一、自己封装URLConnection 连接请求类

   public void downloadFile1() {
    try{
        //下载路径,如果路径无效了,可换成你的下载路径
        String url = "http://c.qijingonline.com/test.mkv";
        String path = Environment.getExternalStorageDirectory().getAbsolutePath();

        final long startTime = System.currentTimeMillis();
        Log.i("DOWNLOAD","startTime="+startTime);
        //下载函数
       String filename=url.substring(url.lastIndexOf("/") + 1);
        //获取文件名
        URL myURL = new URL(url);
        URLConnection conn = myURL.openConnection();
        conn.connect();
        InputStream is = conn.getInputStream();
        int fileSize = conn.getContentLength();//根据响应获取文件大小
        if (fileSize <= 0) throw new RuntimeException("无法获知文件大小 ");
        if (is == null) throw new RuntimeException("stream is null");
        File file1 = new File(path);
        if(!file1.exists()){
            file1.mkdirs();
        }
        //把数据存入路径+文件名
        FileOutputStream fos = new FileOutputStream(path+"/"+filename);
        byte buf[] = new byte[1024];
        int downLoadFileSize = 0;
        do{
            //循环读取
            int numread = is.read(buf);
            if (numread == -1)
            {
                break;
            }
            fos.write(buf, 0, numread);
            downLoadFileSize += numread;
            //更新进度条
        } while (true);

        Log.i("DOWNLOAD","download success");
        Log.i("DOWNLOAD","totalTime="+ (System.currentTimeMillis() - startTime));

        is.close();
    } catch (Exception ex) {
        Log.e("DOWNLOAD", "error: " + ex.getMessage(), ex);
    }
}

这种方式在Android 刚兴起的时候,很少下载封装框架,就自己封装了。虽然一般的文件都能下载,但这种方式缺点很多,不稳定或者各种各样的问题会出现。

二、Android自定的下载管理(会在notification 显示下载的进度,同时可以暂停、重新连接等)

private void downloadFile2(){
    //下载路径,如果路径无效了,可换成你的下载路径
    String url = "http://c.qijingonline.com/test.mkv";
    //创建下载任务,downloadUrl就是下载链接
    DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
    //指定下载路径和下载文件名
    request.setDestinationInExternalPublicDir("", url.substring(url.lastIndexOf("/") + 1));
    //获取下载管理器
    DownloadManager downloadManager= (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
    //将下载任务加入下载队列,否则不会进行下载
    downloadManager.enqueue(request);
}

这种方式其实就是交给了Android系统的另一个app去下载管理。这样的好处不会消耗该APP的 CPU资源。缺点是:控制起来很不灵活。

三、使用第三方 okhttp 网络请求框架

private void downloadFile3(){
    //下载路径,如果路径无效了,可换成你的下载路径
    final String url = "http://c.qijingonline.com/test.mkv";
    final long startTime = System.currentTimeMillis();
    Log.i("DOWNLOAD","startTime="+startTime);

    Request request = new Request.Builder().url(url).build();
    new OkHttpClient().newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            // 下载失败
            e.printStackTrace();
            Log.i("DOWNLOAD","download failed");
        }
        @Override
        public void onResponse(Call call, Response response) throws IOException {
            Sink sink = null;
            BufferedSink bufferedSink = null;
            try {
                String mSDCardPath= Environment.getExternalStorageDirectory().getAbsolutePath();
                File dest = new File(mSDCardPath,   url.substring(url.lastIndexOf("/") + 1));
                sink = Okio.sink(dest);
                bufferedSink = Okio.buffer(sink);
                bufferedSink.writeAll(response.body().source());

                bufferedSink.close();
                Log.i("DOWNLOAD","download success");
                Log.i("DOWNLOAD","totalTime="+ (System.currentTimeMillis() - startTime));
            } catch (Exception e) {
                e.printStackTrace();
                Log.i("DOWNLOAD","download failed");
            } finally {
                if(bufferedSink != null){
                    bufferedSink.close();
                }

            }
        }
    });
}

复制代码
okhttp是一个很有名气的开源框架,目前已经很多大公司都直接使用它作为网络请求库(七牛云SDK, 阿里云SDK)。 且里面集成了很多优势,包括 okio (一个I/O框架,优化内存与CPU)。

在接收数据的时候使用了 okio框架 来做一些I/O处理,okio框架是弥补Java.io 上的不足,节省CPU与内存资源,但这个例子,我没还没看到其效果,也可以自己来接收字符流,然后获取下载的进度

 public void downloadFile(){
        final String url = "http://c.qijingonline.com/test.mkv";
        final long startTime = System.currentTimeMillis();
        Log.i("DOWNLOAD","startTime="+startTime);
        OkHttpClient okHttpClient = new OkHttpClient();

        Request request = new Request.Builder().url(url).build();
        okHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                // 下载失败
                e.printStackTrace();
                Log.i("DOWNLOAD","download failed");
            }
            @Override
            public void onResponse(Call call, Response response) throws IOException {
                InputStream is = null;
                byte[] buf = new byte[2048];
                int len = 0;
                FileOutputStream fos = null;
                // 储存下载文件的目录
                String savePath = Environment.getExternalStorageDirectory().getAbsolutePath();
                try {
                    is = response.body().byteStream();
                    long total = response.body().contentLength();
                    File file = new File(savePath, url.substring(url.lastIndexOf("/") + 1));
                    fos = new FileOutputStream(file);
                    long sum = 0;
                    while ((len = is.read(buf)) != -1) {
                        fos.write(buf, 0, len);
                        sum += len;
                        int progress = (int) (sum * 1.0f / total * 100);
                        // 下载中
//                        listener.onDownloading(progress);
                    }
                    fos.flush();
                    // 下载完成
//                    listener.onDownloadSuccess();
                    Log.i("DOWNLOAD","download success");
                    Log.i("DOWNLOAD","totalTime="+ (System.currentTimeMillis() - startTime));
                } catch (Exception e) {
                    e.printStackTrace();
//                    listener.onDownloadFailed();
                    Log.i("DOWNLOAD","download failed");
                } finally {
                    try {
                        if (is != null)
                            is.close();
                    } catch (IOException e) {
                    }
                    try {
                        if (fos != null)
                            fos.close();
                    } catch (IOException e) {
                    }
                }
            }
        });
    }

综合来看,第三种方案是最佳的,是目前最流行的下载方案。

转载自:https://www.cnblogs.com/xiaoxiaoqingyi/p/7003241.html

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