First post on this site, so forgive me my sins. I am attempting to create a custom ListView layout that is populated by fields from my SQLite Database Adapter class. Below is the method I tried to use for this, and it is called in the onCreate method of its class, as well as the onClick method of a button to save to the Database:
//Method to re-populate custom list view songlist_layout when a new entry is added
private void populateSongList() {
//Cursor to navigate through records of the database
Cursor cursor = myDb.getAllRows();
//Need two arrays to work with the Cursor. First is from field names
String [] fromFieldNames = new String[] {DBAdapter.KEY_ROWID,
DBAdapter.KEY_SONGTITLE,
DBAdapter.KEY_SONGDURATION};
//Second is int array
int [] toViewIDs = new int [] {R.id.textViewSongNumber, R.id.textViewSongName,
R.id.textViewSongDuration};
//Cursor Adapter Object
SimpleCursorAdapter myCursorAdapter;
myCursorAdapter = new SimpleCursorAdapter(getBaseContext(),
R.layout.songlist_layout, cursor, fromFieldNames, toViewIDs,0);
//Need to grab ListView from activity_add_song to set the adapter to it
ListView songList = (ListView)findViewById(R.id.songsListView);
songList.setAdapter(myCursorAdapter);
}
//Method to handle the click event of the Save button, adding the data into the database
public void onClickSaveSong (View v) {
//Song Title and duration are essential fields, so we want to check if they
// have text before saving to the database
if(!TextUtils.isEmpty(etSongTitle.getText().toString()) &&
!TextUtils.isEmpty(etSongDuration.getText().toString())) {
myDb.insertRow(etSongTitle.getText().toString(),
etSongKey.getText().toString(),
etSongTuning.getText().toString(),
etSongDuration.getText().toString());
//Pop-up to inform user the Data has been saved
Toast.makeText(getBaseContext(), "Song Added!", Toast.LENGTH_LONG).show();
}//if
//Otherwise a pop-up to tell the user to enter the essential info
else {Toast.makeText(getBaseContext(), "Enter Title and Duration",
Toast.LENGTH_LONG).show();}
//Call to repopulate songs ListView
populateSongList();
}//onClickSaveSong()
The custom XML Layout for the ListView contains three TextViews to hold the songNumber, the songName and the songDuration:
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Text"
android:id="@+id/textViewSongNumber"
android:paddingRight="10dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Text"
android:id="@+id/textViewSongName"
android:paddingRight="60dp"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Text"
android:id="@+id/textViewSongDuration"
android:paddingRight="70dp"/>
I have read elsewhere that the problem could be because the ListView is grabbing from the wrong ListView ID
ListView songList = (ListView)findViewById(R.id.songsListView);
However comparing it to the XML Layout for the ListView, I don't see how this would be the case:
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/songsListView"
android:layout_below="@+id/imageView"
android:layout_centerHorizontal="true"
android:layout_above="@+id/addSongButton" />
Finally, the logcat:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blob.gigstrofinal/com.blob.gigstrofinal.AddSong}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.blob.gigstrofinal.AddSong.populateSongList(AddSong.java:121)
at com.blob.gigstrofinal.AddSong.onCreate(AddSong.java:45)
I cannot figure this out. I haven't been using Android for long, and a lot of this is over my head, so I would appreciate any help at all on this matter. The App is for a University Project, and it is due next week!
EDIT: I forgot to specify, the Null Pointer Exception is pointing to line 121 of AddSong.java which is: songList.setAdapter(myCursorAdapter);
I am calling the populateSongList()method from the onCreate method in the AddSong class:
public class AddSong extends Activity {
//Declare Database Adapter
DBAdapter myDb;
//Declare EditText objects to be used for each field in the SQLite Database
EditText etSongTitle;
EditText etSongKey;
EditText etSongTuning;
EditText etSongDuration;
@Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_song);
//Initialise EditText objects by assigning them to the corresponding ID
etSongTitle = (EditText)findViewById(R.id.editSongTitle);
etSongKey = (EditText)findViewById(R.id.editSongKey);
etSongTuning = (EditText)findViewById(R.id.editSongTuning);
etSongDuration = (EditText)findViewById(R.id.editSongDuration);
//Call method to open Database
openDB();
//Call to populate songs ListView
populateSongList();
}
and again for the onClickSaveSong method of AddSong.java (see second code snippet of original post.
EDIT2: The full contents of activity_add_song.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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.blob.gigstrofinal.AddSong"
android:background="@color/colorPrimary"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvSongTitle"
android:id="@+id/songTitle"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:textStyle="bold"
android:textSize="13sp"
android:textColor="@color/colorPrimary2" />
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/songTitle"
android:id="@+id/editSongTitle"
android:layout_alignParentStart="true"
android:editable="true"
android:inputType="text"
android:background="#e6e6e6"
android:textColor="@color/colorPrimary3"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvKey"
android:id="@+id/songKey"
android:textStyle="bold"
android:textSize="13sp"
android:textColor="@color/colorPrimary2"
android:layout_marginTop="15dp"
android:layout_below="@+id/editSongTitle"
android:layout_alignParentStart="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/editSongKey"
android:layout_below="@+id/songKey"
android:layout_alignParentStart="true"
android:layout_alignEnd="@+id/editSongTitle"
android:background="#e6e6e6"
android:inputType="text"
android:textColor="@color/colorPrimary3" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvTuning"
android:id="@+id/songTuning"
android:textStyle="bold"
android:textSize="13sp"
android:textColor="@color/colorPrimary2"
android:layout_marginTop="13dp"
android:layout_below="@+id/editSongKey"
android:layout_alignParentStart="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/editSongTuning"
android:layout_below="@+id/songTuning"
android:layout_alignParentStart="true"
android:layout_alignEnd="@+id/editSongKey"
android:background="#e6e6e6"
android:textColor="@color/colorPrimary3"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvDuration"
android:id="@+id/songDuration"
android:textStyle="bold"
android:textSize="13dp"
android:textColor="@color/colorPrimary2"
android:layout_marginTop="15dp"
android:layout_below="@+id/editSongTuning"
android:layout_alignParentStart="true" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/editSongDuration"
android:layout_below="@+id/songDuration"
android:layout_alignParentStart="true"
android:layout_alignEnd="@+id/editSongTuning"
android:background="#e6e6e6"
android:textColor="@color/colorPrimary3"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tvLyrics"
android:id="@+id/songLyrics"
android:textStyle="bold"
android:textSize="13sp"
android:textColor="@color/colorPrimary2"
android:layout_below="@+id/editSongDuration"
android:layout_alignParentStart="true"
android:layout_marginTop="15sp"
android:textIsSelectable="false" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="textMultiLine"
android:ems="10"
android:id="@+id/editSongLyrics"
android:layout_below="@+id/songLyrics"
android:layout_alignParentStart="true"
android:layout_alignEnd="@+id/editSongDuration"
android:background="#e6e6e6"
android:layout_above="@+id/saveButton"
android:layout_marginBottom="20dp"
android:textColor="@color/colorPrimary3"/>
<Button
android:id="@+id/saveButton"
android:text="@string/buttonSaveText"
android:background="@color/colorPrimary"
android:textColor="@color/colorPrimary2"
android:textStyle="bold"
android:textSize="11sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="19dp"
android:layout_marginRight="22dp"
android:onClick="onClickSaveSong"
android:layout_alignParentBottom="true"
/>
<Button
android:id="@+id/backButton"
android:text="@string/backButtonText"
android:background="@color/colorPrimary"
android:textColor="@color/colorPrimary2"
android:textStyle="bold"
android:textSize="11sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onClickBack"
android:layout_alignBottom="@+id/saveButton"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_marginRight="19dp"
/>
</RelativeLayout>
It is perhaps worth mentioning that the ListView itself is not located in Activity_add_song, it is in another Activity activity_songs. Would that cause a null pointer exception?
The problem is that the ListView is not in the layout xml that you're inflating in this Activity.
When you call this in onCreate():
setContentView(R.layout.activity_add_song);
You're inflating the activity_add_song.xml layout xml to the current Window.
Then when you call:
ListView songList = (ListView)findViewById(R.id.songsListView);
It's looking at the currently inflated layout for a ListView with ID songsListView. Since there is no songsListView in the currently inflated layout (activity_add_song.xml), it will be null.
Move all code dealing with songsListView to the Activity that inflates the layout with the ListView.