小编oxx*_*xxi的帖子

尝试学习Audio API,但我得到BufferLoader类的Uncaught引用错误.我正在使用Chrome,它是最新的.本班不应该没有问题吗？

<html>
<head>
<script type=text/javascript>

 window.onload = init;
 var context;
 var bufferLoader;



    function init(){

    context = new webkitAudioContext();
    bufferLoader = new BufferLoader(
          context,
          [
             ' https://dl.dropboxusercontent.com/u/1957768/kdFFO3.wav',
             ' https://dl.dropboxusercontent.com/u/1957768/geniuse%20meodies.wav',
          ],
          finishedLoading 
        );
    bufferLoader.load();
 }

     function finishedLoading(bufferList){
    //make two sources and play them
    var source1 = context.createBufferSource();
    var source2 = context.createBufferSource();
    source1.buffer = bufferList[0];
    source2.buffer = bufferList[1];

    source1.connect(context.destination);
    source2.connect(context.destination);
    source1.start(0);
    source2.start(0);
 }


   </script>
   </head>
   <body>
   </body>
   </html>

我有一个 FlatList，我试图每隔 X 秒滚动浏览数据数组的每个索引。现在我的数组中只有两项，但可能会有更多。当前的代码适用于前两次迭代，但随后它似乎没有正确重置，我得到了scrollToIndex out of range error: index is 2 but maximum is 1. 我认为当currentIndexis时>= data.length我的if语句会setCurrentIndex回到 0 但它似乎不起作用。基本上我想做的是自动循环 Flatlist 中的项目，但每个项目都会暂停几秒钟。

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow strict-local
 */
import 'react-native-gesture-handler';
import React,  {useState, useEffect, useRef} from 'react';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator, HeaderBackButton } from '@react-navigation/stack';
import {
  SafeAreaView,
  StyleSheet,
  ScrollView,
  View,
  Text,
  StatusBar,
  ImageBackground,
  Image,
  TextInput,
  Button, …

我一直在努力解决这个问题.首先,我有一个insertProduct(Product p)方法应该检查数据库中是否存在具有指定代码的产品.如果是这样,此方法将显示错误消息.否则,它应该将产品添加到数据库并将其打印到控制台.我不确定我是否正确这样做.

其次,该deleteProduct(Product p)方法应该删除该insertProduct方法添加的产品.现在的问题是,当我尝试添加产品时,我不断收到SQL异常,然后该deleteProduct方法只是在每次运行程序时都会逐个删除数据库中的产品,直到不存在为止.我不确定这两种方法都有什么问题.

控制台输出:

Derby has been started.

Product list:
bvbn    Murach's Beginning Visual Basic .NET        $49.50
cshp    Murach's C#                                 $49.50
java    Murach's Beginning Java                     $49.50
jsps    Murach's Java Servlets and JSP              $49.50
mcb2    Murach's Mainframe COBOL                    $59.50
sqls    Murach's SQL for SQL Server                 $49.50
zjcl    Murach's OS/390 and z/OS JCL                $62.50

First product:
bvbn    Murach's Beginning Visual Basic .NET        $49.50

Last product:
zjcl    Murach's OS/390 and z/OS JCL                $62.50

Product …

我正在关注正式的Webpack入门指南,我在使用配置部分时收到错误.它说创建一个webpack.config.js文件:

const path = require('path');

module.exports = {
  entry: './src/index.js',
  output: {
    filename: 'main.js',
    path: path.resolve(__dirname, 'dist')
  }
};

然后我运行以下命令: npx webpack --config webpack.config.js

我得到的错误是:

Cannot find module '/Users/Documents/Web_Development/tone/webpack.config.js'

该指南似乎没有提出任何可能出错的想法.我的代码编辑器也告诉我const path = require('path');说"预期JSON对象,数组或文字;

我的目录结构:

webpack.config.json 
package.json.lock
package.json
node_modules/
dist/
   index.html
   main.js
src/
   index.js

的package.json:

{
  "name": "tone",
  "version": "1.0.0",
  "description": "",
  "private": true,
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^6.26.3",
    "webpack": …

试图将变量'randomWord'打印到console.log,但chrome表示它没有定义.它看起来像是我定义的.为什么不打印到console.log？

function strt(){

//get random word from words[] array
var randomWord = words[Math.floor(Math.random()* words.length)];

var wordLength = randomWord.length;


//create a blank boxes or div elements for holding each letter of 
// selected random word
for(i = 0 ; i< wordLength; i++){

var divTag = document.createElement("div");
divTag.id = "div" + i;
divTag.className = 'wordy';
//divTag.innerHTML = randomWord[i];
hangManDiv.appendChild(divTag);

};// end for loop

//disable start button
document.getElementsByName("startB")[0].disabled = true;

return randomWord;

}//end strt()

console.log(randomWord);

我正在尝试从java书籍中进行练习.代码按原样出现,除了设置数据库的路径之外,我还没有在代码中添加任何内容.我在OSX上,所以我不得不安装Apache Derby.每次我构建并运行程序时,我都会得到:

Derby has been started.

Product list:
bvbn    Murach's Beginning Visual Basic .NET        $49.50
cshp    Murach's C#                                 $49.50
java    Murach's Beginning Java                     $49.50
jsps    Murach's Java Servlets and JSP              $49.50
mcb2    Murach's Mainframe COBOL                    $59.50
sqls    Murach's SQL for SQL Server                 $49.50
zjcl    Murach's OS/390 and z/OS JCL                $62.50

Exception in thread "main" java.lang.NullPointerException
First product:
at DBTesterApp.printProduct(DBTesterApp.java:117)
at DBTesterApp.printFirstProduct(DBTesterApp.java:66)
at DBTesterApp.main(DBTesterApp.java:16)
  Java Result: 1
  BUILD SUCCESSFUL (total time: 2 seconds)

我很困惑为什么这个异常一直在发生.我似乎没有发现"主要"代码有什么问题(见下文),我觉得我已经尝试了一切.有什么可能导致这个的任何线索？

import java.sql.*;

public class DBTesterApp
{
private …

我试图通过拼凑示例来在线学习教程.我觉得这应该是播放mp3文件.我正在使用Chrome浏览器,它是最新的.我在控制台上没有任何错误.我不确定我需要更改或添加以使其工作.

   <html>

<head>
<script type="text/javascript">
var context;

var sound1Buffer = null;
var url  = 'https://dl.dropboxusercontent.com/u/1957768/SrtV2.mp3';


function init(){
    try {
        window.AudioContext = window.AudioContext || window.webkitAudioContext;
        context = new AudioContext();
    }

    catch(e) {
        alert("web Audio api is not supported!");
    }
}

window.addEventListener('load', init, false);

function loadDogSound(url){

    var request = new XMLHttpRequest();
    request.open("GET", url, true);
    request.responseType = 'arrayBuffer';

    //decode asynchronously
    request.onload = function(){
        context.decodeAudioData(request.response, function(buffer){
            sound1Buffer = buffer;

        }, onError);
    }
    request.send();
}


function playSound(sound1Buffer){
     var source = context.createBufferSource();
     source.sound1Buffer = sound1Buffer;

     source.connect(context.destination); …