Question

我需要帮助，我一直在同一台计算机上执行此操作，这意味着我已经安装了boost库，并且基于之前的代码，但这次它给了我错误： /tmp/ccpAYzPw.o：在函数`main＆＃39;：

import android.os.Environment;
import java.io.File;
import java.io.FilenameFilter;
import java.util.ArrayList;
import java.util.HashMap;
public class SongsManager {


        final String MEDIA_PATH = Environment.getExternalStorageDirectory().getPath() + "/";
        private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
        private String mp3Pattern = ".mp3";
        // Constructor
        public SongsManager(){

        }

        /**
         * Function to read all mp3 files from sdcard
         * and store the details in ArrayList
         * */
        public ArrayList<HashMap<String, String>> getPlayList(){
            System.out.println(MEDIA_PATH);
            if (MEDIA_PATH != null) {
                File home = new File(MEDIA_PATH);
                File[] listFiles = home.listFiles();
                if (listFiles != null && listFiles.length > 0) {
                    for (File file : listFiles) {
                        System.out.println(file.getAbsolutePath());
                        if (file.isDirectory()) {
                            scanDirectory(file);
                        } else {
                            addSongToList(file);
                        }
                    }
                }
            }
            // return songs list array
            return songsList;
        }

        private void scanDirectory(File directory) {
            if (directory != null) {
                File[] listFiles = directory.listFiles();
                if (listFiles != null && listFiles.length > 0) {
                    for (File file : listFiles) {
                        if (file.isDirectory()) {
                            scanDirectory(file);
                        } else {
                            addSongToList(file);
                        }

                    }
                }
            }
        }

        private void addSongToList(File song) {
            if (song.getName().endsWith(mp3Pattern)) {
                HashMap<String, String> songMap = new HashMap<String, String>();
                songMap.put("songTitle",
                        song.getName().substring(0, (song.getName().length() - 4)));
                songMap.put("songPath", song.getPath());

                // Adding each song to SongList
                songsList.add(songMap);
            }
        }
        /**
         * Class to filter files which are having .mp3 extension
         * */
        class FileExtensionFilter implements FilenameFilter {
            public boolean accept(File dir, String name) {
                return (name.endsWith(".mp3") || name.endsWith(".MP3"));
            }
        }
    }

我花了将近2个小时才知道发生了什么事？但我无法理解为什么，所以我需要你的帮助。

这是我的代码，非常感谢你。

reading_data.cpp:(.text+0x356): undefined reference to `boost::program_options::options_description::m_default_line_length'
reading_data.cpp:(.text+0x361): undefined reference to `boost::program_options::options_description::m_default_line_length'
reading_data.cpp:(.text+0x3a6): undefined reference to `boost::program_options::options_description::options_description(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int, unsigned int)'
reading_data.cpp:(.text+0x3d3): undefined reference to `boost::program_options::options_description::add_options()'
collect2: error: ld returned 1 exit status
<builtin>: recipe for target 'reading_data' failed

Answer 1

您似乎没有链接库。 boost::program_options 不是标题，因此您必须明确链接它：

-lboost_program_options

Answer 2

您意外地在以下行的末尾添加了一个多余的分号：

desc.add_options（）; //是原帖中的拼写错误

您还需要声明用于存储输入选项的变量。

std::string sign;
double week, day, hour, minute, second;
desc.add_options()
        ("sign"  , program_options::value<std::string>(&sign) -> default_value("gbm")    ,"name of the input")
        ("week"  , program_options::value<double>(&week)      -> default_value(1930)     ,"number of the week")
        ("day"   , program_options::value<double>(&day)       -> default_value(0)        ,"number of the day in within the week")
        ("hour"  , program_options::value<double>(&hour)      -> default_value(0)        ,"time in hour")
        ("minute", program_options::value<double>(&minute)    -> default_value(0)        ,"time in minute")
        ("second", program_options::value<double>(&second)    -> default_value(0)        ,"time in second")
        ;

Answer 3

Boost program_options是一个已编译的库，而不是像许多其他boost库一样的头文件因此，您需要在构建时将库链接到您的程序。

如何做到这一点在很大程度上取决于您使用的编译器和平台。

如果你不知道链接是什么，你可以在这里阅读： How does the compilation/linking process work?

<boost program_options =“”options_description.hpp =“”>有什么问题？

3 个答案: