Why am I getting a NullPointerException in this app?
Question
In the app I am developing I am trying to get names out of a database, but am getting this error message:
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
This is extremely frustrating. I have tried using breakpoints and have looked through the code. The Logcat doesn't tell me where the error is, either. Please help :(
MainActivity code:
package com.chromepenguinstudios.namedictionary2;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity implements View.OnClickListener,
TextView.OnEditorActionListener,
AdapterView.OnItemClickListener {
// Global variables, items, arrays and enums
EditText txt_nameField; // Name field
Button btn_submitName; // Get name info button
Button btn_addToFavourites_main; // Add name in textbox to favourites
ListView lst_favourites; // Favourite names list
String name; // Variable where name is stored
String[] favouriteNames; // This is set later when we get the names from the database
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialise variables
txt_nameField = (EditText)findViewById(R.id.txt_name);
btn_submitName = (Button) findViewById(R.id.btn_getName);
btn_addToFavourites_main = (Button) findViewById(R.id.btn_addToFavourites_main);
lst_favourites = (ListView)findViewById(R.id.lst_favourites);
populateListItemsArray();
String logMessage = "";
for (String s : favouriteNames) {
logMessage += s;
}
Log.d("Favourites", logMessage);
ListAdapter myListAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, favouriteNames);
lst_favourites.setAdapter(myListAdapter);
// Give widgets listeners and such like
btn_submitName.setOnClickListener(this); // When button is clicked
btn_addToFavourites_main.setOnClickListener(this); // When button is clicked
txt_nameField.setOnEditorActionListener(this); // When the "Go" button on the textbox is clicked
lst_favourites.setOnItemClickListener(this); // When an item on the list is clicked
populateListView(); // Adds the names to the list view
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_getName:
try {
name = txt_nameField.getText().toString(); // Store name in string
txt_nameField.setText(""); // When user presses back on other activity they are greeted with a fresh text box
// Launch GetNameActivity
Class activity = Class.forName("com.chromepenguinstudios.namedictionary2.GetNameActivity");
Intent launcher = new Intent(this, activity);
launcher.putExtra("name", name);
startActivity(launcher);
}
catch (ClassNotFoundException e) {
e.printStackTrace();
throw new Error("Error: could not launch GetNameActivity!");
}
break;
case R.id.btn_addToFavourites_main:
String title = getString(R.string.dialogue_confirmTitle);
String messageBefore = getString(R.string.dialogue_favouritesMessage);
final String textViewContent = txt_nameField.getText().toString();
String messageAfter = String.format(messageBefore, textViewContent);
new AlertDialog.Builder(this)
.setTitle(title)
.setMessage(messageAfter)
.setPositiveButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
addToFavourites(textViewContent);
}
})
.setNegativeButton(getString(R.string.cancel), null)
.create()
.show();
break;
}
}
// When list is clicked - connection set up in onCreate()
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
String clickedName = String.valueOf(adapterView.getItemAtPosition(position));
}
// When the "Go" button is clicked on the dialogue box
@Override
public boolean onEditorAction(TextView v, int id, KeyEvent event) {
if (id == EditorInfo.IME_ACTION_GO) {
btn_submitName.performClick();
return true; // Tell Android framework that this succeeded
} return false; // Or failed
}
// Sets the adapter for the listview and populates it
private void populateListView() {
// Pass in the single_row (styles ListView) and names list
FavouritesListAdapter adapter = new FavouritesListAdapter(this, R.layout.single_row, favouriteNames);
lst_favourites.setAdapter(adapter);
}
// Put stuff from database in ListView
private void populateListItemsArray() {
FavouriteName entries = new FavouriteName(this); // Get entries from database with this
entries.openDB(); // Open the database to write to and read from
NameResult result = entries.getData(); // Get data from database
favouriteNames = result.getFavouritesAsArray(); // Convert it to a list
entries.closeDB(); // Close the database to keep it safe
}
private void addToFavourites(String name) {
boolean successful = true; // Used in catch and finally statements
try {
FavouriteName entry = new FavouriteName(this);
entry.openDB();
boolean nameInDB = entry.createEntry(name);
if (!nameInDB) {
createAlert(getString(R.string.error_title), getString(R.string.error_addName));
successful = false;
}
entry.closeDB();
} catch (Exception ex) {
successful = false;
createAlert(getString(R.string.error_title), getString(R.string.error_addName));
} finally {
if (successful) {
createAlert(getString(R.string.success_title), getString(R.string.success_addedName));
}
}
}
// Deletes a name from the Favourites list
private void deleteFromFavourites(String name) {
boolean successful = true;
try {
FavouriteName entry = new FavouriteName(this); // Entry to be deleted
entry.openDB(); // Open database
entry.deleteEntry(name); // Get the entry out of the favourites
}
catch (Exception ex) {
successful = false;
createAlert(getString(R.string.error_title), getString(R.string.error_addName));
}
finally {
if (successful) {
createAlert(getString(R.string.error_title), getString(R.string.success_addedName));
}
}
}
// Creates an AlertDialog
private void createAlert(String title, String message) {
new AlertDialog.Builder(this)
.setTitle(title) // Title of dialogue box
.setMessage(message) // Main text
.setPositiveButton(getString(R.string.ok), null) // OK button
.create() // Create the alert
.show(); // Present it to the user
}
// Controls when an action bar menu item is selected
@Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
switch (item.getItemId()) {
case R.id.menu_about:
try {
// Launch about us activity
Class<?> activity = Class.forName("com.chromepenguinstudios.namedictionary2.AboutUsActivity");
Intent launcher = new Intent(this, activity);
startActivity(launcher);
}
catch (ClassNotFoundException ex) {
ex.printStackTrace();
Log.e("Log error", "Couldn't launch the \"About Us\" activity!");
new AlertDialog.Builder(this)
.setTitle(getString(R.string.error_title))
.setMessage(getString(R.string.error_aboutUs));
}
break;
}
return true;
}
// Create the action bar menu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu); // Take XML file and model action bar menu based on that
return true;
}
}
Edit: Here is the entire stack trace:
01-18 13:46:52.633 3542-3542/com.chromepenguinstudios.namedictionary2 I/art﹕ Late-enabling -Xcheck:jni
01-18 13:46:52.757 3542-3542/com.chromepenguinstudios.namedictionary2 W/ActivityThread﹕ Application com.chromepenguinstudios.namedictionary2 is waiting for the debugger on port 8100...
01-18 13:46:52.854 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ Sending WAIT chunk
01-18 13:46:52.926 3542-3553/com.chromepenguinstudios.namedictionary2 I/art﹕ Debugger is active
01-18 13:46:53.054 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ Debugger has connected
01-18 13:46:53.054 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:53.256 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:53.456 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:53.657 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:53.857 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:54.057 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:54.258 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:54.458 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ waiting for debugger to settle...
01-18 13:46:54.658 3542-3542/com.chromepenguinstudios.namedictionary2 I/System.out﹕ debugger has settled (1374)
01-18 13:46:54.906 3542-3542/com.chromepenguinstudios.namedictionary2 D/Favourites﹕ nullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnull
01-18 13:47:00.572 3542-3933/com.chromepenguinstudios.namedictionary2 D/OpenGLRenderer﹕ Render dirty regions requested: true
01-18 13:47:00.735 3542-3542/com.chromepenguinstudios.namedictionary2 D/Atlas﹕ Validating map...
01-18 13:47:00.945 3542-3933/com.chromepenguinstudios.namedictionary2 I/Adreno-EGL﹕ <qeglDrvAPI_eglInitialize:410>: QUALCOMM Build: 10/28/14, c33033c, Ia6306ec328
01-18 13:47:00.946 3542-3933/com.chromepenguinstudios.namedictionary2 I/OpenGLRenderer﹕ Initialized EGL, version 1.4
01-18 13:47:00.965 3542-3933/com.chromepenguinstudios.namedictionary2 D/OpenGLRenderer﹕ Enabling debug mode 0
01-18 13:47:01.073 3542-3542/com.chromepenguinstudios.namedictionary2 D/AndroidRuntime﹕ Shutting down VM
01-18 13:47:01.075 3542-3542/com.chromepenguinstudios.namedictionary2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.chromepenguinstudios.namedictionary2, PID: 3542
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
at android.widget.AbsListView.obtainView(AbsListView.java:2360)
at android.widget.ListView.makeAndAddView(ListView.java:1864)
at android.widget.ListView.fillDown(ListView.java:698)
at android.widget.ListView.fillFromTop(ListView.java:759)
at android.widget.ListView.layoutChildren(ListView.java:1673)
at android.widget.AbsListView.onLayout(AbsListView.java:2148)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.support.v7.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:502)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
at android.view.View.layout(View.java:15596)
at android.view.ViewGroup.layout(ViewGroup.java:4966)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2072)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1829)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
1 answers
solution1
5 2015-01-18 14:06:36
Your problem is caused because your adapter is being populated with null references, as you can see in the log:
01-18 13:46:54.906 3542-3542/com.chromepenguinstudios.namedictionary2 D/Favourites﹕ nullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnull
That is written by:
String logMessage = "";
for (String s : favouriteNames) {
logMessage += s;
}
Log.d("Favourites", logMessage);
Offtopic note: consider using StringBuilder or StringBuffer for string appends
Then, when the ListView tries to create the views for the entries, it can not and it retrieves null.
You should check your function:
// Put stuff from database in ListView
private void populateListItemsArray() {
FavouriteName entries = new FavouriteName(this); // Get entries from database with this
entries.openDB(); // Open the database to write to and read from
NameResult result = entries.getData(); // Get data from database
favouriteNames = result.getFavouritesAsArray(); // Convert it to a list
entries.closeDB(); // Close the database to keep it safe
}
When you fix it you'll be able to populate the list.
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