Android学习笔记——download
1.该工程的功能是实现从网上的链接下载一个lrc文件和一个mp3文件
以下代码是MainActivity.java中的代码
package com.example.download; import com.example.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 { /** Called when the activity is first created. */ private Button downloadTxtButton; private Button downloadMp3Button; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); downloadTxtButton = (Button)findViewById(R.id.downloadTxt); downloadTxtButton.setOnClickListener(new DownloadTxtListener()); downloadMp3Button = (Button)findViewById(R.id.downloadMp3); downloadMp3Button.setOnClickListener(new DownloadMp3Listener()); } class DownloadTxtListener implements OnClickListener{ public void onClick(View v) { HttpDownloader httpDownloader = new HttpDownloader(); int lrc = httpDownloader.downFile("http://play.baidu.com/data2/lrc/121017633/121017633.lrc", "voa/", "1201250291414036861128.lrc"); System.out.println(lrc); } } class DownloadMp3Listener implements OnClickListener{ public void onClick(View v) { // TODO Auto-generated method stub HttpDownloader httpDownloader = new HttpDownloader(); int result = httpDownloader.downFile("http://cdn.y.baidu.com/yinyueren/532bfdb43a336a584533ff61a7289503.mp3", "voa/", "江南.mp3"); System.out.println(result); } } }
以下代码是FileUtils.java中的代码
package com.example.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); byte buffer [] = new byte[4 * 1024]; int len=-1; while((len=input.read(buffer)) != -1){ //在这里使用另一个重载，防止流写入的问题. output.write(buffer,0,len); } output.flush(); } catch(Exception e){ e.printStackTrace(); } finally{ try{ output.close(); } catch(Exception e){ e.printStackTrace(); } } return file; } }
以下代码是HttpDownloader.java中的代码
package com.example.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; /** * 根据URL下载文件，前提是这个文件当中的内容是文本，函数的返回值就是文件当中的内容 * 1.创建一个URL对象 * 2.通过URL对象，创建一个HttpURLConnection对象 * 3.得到InputStram * 4.从InputStream当中读取数据 * @param urlStr * @return */ public String download(String urlStr) { StringBuffer sb = new StringBuffer(); String line = null; BufferedReader buffer = null; try { // 创建一个URL对象 url = new URL(urlStr); // 创建一个Http连接 HttpURLConnection urlConn = (HttpURLConnection) url .openConnection(); // 使用IO流读取数据 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(); } /** * 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 */ 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; } /** * 根据URL得到输入流 * * @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; } }
以下代码是activity_main.xml中的代码
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/LinearLayout1" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" tools:context="${relativePackage}.${activityClass}" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello_world" /> <Button android:id="@+id/downloadTxt" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="downloadTxt" /> <Button android:id="@+id/downloadMp3" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="downloadMp3" /> </LinearLayout>
以下代码是AndroidManifest.xml中的代码
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.download"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="8" />
<!-- 访问网络和操作SD卡 加入的两个权限配置-->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>
2.该工程实现下载一个xml文件，并解析
转自http://blog.csdn.net/sam_zhang1984
XML 解析主要需要进行下列步骤：
1. 创建事件处理程序
2. 创建 SAX 解析器
3. 将事件处理程序分配给解析器
4. 对文档进行解析，将每个事件发送给处理程序。
以下的代码是MainActivity.java中的代码
package com.example.xml;
import java.io.StringReader;
import javax.xml.parsers.SAXParserFactory;
import com.example.utils.HttpDownloader;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
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 {
/** Called when the activity is first created. */
private Button parseButton ;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
parseButton = (Button)findViewById(R.id.parseButton);
parseButton.setOnClickListener(new ParseButtonListener());
}
class ParseButtonListener implements OnClickListener{
public void onClick(View v) {
HttpDownloader hd = new HttpDownloader();
String resultStr = hd.download("http://192.168.1.107:8081/voa1500/test.xml");
System.out.println(resultStr);
try{
//创建一个SAXParserFactory
SAXParserFactory factory = SAXParserFactory.newInstance();
XMLReader reader = factory.newSAXParser().getXMLReader();
//为XMLReader设置内容处理器
reader.setContentHandler(new MyContentHandler());
//开始解析文件
reader.parse(new InputSource(new StringReader(resultStr)));
}
catch(Exception e){
e.printStackTrace();
}
}
}
}
以下的代码是MyContentHandler.java中的代码
package com.example.xml;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class MyContentHandler extends DefaultHandler {
String hisname, address, money, sex, status;
String tagName;
public void startDocument() throws SAXException {
System.out.println("````````begin````````");
}
public void endDocument() throws SAXException {
System.out.println("````````end````````");
}
public void startElement(String namespaceURI, String localName,
String qName, Attributes attr) throws SAXException {
tagName = localName;
if (localName.equals("worker")) {
//获取标签的全部属性
for (int i = 0; i < attr.getLength(); i++) {
System.out.println(attr.getLocalName(i) + "=" + attr.getValue(i));
}
}
}
public void endElement(String namespaceURI, String localName, String qName)
throws SAXException {
//在workr标签解析完之后，会打印出所有得到的数据
tagName = "";
if (localName.equals("worker")) {
this.printout();
}
}
public void characters(char[] ch, int start, int length)
throws SAXException {
if (tagName.equals("name"))
hisname = new String(ch, start, length);
else if (tagName.equals("sex"))
sex = new String(ch, start, length);
else if (tagName.equals("status"))
status = new String(ch, start, length);
else if (tagName.equals("address"))
address = new String(ch, start, length);
else if (tagName.equals("money"))
money = new String(ch, start, length);
}
private void printout() {
System.out.print("name: ");
System.out.println(hisname);
System.out.print("sex: ");
System.out.println(sex);
System.out.print("status: ");
System.out.println(status);
System.out.print("address: ");
System.out.println(address);
System.out.print("money: ");
System.out.println(money);
System.out.println();
}
}
以下的代码是FileUtils.java中的代码
package com.example.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);
byte buffer [] = new byte[4 * 1024];
int len=-1;
while((len=input.read(buffer)) != -1){
//在这里使用另一个重载，防止流写入的问题.
output.write(buffer,0,len);
}
output.flush();
}
catch(Exception e){
e.printStackTrace();
}
finally{
try{
output.close();
}
catch(Exception e){
e.printStackTrace();
}
}
return file;
}
}
以下的代码是HttpDownloader.java中的代码
package com.example.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;
/**
* 根据URL下载文件，前提是这个文件当中的内容是文本，函数的返回值就是文件当中的内容
* 1.创建一个URL对象
* 2.通过URL对象，创建一个HttpURLConnection对象
* 3.得到InputStram
* 4.从InputStream当中读取数据
* @param urlStr
* @return
*/
public String download(String urlStr) {
StringBuffer sb = new StringBuffer();
String line = null;
BufferedReader buffer = null;
try {
// 创建一个URL对象
url = new URL(urlStr);
// 创建一个Http连接
HttpURLConnection urlConn = (HttpURLConnection) url
.openConnection();
// 使用IO流读取数据
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();
}
/**
* 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
*/
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;
}
/**
* 根据URL得到输入流
*
* @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;
}
}
以下的代码是activity_main.xml中的代码
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<Button
android:id="@+id/parseButton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="开始解析XML"/>
</LinearLayout>
本文只发表于博客园和tonglin0325的博客，作者：tonglin0325，转载请注明原文链接：https://www.cnblogs.com/tonglin0325/p/4581960.html
