Android 文件下载三种基本方式
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。
