我正在尝试执行以下代码将文件从android模拟器传输到pc。应用程序强制关闭，我在logcat中看到以下错误消息：
12-03 16:56:33.503: D/AndroidRuntime(1145): Shutting down VM
12-03 16:56:33.503: D/AndroidRuntime(1145): --------- beginning of crash
12-03 16:56:33.517: E/AndroidRuntime(1145): FATAL EXCEPTION: main
12-03 16:56:33.517: E/AndroidRuntime(1145): Process: com.example.androidfiletransfer, PID: 1145
12-03 16:56:33.517: E/AndroidRuntime(1145): java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.OutputStream java.net.Socket.getOutputStream()' on a null object reference
12-03 16:56:33.517: E/AndroidRuntime(1145): at com.example.androidfiletransfer.MainActivity$1.onClick(MainActivity.java:77)
12-03 16:56:33.517: E/AndroidRuntime(1145): at android.view.View.performClick(View.java:4756)
12-03 16:56:33.517: E/AndroidRuntime(1145): at android.view.View$PerformClick.run(View.java:19749)
12-03 16:56:33.517: E/AndroidRuntime(1145): at android.os.Handler.handleCallback(Handler.java:739)
控制台中显示以下消息：
Server started. Listening to the port 4444
Receiving...
mybytearray: 100000000
current: -1
bytes read: -1
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
at java.lang.System.arraycopy(Native Method)
at java.io.BufferedOutputStream.write(Unknown Source)
at Javafilereceive.main(Javafilereceive.java:53)
我尝试过研究这个错误，但我无法解决它。由于我是Android的新手，如果有人可以帮我解决这个问题，那将会很有帮助。
客户端代码：
package com.example.androidfiletransfer;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.StrictMode;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.io.BufferedInputStream;
public class MainActivity extends Activity {
//EditText textOut;
TextView textIn;
Socket client;
FileInputStream fileInputStream;
BufferedInputStream bufferedInputStream;
OutputStream outputStream;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
// textOut = (EditText)findViewById(R.id.textout);
Button buttonSend = (Button)findViewById(R.id.send);
textIn = (TextView)findViewById(R.id.textin);
buttonSend.setOnClickListener(buttonSendOnClickListener);
}
Button.OnClickListener buttonSendOnClickListener
= new Button.OnClickListener(){
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Socket socket;
DataOutputStream dataOutputStream;
DataInputStream dataInputStream;
//File file = new File("/mnt/media_rw/sdcard/download/vivd_flowers-wide.jpg"); //create file instance
File dir = Environment.getExternalStorageDirectory();
File file = new File(dir, "Sample.txt");
System.out.println("file length: " + file.length());
try {
socket = new Socket("<ip address", 4444);
byte[] mybytearray = new byte[(int) file.length()]; //create a byte array to file
// dataOutputStream = new DataOutputStream(socket.getOutputStream());
// dataInputStream = new DataInputStream(socket.getInputStream());
// dataOutputStream.writeUTF(textOut.getText().toString());
// textIn.setText(dataInputStream.readUTF());
System.out.println("mybytearray in android: " + mybytearray.length);
fileInputStream = new FileInputStream(file);
bufferedInputStream = new BufferedInputStream(fileInputStream);
bufferedInputStream.read(mybytearray, 0, mybytearray.length); //read the file
System.out.println("Read into buffer");
outputStream = client.getOutputStream();
outputStream.write(mybytearray, 0, mybytearray.length); //write file to the output stream byte by byte
System.out.println("Written to buffer");
outputStream.flush();
bufferedInputStream.close();
outputStream.close();
client.close();
textIn.setText("File Sent");
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
}
服务器代码：
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Javafilereceive {
private static ServerSocket serverSocket;
private static Socket clientSocket;
private static InputStream inputStream;
private static FileOutputStream fileOutputStream;
private static BufferedOutputStream bufferedOutputStream;
private static int filesize = 100000000; // filesize temporary hardcoded
private static int bytesRead;
private static int current = 0;
public static void main(String[] args) throws IOException {
serverSocket = new ServerSocket(4444); //Server socket
System.out.println("Server started. Listening to the port 4444");
clientSocket = serverSocket.accept();
byte[] mybytearray = new byte[filesize]; //create byte array to buffer the file
inputStream = clientSocket.getInputStream();
fileOutputStream = new FileOutputStream("D:\\output.jpg");
bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
System.out.println("Receiving...");
System.out.println("mybytearray: " + mybytearray.length);
//following lines read the input slide file byte by byte
bytesRead = inputStream.read(mybytearray, 0, mybytearray.length);
current = bytesRead;
System.out.println("current: " + current);
do {
bytesRead = inputStream.read(mybytearray, current, (mybytearray.length - current));
System.out.println("bytes read: " + bytesRead);
if (bytesRead >= 0) {
current += bytesRead;
}
} while (bytesRead > -1);
bufferedOutputStream.write(mybytearray, 0, current);
bufferedOutputStream.flush();
bufferedOutputStream.close();
inputStream.close();
clientSocket.close();
serverSocket.close();
System.out.println("Sever recieved the file");
}
}
我已经放了一些println语句来查看是否从模拟器中选择了文件，但看起来并非如此。你能否告诉我如何在android中指定文件路径。
答案 0 :(得分：3)
欢迎堆栈溢出！
您没有为初学者正确初始化套接字。
应该是
client = new Socket("192.18.2.22",4444);
其中“192.19.2.22”是您服务器的IP。
另外，尝试很好地格式化代码以使其可读。