Java 在对话框窗口中断线程

在setOnClickListener（）中，我运行进程对话框并调用函数在服务器上上载文件

btnUpload.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                if (!imageFilePath.equals(("")))

                    if (imageFilePath != null) {

                        dialog = new ProgressDialog(MainActivity.this);
                        dialog.setMessage("Uploading image...");
                        dialog.setCancelable(false);
                        dialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancel", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                dialog.dismiss();
                            }
                        });
                        dialog.show();

                        new Thread(new Runnable() {
                            @Override
                            public void run() {

                                uploadFile(fileForUpload);

                            }
                        }).start();
                    } else {
                        Toast.makeText(MainActivity.this, "Please choose a File First", Toast.LENGTH_SHORT).show();
                    }

            }
        });
        }

 public int uploadFile(final String selectedFilePath) {

        int serverResponseCode = 0;

        HttpURLConnection connection;
        DataOutputStream dataOutputStream;
        String lineEnd = "\r\n";
        String twoHyphens = "--";
        String boundary = "*****";


        int bytesRead, bytesAvailable, bufferSize;
        byte[] buffer;
        int maxBufferSize = 1 * 1024 * 1024;
        File selectedFile = new File(selectedFilePath);


        String[] parts = selectedFilePath.split("/");
        final String fileName = parts[parts.length - 1];

        if (!selectedFile.isFile()) {
            dialog.dismiss();

            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    //tvFileName.setText("Source File Doesn't Exist: " + selectedFilePath);
                }
            });
            return 0;
        } else {
            try {
                FileInputStream fileInputStream = new FileInputStream(selectedFile);
                URL url = new URL(SERVER_URL);
                connection = (HttpURLConnection) url.openConnection();
                connection.setConnectTimeout(60000);
                connection.setDoInput(true);//Allow Inputs
                connection.setDoOutput(true);//Allow Outputs
                connection.setUseCaches(false);//Don't use a cached Copy
                connection.setRequestMethod("POST");
                connection.setRequestProperty("Connection", "Keep-Alive");
                connection.setRequestProperty("ENCTYPE", "multipart/form-data");
                connection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
                connection.setRequestProperty("uploaded_file", selectedFilePath);

                //creating new dataoutputstream
                dataOutputStream = new DataOutputStream(connection.getOutputStream());

                //writing bytes to data outputstream
                dataOutputStream.writeBytes(twoHyphens + boundary + lineEnd);
                dataOutputStream.writeBytes("Content-Disposition: form-data; name=\"uploaded_file\";filename=\""
                        + selectedFilePath + "\"" + lineEnd);

                dataOutputStream.writeBytes(lineEnd);

                //returns no. of bytes present in fileInputStream
                bytesAvailable = fileInputStream.available();
                //selecting the buffer size as minimum of available bytes or 1 MB
                bufferSize = Math.min(bytesAvailable, maxBufferSize);
                //setting the buffer as byte array of size of bufferSize
                buffer = new byte[bufferSize];

                //reads bytes from FileInputStream(from 0th index of buffer to buffersize)
                bytesRead = fileInputStream.read(buffer, 0, bufferSize);

                //loop repeats till bytesRead = -1, i.e., no bytes are left to read
                while (bytesRead > 0) {
                    //write the bytes read from inputstream
                    dataOutputStream.write(buffer, 0, bufferSize);
                    bytesAvailable = fileInputStream.available();
                    bufferSize = Math.min(bytesAvailable, maxBufferSize);
                    bytesRead = fileInputStream.read(buffer, 0, bufferSize);
                }

                dataOutputStream.writeBytes(lineEnd);
                dataOutputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

                serverResponseCode = connection.getResponseCode();
                String serverResponseMessage = connection.getResponseMessage();

                Log.i("NETWORK", "Server Response is: " + serverResponseMessage + ": " + serverResponseCode);

                //response code of 200 indicates the server status OK
                if (serverResponseCode == 200) {

                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            //tvFileName.setText("File Upload completed.\n\n You can see the uploaded file here: \n\n" + "http://coderefer.com/extras/uploads/"+ fileName);
                            Toast.makeText(MainActivity.this, "Image is uploaded!", Toast.LENGTH_SHORT);
                        }
                    });
                } else
                {
                    Toast.makeText(MainActivity.this, "Error while uploading file!", Toast.LENGTH_SHORT);
                }

                //closing the input and output streams
                fileInputStream.close();
                dataOutputStream.flush();
                dataOutputStream.close();


            } catch (FileNotFoundException e) {
                e.printStackTrace();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(MainActivity.this, "File Not Found", Toast.LENGTH_SHORT).show();
                    }
                });
            } catch (MalformedURLException e) {
                e.printStackTrace();
                Toast.makeText(MainActivity.this, "URL error!", Toast.LENGTH_SHORT).show();

            } catch (IOException e) {
                e.printStackTrace();
                Toast.makeText(MainActivity.this, "Cannot Read/Write File!", Toast.LENGTH_SHORT).show();
            }
            dialog.dismiss();
            return serverResponseCode;
        }
    }

---

如何设置取消按钮来停止上传文件的线程？

实现后台操作，该操作同时具有

Cancel（）

和

isCancelled（）

方法。

上传文件（）方法在哪里？在同一个类-MainActivity（）中，我看不到它。如果修改，则发布