小编Fil*_*tys的帖子

I got stuck recently with Angular route guards. CanActive runs only once when the page is loaded and does not run on route change within the guarded route. I think this was changed because it used to run on each change. From what I read in forums, I should use CanActivateChild. The thing is, our application consists of several modules, that have several route descendants and when I use CanActivateChild in root module, it is called several times when changing …

我目前正在努力使用我们的 Ionic3 应用程序。我似乎无法找到如何使用 BT 打印机和蓝牙串行插件打印图像。打印文本就好了。

我们正在使用此文档（由我的前同事找到）驱动程序命令文档测试 RPP02N-BU 打印机 ，但我无法获得

选择位图模式

上班。

我们首先将上传的图像调整为不超过 300 像素，然后将其转换为黑白。打印时，我们迭代图像并创建二进制字符串，然后将其转换为字节。这些字节跟在 SELECT BIT IMAGE MODE 命令之后。

我们的代码（在 TypeScript 中）如下：

/**
 * Image to printer command
 * @param image 
 */
public static getImagePrintData(image: HTMLImageElement): Buffer {
    // Initialize list of commands
    let command: number[] = [ 0x1b, 0x2a, 33, 255, 3 ];

    // Get image bytes
    let bytes = this.getImageBytes(image);

    // Add bytes to command
    bytes.forEach((byte) => command.push(byte));

    // Return command
    return new Buffer(command);
}

/** …