TDLightTelegramBots/TelegramBots.wiki/FAQ.md

• How to get picture?
• How to send photos?
• How to use custom keyboards?
• How can I run my bot?
• How can I compile my project?

How to download photo?

To download a picture (or any other file), you will need the file_path of the file. Let start by finding the photo we want to download, the following method will extract the PhotoSize from a photo sent to the bot (in our case, we are taken the bigger size of those provided):

public PhotoSize getPhoto(Update update) {
    // Check that the update contains a message and the message has a photo
    if (update.hasMessage() && update.getMessage().hasPhoto()) {
        // When receiving a photo, you usually get different sizes of it
        List<PhotoSize> photos = update.getMessage().getPhoto();

        // We fetch the bigger photo
        return photos.stream()
                .sorted(Comparator.comparing(PhotoSize::getFileSize).reversed())
                .findFirst()
                .orElse(null);
    }

    // Return null if not found
    return null;
}

Once we have the photo we have to options: The file_path is already present or we need to get it, the following method will handle both of them and return the final file_path:

public String getFilePath(PhotoSize photo) {
    Objects.requireNonNull(photo);

    if (photo.hasFilePath()) { // If the file_path is already present, we are done!
        return photo.getFilePath();
    } else { // If not, let find it
        // We create a GetFile method and set the file_id from the photo
        GetFile getFileMethod = new GetFile();
        getFileMethod.setFileId(photo.getFileId());
        try {
            // We execute the method using AbsSender::getFile method.
            File file = getFile(getFileMethod);
            // We now have the file_path
            return file.getFilePath();
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }
    
    return null; // Just in case
}

Now that we have the file_path we can download it:

public java.io.File downloadPhotoByFilePath(String filePath) {
    try {
        // Download the file calling AbsSender::downloadFile method
        return downloadFile(filePath);
    } catch (TelegramApiException e) {
        e.printStackTrace();
    }

    return null;
}

The returned java.io.File object will be your photo

How to send photos?

There are several method to send a photo to an user using sendPhoto method: With a file_id, with an url or uploading the file. In this example, we assume that we already have the chat_id where we want to send the photo:

    public void sendImageFromUrl(String url, String chatId) {
        // Create send method
        SendPhoto sendPhotoRequest = new SendPhoto();
        // Set destination chat id
        sendPhotoRequest.setChatId(chatId);
        // Set the photo url as a simple photo
        sendPhotoRequest.setPhoto(url);
        try {
            // Execute the method
            sendPhoto(sendPhotoRequest);
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }

    public void sendImageFromFileId(String fileId, String chatId) {
        // Create send method
        SendPhoto sendPhotoRequest = new SendPhoto();
        // Set destination chat id
        sendPhotoRequest.setChatId(chatId);
        // Set the photo url as a simple photo
        sendPhotoRequest.setPhoto(fileId);
        try {
            // Execute the method
            sendPhoto(sendPhotoRequest);
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }

    public void sendImageUploadingAFile(String filePath, String chatId) {
        // Create send method
        SendPhoto sendPhotoRequest = new SendPhoto();
        // Set destination chat id
        sendPhotoRequest.setChatId(chatId);
        // Set the photo file as a new photo (You can also use InputStream with a method overload)
        sendPhotoRequest.setNewPhoto(new File(filePath));
        try {
            // Execute the method
            sendPhoto(sendPhotoRequest);
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }

How to use custom keyboards?

Custom keyboards can be appended to messages using the setReplyMarkup. In this example, we will build a simple ReplyKeyboardMarkup with two rows and three buttons per row, but you can also use other types like ReplyKeyboardHide, ForceReply or InlineKeyboardMarkup:

    public void sendCustomKeyboard(String chatId) {
        SendMessage message = new SendMessage();
        message.setChatId(chatId);
        message.setText("Custom message text");

        // Create ReplyKeyboardMarkup object
        ReplyKeyboardMarkup keyboardMarkup = new ReplyKeyboardMarkup();
        // Create the keyboard (list of keyboard rows)
        List<KeyboardRow> keyboard = new ArrayList<>();
        // Create a keyboard row
        KeyboardRow row = new KeyboardRow();
        // Set each button, you can also use KeyboardButton objects if you need something else than text
        row.add("Row 1 Button 1");
        row.add("Row 1 Button 2");
        row.add("Row 1 Button 3");
        // Add the first row to the keyboard
        keyboard.add(row);
        // Create another keyboard row
        row = new KeyboardRow();
        // Set each button for the second line
        row.add("Row 2 Button 1");
        row.add("Row 2 Button 2");
        row.add("Row 2 Button 3");
        // Add the second row to the keyboard
        keyboard.add(row);
        // Set the keyboard to the markup
        keyboardMarkup.setKeyboard(keyboard);
        // Add it to the message
        message.setReplyMarkup(keyboardMarkup);

        try {
            // Send the message
            sendMessage(message);
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
    }

How can I run my bot?

You don't need to spend a lot of money into hosting your own telegram bot. Basically, there are two options around how to host:

1. Hosting on your own hardware. It can be a Mini-PC like a Raspberry Pi. The costs for the hardware (~35€) and annual costs for power (~7-8€) are low. Keep in mind that your internet connection might be limited and a Mini-Pc is not ideal for a large users base.
2. Run your bot in a Virtual Server/dedicated root server. There are many hosters out there that are providing cheap servers that fit your needs. The cheapest one should be openVZ-Containers or a KVM vServer. Example providers are Hetzner, DigitalOcean, (are providing systems that have a high availability but cost's a bit more) and OVH

How can I compile my project?

This is just one way, how you can compile it (here with maven). The example below below is compiling the TelegramBotsExample repo.