我通过套接字进行了客户端 - 服务器聊天，效果很好。现在我想为服务器（Android手机）添加一个选项来从客户端（pc应用程序）抓取屏幕截图。创建屏幕截图工作正常，但每次从客户端到服务器的传输都失败。
CLIENT-SIDE / SENDER：
在我将图像直接写入输出流之前，我在服务器端出错，所以我尝试了这种方式，但它也是一样的。
public class ClientScreenshotThread implements Runnable {
// - Software Init - //
private Socket transferSocket;
private BufferedImage screenshot;
private Robot robot;
private BufferedWriter outToServer;
private FileInputStream inStream;
private DataOutputStream outStream;
// - Var Init - //
private final int SERVER_TRANSFER_PORT = 65000;
private int screenWidth, screenHeight;
// -------------------------------------------------- //
public ClientScreenshotThread() {
}
@Override
public void run() {
try {
SocketAddress sockaddr = new InetSocketAddress(Client.SERVER_IP, SERVER_TRANSFER_PORT);
transferSocket = new Socket();
transferSocket.connect(sockaddr, 5000); // 5sec Timeout
Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
robot = new Robot();
screenWidth = dimension.width;
screenHeight = dimension.height;
Rectangle screen = new Rectangle(screenWidth, screenHeight);
screenshot = robot.createScreenCapture(screen);
ImageIO.write(screenshot, "png", new File("/Users/chris/Downloads/screenshot.png"));
File file = new File("/Users/chris/Downloads/screenshot.png");
inStream = new FileInputStream(file);
byte[] buffer = new byte[4096];
// prepare server for receiving the screenshot
outToServer = new BufferedWriter(new OutputStreamWriter(transferSocket.getOutputStream()));
outToServer.write("#!<cmd>screenshot");
outToServer.newLine();
outToServer.flush();
// send the screenshot to the server
outStream = new DataOutputStream(transferSocket.getOutputStream());
int n;
int i = 0;
while((n = inStream.read(buffer)) != -1) {
i++;
System.out.println(i + ". Byte[" + n + "]");
outStream.write(buffer, 0, n);
outStream.flush();
}
} catch(AWTException e1) {
System.out.println("AWT: " + e1.getMessage().toString());
} catch(IOException e2) {
System.out.println("IO: " + e2.getMessage().toString());
} finally {
try {
// close streams and socket
inStream.close();
outToServer.close();
transferSocket.close();
} catch(IOException e) {
System.out.println(e.getMessage().toString());
}
}
}
}
服务器端/接收器：
我总是在：
获得“NullPointerException”bmp.compress（Bitmap.CompressFormat.PNG，100，fileOutStream）;
public class ServerTransferThread implements Runnable {
// - Software Init - //
private ServerSocket serverTransferSocket;
private Handler handler;
private BufferedReader inFromClient;
private DataInputStream inStream;
private ByteArrayOutputStream content;
private FileOutputStream fileOutStream;
// - Var Init - //
private final String TAG = "xxx";
private final int SERVER_TRANSFER_PORT = 65000;
// -------------------------------------------------- //
public ServerTransferThread(Handler _handler) {
this.handler = _handler;
}
@Override
public void run() {
Log.d(TAG, "ServerTransferThread: run()");
try {
serverTransferSocket = new ServerSocket(SERVER_TRANSFER_PORT);
while(ServerActivity.SERVER_STATE == true) {
Socket socket = serverTransferSocket.accept();
Log.d(TAG, "ServerTransferThread: accepted()");
inFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
Log.d(TAG, "ServerTransferThread: bufferedReader()");
String message = "";
if((message = inFromClient.readLine()) != null) {
if(message.equals("#!<cmd>screenshot")) {
receiveScreenshot(socket);
}
}
}
} catch(IOException e) {
Log.e(TAG, "ServerTransferThread 1: " + e.getMessage().toString());
} finally {
try {
inFromClient.close();
serverTransferSocket.close();
} catch (IOException e) {
Log.e(TAG, "ServerTransferThread 2: " + e.getMessage().toString());
}
}
}
private void receiveScreenshot(Socket socketX) {
Log.d(TAG, "ServerTransferThread: receiveScreenshot()");
try {
handler.sendMessage(buildMessage("> Receiving screenshot.."));
inStream = new DataInputStream(socketX.getInputStream());
byte[] buffer = new byte[4096];
content = new ByteArrayOutputStream();
inStream = new DataInputStream(socketX.getInputStream());
int n;
while((n = inStream.read()) != -1) {
content.write(buffer, 0, n); // HERE I "OUT OF MEMORY"
content.flush();
}
File directory = new File(ServerActivity.APP_FOLDER_PATH);
File screenshot = new File(ServerActivity.APP_FOLDER_PATH + "/" + "screenshot.png");
if(!directory.exists())
directory.mkdirs();
if(!screenshot.exists()) {
screenshot.createNewFile();
}
else {
screenshot.delete();
screenshot.createNewFile();
}
fileOutStream = new FileOutputStream(screenshot);
Bitmap bmp = BitmapFactory.decodeByteArray(content.toByteArray(), 0, content.size());
bmp.compress(Bitmap.CompressFormat.PNG, 100, fileOutStream);
handler.sendMessage(buildMessage("> Screenshot received sucessfully!"));
} catch(IOException e1) {
Log.e(TAG, "ServerTransferThread 3: " + e1.getMessage().toString());
} finally {
try {
inStream.close();
content.close();
fileOutStream.close();
socketX.close();
} catch (IOException e) {
Log.e(TAG, "ServerTransferThread 4: " + e.getMessage().toString());
}
}
}
private Message buildMessage(String text) {
Log.d(TAG, "ServerTransferThread: buildMessage()");
Message msg = handler.obtainMessage();
Bundle bundle = new Bundle();
bundle.putString("MESSAGE", text);
msg.setData(bundle);
return msg;
}
这是我的Logcat输出：
08-20 19:01:18.285: D/skia(5383): --- SkImageDecoder::Factory returned null
08-20 19:01:18.295: W/dalvikvm(5383): threadid=12: thread exiting with uncaught exception (group=0x40c6b1f8)
08-20 19:01:18.295: E/AndroidRuntime(5383): FATAL EXCEPTION: Thread-3051
08-20 19:01:18.295: E/AndroidRuntime(5383): java.lang.NullPointerException
08-20 19:01:18.295: E/AndroidRuntime(5383): at net.api.speak.wifi.ServerTransferThread.receiveScreenshot(ServerTransferThread.java:114)
08-20 19:01:18.295: E/AndroidRuntime(5383): at net.api.speak.wifi.ServerTransferThread.run(ServerTransferThread.java:58)
08-20 19:01:18.295: E/AndroidRuntime(5383): at java.lang.Thread.run(Thread.java:856)
08-20 19:01:27.820: D/Speak WiFi(5383): Server: onDestroy()
08-20 19:01:27.830: E/Speak WiFi(5383): Server: Socket closed
08-20 19:01:27.830: E/Speak WiFi(5383): ServerThread: Socket closed
编辑：遇到麻烦后，我找到了文件传输问题的最终解决方案！那是：
最终服务器端：
int bytecount = 2048;
byte[] buf = new byte[bytecount];
OutputStream OUT = socket.getOutputStream();
BufferedOutputStream BuffOUT = new BufferedOutputStream(OUT, bytecount);
FileInputStream in = new FileInputStream(itemPath);
int i = 0;
while ((i = in.read(buf, 0, bytecount)) != -1) {
BuffOUT.write(buf, 0, i);
BuffOUT.flush();
}
最终客户端：
FileOutputStream outToFile = new FileOutputStream(FileName);
int bytecount = 2048;
byte[] buf = new byte[bytecount];
// Create an inputstream for the file data to arrive
InputStream IN = socket.getInputStream();
BufferedInputStream BuffIN = new BufferedInputStream(IN, bytecount);
// Receiving file..
int i = 0;
int filelength = 0;
while((i = BuffIN.read(buf, 0, bytecount)) != -1) {
filelength += i;
outToFile.write(buf, 0, i);
outToFile.flush();
}
答案 0 :(得分：0)
您是否可以将收到的字节直接写入FileOutputStream。 在像智能手机这样相当有限的设备上将png转换为位图有时会引起问题。
您是否需要在接收方创建Bitmap对象？
如果没有，你可以这样做：
InputStream is = socketX.getInputStream();
FileOutputStream outputFile = new FileOutputStream(screenshot);
int n;
while ((n = is.read(data, 0, data.length)) != -1) {
outputFile.write(data, 0, n);
}
我还没有测试过代码。
答案 1 :(得分：0)
NullPointerException是因为BitmapFactory.decodeByteArray返回：已解码的位图，如果图像无法解码，则返回null。
服务器端（在receiveScreenshot（）方法内），将InputStream字节写入ByteArrayOutputStream'content'变量的部分不正确，因为inStream.read()应为inStream.read(buffer)
可以解释Out of Memory错误，因为read()方法一次只读取一个字节，然后对于每个字节，总是写一个4096字节的完整缓冲区。
编辑：一旦你编写了fileOutputStream中的所有字节，并且你不想直接提供字节（因为在你的情况下，它是什么没有），将OutputStream压缩为png工作）：
// Write bytes inside fileOutStream
Bitmap bmp = BitmapFactory.decodeFile(screenshot.getAbsolutePath());
bmp.compress(Bitmap.CompressFormat.PNG, 100, fileOutStream);
fileOutStream.close();
这应该可以满足您的需求，但是因为你应该已经知道里面的字节所以很难解码文件。