【android开发】下载文件工具类

最新推荐文章于 2021-05-25 15:58:55 发布

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最新推荐文章于 2021-05-25 15:58:55 发布

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分类专栏： Android 文章标签： Android Java OS .net

本文链接：https://blog.youkuaiyun.com/smallbaby_dns/article/details/83811596

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本文介绍了一个用于Android系统的实用工具类，该工具类包括了创建文件、创建目录、判断文件是否存在等针对SD卡的操作，并实现了从HTTP源下载文件到SD卡的功能。

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FileUtils.java 主要用来操作SD卡上的文件夹和文件

package com.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.os.Environment;

public class FileUtils {

	private String SDPATH;

	public String getSDPATH() {
		return SDPATH;
	}

	public FileUtils() {
		SDPATH = Environment.getExternalStorageDirectory() + "/";
	}

	/**
	 * 在SD卡上創建文件
	 * @param fileName
	 * @return
	 * @throws IOException
	 */
	public File createSDFile (String fileName) throws IOException {
		File file = new File(SDPATH+fileName);
		if (file.exists()) {
			file.createNewFile();
		}
		return file;
	}
	
	/**
	 * 在SD卡上創建目錄
	 * @param dirName
	 * @return
	 */
	public File createSDDir(String dirName) {
		File dir = new File(SDPATH+dirName);
		if (!dir.isDirectory()) {
			dir.mkdir();
		}
		return dir;
	}
	
	/**
	 * 判斷SD卡上的文件夾是否存在
	 * @param fileName
	 * @return
	 */
	public boolean isFileExist(String fileName) {
		File file = new File(SDPATH+fileName);
		return file.exists();
	}
	
	/**
	 * 将文件下载到SD卡上
	 * @param path
	 * @param fileName
	 * @param input
	 * @return
	 */
	public File writer2SDFromIinput(String path, String fileName,
			InputStream input) {
		File file = null;
		OutputStream output = null;
		try {
			// 创建目录 dir.mkdir(); 
			createSDDir(path);
			file = createSDFile(path+fileName);
			output = new FileOutputStream(file);
			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;
	}
}

httpDownload.java 下载文件

package com.utils;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpDownloader {

	private URL url = null;

	/**
	 * 下载文件
	 * @param urlStr url
	 * @return
	 */
	public String download(String urlStr) {
		StringBuffer sb = new StringBuffer();
		String line = null;
		BufferedReader buffer = null;
		try {
			url = new URL(urlStr);

			HttpURLConnection urlConn = (HttpURLConnection) url
					.openConnection();
			buffer = new BufferedReader(new InputStreamReader(urlConn
					.getInputStream()));
			while ((line = buffer.readLine()) != null) {
				sb.append(line);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				buffer.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return sb.toString();
	}
	
	/**
	 * 
	 * @param urlStr
	 * @param path SD哪个目录上
	 * @param fileName 要存放的文件名
	 * @return
	 */
	public int downFile(String urlStr,String path,String fileName) {
		InputStream in = null;
			FileUtils fu = new FileUtils();
			 if (fu.isFileExist(path+fileName)) {
				return 1;
			}
				try {
					in = getInputStreamFromUrl(urlStr);
					File resultFile = fu.writer2SDFromIinput(path, fileName, in);
					if (resultFile == null) {
						return -1;
					}
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}finally {
					
					try {
						in.close();
					}catch(Exception e) {
						e.printStackTrace();
						return -1;
					}
				}
				return 0;
	}
	
	/**
	 * get stream from url
	 * @param urlStr
	 * @return
	 * @throws IOException
	 */
	public InputStream getInputStreamFromUrl(String urlStr) throws IOException {
		url = new URL(urlStr);
		HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();
		InputStream inputStream = urlConn.getInputStream();
		return inputStream;
	}
	
}