帮我用Okhttp 封装一个Android的文件断点下载器
时间: 2024-06-10 10:03:48 浏览: 22
好的。使用Okhttp进行文件断点下载,可以实现网络不稳定情况下,下载任务可以从上一次中断的位置继续下载,避免重复下载浪费网络资源和时间。下面是一个简单实现的代码示例:
```java
public class FileDownloader {
private OkHttpClient client;
private Call call;
private String url;
private String saveDir;
private String fileName;
private long startPosition;
private long currentPosition;
private boolean isDownloading = false;
public FileDownloader(String url, String saveDir, String fileName, long startPosition) {
this.url = url;
this.saveDir = saveDir;
this.fileName = fileName;
this.startPosition = startPosition;
this.currentPosition = startPosition;
this.client = new OkHttpClient.Builder().build();
}
public void startDownload() {
isDownloading = true;
Request request = new Request.Builder()
.url(url)
.addHeader("Range", "bytes=" + currentPosition + "-")
.build();
call = client.newCall(request);
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
isDownloading = false;
e.printStackTrace();
}
@Override
public void onResponse(Call call, Response response) throws IOException {
RandomAccessFile randomAccessFile = null;
InputStream is = null;
try {
//获取文件长度
long contentLength = response.body().contentLength();
//设置文件存储路径
File saveFile = new File(saveDir, fileName);
//判断文件是否存在,不存在则创建
if (!saveFile.exists()) {
saveFile.createNewFile();
}
//获取随机读写文件权限
randomAccessFile = new RandomAccessFile(saveFile, "rw");
//设置文件长度
randomAccessFile.setLength(contentLength);
//设置文件写入的起始位置
randomAccessFile.seek(currentPosition);
//获取输入流
is = response.body().byteStream();
byte[] buffer = new byte[2048];
int len = 0;
//开始读取网络数据,并写入本地文件
while ((len = is.read(buffer)) != -1) {
randomAccessFile.write(buffer, 0, len);
currentPosition += len;
}
//关闭输入输出流
response.close();
is.close();
randomAccessFile.close();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (randomAccessFile != null) {
randomAccessFile.close();
}
if (is != null) {
is.close();
}
isDownloading = false;
}
}
});
}
public void stopDownload() {
if (isDownloading && call != null) {
isDownloading = false;
call.cancel();
}
}
public boolean isDownloading() {
return isDownloading;
}
public long getCurrentPosition() {
return currentPosition;
}
}
```
这个封装的类可以在Android应用中使用。使用方法如下:
```java
String url = "http://www.example.com/yourfile.mp4";
String saveDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();
String fileName = "yourfile.mp4";
long startPosition = 0;
FileDownloader downloader = new FileDownloader(url, saveDir, fileName, startPosition);
downloader.startDownload();
```
其中,url为资源文件的下载链接,saveDir为文件保存的目录,fileName为文件名,startPosition为起始下载位置。使用`downloader.stopDownload()`方法可以停止下载任务。使用`downloader.getCurrentPosition()`方法可以获取当前下载位置。
相关推荐
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![zip](https://img-home.csdnimg.cn/images/20210720083736.png)
![pdf](https://img-home.csdnimg.cn/images/20210720083512.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)