网络请求 当我们遇到调用很多次为了减少代码量和内存的占用 我们可以写一个工具类 每次需要我们可以直接调用 单例模式

package com.example.day8_2;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.AsyncTask;
import android.widget.ImageView;

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.util.List;

public class Util {

//单例
private static Util instance;

//私有构造方法
private Util() {
}

//提供方法,获取对象
public static Util getInstance() {
    if(instance == null) {
        instance = new Util();
    }
    return instance;
}

public static T jiexi(String lujing,Class clazz){
T t = (T) new Gson().fromJson(getRequest(lujing), clazz);
return t;
}

//普通get请求
public static String getRequest(String UrlPath){
    try {
        URL url = new URL(UrlPath);
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        int responseCode = urlConnection.getResponseCode();
        if(responseCode == 200){
            String result = Tostring(urlConnection.getInputStream());

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


public static void bitmap(String url, final ImageView imageView){

    new AsyncTask<String, Void, Bitmap>() {
        @Override
        protected Bitmap doInBackground(String... strings) {
            Bitmap bitmap = Util.getBitmap(strings[0]);
            return bitmap;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            imageView.setImageBitmap(bitmap);
        }
    }.execute(url);

}

public static Bitmap getBitmap(String url){

    try {
        URL urll = new URL(url);
        HttpURLConnection urlConnection = (HttpURLConnection) urll.openConnection();
        int responseCode = urlConnection.getResponseCode();
        if(responseCode == 200){
            Bitmap bitmap = BitmapFactory.decodeStream(urlConnection.getInputStream());
            return bitmap;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

    return null;
}

private static String Tostring(InputStream inputStream) throws IOException {

    StringBuilder stringBuilder = new StringBuilder();

    InputStreamReader inputStreamReader = new InputStreamReader(inputStream);

    BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

    for(String mmp = bufferedReader.readLine();mmp!=null;mmp = bufferedReader.readLine()){

        stringBuilder.append(mmp);
    }
    return stringBuilder.toString();
}

}