在Android中抛出空指针异常 [英] Throwing null pointer exception in Android
问题描述
我试图获取从音频目录的音频文件,我使用下面code。我无法弄清楚为什么这个条件如果(home.listFiles(新FileExtensionFilter())长方式> 0)
抛出一个错误。 code给出如下。
乌里allsongsuri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
最后弦乐MEDIA_PATH = allsongsuri.toString();
私人的ArrayList<&HashMap的LT;字符串,字符串>> songsList =新的ArrayList<&HashMap的LT;字符串,字符串>>();公众的ArrayList<&HashMap的LT;字符串,字符串>> getPlayList(){
的System.out.println( - + MEDIA_PATH);
文件首页=新的文件(MEDIA_PATH); 如果(home.listFiles(新FileExtensionFilter())长度方式> 0){
对于(文件文件:home.listFiles(新FileExtensionFilter())){
HashMap的<字符串,字符串>歌=新的HashMap<字符串,字符串>();
song.put(SONGTITLE,file.getName()子串(0,(file.getName()长度() - 4))。);
song.put(songPath,file.getPath()); //添加每一首歌的SongList
songsList.add(歌曲);
}
}
返回songsList;
}类FileExtensionFilter实现了FilenameFilter {
公共布尔接受(文件目录,字符串名称){
回报(name.endsWith(MP3)|| name.endsWith()MP3);
}
我需要使用HashMap中存储的音频文件的ArrayList中。我想这个例子中存储列表文件
的http://android-er.blogspot.in/2012/02/list-audio-media-in-mediastoreaudiomedi.html 。使用这个例子中,我尝试了很多到列表存储在ArrayList中为我reqirement需要的。但没成功。
我需要帮助。我要存储在ArrayList中的音频文件。
公共类SongsManager {
最后弦乐MEDIA_PATH = Environment.getExternalStorageDirectory()
.getPath()+/;
私人的ArrayList<&HashMap的LT;字符串,字符串>> songsList =新的ArrayList<&HashMap的LT;字符串,字符串>>();
私人字符串mp3Pattern =.MP3 //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<&HashMap的LT;字符串,字符串>> 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)){
HashMap的<字符串,字符串> songMap =新的HashMap<字符串,字符串>();
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);
}
}
}
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"));
}
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.
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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