在Android中抛出空指针异常 [英] Throwing null pointer exception in Android
问题描述
我正在尝试从音频目录中获取音频文件,为此我使用了以下代码.我无法弄清楚为什么这种情况 if (home.listFiles(new FileExtensionFilter()).length > 0)
会引发错误.代码如下.
I'm trying to fetch an audio file from the audio directory, for that I'm using below code. I'm not able to figure out why this condition if (home.listFiles(new FileExtensionFilter()).length > 0)
is throwing an error. Code is given below.
Uri allsongsuri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
final String MEDIA_PATH = allsongsuri.toString();
private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
public ArrayList<HashMap<String, String>> getPlayList(){
System.out.println(" -- "+MEDIA_PATH);
File home = new File(MEDIA_PATH);
if (home.listFiles(new FileExtensionFilter()).length > 0) {
for (File file : home.listFiles(new FileExtensionFilter())) {
HashMap<String, String> song = new HashMap<String, String>();
song.put("songTitle", file.getName().substring(0, (file.getName().length() - 4)));
song.put("songPath", file.getPath());
// Adding each song to SongList
songsList.add(song);
}
}
return songsList;
}
class FileExtensionFilter implements FilenameFilter {
public boolean accept(File dir, String name) {
return (name.endsWith(".mp3") || name.endsWith(".MP3"));
}
我需要使用 hashMap 将音频文件存储在 ArrayList 中.我试过这个例子将文件存储在列表中http://android-er.blogspot.in/2012/02/list-audio-media-in-mediastoreaudiomedi.html .使用这个例子,我尝试了很多将列表存储在 ArrayList 中,因为我的需求需要它.但是没有成功.我需要帮助.我必须将音频文件存储在 Arraylist 中.
I need to store audio file in ArrayList using hashMap. I tried this example to store file in List http://android-er.blogspot.in/2012/02/list-audio-media-in-mediastoreaudiomedi.html . Using this example I tried a lot to store the list in ArrayList as my reqirement need that. But didn't succeed. I need help. I have to store Audio file in Arraylist.
推荐答案
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 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);
}
}
}
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