<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical">

  <ImageView
    android:id="@+id/show"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scaleType="fitCenter" />
</LinearLayout>

package com.fukaimei.urltest;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

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

public class MainActivity extends AppCompatActivity {

  ImageView show;
  // 代表从网络下载得到的图片
  Bitmap bitmap;
  Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      if (msg.what == 0x123) {
        // 使用ImageView显示该图片
        show.setImageBitmap(bitmap);
      }
    }
  };

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    show = (ImageView) findViewById(R.id.show);
    new Thread() {
      @Override
      public void run() {
        try {
          // 定义一个URL对象
          URL url = new URL("http://172.xx.xxx.xxx:8080/fukaimei/android_vs_ios.jpg");
          // 打开该URL对应的资源的输入流
          InputStream is = url.openStream();
          // 从InputStream中解析出图片
          bitmap = BitmapFactory.decodeStream(is);
          // 发送消息，通知UI组件的资源的输入流
          handler.sendEmptyMessage(0x123);
          is.close();
          // 再次打开URL对应的资源的输入流
          is = url.openStream();
          // 打开手机文件对应的输入流
          OutputStream os = openFileOutput("android_vs_ios.jpg", MODE_PRIVATE);
          byte[] buff = new byte[1024];
          int hasRead = 0;
          // 将URL对应的资源下载到本地
          while ((hasRead = is.read(buff)) > 0) {
            os.write(buff, 0, hasRead);
          }
          is.close();
          os.close();
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    }.start();
  }
}

<!-- 授权访问互联网-->
  <uses-permission android:name="android.permission.INTERNET" />