网络图片查看器

软件界面

MainActivity.java

package com.peng.image_show;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;

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

public class MainActivity extends AppCompatActivity {
    private ImageView iv;
    private EditText et_path;

    /*private Handler handle = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            Bitmap bitmap = (Bitmap) msg.obj;
            iv.setImageBitmap(bitmap);
        }
    };*/
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_path = (EditText) findViewById(R.id.et_path);
        iv = (ImageView) findViewById(R.id.iv);
    }

    public void click(View view) {
        new Thread() {
            public void run() {
                try {
                    //获取图片路径
                    String path = et_path.getText().toString().trim();
                    //File file = new File(getCacheDir(), Base64.encodeToString(path.getBytes(),Base64.DEFAULT);
                    File file = new File(getCacheDir(), "test.png");
                    if (file.exists() && file.length() > 0) {
                        //使用缓存图片
                        System.out.println("---->>>>>>>>>>使用缓存的图片");
                        final Bitmap cacheBitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
                 /*   Message msg = Message.obtain();
                    msg.obj = cacheBitmap;
                    handle.sendMessage(msg);*/
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                iv.setImageBitmap(cacheBitmap);
                            }
                        });
                    } else {
                        System.out.println("---->>>>>>>>>>使用网络的图片");
                        //第一次访问连接网络

                        //创建url对象
                        URL url = new URL(path);
                        //获取httpurlconnection
                        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                        //连接方式
                        conn.setRequestMethod("GET");
                        conn.setConnectTimeout(5000);
                        //获取服务器的状态码
                        int code = conn.getResponseCode();
                        if (code == 200) {
                            //获取图片的数据,不管什么数据,都是流的形式返回
                            InputStream in = conn.getInputStream();
                            file = new File(getCacheDir(), "test.png");
                            FileOutputStream fos = new FileOutputStream(file);
                            //fos文件输出流
                            int len = -1;
                            byte[] buffer = new byte[1024];
                            while ((len = in.read(buffer)) != -1) {
                                fos.write(buffer, 0, len);
                            }
                            fos.close();
                            in.close();

                            //获取位图工厂,获取bitmap
                            final Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());

                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    //run方法一定执行在UI线里
                                    iv.setImageBitmap(bitmap);
                                }
                            });
                    /*Message msg =Message.obtain();//msg的静态方法,减少对象的创建
                    msg.obj =bitmap;
                    handle.sendMessage(msg);//发消息*/
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }.start();


    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context="com.peng.image_show.MainActivity">

    <EditText
        android:id="@+id/et_path"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入查看的网址"
        android:text="http://www.pptbz.com/pptpic/UploadFiles_6909/201204/2012041411433867.jpg" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click"
        android:text="查看" />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

需加权限

<uses-permission android:name="android.permission.INTERNET"></uses-permission>