网络数据存到本地，无网络时取出本地数据

package com.bwie.imageloadercache;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Environment;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;

import com.google.gson.Gson;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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 lv;


@RequiresApi(api = Build.VERSION_CODES.M)
@Override
    protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

lv = (ListView) findViewById(R.id.lv);


boolean b = getnetState(getApplicationContext());
if(b){
            System.out.println("有网网网网网网网网网网网网网网网网网网网网网网网");
        loadData("http://japi.juhe.cn/health_knowledge/infoList?key=0efb839c8e13e91a0e928f8164048a5d");
        }else{
            System.out.println("没网网网网网网网网网网网网网网网网网网网网网网网");
// lv.setAdapter(new Myadapter(list));
            try {
                File file = new File(getCacheDir(), "info.txt");
                InputStream is= new FileInputStream(file);
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bytes = new byte[1024];
int len = 0;

while ((len = is.read(bytes)) != -1) {
                    baos.write(bytes, 0, len);
                }
                is.close();
                baos.close();
                String s=baos.toString();
                Gson gson = new Gson();
                HealthInfo healthInfo = gson.fromJson(s, HealthInfo.class);
                List<HealthInfo.ResultBean.DataBean> list = healthInfo.getResult().getData();

lv.setAdapter(new Myadapter(list));


            } catch (Exception e) {
                e.printStackTrace();
            }
        }



    }

private void loadData(String path) {
        System.out.println("******************loadData");

new AsyncTask<String, Void, String>() {
@Override
            protected String doInBackground(String... params) {
try {
                    System.out.println("******************doInBackground");
                    HttpURLConnection connection = (HttpURLConnection) new URL(params[0]).openConnection();
                    connection.setRequestMethod("GET");
                    connection.setConnectTimeout(5000);
                    connection.setReadTimeout(5000);
if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                        System.out.println("******************HTTP_OK");
                        InputStream is = connection.getInputStream();

                        File file = new File(getCacheDir(),"info.txt");
                        OutputStream os = new FileOutputStream(file);
                        ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bytes = new byte[1024];
int len = 0;

while ((len = is.read(bytes)) != -1) {
                            baos.write(bytes, 0, len);
                            os.write(bytes, 0, len);
                        }
                        os.close();
                        is.close();
                        baos.close();
                        System.out.println("写完完完完完完完完完完完完完");
return baos.toString();
                    }

                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
return null;
            }

@Override
            protected void onPostExecute(String s) {
                System.out.println("******************onPostExecute");
super.onPostExecute(s);
if (s != null) {
                    Gson gson = new Gson();
                    HealthInfo healthInfo = gson.fromJson(s, HealthInfo.class);
                    List<HealthInfo.ResultBean.DataBean> list = healthInfo.getResult().getData();

lv.setAdapter(new Myadapter(list));
                }
            }
        }.execute(path);
    }

class Myadapter extends BaseAdapter {

        DisplayImageOptions options;
        List<HealthInfo.ResultBean.DataBean> list;

public Myadapter(List<HealthInfo.ResultBean.DataBean> list) {
this.list = list;
options = new DisplayImageOptions.Builder()
                    .cacheOnDisk(true)
                    .cacheInMemory(true)
                    .build();
        }

@Override
        public int getCount() {
return list != null ? list.size() : 0;
        }

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

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

@Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView = new ImageView(getApplicationContext());

            ImageLoader.getInstance().displayImage(list.get(position).getImg(), imageView, options);

return imageView;
        }
    }

@RequiresApi(api = Build.VERSION_CODES.M)
boolean getnetState(Context context) {
        ConnectivityManager mannager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetworkInfo = mannager.getActiveNetworkInfo();

return activeNetworkInfo != null && activeNetworkInfo.isConnected();
    }
}