Android网络文件下载模块整理
16lz
2021-01-25
一、知识基础
tomcat服务器配置
理解http协议
理解javaIO操作相关知识
SDcard操作知识
Android 权限配置
二、实现步骤
1、从网上获取资源
1 public String download(String urlStr) { 2 StringBuffer sb = new StringBuffer(); 3 String line = null; 4 BufferedReader buffer = null; 5 try { 6 // 创建一个URL对象 7 url = new URL(urlStr); 8 // 创建一个Http连接 9 HttpURLConnection urlConn = (HttpURLConnection) url10 .openConnection();11 // 使用IO流读取数据12 buffer = new BufferedReader(new InputStreamReader(urlConn13 .getInputStream()));14 while ((line = buffer.readLine()) != null) {15 sb.append(line);16 }17 } catch (Exception e) {18 e.printStackTrace();19 } finally {20 try {21 buffer.close();22 } catch (Exception e) {23 e.printStackTrace();24 }25 }26 return sb.toString();27 }28 29 /**30 * 该函数返回整形 -1:代表下载文件出错 0:代表下载文件成功 1:代表文件已经存在31 */32 public int downFile(String urlStr, String path, String fileName) {33 InputStream inputStream = null;34 try {35 FileUtils fileUtils = new FileUtils();36 37 if (fileUtils.isFileExist(path + fileName)) {38 return 1;39 } else {40 inputStream = getInputStreamFromUrl(urlStr);41 File resultFile = fileUtils.write2SDFromInput(path,fileName, inputStream);42 if (resultFile == null) {43 return -1;44 }45 }46 } catch (Exception e) {47 e.printStackTrace();48 return -1;49 } finally {50 try {51 inputStream.close();52 } catch (Exception e) {53 e.printStackTrace();54 }55 }56 return 0;57 }58 59 /**60 * 根据URL得到输入流61 * 62 * @param urlStr63 * @return64 * @throws MalformedURLException65 * @throws IOException66 */67 public InputStream getInputStreamFromUrl(String urlStr)68 throws MalformedURLException, IOException {69 url = new URL(urlStr);70 HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();71 InputStream inputStream = urlConn.getInputStream();72 return inputStream;73 }74 }从网络下载文件
2、将资源写入SDcard
public class FileUtils { private String SDPATH; public String getSDPATH() { return SDPATH; } public FileUtils() { //得到当前外部存储设备的目录 // /SDCARD SDPATH = Environment.getExternalStorageDirectory() + "/"; } /** * 在SD卡上创建文件 * * @throws IOException */ public File creatSDFile(String fileName) throws IOException { File file = new File(SDPATH + fileName); file.createNewFile(); return file; } /** * 在SD卡上创建目录 * * @param dirName */ public File creatSDDir(String dirName) { File dir = new File(SDPATH + dirName); dir.mkdirs(); return dir; } /** * 判断SD卡上的文件夹是否存在 */ public boolean isFileExist(String fileName){ File file = new File(SDPATH + fileName); return file.exists(); } /** * 将一个InputStream里面的数据写入到SD卡中 */ public File write2SDFromInput(String path,String fileName,InputStream input){ File file = null; OutputStream output = null; try{ creatSDDir(path); file = creatSDFile(path + fileName); output = new FileOutputStream(file);//写入数据 byte buffer [] = new byte[4 * 1024]; while((input.read(buffer)) != -1){ output.write(buffer); } output.flush(); } catch(Exception e){ e.printStackTrace(); } finally{ try{ output.close(); } catch(Exception e){ e.printStackTrace(); } } return file; }}SDCard 读写操作
三、版本说明
程序源码来源Mars老师,表示感谢
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