android tab content does not show up - android-tabs

Question

I'm currently learning to build app for Android, and I use Android Studio to do so.
I searched for similar posts but did not find what could help me.
My goal is to have an Activity with a tabHost and 4 Tabs (for the moment). I will put the code after giving some details.
To begin, I'm just focused on two tabs on which I would like to:
- put a button to start (on the first Tab) a dedicated activity to create an item (contact item),
- Display the Contact list on the second Tab.
My problem : The button is correctly visible and works fine (I can create a Contact). i also have a function checking wheter a contact already exists or not (correctly working).
What's not working is when I select the second Tab, my list won't show up and I can't see my contacts.
This my General Activity :
package avappmobile.fourwe;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TabHost;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class General extends Activity {
List<Contact> Contacts = new ArrayList<Contact>();
List<Stuff> Stuffs = new ArrayList<Stuff>();
List<Money> Moneys = new ArrayList<Money>();
ListView contactListView;
DatabaseContactHandler dbContactHandler;
DatabaseMoneyHandler dbMoneyHandler;
DatabaseStuffHandler dbStuffHandler;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_general);
TabHost tabHost = (TabHost) findViewById(R.id.tabHost);
contactListView = (ListView) findViewById(R.id.listViewContact);
dbContactHandler = new DatabaseContactHandler(getApplicationContext());
dbMoneyHandler = new DatabaseMoneyHandler(getApplicationContext());
dbStuffHandler = new DatabaseStuffHandler(getApplicationContext());
tabHost.setup();
TabHost.TabSpec tabSpec = tabHost.newTabSpec("home");
tabSpec.setContent(R.id.tabHome);
tabSpec.setIndicator("Home");
tabHost.addTab(tabSpec);
tabHost.newTabSpec("contact");
tabSpec.setContent(R.id.tabContact);
tabSpec.setIndicator("Contact");
tabHost.addTab(tabSpec);
tabHost.newTabSpec("money");
tabSpec.setContent(R.id.tabMoney);
tabSpec.setIndicator("Money");
tabHost.addTab(tabSpec);
tabHost.newTabSpec("stuff");
tabSpec.setContent(R.id.tabStuff);
tabSpec.setIndicator("Stuff");
tabHost.addTab(tabSpec);
if (dbContactHandler.getContactsCount() != 0)
Contacts.addAll(dbContactHandler.getAllContacts());
populateList();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.general, menu);
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.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void goToContactCreation(View view) {
Intent intent = new Intent(this, ContactCreation.class);
startActivity(intent);
}
//Contact
private void populateList() {
ArrayAdapter<Contact> adapter = new ContactListAdapter();
contactListView.setAdapter(adapter);
}
private class ContactListAdapter extends ArrayAdapter<Contact> {
public ContactListAdapter() {
super (General.this, R.layout.contact_listview, Contacts);
}
#Override
public View getView(int position, View view, ViewGroup parent) {
if (view == null)
view = getLayoutInflater().inflate(R.layout.contact_listview, parent, false);
Contact currentContact = Contacts.get(position);
TextView firstName = (TextView) view.findViewById(R.id.txtFirstName);
firstName.setText(currentContact.getFirstName());
TextView lastName = (TextView) view.findViewById(R.id.txtLastName);
lastName.setText(currentContact.getLastName());
return view;
}
}
}
My DbContactHandler :
package avappmobile.fourwe;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import java.util.List;
/**
* Created by a.vescera on 13/11/2014.
*/
public class DatabaseContactHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "fourWe",
TABLE_CONTACTS = "contacts",
KEY_ID = "id",
KEY_FIRSTNAME = "firstName",
KEY_LASTNAME = "lastName",
KEY_PHONE = "phone",
KEY_EMAIL = "email",
KEY_MONEYLEND = "moneyLend",
KEY_MONEYBORROWED = "moneyBorrowed",
KEY_STUFFLEND = "stuffLend",
KEY_STUFFBORROWED = "stuffBorrowed";
public DatabaseContactHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE " + TABLE_CONTACTS + "(" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_FIRSTNAME + " TEXT," +
KEY_LASTNAME + " TEXT," + KEY_PHONE + " TEXT," + KEY_EMAIL + " TEXT," + KEY_MONEYLEND + " INTEGER," + KEY_MONEYBORROWED + " INTEGER," +
KEY_STUFFLEND + " INTEGER," + KEY_STUFFBORROWED + " INTEGER)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
onCreate(db);
}
// Method to create a contact.
public void createContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_FIRSTNAME, contact.getFirstName());
values.put(KEY_LASTNAME, contact.getLastName());
values.put(KEY_PHONE, contact.getPhone());
values.put(KEY_EMAIL, contact.getEmail());
values.put(KEY_MONEYLEND, 0);
values.put(KEY_MONEYBORROWED, 0);
values.put(KEY_STUFFLEND, 0);
values.put(KEY_STUFFBORROWED, 0);
db.insert(TABLE_CONTACTS, null, values);
db.close();
}
// Method to get the details of a specific contact by an id.
public Contact getContactId(int id) {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID, KEY_FIRSTNAME, KEY_LASTNAME, KEY_PHONE, KEY_EMAIL, KEY_MONEYLEND,
KEY_MONEYBORROWED, KEY_STUFFLEND, KEY_STUFFBORROWED }, KEY_ID + "=?", new String[] { String.valueOf(id) }, null, null, null, null );
if (cursor != null)
cursor.moveToFirst();
Contact contact = new Contact(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4),
Integer.parseInt(cursor.getString(5)),Integer.parseInt(cursor.getString(6)),Integer.parseInt(cursor.getString(7)),Integer.parseInt(cursor.getString(8)));
db.close();
cursor.close();
return contact;
}
// Method to get the details of a specific contact by firstName and lastName.
public Boolean getContact(String firstName, String lastName) {
SQLiteDatabase db = getReadableDatabase();
Contact contact;
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID, KEY_FIRSTNAME, KEY_LASTNAME, KEY_PHONE, KEY_EMAIL, KEY_MONEYLEND,
KEY_MONEYBORROWED, KEY_STUFFLEND, KEY_STUFFBORROWED }, KEY_FIRSTNAME + "=?" + " AND " + KEY_LASTNAME + "=?", new String[] { firstName, lastName }, null, null, null, null );
if (cursor != null && cursor.moveToFirst()) {
db.close();
cursor.close();
return true;
} else {
db.close();
cursor.close();
return false;
}
}
// Method to delete a specific contact.
public void deleteContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
db.delete(TABLE_CONTACTS, KEY_ID + "=?", new String[] { String.valueOf(contact.getId()) });
db.close();
}
// Method to get the total number of existing contacts into the DB.
public int getContactsCount() {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CONTACTS, null);
int count = cursor.getCount();
db.close();
cursor.close();
return count;
}
// Method to update the details of a specific contact.
public int updateContact(Contact contact) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_FIRSTNAME, contact.getFirstName());
values.put(KEY_LASTNAME, contact.getLastName());
values.put(KEY_PHONE, contact.getPhone());
values.put(KEY_EMAIL, contact.getEmail());
values.put(KEY_MONEYLEND, contact.getMoneyLend());
values.put(KEY_MONEYBORROWED, contact.getMoneylBorrowed());
values.put(KEY_STUFFLEND, contact.getStuffLend());
values.put(KEY_STUFFBORROWED, contact.getStuffBorrowed());
int rowsAffected = db.update(TABLE_CONTACTS, values, KEY_ID + "=?", new String[] { String.valueOf(contact.getId()) });
db.close();
return rowsAffected;
}
// Method to get the list of the details of all the contacts present into the DB.
public List<Contact> getAllContacts() {
List<Contact> contacts = new ArrayList<Contact>();
SQLiteDatabase db = getWritableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CONTACTS, null);
if (cursor.moveToFirst()) {
do {
contacts.add(new Contact(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), cursor.getString(4),
Integer.parseInt(cursor.getString(5)),Integer.parseInt(cursor.getString(6)),Integer.parseInt(cursor.getString(7)),Integer.parseInt(cursor.getString(8))));
}
while (cursor.moveToNext());
}
cursor.close();
db.close();
return contacts;
}
}
I don't put the detail of the Contact class, but if you think you need it, please feel free to ask me.
I put then the Design part of my main activity:
<LinearLayout 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="avappmobile.fourwe.General">
<TabHost
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/tabHost">
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TabWidget
android:id="#android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content"></TabWidget>
<FrameLayout
android:id="#android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
android:id="#+id/tabHome"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/new_contact"
android:id="#+id/btnNewContact"
android:onClick="goToContactCreation"
android:enabled="true"
android:layout_gravity="right" />
</LinearLayout>
<LinearLayout
android:id="#+id/tabContact"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="#string/contacts_list"
android:id="#+id/txtMyContacts"
android:layout_gravity="center_horizontal"
android:layout_marginTop="10dp" />
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/listViewContact"
android:layout_marginTop="20dp" />
</LinearLayout>
<LinearLayout
android:id="#+id/tabMoney"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"></LinearLayout>
<LinearLayout
android:id="#+id/tabStuff"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"></LinearLayout>
</FrameLayout>
</LinearLayout>
</TabHost>
</LinearLayout>
And the layout created to display my contacts on the secont Tab.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="#string/first_name_contact"
android:id="#+id/txtFirstName"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:id="#+id/txtLastName"
android:layout_gravity="center_horizontal"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:text="#string/first_name_contact"
android:singleLine="false" />
</RelativeLayout>
Thanks.

Answer 1

After further investigation on internet, I found that with the latest version of android, it might be more interesting to show a file with tab (and each tab having a different file, which is my goal) using the ViewPager.
A quick and correctly defined tutorial is available here : http://architects.dzone.com/articles/android-tutorial-using.
I then close my subject since I'm now focused on this way of doing my work.
Regards.