我有一个音乐播放器应用程序，它应该打开并在您的手机/SD 卡上显示曲目列表，但是当我启动该应用程序时，它什么也没显示。
我遵循了一个教程，所以我并不完全清楚应该做什么。特别是使用 xml ListView：http ://www.androidhive.info/2012/03/android-building-audio-player-tutorial/
以下是我的 java 类，它们对可能导致这种情况的原因很重要：
图书馆.java
public class Library extends ListActivity {
// Songs list
public ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.library);
ArrayList<HashMap<String, String>> songsListData = new ArrayList<HashMap<String, String>>();
TrackManager plm = new TrackManager();
// get all songs from sdcard
this.songsList = plm.getPlayList();
// looping through playlist
for (int i = 0; i < songsList.size(); i++) {
// creating new HashMap
HashMap<String, String> song = songsList.get(i);
// adding HashList to ArrayList
songsListData.add(song);
}
// Adding menuItems to ListView
ListAdapter adapter = new SimpleAdapter(this, songsListData, R.layout.libraryitem, new String[] { "songTitle" }, new int[] { R.id.songTitle });
setListAdapter(adapter);
// selecting single ListView item
ListView lv = getListView();
// listening to single listitem click
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
// getting listitem index
int songIndex = position;
// Starting new intent
Intent in = new Intent(getApplicationContext(), Player.class);
// Sending songIndex to PlayerActivity
in.putExtra("songIndex", songIndex);
setResult(100, in);
// Closing PlayListView
finish();
}
});
}
TrackManager.java
public class TrackManager {
// SDCard Path
final String MEDIA_PATH = new String(Environment.getExternalStorageDirectory().getPath());
private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
// Constructor
public TrackManager() {
}
// Function to read all mp3 files from sdcard and store the details in
// ArrayList
public ArrayList<HashMap<String, String>> getPlayList() {
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 songs list array
return songsList;
}
// 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"));
}
}
}
我有一些 xml 布局显示这些类应该填充的列表视图，但我只是得到一个空白的空列表，就像那里什么都没有：
更新
库.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#111111"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".Library" >
<TextView
android:id="@+id/tvTracks"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tracks"
android:textSize="20sp" />
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_below="@+id/tvTracks"
android:divider="#999999"
android:dividerHeight="1dp"
android:listSelector="@drawable/list_selector" />
</RelativeLayout>
列表视图的 libraryitem.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/list_selector"
android:orientation="vertical"
android:padding="5dp"
tools:ignore="SelectableText" >
<TextView
android:id="@+id/songTitle"
android:text="@string/title"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:padding="5dp"
android:textSize="15sp" />
</RelativeLayout>
希望有人能解决我的问题..