Android TCP 文件客户端与服务器DEMO

转载 于 2013-10-29 23:39:55 发布 · 823 阅读 · 0

本文介绍了使用Java实现的文件下载服务器与客户端的功能，包括多线程处理、文件下载请求验证与文件传输流程。

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主要功能是：

1、TCP服务器提供文件下载服务，服务器支持多线程。

 

2、TCP Client从服务器上下载指定的文件，Client也支持多线程。

 

首先是服务器，服务器是在PC机上，JAVA运行环境，主要参考网上的代码，自己做了支持多线程处理，代码如下：

/file:DownloadServer.java   
import java.net.*;  
import java.io.*;  
class ServerOneDownload extends Thread {  
    private Socket socket = null;  
    private String downloadRoot = null;  
    private static final int Buffer = 8 * 1024;  
    public ServerOneDownload(Socket socket, String downloadRoot) {  
        super();  
        this.socket = socket;  
        this.downloadRoot = downloadRoot;  
        start();  
    }  
    // 检查文件是否真实存在，核对下载密码，若文件不存在或密码错误，则返回-1，否则返回文件长度  
    // 此处只要密码不为空就认为是正确的  
    private long getFileLength(String fileName, String password) {  
        // 若文件名或密码为null，则返回-1  
        if ((fileName == null) || (password == null))  
            return -1;  
        // 若文件名或密码长度为0，则返回-1  
        if ((fileName.length() == 0) || (password.length() == 0))  
            return -1;  
        String filePath = downloadRoot + fileName; // 生成完整文件路径  
        System.out.println("DownloadServer getFileLength----->" + filePath);  
        File file = new File(filePath);  
        // 若文件不存在，则返回-1  
        if (!file.exists())  
            return -1;  
        return file.length(); // 返回文件长度  
    }  
    // 用指定输出流发送指定文件  
    private void sendFile(DataOutputStream out, String fileName)  
            throws Exception {  
        String filePath = downloadRoot + fileName; // 生成完整文件路径  
        // 创建与该文件关联的文件输入流  
        FileInputStream in = new FileInputStream(filePath);  
        System.out.println("DownloadServer sendFile----->" + filePath);  
        byte[] buf = new byte[Buffer];  
        int len;  
        // 反复读取该文件中的内容，直到读到的长度为-1  
        while ((len = in.read(buf)) >= 0) {  
            out.write(buf, 0, len); // 将读到的数据，按读到的长度写入输出流  
            out.flush();  
        }  
        out.close();  
        in.close();  
    }  
    // 提供下载服务  
    public void download() throws IOException {  
        System.out.println("启动下载... ");  
        System.out.println("DownloadServer currentThread--->"  
                + currentThread().getName());  
        System.out.println("DownloadServer currentThread--->"  
                + currentThread().getId());  
        // 获取socket的输入流并包装成BufferedReader  
        BufferedReader in = new BufferedReader(new InputStreamReader(  
                socket.getInputStream()));  
        // 获取socket的输出流并包装成DataOutputStream  
        DataOutputStream out = new DataOutputStream(socket.getOutputStream());  
        try {  
            String parameterString = in.readLine(); // 接收下载请求参数  
            // 下载请求参数字符串为自定义的格式，由下载文件相对于下载根目录的路径和  
            // 下载密码组成，两者间以字符 "@ "分隔，此处按 "@ "分割下载请求参数字符串  
            String[] parameter = parameterString.split("@ ");  
            String fileName = parameter[0]; // 获取相对文件路径  
            String password = parameter[1]; // 获取下载密码  
            // 打印请求下载相关信息  
            System.out.print(socket.getInetAddress().getHostAddress()  
                    + "提出下载请求， ");  
            System.out.println("请求下载文件: " + fileName);  
            // 检查文件是否真实存在，核对下载密码，获取文件长度  
            long len = getFileLength(fileName, password);  
            System.out.println("download fileName----->" + fileName);  
            System.out.println("download password----->" + password);  
            out.writeLong(len); // 向客户端返回文件大小  
            out.flush();  
            // 若获取的文件长度大于等于0,则允许下载，否则拒绝下载  
            if (len >= 0) {  
                System.out.println("允许下载 ");  
                System.out.println("正在下载文件 " + fileName + "... ");  
                sendFile(out, fileName); // 向客户端发送文件  
                System.out.println(fileName +": "+"下载完毕 ");  
            } else {  
                System.out.println("下载文件不存在或密码错误，拒绝下载！ ");  
            }  
        } catch (Exception e) {  
            System.out.println(e.toString());  
        } finally {  
            socket.close(); // 关闭socket  
        }  
    }  
    @Override  
    public void run() {  
        try {  
            download();  
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
        // TODO Auto-generated method stub  
        super.run();  
    }  
}  
public class DownloadServer {  
    private final static int port = 65525;  
    private static String root = "C:// "; // 下载根目录  
    public static void main(String[] args) throws IOException {  
        String temp = null;  
        // 监听端口  
        try {  
            // 包装标准输入为BufferedReader  
            BufferedReader systemIn = new BufferedReader(new InputStreamReader(  
                    System.in));  
            while (true) {  
                System.out.print("请输入下载服务器的下载根目录： ");  
                root = systemIn.readLine().trim(); // 从标准输入读取下载根目录  
                File file = new File(root);  
                // 若该目录确实存在且为目录，则跳出循环  
                if ((file.exists()) && (file.isDirectory())) {  
                    temp = root.substring(root.length() - 1, root.length());  
                    if (!temp.equals("//"))  
                        root += "//";  
                }  
                break;  
            }  
        } catch (Exception e) {  
            System.out.println(e.toString());  
        }  
        ServerSocket serverSocket = new ServerSocket(port);  
        System.out.println("Server start...");  
        try {  
            while (true) {  
                Socket socket = serverSocket.accept();  
                new ServerOneDownload(socket, root);  
            }  
        } finally {  
            serverSocket.close();  
        }  
    }  
}  
[java] view plaincopyprint?
//file:DownloadServer.java   
import java.net.*;  
import java.io.*;  
class ServerOneDownload extends Thread {  
    private Socket socket = null;  
    private String downloadRoot = null;  
    private static final int Buffer = 8 * 1024;  
    public ServerOneDownload(Socket socket, String downloadRoot) {  
        super();  
        this.socket = socket;  
        this.downloadRoot = downloadRoot;  
        start();  
    }  
    // 检查文件是否真实存在，核对下载密码，若文件不存在或密码错误，则返回-1，否则返回文件长度  
    // 此处只要密码不为空就认为是正确的  
    private long getFileLength(String fileName, String password) {  
        // 若文件名或密码为null，则返回-1  
        if ((fileName == null) || (password == null))  
            return -1;  
        // 若文件名或密码长度为0，则返回-1  
        if ((fileName.length() == 0) || (password.length() == 0))  
            return -1;  
        String filePath = downloadRoot + fileName; // 生成完整文件路径  
        System.out.println("DownloadServer getFileLength----->" + filePath);  
        File file = new File(filePath);  
        // 若文件不存在，则返回-1  
        if (!file.exists())  
            return -1;  
        return file.length(); // 返回文件长度  
    }  
    // 用指定输出流发送指定文件  
    private void sendFile(DataOutputStream out, String fileName)  
            throws Exception {  
        String filePath = downloadRoot + fileName; // 生成完整文件路径  
        // 创建与该文件关联的文件输入流  
        FileInputStream in = new FileInputStream(filePath);  
        System.out.println("DownloadServer sendFile----->" + filePath);  
        byte[] buf = new byte[Buffer];  
        int len;  
        // 反复读取该文件中的内容，直到读到的长度为-1  
        while ((len = in.read(buf)) >= 0) {  
            out.write(buf, 0, len); // 将读到的数据，按读到的长度写入输出流  
            out.flush();  
        }  
        out.close();  
        in.close();  
    }  
    // 提供下载服务  
    public void download() throws IOException {  
        System.out.println("启动下载... ");  
        System.out.println("DownloadServer currentThread--->"  
                + currentThread().getName());  
        System.out.println("DownloadServer currentThread--->"  
                + currentThread().getId());  
        // 获取socket的输入流并包装成BufferedReader  
        BufferedReader in = new BufferedReader(new InputStreamReader(  
                socket.getInputStream()));  
        // 获取socket的输出流并包装成DataOutputStream  
        DataOutputStream out = new DataOutputStream(socket.getOutputStream());  
        try {  
            String parameterString = in.readLine(); // 接收下载请求参数  
            // 下载请求参数字符串为自定义的格式，由下载文件相对于下载根目录的路径和  
            // 下载密码组成，两者间以字符 "@ "分隔，此处按 "@ "分割下载请求参数字符串  
            String[] parameter = parameterString.split("@ ");  
            String fileName = parameter[0]; // 获取相对文件路径  
            String password = parameter[1]; // 获取下载密码  
            // 打印请求下载相关信息  
            System.out.print(socket.getInetAddress().getHostAddress()  
                    + "提出下载请求， ");  
            System.out.println("请求下载文件: " + fileName);  
            // 检查文件是否真实存在，核对下载密码，获取文件长度  
            long len = getFileLength(fileName, password);  
            System.out.println("download fileName----->" + fileName);  
            System.out.println("download password----->" + password);  
            out.writeLong(len); // 向客户端返回文件大小  
            out.flush();  
            // 若获取的文件长度大于等于0,则允许下载，否则拒绝下载  
            if (len >= 0) {  
                System.out.println("允许下载 ");  
                System.out.println("正在下载文件 " + fileName + "... ");  
                sendFile(out, fileName); // 向客户端发送文件  
                System.out.println(fileName +": "+"下载完毕 ");  
            } else {  
                System.out.println("下载文件不存在或密码错误，拒绝下载！ ");  
            }  
        } catch (Exception e) {  
            System.out.println(e.toString());  
        } finally {  
            socket.close(); // 关闭socket  
        }  
    }  
    @Override  
    public void run() {  
        try {  
            download();  
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
        // TODO Auto-generated method stub  
        super.run();  
    }  
}  
public class DownloadServer {  
    private final static int port = 65525;  
    private static String root = "C:// "; // 下载根目录  
    public static void main(String[] args) throws IOException {  
        String temp = null;  
        // 监听端口  
        try {  
            // 包装标准输入为BufferedReader  
            BufferedReader systemIn = new BufferedReader(new InputStreamReader(  
                    System.in));  
            while (true) {  
                System.out.print("请输入下载服务器的下载根目录： ");  
                root = systemIn.readLine().trim(); // 从标准输入读取下载根目录  
                File file = new File(root);  
                // 若该目录确实存在且为目录，则跳出循环  
                if ((file.exists()) && (file.isDirectory())) {  
                    temp = root.substring(root.length() - 1, root.length());  
                    if (!temp.equals("//"))  
                        root += "//";  
                }  
                break;  
            }  
        } catch (Exception e) {  
            System.out.println(e.toString());  
        }  
        ServerSocket serverSocket = new ServerSocket(port);  
        System.out.println("Server start...");  
        try {  
            while (true) {  
                Socket socket = serverSocket.accept();  
                new ServerOneDownload(socket, root);  
            }  
        } finally {  
            serverSocket.close();  
        }  
    }  
}


File Download Client

Client输入IP和文件名即可直接从服务器上下载，还是看代码。

 

[java] view plaincopyprint?
//file:DownLoadClient.java   
package org.piaozhiye.study;  
import java.io.IOException;  
import java.net.Socket;  
import android.app.Activity;  
import android.os.Bundle;  
import android.view.View;  
import android.widget.Button;  
import android.widget.EditText;  
public class DownLoadClient extends Activity {  
    private Button download = null;  
    private EditText et_serverIP = null;  
    private EditText et_fileName= null;  
    private String downloadFile = null;  
    private final static int PORT = 65525;  
    private final static String defaultIP = "192.168.0.100";  
    private static String serverIP = null;  
    private Socket socket;  
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        download = (Button)findViewById(R.id.download);  
        et_serverIP= (EditText)findViewById(R.id.et_serverip);  
        et_fileName = (EditText)findViewById(R.id.et_filename);  
        et_serverIP.setText("192.168.0.100");  
        
      download.setOnClickListener(new View.OnClickListener() {  
              
            @Override  
            public void onClick(View v) {  
                 serverIP = et_serverIP.getText().toString();  
                 if(serverIP == null){  
                     serverIP = defaultIP;  
                 }  
                 System.out.println("DownLoadClient serverIP--->" + serverIP );  
                    System.out.println("DownLoadClient MainThread--->" + Thread.currentThread().getId() );  
                      
                try{  
                    socket = new Socket(serverIP, PORT);  
                      
                }catch(IOException e){  
                      
                }  
                 downloadFile = et_fileName.getText().toString();  
            Thread downFileThread = new Thread(new DownFileThread(socket, downloadFile));  
            downFileThread.start();  
                System.out.println("DownLoadClient downloadFile--->" + downloadFile );  
            }  
        });  
         
    }  
}  
[java] view plaincopyprint?
//file:DownLoadClient.java   
package org.piaozhiye.study;  
import java.io.IOException;  
import java.net.Socket;  
import android.app.Activity;  
import android.os.Bundle;  
import android.view.View;  
import android.widget.Button;  
import android.widget.EditText;  
public class DownLoadClient extends Activity {  
    private Button download = null;  
    private EditText et_serverIP = null;  
    private EditText et_fileName= null;  
    private String downloadFile = null;  
    private final static int PORT = 65525;  
    private final static String defaultIP = "192.168.0.100";  
    private static String serverIP = null;  
    private Socket socket;  
    /** Called when the activity is first created. */  
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        download = (Button)findViewById(R.id.download);  
        et_serverIP= (EditText)findViewById(R.id.et_serverip);  
        et_fileName = (EditText)findViewById(R.id.et_filename);  
        et_serverIP.setText("192.168.0.100");  
        
      download.setOnClickListener(new View.OnClickListener() {  
              
            @Override  
            public void onClick(View v) {  
                 serverIP = et_serverIP.getText().toString();  
                 if(serverIP == null){  
                     serverIP = defaultIP;  
                 }  
                 System.out.println("DownLoadClient serverIP--->" + serverIP );  
                    System.out.println("DownLoadClient MainThread--->" + Thread.currentThread().getId() );  
                      
                try{  
                    socket = new Socket(serverIP, PORT);  
                      
                }catch(IOException e){  
                      
                }  
                 downloadFile = et_fileName.getText().toString();  
            Thread downFileThread = new Thread(new DownFileThread(socket, downloadFile));  
            downFileThread.start();  
                System.out.println("DownLoadClient downloadFile--->" + downloadFile );  
            }  
        });  
         
    }  
}

 

file:DownFileThread.java

 

[java] view plaincopyprint?
package org.piaozhiye.study;  
import java.io.BufferedInputStream;  
import java.io.DataInputStream;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.OutputStreamWriter;  
import java.io.PrintWriter;  
import java.net.Socket;  
public class DownFileThread extends Thread {  
    private Socket socket;  
    private String downloadFile;  
    private final static int Buffer = 8 * 1024;  
    public DownFileThread(Socket socket, String downloadFile) {  
        super();  
        this.socket = socket;  
        this.downloadFile = downloadFile;  
    }  
    public Socket getSocket() {  
        return socket;  
    }  
    public void setSocket(Socket socket) {  
        this.socket = socket;  
    }  
    public String getDownloadFile() {  
        return downloadFile;  
    }  
    public void setDownloadFile(String downloadFile) {  
        this.downloadFile = downloadFile;  
    }  
    // 向服务器提出下载请求，返回下载文件的大小  
    private long request(String fileName, String password) throws IOException {  
        // 获取socket的输入流并包装成DataInputStream  
        DataInputStream in = new DataInputStream(socket.getInputStream());  
        // 获取socket的输出流并包装成PrintWriter  
        PrintWriter out = new PrintWriter(new OutputStreamWriter(  
                socket.getOutputStream()));  
        // 生成下载请求字符串  
        String requestString = fileName + "@ " + password;  
        out.println(requestString); // 发出下载请求  
        out.flush();  
        return in.readLong(); // 接收并返回下载文件长度  
    }  
    // 接收并保存文件  
    private void receiveFile(String localFile) throws Exception {  
        // 获取socket的输入流并包装成BufferedInputStream  
        BufferedInputStream in = new BufferedInputStream(  
                socket.getInputStream());  
        // 获取与指定本地文件关联的文件输出流  
        FileOutputStream out = new FileOutputStream(localFile);  
        byte[] buf = new byte[Buffer];  
        int len;  
        // 反复读取该文件中的内容，直到读到的长度为-1  
        while ((len = in.read(buf)) >= 0) {  
            out.write(buf, 0, len); // 将读到的数据，按读到的长度写入输出流  
            out.flush();  
        }  
        out.close();  
        in.close();  
    }  
    // 从服务器下载文件  
    public void download(String downloadFile) throws Exception {  
        try {  
            String password = "password";  
            // String downloadFile ="imissyou.mp3";  
            String localpath = "/sdcard/";  
            String localFile = localpath + downloadFile;  
            long fileLength = request(downloadFile, password);  
            // 若获取的文件长度大于等于0，说明允许下载，否则说明拒绝下载  
            if (fileLength >= 0) {  
                System.out.println("fileLength: " + fileLength + " B");  
                System.out.println("downing...");  
                receiveFile(localFile); // 从服务器接收文件并保存至本地文件  
                System.out.println("file:" + downloadFile + " had save to "  
                        + localFile);  
            } else {  
                System.out.println("download " + downloadFile + " error! ");  
            }  
        } catch (IOException e) {  
            System.out.println(e.toString());  
        } finally {  
            socket.close(); // 关闭socket  
        }  
    }  
    @Override  
    public void run() {  
        System.out.println("DownFileThread currentThread--->"  
                + DownFileThread.currentThread().getId());  
        // TODO Auto-generated method stub  
        try {  
            download(downloadFile);  
        } catch (Exception e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
        super.run();  
    }  
      
}  
[java] view plaincopyprint?
package org.piaozhiye.study;  
import java.io.BufferedInputStream;  
import java.io.DataInputStream;  
import java.io.FileOutputStream;  
import java.io.IOException;  
import java.io.OutputStreamWriter;  
import java.io.PrintWriter;  
import java.net.Socket;  
public class DownFileThread extends Thread {  
    private Socket socket;  
    private String downloadFile;  
    private final static int Buffer = 8 * 1024;  
    public DownFileThread(Socket socket, String downloadFile) {  
        super();  
        this.socket = socket;  
        this.downloadFile = downloadFile;  
    }  
    public Socket getSocket() {  
        return socket;  
    }  
    public void setSocket(Socket socket) {  
        this.socket = socket;  
    }  
    public String getDownloadFile() {  
        return downloadFile;  
    }  
    public void setDownloadFile(String downloadFile) {  
        this.downloadFile = downloadFile;  
    }  
    // 向服务器提出下载请求，返回下载文件的大小  
    private long request(String fileName, String password) throws IOException {  
        // 获取socket的输入流并包装成DataInputStream  
        DataInputStream in = new DataInputStream(socket.getInputStream());  
        // 获取socket的输出流并包装成PrintWriter  
        PrintWriter out = new PrintWriter(new OutputStreamWriter(  
                socket.getOutputStream()));  
        // 生成下载请求字符串  
        String requestString = fileName + "@ " + password;  
        out.println(requestString); // 发出下载请求  
        out.flush();  
        return in.readLong(); // 接收并返回下载文件长度  
    }  
    // 接收并保存文件  
    private void receiveFile(String localFile) throws Exception {  
        // 获取socket的输入流并包装成BufferedInputStream  
        BufferedInputStream in = new BufferedInputStream(  
                socket.getInputStream());  
        // 获取与指定本地文件关联的文件输出流  
        FileOutputStream out = new FileOutputStream(localFile);  
        byte[] buf = new byte[Buffer];  
        int len;  
        // 反复读取该文件中的内容，直到读到的长度为-1  
        while ((len = in.read(buf)) >= 0) {  
            out.write(buf, 0, len); // 将读到的数据，按读到的长度写入输出流  
            out.flush();  
        }  
        out.close();  
        in.close();  
    }  
    // 从服务器下载文件  
    public void download(String downloadFile) throws Exception {  
        try {  
            String password = "password";  
            // String downloadFile ="imissyou.mp3";  
            String localpath = "/sdcard/";  
            String localFile = localpath + downloadFile;  
            long fileLength = request(downloadFile, password);  
            // 若获取的文件长度大于等于0，说明允许下载，否则说明拒绝下载  
            if (fileLength >= 0) {  
                System.out.println("fileLength: " + fileLength + " B");  
                System.out.println("downing...");  
                receiveFile(localFile); // 从服务器接收文件并保存至本地文件  
                System.out.println("file:" + downloadFile + " had save to "  
                        + localFile);  
            } else {  
                System.out.println("download " + downloadFile + " error! ");  
            }  
        } catch (IOException e) {  
            System.out.println(e.toString());  
        } finally {  
            socket.close(); // 关闭socket  
        }  
    }  
    @Override  
    public void run() {  
        System.out.println("DownFileThread currentThread--->"  
                + DownFileThread.currentThread().getId());  
        // TODO Auto-generated method stub  
        try {  
            download(downloadFile);  
        } catch (Exception e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
        super.run();  
    }  
      
}

 

 

layout.xml

[xhtml] view plaincopyprint?
<?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="wrap_content"   
    android:layout_height="wrap_content"   
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
    android:text="服务器IP:"  
    />  
    <EditText  
    android:id="@+id/et_serverip"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
      
    />  
      
    <TextView   
    android:layout_width="wrap_content"   
    android:layout_height="wrap_content"   
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
    android:text="下载文件名:"  
    />  
    <EditText  
    android:id="@+id/et_filename"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
      
    />  
    <Button  
    android:id="@+id/download"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:text="download"  
    />  
</LinearLayout>  
[xhtml] view plaincopyprint?
<?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="wrap_content"   
    android:layout_height="wrap_content"   
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
    android:text="服务器IP:"  
    />  
    <EditText  
    android:id="@+id/et_serverip"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
      
    />  
      
    <TextView   
    android:layout_width="wrap_content"   
    android:layout_height="wrap_content"   
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
    android:text="下载文件名:"  
    />  
    <EditText  
    android:id="@+id/et_filename"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:paddingLeft="10dp"  
    android:paddingRight="10dp"  
    android:paddingTop="5dp"  
    android:paddingBottom="5dp"  
      
    />  
    <Button  
    android:id="@+id/download"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:text="download"  
    />  
</LinearLayout>


 

同时别忘了权限：

<uses-permission android:name="android.permission.INTERNET" />

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