自己写的异步下载 安卓

import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.URL;import android.os.AsyncTask;public class AsyncDownload extends AsyncTask<String, Void, File> {private String mUrl;private String mDestinationPath;@Overrideprotected File doInBackground(String... params) {mUrl = params[0];mDestinationPath =params[1];File file = null;try{URL url = new URL(mUrl);HttpURLConnection conn =(HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(8000);int code = conn.getResponseCode();if(code == 200){    file = new File(mDestinationPath);InputStream is = conn.getInputStream();OutputStream os = new FileOutputStream(file);byte[] buffer = new byte[4096]; int len;while((len = is.read(buffer))!=-1){os.write(buffer,0,len);}os.close();is.close();}} catch (IOException e) {e.printStackTrace();}return file;}}

需要的权限：

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