I am making a music player application for my Computing project. I got it working but found that using objects would get more more marks. As a result, I changed some of my code to incorporate the use of objects, but it doesn’t work when I execute my application. Btw I am quite new to Java so it’s possible I made a silly mistake.
When I used this code the function I tried to implement worked:
private void SongTitleEndTime(){
try {
TextViewSongTitle = (TextView)findViewById(R.id.songTitle);
if (id != 0 ){
String where = MediaStore.Audio.Media._ID + " = " + "'" + id + "'";
final Cursor mCursor = managedQuery(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
new String[] {MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media._ID.toString(), MediaStore.Audio.Media.ALBUM_ID.toString()}, where , null,
null);
mCursor.moveToFirst();
String title = mCursor.getString(0);
String artist = mCursor.getString(1);
String name = title + " - " + artist;
TextViewSongTitle.setText(name);
String fulltime;
albumfullid = Long.parseLong(mCursor.getString(3));
TextView EndTime = (TextView) findViewById(R.id.endtime);
long Minutes = TimeUnit.MILLISECONDS.toMinutes(mMediaPlayer.getDuration());
long Seconds = TimeUnit.MILLISECONDS.toSeconds(mMediaPlayer.getDuration()) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(mMediaPlayer.getDuration()));
if (Seconds < 10) {
String second = "0" + String.valueOf(Seconds);
fulltime = Minutes + ":" + second;
} else {
//else display as normal
fulltime = Minutes + ":" + Seconds;
}
EndTime.setText(fulltime);
//display the duration of song
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalStateException e) {
e.printStackTrace();
} //catch for errors
}
But when I tried this, I got an error:
Main Class:
private void SongTitleEndTime() {
try {
final TextView TextViewSongTitle = (TextView) findViewById(R.id.songTitle);
if (CurrentSongID != 0) {
final Song CurrentSong = new Song(CurrentSongID);
SongName = CurrentSong.SongName;
TextViewSongTitle.setText(SongName);
AlbumID = CurrentSong.AlbumID;
final TextView EndTime = (TextView) findViewById(R.id.endtime);
final String TotalSongDuration = CurrentSong.TotalDuration;
EndTime.setText(TotalSongDuration);
}
} catch (final IllegalArgumentException e) {
e.printStackTrace();
} catch (final IllegalStateException e) {
e.printStackTrace();
}
}
Object Class:
package com.example.music.test;
import java.util.concurrent.TimeUnit;
import android.app.Activity;
import android.database.Cursor;
import android.provider.BaseColumns;
import android.provider.MediaStore;
import android.provider.MediaStore.Audio.AudioColumns;
import android.provider.MediaStore.MediaColumns;
public class Song extends Activity {
private final String where;
public String SongName;
public long AlbumID;
public String TotalDuration;
public Song(final long SongID) {
where = MediaStore.Audio.Media._ID + " = " + "'" + SongID + "'";
final Cursor mCursor = managedQuery(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
new String[] { MediaStore.Audio.Media.TITLE, MediaStore.Audio.Media.ARTIST,
MediaStore.Audio.Media._ID.toString(),
MediaStore.Audio.Media.ALBUM_ID.toString() }, where, null, null);
mCursor.moveToFirst();
final String SongTitle = getSongTitle(mCursor);
final String SongArtist = getSongArtist(mCursor);
SongName = SongTitle + " - " + SongArtist;
AlbumID = getAlbumID(mCursor);
TotalDuration = getTotalDuration();
}
public String getSongTitle(final Cursor mCursor) {
final String songtitle = mCursor.getString(0);
return songtitle;
}
public String getSongArtist(final Cursor mCursor) {
final String songartist = mCursor.getString(1);
return songartist;
}
public long getAlbumID(final Cursor mCursor) {
final long AlbumID = Long.parseLong(mCursor.getString(3));
return AlbumID;
}
public String getTotalDuration() {
String TotalTime;
final long Minutes = TimeUnit.MILLISECONDS
.toMinutes(Player.mMediaPlayer.getDuration());
final long Seconds = TimeUnit.MILLISECONDS
.toSeconds(Player.mMediaPlayer.getDuration())
- TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS
.toMinutes(Player.mMediaPlayer.getDuration()));
if (Seconds < 10) {
final String second = "0" + String.valueOf(Seconds);
TotalTime = Minutes + ":" + second;
} else {
TotalTime = Minutes + ":" + Seconds;
}
return TotalTime;
}
}
The error I get is:
01-02 21:55:41.941: E/AndroidRuntime(717): FATAL EXCEPTION: main
01-02 21:55:41.941: E/AndroidRuntime(717): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.music.test/com.example.music.test.Player}: java.lang.NullPointerException
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread.access$600(ActivityThread.java:130)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.os.Handler.dispatchMessage(Handler.java:99)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.os.Looper.loop(Looper.java:137)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-02 21:55:41.941: E/AndroidRuntime(717): at java.lang.reflect.Method.invokeNative(Native Method)
01-02 21:55:41.941: E/AndroidRuntime(717): at java.lang.reflect.Method.invoke(Method.java:511)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-02 21:55:41.941: E/AndroidRuntime(717): at dalvik.system.NativeStart.main(Native Method)
01-02 21:55:41.941: E/AndroidRuntime(717): Caused by: java.lang.NullPointerException
01-02 21:55:41.941: E/AndroidRuntime(717): at android.content.ContextWrapper.getContentResolver(ContextWrapper.java:91)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.Activity.managedQuery(Activity.java:1737)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.example.music.test.Song.<init>(Song.java:21)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.example.music.test.Player.SongTitleEndTime(Player.java:90)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.example.music.test.Player.AllActivities(Player.java:80)
01-02 21:55:41.941: E/AndroidRuntime(717): at com.example.music.test.Player.onCreate(Player.java:66)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.Activity.performCreate(Activity.java:5008)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
01-02 21:55:41.941: E/AndroidRuntime(717): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
01-02 21:55:41.941: E/AndroidRuntime(717): ... 11 more
Song is an Activity. Thus you can’t call manageQuery before onCreate has been called. That’s your error.