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Android Build a Self-Destructing Message Android App Sending Messages Adding a Send Button

ahmet yuva
ahmet yuva
17,595 Points

NullpointerException please help me i could not make it work.

my recipientsActivity is this

package com.ahmetyuva.ribbit;

import android.app.AlertDialog;
import android.app.ListActivity;
import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseRelation;
import com.parse.ParseUser;

import java.util.List;


public class RecipientsActivity extends ListActivity{

    public static final String TAG = RecipientsActivity.class.getSimpleName();

    protected List<ParseUser> mFriends;
    protected ParseRelation<ParseUser> mFriendsRelation;
    protected ParseUser mCurrentUser;

    protected MenuItem mSendMenuItem;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recipients);

        getActionBar().setDisplayHomeAsUpEnabled(true);

        getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
    }

    @Override
    public void onResume() {
        super.onResume();

        mCurrentUser = ParseUser.getCurrentUser();
        mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

        ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
        query.addAscendingOrder(ParseConstants.KEY_USERNAME);
        query.findInBackground(new FindCallback<ParseUser>() {
            @Override
            public void done(List<ParseUser> friends, ParseException e) {

                if(e == null) {

                    mFriends = friends;

                    String[] usernames = new String[mFriends.size()];
                    int i = 0;
                    for (ParseUser user : mFriends) {
                        usernames[i] = user.getUsername();
                        i++;

                    }                   ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                            getListView().getContext(),
                            android.R.layout.simple_list_item_checked,
                            usernames);
                    setListAdapter(adapter);
                }
                else{

                    Log.e(TAG, e.getMessage());
                    AlertDialog.Builder builder = new AlertDialog.Builder(RecipientsActivity.this);
                    builder.setMessage(e.getMessage())
                            .setTitle(R.string.error_title)
                            .setPositiveButton(android.R.string.ok, null);

                    AlertDialog dialog = builder.create();
                    dialog.show();

                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_recipients, menu);
        mSendMenuItem = menu.getItem(0);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        switch (item.getItemId()){
            case android.R.id.home:

                NavUtils.navigateUpFromSameTask(this);
                return true;
            case R.id.action_send:
                return true;
        }
      /*  int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
*/
        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        if (l.getCheckedItemCount() > 0) {
            mSendMenuItem.setVisible(true);
        } else {
            mSendMenuItem.setVisible(false);
        }
    }
}
menu_recipients.xml
<menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      tools:context="com.ahmetyuva.ribbit.RecipientsActivity">
    <item android:id="@+id/action_send"
          android:title="Send"
          android:orderInCategory="100"
          app:showAsAction="always"
          android:visible="true"
          android:icon="@drawable/ic_action_send_now"
        />


</menu>
activity_recipients.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"
                tools:context="com.ahmetyuva.ribbit.RecipientsActivity">

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:id="@android:id/list"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"/>

    <TextView
        android:id="@android:id/empty"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/empty_recipients_list_message"
        />

</RelativeLayout>

my error log is here

04-13 11:19:05.148 1956-1956/? E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ahmetyuva.ribbit/com.ahmetyuva.ribbit.RecipientsActivity}: java.lang.NullPointerException at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) at android.app.ActivityThread.access$600(ActivityThread.java:141) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException at com.ahmetyuva.ribbit.RecipientsActivity.onCreate(RecipientsActivity.java:40) at android.app.Activity.performCreate(Activity.java:5104) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)             at android.app.ActivityThread.access$600(ActivityThread.java:141)             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)             at android.os.Handler.dispatchMessage(Handler.java:99)             at android.os.Looper.loop(Looper.java:137)             at android.app.ActivityThread.main(ActivityThread.java:5041)             at java.lang.reflect.Method.invokeNative(Native Method)             at java.lang.reflect.Method.invoke(Method.java:511)             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)             at dalvik.system.NativeStart.main(Native Method)

and manifest part is this

manifest.xml
        <activity
            android:name=".RecipientsActivity"
            android:label="@string/title_activity_recipients"
            android:parentActivityName=".MainActivity"
            android:screenOrientation="portrait">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.ahmetyuva.ribbit.MainActivity" />
        </activity>

i tried everything but still nothing changed please help me

kind regards

4 Answers

Andrew Zhang
Andrew Zhang
4,364 Points

Ok, I've got it working, had to extend to ActionBar Activity and modify the listview code a bit:

package zepplez.com.cquets;

import android.app.AlertDialog;
import android.app.ListActivity;
import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseRelation;
import com.parse.ParseUser;

import java.util.List;


public class RecipientsActivity extends ActionBarActivity{

    public static final String TAG = RecipientsActivity.class.getSimpleName();

    protected List<ParseUser> mFriends;
    protected ParseRelation<ParseUser> mFriendsRelation;
    protected ParseUser mCurrentUser;
    protected MenuItem mSendMenuItem;
   protected ListView recipientsListView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recipients);
        recipientsListView = (ListView) findViewById(R.id.recipientListView);
        recipientsListView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
        recipientsListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                if (recipientsListView.getCheckedItemCount() > 0){
                    mSendMenuItem.setVisible(true);
                } else {
                    mSendMenuItem.setVisible(false);
                }
            }
        });
    }

    public void onResume() {
        super.onResume();
        mCurrentUser = ParseUser.getCurrentUser();
        mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

        //setProgressBarIndeterminateVisibility(true);

        ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
        query.addAscendingOrder(ParseConstants.KEY_USERNAME);
        query.findInBackground(new FindCallback<ParseUser>() {
            @Override
            public void done(List<ParseUser> friends, ParseException e) {
               // setProgressBarIndeterminateVisibility(false);

                if (e == null) {
                    mFriends = friends;

                    String[] usernames = new String[mFriends.size()];
                    int i = 0;
                    for (ParseUser user : mFriends) {
                        usernames[i] = user.getUsername();
                        i++;
                    }
                    ArrayAdapter<String> adapter = new ArrayAdapter<String>(recipientsListView.getContext(),
                            android.R.layout.simple_list_item_checked,
                            usernames);
                    recipientsListView.setAdapter(adapter);
                } else {
                    Log.e(TAG, e.getMessage());
                    AlertDialog.Builder builder = new AlertDialog.Builder(RecipientsActivity.this);
                    builder.setMessage(e.getMessage())
                            .setTitle(R.string.error_title)
                            .setPositiveButton(android.R.string.ok, null);
                    AlertDialog dialog = builder.create();
                    dialog.show();
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_recipients, menu);
        mSendMenuItem = menu.getItem(0);
        return (super.onCreateOptionsMenu(menu));
    }
}
ahmet yuva
ahmet yuva
17,595 Points

recipientsListView = (ListView) findViewById(R.id.recipientListView); in this line can you give me recipientListView and where did you put it

Andrew Zhang
Andrew Zhang
4,364 Points

at the top

   protected ListView recipientsListView;
Ureche Gabriel-Terry
Ureche Gabriel-Terry
5,566 Points
 recipientEmptyTextView = (TextView) findViewById(R.id.recipientEmptyView); 
recipientsListView.setEmptyView(recipientEmptyTextView);

Add at the top

The error is at line 40 of RecipientsActivity.java. Which line of code is that?

ahmet yuva
ahmet yuva
17,595 Points

getActionBar().setDisplayHomeAsUpEnabled(true);

is line 40 in that class

OK - it is the ActionBar, then. This may relate to the problem Andrew has highlighted.

You can try deleting the line android:theme="@style/AppTheme" in your AndroidManifest and replacing it with, android:theme="@android:style/Theme.Holo.Light" - that may work but it seems there may be other issues with the code rather than the theme's lack of an action bar.

If you do try the above, keep a note of what you delete in case it makes no difference!!

Steve.

Can you post all of the AndroidManifest.xml file, please. I need to see what theme you've got running. You're using an ActionBar that needs a theme that has one, else getActionBar() will return null - that's the error we're seeing here.

I'd suggest adding:

android:theme="@android:style/Theme.Holo.Light"

into your application part of the AndroidManifest.xml but you also need to delete a line or two. Once you've posted your code, I'll know what to delete.

Steve.

Andrew Zhang
Andrew Zhang
4,364 Points

Hi Steve

I've got the same issue where the actionbar does not appear when we're extending ListActivity, therefore the getItem is returning null.

Looking around the website, it seems like theme isn't the issue (i tried changing it, and then the app won't even load), it's more to do with extending ListActivity is not being used anymore and we should be using ListFragment (See: http://stackoverflow.com/questions/20524008/combining-listactivity-and-actionbaractivity)

Were you able to get the code to work under the Android Studio environment? Would love to see how you did it.

I got another student's code working where the getActionBar() was returning null. I changed the theme, as above.

The issue in that case wasn't the ListActivity so this must be a different issue. The Stack Overflow post covers that off pretty thoroughly.

Steve.

ahmet yuva
ahmet yuva
17,595 Points

my androidmanifest is this one

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.ahmetyuva.ribbit" >

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<uses-feature
    android:name="android.hardware.camera"
    android:required="true" />

<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

<!--
  IMPORTANT: Change "com.parse.starter.permission.C2D_MESSAGE" in the lines below
  to match your app's package name + ".permission.C2D_MESSAGE".
-->
<permission
    android:name="com.ahmetyuva.ribbit.permission.C2D_MESSAGE"
    android:protectionLevel="signature" />

<uses-permission android:name="com.ahmetyuva.ribbit.permission.C2D_MESSAGE" />

<application
    android:name=".RibbitApplication"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".LoginActivity"
        android:label="@string/title_activity_login"
        android:screenOrientation="portrait" >
    </activity>
    <activity
        android:name=".SignUpActivity"
        android:label="@string/title_activity_sign_up"
        android:parentActivityName=".LoginActivity"
        android:screenOrientation="portrait" >
    </activity>
    <activity
        android:name=".EditFriendsActivity"
        android:label="@string/title_activity_edit_friends"
        android:parentActivityName=".MainActivity" >
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.ahmetyuva.ribbit.MainActivity" />
    </activity>

    <service android:name="com.parse.PushService" />

    <receiver android:name="com.parse.ParseBroadcastReceiver" >
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
            <action android:name="android.intent.action.USER_PRESENT" />
        </intent-filter>
    </receiver>
    <receiver
        android:name="com.parse.ParsePushBroadcastReceiver"
        android:exported="false" >
        <intent-filter>
            <action android:name="com.parse.push.intent.RECEIVE" />
            <action android:name="com.parse.push.intent.DELETE" />
            <action android:name="com.parse.push.intent.OPEN" />
        </intent-filter>
    </receiver>
    <receiver
        android:name="com.parse.GcmBroadcastReceiver"
        android:permission="com.google.android.c2dm.permission.SEND" >
        <intent-filter>
            <action android:name="com.google.android.c2dm.intent.RECEIVE" />
            <action android:name="com.google.android.c2dm.intent.REGISTRATION" />

<!-- IMPORTANT: Change "com.parse.starter" to match your app's package name. --> <category android:name="com.ahmetyuva.ribbit" /> </intent-filter> </receiver>

    <activity
        android:name=".RecipientsActivity"
        android:label="@string/title_activity_recipients"
        android:parentActivityName=".MainActivity"
        android:screenOrientation="portrait">
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.ahmetyuva.ribbit.MainActivity" />
    </activity>
</application>

</manifest>

Sorry Ahmet,

You're best referring to Andrew's link to Stack Overflow as that seems to be the problem here.

It seems the course needs updating to take Android's progress into account.

Steve.

ahmet yuva
ahmet yuva
17,595 Points

my styles.xml is this one <resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Customize your theme here. -->
</style>

</resources>

In which case, it is definitely the issue that Andrew has highlighted!

JIHOON JUNG
JIHOON JUNG
10,927 Points

Andrew Zhang, Thank you, I had same issue, but with your code, it finally worked :D