Android 下载文件及写入SD卡

zjx2388

浏览: 1304450 次
性别:
来自: 北京

最近访客更多访客>>

lesliehanhan

sosoab

double_h

pp_dadi

博主相关

博客

微博

相册

留言

关于我

文章分类

社区版块

存档分类

博客分类：

Android

Android Java OS Google .net

Android 下载文件及写入SD卡,实例代码

<?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"
    >
<Button  
	android:id="@+id/downloadTxt"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="下载文本文件"
    />

<Button  
	android:id="@+id/downloadMp3"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="下载MP3文件"
    />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.learning.example"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Download"
                  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>

package com.learning.example.util;

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本当中的内容
	 * 1.创建一个URL对象
	 * 2.通过URL对象,创建一个HttpURLConnection对象
	 * 3.得到InputStream
	 * 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 {
			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 (IOException e) {
				e.printStackTrace();
			}
		}
		return sb.toString();
	}

	/**
	 * 
	 * @param urlStr
	 * @param path
	 * @param fileName
	 * @return 
	 * 		-1:文件下载出错
	 * 		 0:文件下载成功
	 * 		 1: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 (IOException e) {
				e.printStackTrace();
			}
		}
		return 0;
	}
	
	/**
	 * 根据URL得到输入流
	 * @param urlStr
	 * @return
	 */
	public InputStream getInputStreamFromURL(String urlStr) {
		HttpURLConnection urlConn = null;
		InputStream inputStream = null;
		try {
			url = new URL(urlStr);
			urlConn = (HttpURLConnection)url.openConnection();
			inputStream = urlConn.getInputStream();
			
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		return inputStream;
	}
}

package com.learning.example.util;

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;
	
	private int FILESIZE = 4 * 1024; 
	
	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
	 * @param fileName
	 * @return
	 * @throws IOException
	 */
	public File createSDFile(String fileName) throws IOException{
		File file = new File(SDPATH + fileName);
		file.createNewFile();
		return file;
	}
	
	/**
	 * 在SD卡上创建目录
	 * @param dirName
	 * @return
	 */
	public File createSDDir(String dirName){
		File dir = new File(SDPATH + dirName);
		dir.mkdir();
		return dir;
	}
	
	/**
	 * 判断SD卡上的文件夹是否存在
	 * @param fileName
	 * @return
	 */
	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
	 * @param path
	 * @param fileName
	 * @param input
	 * @return
	 */
	public File write2SDFromInput(String path,String fileName,InputStream input){
		File file = null;
		OutputStream output = null;
		try {
			createSDDir(path);
			file = createSDFile(path + fileName);
			output = new FileOutputStream(file);
                            byte[] buffer = new byte[FILESIZE];

			/*真机测试，这段可能有问题，请采用下面网友提供的
                           	while((input.read(buffer)) != -1){
				output.write(buffer);
			}
                            */

                           /* 网友提供 begin */
                           int length;
                           while((length=(input.read(buffer))) >0){
                                 output.write(buffer,0,length);
                           }
                           /* 网友提供 end */

			output.flush();
		} 
		catch (Exception e) {
			e.printStackTrace();
		}
		finally{
			try {
				output.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return file;
	}

}

package com.learning.example;

import com.learning.example.util.HttpDownloader;

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

public class Download extends Activity {
	private Button downlaodTxtButton ;
	private Button downlaodMP3Button ;
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        downlaodTxtButton = (Button)findViewById(R.id.downloadTxt);
        downlaodTxtButton.setOnClickListener(new DownloadTxtListener());
        
        downlaodMP3Button = (Button)findViewById(R.id.downloadMp3);
        downlaodMP3Button.setOnClickListener(new DownloadMP3Listener());
    }
    
    class DownloadTxtListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			HttpDownloader downloader = new HttpDownloader();
			String lrc = downloader.download("http://172.16.11.9:8080/test/1.lrc");
			System.out.println(lrc);
		}
    	
    }
    
    class DownloadMP3Listener implements OnClickListener{

		@Override
		public void onClick(View v) {
			HttpDownloader downloader = new HttpDownloader();
			int result = downloader.downFile("http://172.16.11.9:8080/test/1.mp3", "voa/", "1.map3");
			System.out.println(result);
		}
    	
    }
}

Notice:访问网络和操作SD卡记得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"/>

分享到：

OracleOraDb10g_home1TNSListener 服务消失 ... | 10个压力面试题及解答技巧

2011-01-05 13:50
浏览 39229
评论(15)
分类:移动开发
查看更多

15 楼 wenjin 2015-04-16

不知楼主是不还在想请叫一下我自己开的Tomcat下载一个文件Copy了你的代码也做了修改但是总是报NullPointerException 错误在关闭buffer的时候出错啦，忘楼主能解答

14 楼 liyi0531 2014-10-09

可以下载了。修改代码如下：

在MainActivity文件的setContentView(R.layout.activity_main)下面加上如下代码

if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}

13 楼 itlinux 2012-12-24

zjx2388 写道

fanfq 写道

zjx2388 写道

renwolang521 写道

private int FILESIZE = 4 * 1024; 
byte[] buffer = new byte[FILESIZE];  
while((input.read(buffer)) != -1){  
    output.write(buffer);  
}  
output.flush();

作者这些有没有试过呢？
这段代码难道没有问题吗？
将流读入buffer的时候，通常是读多少length，写多少length，对吧？
你这样下载下来的mp3能播放吗？

测试过的,能播放,不过是在模拟器上,没在真机测试这个

你如果觉得不对,如果方便,请上传你的代码,谢谢!

这段代码要是没有问题就见鬼了。。
你要上传代码，我就上传了。免得你的代码误导初学者。
int length;
while((length=(input.read(buffer))) >0){
output.write(buffer,0,length);
}

谢谢，这段代码上传的MP3大小是控制在4M的，如果大了，肯定空间不够，没上传完啊，这只是测试代码，不能商用的代码，肯定有很多限制的

使用原代码真机测试下载的android APK文件无法正常使用，用fanfq给的代码就可以了。顶fanfq，也感谢Lz分享。

12 楼 zjx2388 2012-08-07

fanfq 写道

zjx2388 写道

renwolang521 写道

private int FILESIZE = 4 * 1024; 
byte[] buffer = new byte[FILESIZE];  
while((input.read(buffer)) != -1){  
    output.write(buffer);  
}  
output.flush();

作者这些有没有试过呢？
这段代码难道没有问题吗？
将流读入buffer的时候，通常是读多少length，写多少length，对吧？
你这样下载下来的mp3能播放吗？

测试过的,能播放,不过是在模拟器上,没在真机测试这个

你如果觉得不对,如果方便,请上传你的代码,谢谢!

谢谢，这段代码上传的MP3大小是控制在4M的，如果大了，肯定空间不够，没上传完啊，这只是测试代码，不能商用的代码，肯定有很多限制的

11 楼 fanfq 2012-08-01

zjx2388 写道

renwolang521 写道

private int FILESIZE = 4 * 1024; 
byte[] buffer = new byte[FILESIZE];  
while((input.read(buffer)) != -1){  
    output.write(buffer);  
}  
output.flush();

作者这些有没有试过呢？
这段代码难道没有问题吗？
将流读入buffer的时候，通常是读多少length，写多少length，对吧？
你这样下载下来的mp3能播放吗？

测试过的,能播放,不过是在模拟器上,没在真机测试这个

你如果觉得不对,如果方便,请上传你的代码,谢谢!

10 楼 zdfeng 2011-10-09

我喜欢，java看着就是爽，虽然是android，基础，还是java。好风格，好作者。

9 楼菜刀闯天下 2011-09-08

tscfengkui 写道

可能你的模拟器上没有sdcard原因造成的，设置模拟器的size就会出现sdcard

thanks 问题解决

8 楼 tscfengkui 2011-08-30

可能你的模拟器上没有sdcard原因造成的，设置模拟器的size就会出现sdcard

7 楼 zjx2388 2011-03-31

renwolang521 写道

private int FILESIZE = 4 * 1024; 
byte[] buffer = new byte[FILESIZE];  
while((input.read(buffer)) != -1){  
    output.write(buffer);  
}  
output.flush();

作者这些有没有试过呢？
这段代码难道没有问题吗？
将流读入buffer的时候，通常是读多少length，写多少length，对吧？
你这样下载下来的mp3能播放吗？

测试过的,能播放,不过是在模拟器上,没在真机测试这个

你如果觉得不对,如果方便,请上传你的代码,谢谢!

6 楼 renwolang521 2011-03-30

private int FILESIZE = 4 * 1024; 
byte[] buffer = new byte[FILESIZE];  
while((input.read(buffer)) != -1){  
    output.write(buffer);  
}  
output.flush();

作者这些有没有试过呢？
这段代码难道没有问题吗？
将流读入buffer的时候，通常是读多少length，写多少length，对吧？
你这样下载下来的mp3能播放吗？

5 楼 tiantianhappy 2011-03-21

zjx2388 写道

tiantianhappy 写道

你是在手机真机上测试的,还是模拟器,报错是没有找到文件,你必需先有能下载的文件才行.

谢谢，问题解决了。就是因为找不到文件

4 楼 zjx2388 2011-03-07

jackqdyulei 写道

这段代码有点小错误~
public int downFile(String urlStr, String path, String fileName) 函数中，如果文件已存在，会直接return 1并跳转到finally语句（注意此时 inputStream=null），执行 inputStream.close()时会发生空指针引用错误但却没有catch，因此需要多加一个catch语句~

谢谢

3 楼 jackqdyulei 2011-03-06

2 楼 zjx2388 2011-02-14

tiantianhappy 写道

你是在手机真机上测试的,还是模拟器,报错是没有找到文件,你必需先有能下载的文件才行.

1 楼 tiantianhappy 2011-02-10

你好，请教一个问题，我和你写的代码一摸一样，可是我的运行总是报错，错误如下：
02-10 11:50:46.118: ERROR/vold(27): Error opening switch name path '/sys/class/switch/test2' (No such file or directory)
02-10 11:50:46.118: ERROR/vold(27): Error bootstrapping switch '/sys/class/switch/test2' (No such file or directory)
02-10 11:50:46.118: ERROR/vold(27): Error opening switch name path '/sys/class/switch/test' (No such file or directory)
02-10 11:50:46.118: ERROR/vold(27): Error bootstrapping switch '/sys/class/switch/test' (No such file or directory)
02-10 11:50:55.977: ERROR/MemoryHeapBase(51): error opening /dev/pmem: No such file or directory
02-10 11:50:55.977: ERROR/SurfaceFlinger(51): Couldn't open /sys/power/wait_for_fb_sleep or /sys/power/wait_for_fb_wake
02-10 11:50:56.077: ERROR/libEGL(51): couldn't load <libhgl.so> library (Cannot load library: load_library[984]: Library 'libhgl.so' not found)
02-10 11:50:56.507: ERROR/libEGL(62): couldn't load <libhgl.so> library (Cannot load library: load_library[984]: Library 'libhgl.so' not found)
02-10 11:50:58.998: ERROR/BatteryService(51): Could not open '/sys/class/power_supply/usb/online'
02-10 11:50:59.008: ERROR/BatteryService(51): Could not open '/sys/class/power_supply/battery/batt_vol'
02-10 11:50:59.008: ERROR/BatteryService(51): Could not open '/sys/class/power_supply/battery/batt_temp'
02-10 11:50:59.498: ERROR/EventHub(51): could not get driver version for /dev/input/mouse0, Not a typewriter
02-10 11:50:59.498: ERROR/EventHub(51): could not get driver version for /dev/input/mice, Not a typewriter
02-10 11:50:59.747: ERROR/System(51): Failure starting core service
02-10 11:50:59.747: ERROR/System(51): java.lang.SecurityException
02-10 11:50:59.747: ERROR/System(51):     at android.os.BinderProxy.transact(Native Method)
02-10 11:50:59.747: ERROR/System(51):     at android.os.ServiceManagerProxy.addService(ServiceManagerNative.java:146)
02-10 11:50:59.747: ERROR/System(51):     at android.os.ServiceManager.addService(ServiceManager.java:72)
02-10 11:50:59.747: ERROR/System(51):     at com.android.server.ServerThread.run(SystemServer.java:162)
02-10 11:50:59.757: ERROR/AndroidRuntime(51): Crash logging skipped, no checkin service
02-10 11:51:00.798: ERROR/LockPatternKeyguardView(51): Failed to bind to GLS while checking for account
02-10 11:51:03.998: ERROR/ActivityThread(93): Failed to find provider info for com.google.settings
02-10 11:51:03.998: ERROR/ActivityThread(93): Failed to find provider info for com.google.settings
02-10 11:51:06.267: ERROR/ApplicationContext(51): Couldn't create directory for SharedPreferences file shared_prefs/wallpaper-hints.xml
02-10 11:51:14.297: ERROR/MediaPlayerService(31): Couldn't open fd for content://settings/system/notification_sound
02-10 11:51:14.328: ERROR/MediaPlayer(51): Unable to to create media player
02-10 11:51:08.398: ERROR/ActivityThread(91): Failed to find provider info for android.server.checkin
02-10 11:51:10.668: ERROR/ActivityThread(91): Failed to find provider info for android.server.checkin
02-10 11:51:10.887: ERROR/ActivityThread(91): Failed to find provider info for android.server.checkin
02-10 11:57:08.328: ERROR/AndroidRuntime(224): Uncaught handler: thread main exiting due to uncaught exception
02-10 11:57:08.338: ERROR/AndroidRuntime(224): java.lang.NullPointerException
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.wjl.HttpDownLoader.download(HttpDownLoader.java:53)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.wjl.DownLoadActivity$DownLoadTextListener.onClick(DownLoadActivity.java:33)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.View.performClick(View.java:2344)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.View.onTouchEvent(View.java:4133)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.widget.TextView.onTouchEvent(TextView.java:6510)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.View.dispatchTouchEvent(View.java:3672)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1712)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1202)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.app.Activity.dispatchTouchEvent(Activity.java:1987)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1696)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1658)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.os.Looper.loop(Looper.java:123)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at android.app.ActivityThread.main(ActivityThread.java:4203)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at java.lang.reflect.Method.invokeNative(Native Method)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at java.lang.reflect.Method.invoke(Method.java:521)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
02-10 11:57:08.338: ERROR/AndroidRuntime(224):     at dalvik.system.NativeStart.main(Native Method)

我实在是不知道那里错了，请您帮忙解决一下，万分感谢。

发表评论

您还没有登录,请您登录后再发表评论

最近访客更多访客>>

博主相关

文章分类

社区版块

存档分类

最新评论