                } catch (MalformedURLException e) {

                    e.printStackTrace();

                } catch (IOException e) {

                    e.printStackTrace();

                }

                return null;

            }

            @Override

            protected void onPostExecute(String s) {

                //解析

                Gson gson = new Gson();

                DataDataBean dataDataBean = gson.fromJson(s, DataDataBean.class);

                List<DataDataBean.ResultBean.DataBean.StepsBean> steps = dataDataBean.getResult().getData().get(0).getSteps();

                for (DataDataBean.ResultBean.DataBean.StepsBean st: steps) {

                    list.add(st.getImg());

                }

                //现在图片集合有数据,,,,展示图片,,,展示第一张图片

                ImageLoader.getInstance().displayImage(list.get(0),imageView,ImageLoaderUtil.getDefaultOption());

                //发送延时消息

                handler.sendEmptyMessageDelayed(0,3000);

            }

        };

        asyncTask.execute();

    }

}

——————————工具类Stringutils类代码

public static String streamToString(InputStream inputStream, String charset) {

        try {

            InputStreamReader inputStreamReader = new InputStreamReader(inputStream,charset);

            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

            String s = null;

            StringBuilder builder = new StringBuilder();

            while ((s = bufferedReader.readLine()) != null){

                builder.append(s);

            }

            bufferedReader.close();

            return builder.toString();

        } catch (Exception e) {

            e.printStackTrace();

        }

        return  null;

    }