android网络图片查看器

package com.itheima.netimageviewer;

import java.io.BufferedReader;
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.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.res.Resources.Theme;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity {
    protected static final int LOAD_IMAGE = 1;
    protected static final int LOAD_ERROR = 2;
    // 服务器所有图片的路径
    private List<String> paths;
    private ImageView iv;
    /**
     * 当前的位置
     */
    private int currentPosition = 0;

    //1.创建一个消息处理器
    private Handler handler = new Handler(){
        //3.处理消息
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case LOAD_IMAGE:
                Bitmap bitmap = (Bitmap) msg.obj;
                iv.setImageBitmap(bitmap);
                break;

            case LOAD_ERROR:
                Toast.makeText(getApplicationContext(), (String)msg.obj, 0).show();
                break;
            }

        };
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        iv = (ImageView) findViewById(R.id.iv);
        // 1.连接服务器 获取所有的图片的目录信息
        loadAllImagePath(); 

    }

    /**
     * 开始加载图标,在从服务器获取完毕资源路径之后执行
     */
    private void beginLoadImage() {
        // TODO:把每个图片的路径获取出来, 通过路径加载图片.
        try {
            paths = new ArrayList<String>();
            File file = new File(getCacheDir(), "info.txt");
            FileInputStream fis = new FileInputStream(file);
            BufferedReader br = new BufferedReader(new InputStreamReader(fis));
            String line;
            while ((line = br.readLine()) != null) {
                paths.add(line);
            }
            fis.close();
            // 2.加载图片资源
            loadImageByPath(paths.get(currentPosition));
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    /**
     * 通过路径获取图片资源
     *
     * @param path
     *            图片的路径
     * @return
     */
    private void loadImageByPath(final String path) {
        new Thread() {
            public void run() {
                try {
                    Thread.sleep(2000);
                    // 判断缓存是否存在,如果存在就那缓存图片,如果不存在才去获取服务器的资源
                    File file = new File(getCacheDir(), path.replace("/", "")
                            + ".jpg");
                    if (file.exists() && file.length() > 0) {
                        System.out.println("通过缓存把图片资源获取出来....");
                        // 缓存存在
                        //iv.setImageBitmap( BitmapFactory.decodeFile(file.getAbsolutePath()));
                        //2.子线程想去更新ui,发送消息
                        Message msg = Message.obtain();
                        msg.what = LOAD_IMAGE;
                        msg.obj = BitmapFactory.decodeFile(file.getAbsolutePath());
                        handler.sendMessage(msg);
                    } else {
                        System.out.println("通过访问网络把图片资源获取出来....");
                        URL url = new URL(path);
                        HttpURLConnection conn = (HttpURLConnection) url
                                .openConnection();
                        conn.setRequestMethod("GET");
                        int code = conn.getResponseCode();
                        if (code == 200) {
                            InputStream is = conn.getInputStream();
                            // 内存中的图片
                            Bitmap bitmap = BitmapFactory.decodeStream(is);
                            // 如果图片被下载完毕了,应该把图片缓存起来.
                            // CompressFormat.JPEG 压缩的方式 png jpg
                            // 100 压缩比例 100 无损压缩
                            // stream 把图片写入到哪个缓存流里面
                            FileOutputStream stream = new FileOutputStream(file);
                            bitmap.compress(CompressFormat.JPEG, 100, stream);
                            stream.close();
                            is.close();
                            Message msg = Message.obtain();
                            msg.obj = bitmap;
                            msg.what = LOAD_IMAGE;
                            handler.sendMessage(msg);
                            //iv.setImageBitmap(bitmap);
                        } else {
                            //Toast.makeText(MainActivity.this, "获取失败", 0).show();
                            Message msg = Message.obtain();
                            msg.what = LOAD_ERROR;
                            msg.obj = "获取失败";
                            handler.sendMessage(msg);
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                    Toast.makeText(MainActivity.this, "获取失败", 0).show();
                    Message msg = Message.obtain();
                    msg.what = LOAD_ERROR;
                    msg.obj = "获取失败";
                    handler.sendMessage(msg);
                }
            };
        }.start();
    }

    /**
     * 获取全部图片资源的路径
     */
    private void loadAllImagePath() {
        new Thread() {
            public void run() {
                // 浏览器发送一个get请求就可以把服务器的数据获取出来.
                // 用代码模拟一个http的get请求
                try {
                    // 1.得到服务器资源的路径
                    URL url = new URL("http://192.168.1.109:8080/img/gaga.html");
                    // 2.通过这个路径打开浏览器的连接.
                    HttpURLConnection conn = (HttpURLConnection) url
                            .openConnection();// ftp
                                                // http
                                                // https
                                                // rtsp
                    // 3.设置请求方式为get请求
                    conn.setRequestMethod("GET");// 注意get只能用大写 不支持小写
                    // 为了有一个更好的用户ui提醒,获取服务器的返回状态码
                    int code = conn.getResponseCode();// 200 ok 404资源没有找到 503
                                                        // 服务器内部错误
                    if (code == 200) {
                        // 4.获取服务器的返回的流
                        InputStream is = conn.getInputStream();
                        File file = new File(getCacheDir(), "info.txt");
                        FileOutputStream fos = new FileOutputStream(file);
                        byte[] buffer = new byte[1024];
                        int len = 0;
                        while ((len = is.read(buffer)) != -1) {
                            fos.write(buffer, 0, len);
                        }
                        is.close();
                        fos.close();
                        beginLoadImage();
                    } else if (code == 404) {
                        Message msg = Message.obtain();
                        msg.what = LOAD_ERROR;
                        msg.obj = "获取失败,资源没有找到";
                        handler.sendMessage(msg);
                        //Toast.makeText(MainActivity.this, "获取失败,资源没有找到", 0).show();
                    } else {
                        //Toast.makeText(MainActivity.this, "服务器异常", 0).show();
                        Message msg = Message.obtain();
                        msg.what = LOAD_ERROR;
                        msg.obj = "服务器异常";
                        handler.sendMessage(msg);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                    //Toast.makeText(MainActivity.this, "获取失败", 0).show();
                    Message msg = Message.obtain();
                    msg.what = LOAD_ERROR;
                    msg.obj = "获取失败";
                    handler.sendMessage(msg);
                }
            };
        }.start();
    }

    /**
     * 上一张
     *
     * @param view
     */
    public void pre(View view) {
        currentPosition--;
        if (currentPosition < 0) {
            currentPosition = paths.size() - 1;
        }
        loadImageByPath(paths.get(currentPosition));

    }

    /**
     * 下一张
     *
     * @param view
     */
    public void next(View view) {
        currentPosition++;
        if (currentPosition == paths.size()) {
            currentPosition = 0;
        }
        loadImageByPath(paths.get(currentPosition));

    }

}

添加权限

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