文件下载工具类

package com.vibexie.util;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * VibeXie created in 4.11.2015 @vibexie.com
 *
 * 下载文件的工具类
 *
 * 1.downloadAndReturnViaCallback方法可以选择保存文件，并且可以通过接口回调得到下载的文件
 * 示例(下载图片并显示在ImageView中)：
 *  Download download=new Download(MainActivity.this);
 *  download.downloadAndReturnViaCallback(url,true,"/tmp","tmp.jpg",new Download.DownloadCallback() {
 *      @Override
 *      public void callbackDownload(byte[] result) {
 *      Bitmap bitmap= BitmapFactory.decodeByteArray(result,0,result.length);
 *      imageView.setImageBitmap(bitmap);
 *      }
 *  });
 *
 *  2.justDownloadAndSave方法直接下载并保存文件到sd卡
 *
 *  3.注意添加网络和写sd卡权限
 */
public class Download {

    private ProgressDialog progressDialog;

    /**
     * 构造函数
     * @param context
     */
    Download(Context context){
        progressDialog=new ProgressDialog(context);
        progressDialog.setTitle("提示");
        progressDialog.setMessage("正在拼命加载...");
    }

    /**
     * 回调接口
     */
    public interface DownloadCallback{
        public void callbackDownload(byte[] result);
    }

    /**
     * 直接根据路径下载并保存
     * @param internetPath  网络下载路径,字符串格式
     * @param savePath      保存到本地存储卡的路径，注意是文件夹格式,如:/tmp
     * @param fileName      存使用的文件名，格式如:tmp.jpg
     */
    public void justDownloadAndSave(String internetPath,final String savePath,String fileName){
        downloadAndReturnViaCallback(internetPath,true,savePath,fileName,null);
    }

    /**
     * 下载保存并回调返回
     * @param internetPath  网络下载路径
     * @param save          是否保存到本地，若为false,savePath和fileName为null
     * @param savePath      保存到本地存储卡的路径，注意是文件夹格式,如:/tmp
     * @param fileName      保存使用的文件名，格式如:tmp.jpg
     * @param downloadCallback 回调下载的文件
     */
    public void downloadAndReturnViaCallback(final String internetPath, final boolean save,final String savePath, final String fileName, final DownloadCallback downloadCallback){

        final Handler handler=new Handler() {
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);

                /**
                 * 如果downloadCallback不为null,说明是直接调用downloadAndReturnViaCallback
                 * 而不是调用justDownloadAndSave，调用justDownloadAndSave则无需handle处理
                 */
                if(downloadCallback!=null){
                    byte[] result=(byte[])msg.obj;
                    downloadCallback.callbackDownload(result);
                }

                if(msg.what==1){
                    progressDialog.dismiss();
                }
            }
        };

        /**
         * 下载线程类实现Runnable接口
         */
        class MyThread implements Runnable{
            @Override
            public void run() {
                HttpClient httpClient=new DefaultHttpClient();
                HttpGet httpGet=new HttpGet(internetPath);
                try {
                    HttpResponse httpResponse=httpClient.execute(httpGet);
                    if(httpResponse.getStatusLine().getStatusCode()==200){
                        byte[] result= EntityUtils.toByteArray(httpResponse.getEntity());

                        /**
                         * 保存文件
                         */
                        if(save) {
                            saveFile(savePath,fileName,result);
                        }

                        Message message=Message.obtain();

                        /**
                         * 如果downloadCallback不为null,说明是直接调用downloadAndReturnViaCallback
                         * 而不是调用justDownloadAndSave，调用justDownloadAndSave则无需handle处理
                         */
                        if(downloadCallback!=null){
                            message.obj=result;
                        }

                        /**
                         * 下载结束标志位，1表示结束
                         */
                        message.what=1;
                        handler.sendMessage(message);

                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }finally {
                    /**
                     * 关闭http连接
                     */
                    httpClient.getConnectionManager().shutdown();
                }
            }
        }

        /**
         * 启动下载线程
         */
        new Thread(new MyThread()).start();

        /**
         * 显示Dialog
         */
        progressDialog.show();
    }


    /**
     * 保存文件
     * @param savePath  下载路径
     * @param result    要保存的byte[]流
     */
    private void saveFile(String savePath,String fileName,byte[] result){
        /**
         * 判断sd卡是否存在,不存在直接返回
         */
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_UNMOUNTED)){
            return;
        }
        /**
         * 路径不存在则创建文件路径
         */
        File tmp=new File(Environment.getExternalStorageDirectory()+savePath);
        if(!tmp.exists()){
            tmp.mkdirs();
        }

        File file=new File(tmp,fileName);
        try{
            OutputStream outputStream=new FileOutputStream(file);
            outputStream.write(result,0,result.length);
            outputStream.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}