android_文件下載

android 在網絡上下載文件

步驟 :

1.使用HTTP協議下載文件

- 創建一個HttpURLConnection對象 : HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();

- 獲取一個InputStream對象 : urlConn.getInputStream()

- 訪問網絡的權限 : android.permission.INTERNET

2.將下載的文件寫入SDCARD

- 得到當前設備SD卡的目錄 : Environment.getExternalStrageDirectory()

- 訪問SD卡的權限 : android.permission.WRITE_EXTERNAL_STORAGE

代碼 :

activity_main.xml

MainActivity.java

package com.chay.download;

import com.chay.utils.HttpDownloader;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
	
	String urlStr_txt = "http://192.168.56.1:8080/mp3/wan.lrc";
	String urlStr_mp3 = "http://192.168.56.1:8080/mp3/wan.mp3";
	String path = "mp3/";
	String fileName = "wan.mp3";
	private Button downloadTxtButton;
	private Button downloadMp3Button;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		downloadTxtButton = (Button) findViewById(R.id.btn_txt);
		downloadTxtButton.setOnClickListener(new DownloadTxtListener());
		downloadMp3Button = (Button) findViewById(R.id.btn_mp3);
		downloadMp3Button.setOnClickListener(new DownloadMp3Listener());
	}

	//下載歌詞文件按鈕監聽器
	class DownloadTxtListener implements OnClickListener {
		@Override
		public void onClick(View v) {
			Thread t = new DownloadTxtThread();  
            t.start();
            System.out.println("txt--->");
		}
	}
	//下載歌詞文件線程
	class DownloadTxtThread extends Thread{
		@Override
		public void run() {
			HttpDownloader httpDownloader = new HttpDownloader();
			String lrc = httpDownloader.download(urlStr_txt);
			System.out.println(lrc);
		}
	}
	//下載MP3文件按鈕監聽器
	class DownloadMp3Listener implements OnClickListener {
		@Override
		public void onClick(View v) {
			Thread h = new DownMp3Thread();
			h.start();
			System.out.println("mp3--->");
		}
	}
	//下載MP3文件線程
	class DownMp3Thread extends Thread{
		@Override
		public void run() {
			HttpDownloader httpDownloader = new HttpDownloader();
			int result = httpDownloader.downFile(urlStr_mp3, path, fileName);
			System.out.println(result);
		}
	}	
}

工具類:
HttpDownloader.java

package com.chay.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.MalformedURLException;
import java.net.URL;

public class HttpDownloader {
	private URL url = null;

	/**
	 * 根據URL下載文件，前提是這個文件當中的內容是文本，函數的返回值就是文件當中的內容
	 * 1.創建一個URL對象
	 * 2.通過URL對象，創建一個HttpURLConnection對象
	 * 3.得到InputStram
	 * 4.從InputStream當中讀取數據
	 * @param urlStr
	 * @return
	 */
	public String download(String urlStr) {
		StringBuffer sb = new StringBuffer();
		String line = null;
		BufferedReader buffer = null;
		try {
			// 創建一個URL對象
			url = new URL(urlStr);
			// 創建一個Http連接
			HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
			// 使用IO流讀取數據
			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();
	}

	/**
	 * 該函數返回整形 -1：代表下載文件出錯      0：代表下載文件成功      1：代表文件已經存在
	 */
	public int downFile(String urlStr, String path, String fileName) {
		InputStream inputStream = null;
		try {
			FileUtils fileUtils = new FileUtils();
			
			if (fileUtils.isFileExist(path + fileName)) {
				return 1;
			} else {
				inputStream = getInputStreamFromUrl(urlStr);
				File resultFile = fileUtils.write2SDFromInput(path,fileName, inputStream);
				if (resultFile == null) {
					return -1;
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
			return -1;
		} finally {
			try {
				inputStream.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		return 0;
	}

	/**
	 * 根據URL得到輸入流
	 * 
	 * @param urlStr
	 * @return
	 * @throws MalformedURLException
	 * @throws IOException
	 */
	public InputStream getInputStreamFromUrl(String urlStr)
			throws MalformedURLException, IOException {
		url = new URL(urlStr);
		HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
		InputStream inputStream = urlConn.getInputStream();
		return inputStream;
	}
}

FileUtils.java

package com.chay.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() {
		//得到當前外部存儲設備的目錄
		// /SDCARD
		SDPATH = Environment.getExternalStorageDirectory() + "/";
	}
	/**
	 * 在SD卡上創建文件
	 * 
	 * @throws IOException
	 */
	public File creatSDFile(String fileName) throws IOException {
		File file = new File(SDPATH + fileName);
		file.createNewFile();
		return file;
	}
	
	/**
	 * 在SD卡上創建目錄
	 * 
	 * @param dirName
	 */
	public File creatSDDir(String dirName) {
		File dir = new File(SDPATH + dirName);
		dir.mkdirs();
		return dir;
	}

	/**
	 * 判斷SD卡上的文件夾是否存在
	 */
	public boolean isFileExist(String fileName){
		File file = new File(SDPATH + fileName);
		return file.exists();
	}
	
	/**
	 * 將一個InputStream裡面的數據寫入到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);
			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;
	}
}

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