如何保存一个ArrayList文件？ [英] How to save an Arraylist to file?

问题描述

我想写ArrayList的一个文件。但我不知道怎么办。
也许你能帮助我。我怎样才能将它保存到一个文件？并且是code好这么远？也许你有足够的时间通过它来看看。
非常感谢，Vinzenz

 公共类SongsManager {最后弦乐MEDIA_PATH = Environment.getExternalStorageDirectory（）
        .getPath（）+/;
私人的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; songsList =新的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT;（）;
私人字符串mp3Pattern =.MP3
私人字符串mp4Pattern =.MP4
私人字符串MP3Pattern =.MP3
私人字符串MP4Pattern =.MP4//构造
公共SongsManager（）{}/ **
 *功能读取所有MP3文件，并存储在细节
 * ArrayList的
 * * /
公众的ArrayList＆LT;＆HashMap的LT;字符串，字符串＆GT;＆GT; getPlayList（）{
    的System.out.println（MEDIA_PATH）;
    如果（MEDIA_PATH！= NULL）{
        文件首页=新的文件（MEDIA_PATH）;
        文件[] listFiles = home.listFiles（）;
        如果（listFiles =空＆放大器;！＆放大器; listFiles.length大于0）{
            对于（文件文件：listFiles）{
                的System.out.println（file.getAbsolutePath（））;
                如果（file.isDirectory（））{
                    scanDirectory（文件）;
                }其他{
                    addSongToList（文件）;
                }
            }
        }
    }
    //返回歌曲列表数组
    返回songsList;
}私人无效scanDirectory（文件目录）{
    如果（目录！= NULL）{
        文件[] listFiles = directory.listFiles（）;
        如果（listFiles =空＆放大器;！＆放大器; listFiles.length大于0）{
            对于（文件文件：listFiles）{
                如果（file.isDirectory（））{
                    scanDirectory（文件）;
                }其他{
                    addSongToList（文件）;
                }            }
        }
    }
}私人无效addSongToList（文件歌曲）{
    如果（song.getName（）。的endsWith（mp3Pattern）|| song.getName（）。的endsWith（mp4Pattern）|| song.getName（）。的endsWith（MP4Pattern）|| song.getName（）的endsWith。（MP3Pattern））{
        HashMap的＆LT;字符串，字符串＆GT; songMap =新的HashMap＆LT;字符串，字符串＆GT;（）;
        songMap.put（SONGTITLE
                。song.getName（）子串（0，（song.getName（）长度（） -  4）））;
        songMap.put（songPath，song.getPath（））;        //添加每一首歌的SongList
        songsList.add（songMap）;
    }
}
私人无效saveFiletoTXT（）{
    尝试{
        java.io.FileOutputStream中的FOS =新java.io.FileOutputStream中（/ SD卡/）;
        java.io.ObjectOutputStream中OOS =新java.io.ObjectOutputStream中（FOS）;        oos.writeObject（（java.util.ArrayList中）songsList）;
        oos.flush（）;
        fos.close（）;
        }
        赶上（例外五）{}
}
}
 

解决方案

虽然你可以从字面上连载的的ArrayList ，我真的不认为你想这样做。我觉得更有意义，使用 android.database.sqlite包描述的这里。

I want to write the arraylist to a file. But I don't know how. Maybe you can help me. How can I save it to a File? And is the code good so far? Maybe you've enough time to look through it. Thanks a lot, Vinzenz

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";
private String mp4Pattern = ".mp4";
private String MP3Pattern = ".MP3";
private String MP4Pattern = ".MP4";

// Constructor
public SongsManager() {

}

/**
 * Function to read all mp3 files 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) || song.getName().endsWith(mp4Pattern) || song.getName().endsWith(MP4Pattern) || 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);
    }
}
private void saveFiletoTXT() {
    try{
        java.io.FileOutputStream fos = new java.io.FileOutputStream("/sdcard/");
        java.io.ObjectOutputStream oos = new java.io.ObjectOutputStream(fos);

        oos.writeObject((java.util.ArrayList) songsList);
        oos.flush();
        fos.close();
        }
        catch(Exception e){}
}
}

解决方案

While you could literally serialize an ArrayList, I really don't think you want to do that. I think it makes more sense to store its contents in SQLLite using the android.database.sqlite package as described here.

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