First Android App | Step 4 - Spinner to select default city

Welcome Back!!

This is the step 4 on our way to build a fully functional e-commerce application from scratch.

In step 3, we created the Splash screen which downloaded the list of Cities from the server in JSON format using AsyncTask. In this post, we are going to build the City selection screen. This screen will only come once on first time login of the user post installation. Once the user selects the default city, next time onwards, the application will move directly to HomeScreen from the StartScreen and skip CityScreen completely.

The complete working of this part has been explained in my youtube video.

The final output will look like this.

The source code is as follows:

activity_city_screen.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:background="#B22222"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".CityScreen" >

    <TextView
        android:id="@+id/SelectCityText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:gravity="center"
        android:text="@string/selectcity"
        android:layout_marginTop="120dp"
        android:textColor="#ffffff"
        android:textSize="28sp" />
    
    
    <Spinner
        android:id="@+id/spinner1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="30dp"
        android:layout_below="@+id/SelectCityText"
        android:popupBackground="#470E0E" />

</RelativeLayout>

spinner_item.xml

<?xml version="1.0" encoding="utf-8"?>

<TextView  
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:textSize="20dip"
    android:gravity="left"  
    android:textColor="#ffffff"         
    android:padding="5dip"/>

CityScreen.java

package com.zing.basket;

import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.Typeface;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;


public class CityScreen extends Activity {
 
 SQLiteDatabase sqLite;
 Spinner city_spinner;

 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_city_screen);
  
  Typeface type= Typeface.createFromAsset(getAssets(),"fonts/book.TTF");
  
  //This section is to hide the action bar. 
  ActionBar actionBar = getActionBar();
  actionBar.hide();
  
  //Ideally SQL should be handled in a separate helper, but for ease of understanding to start off, I
  //have kept the code here. 
  sqLite=this.openOrCreateDatabase("basketbuddy", MODE_PRIVATE, null);
  
  Cursor c=sqLite.rawQuery("SELECT CITY_NAME FROM CITY_LIST",null);
  
  //ideally atleast 1 city should be there in city_name. As I have already synced this with the server
  // in StartScreen.java
  
  if (c.getCount()== 0)
  {
   Toast.makeText(getApplicationContext(), "Oh ho..Some unexpected problem. Please restart the application", Toast.LENGTH_LONG).show();
   
  }
  
  TextView city_selection=(TextView) findViewById(R.id.SelectCityText);
  city_selection.setTypeface(type);
  
  //defining the array that will hold the City Names. 
  String[] city_name_db=new String[(c.getCount()+1)];
    
    
  //by default, the first entry for city list is "Choose City". We will understand why 
  //this is necessary later.
  city_name_db[0] = "Choose City";
  
  //moving the city names from sqlite to an array city_name_db
  if(c.moveToFirst())
  {
   int count=1;
   do{
    city_name_db[count]=c.getString(0);
    count++;
   }while(c.moveToNext());
  }
  
  //creating an ArrayAdapter for the spinner and then associating the city ArrayAdapter
  //to the spinner.
  
  ArrayAdapter aa=new ArrayAdapter(getApplicationContext(),R.layout.spinner_item,city_name_db);
  city_spinner = (Spinner) findViewById(R.id.spinner1);
  city_spinner.setAdapter(aa);
  
  //There is an inherent problem with Spinners. Lets assume that there are 3 cities Delhi, Gurgaon and Noida. The
  //moment I populate these 3 cities to the spinner, by default Delhi will get selected as this is the 
  //first entry. OnItemSelectedListener will get triggered immediately with Delhi as selection and the code 
  //will proceed. Net net, even the default first value is taken as an ItemSelected trigger. 
  
  //the way to bypass this is to add a default value 'Choose City' in the ArrayAdapter list. And then
  //inside the onItemSelected method, ignore if 'Choose City' has been selected. 
  
  //SetOnItemSelectedListener listens for any change in item selected, if found thn it will call onItemSelected method. 
  
  city_spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

   @Override
   public void onItemSelected(AdapterView parent, View view,
     int position, long id) 
   {
    if (parent.getItemAtPosition(position).equals("Choose City"))
    {
     //do nothing.
     
    }
    else
    {
     // save the selected city as a default city for shopping
     //this city selection is saved in DB. We may even decide to send this data to server, 
     //however in this example, we are not doing so. 
     
     String city_name=city_spinner.getSelectedItem().toString();
     Cursor c=sqLite.rawQuery("SELECT CITY_NAME FROM USER_PREF",null);
     if (c.getCount()== 0)
     {
      sqLite.execSQL("insert into USER_PREF (CITY_NAME, VOICE_ON) VALUES ('"+city_name+"','Y','Y')");
     }
     if(c.moveToFirst())
     {
      sqLite.execSQL("update USER_PREF set CITY_NAME = '"+city_name+"'");
     }
     
     //Intent intent=new Intent(CityScreen.this,HomeScreen.class);
     //startActivity(intent);
     sqLite.close();
     finish();
    }
   }

   @Override
   public void onNothingSelected(AdapterView arg0) 
   {
    // TODO Auto-generated method stub
    
   }
  });
   
 }
 
 @Override
 protected void onPostCreate(Bundle savedInstanceState) {
  super.onPostCreate(savedInstanceState);
 }
 
 @Override
 public void onResume()
 {
  super.onResume();
  
 }
 
 @Override
 public void onPause()
 {
  super.onPause();
 }

}

Remove the commenting from these 2 lines of code from StartScreen.java inside the onPostExecute method of AsyncTask

Intent intent=new Intent(StartScreen.this,CityScreen.class);
startActivity(intent);

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zing.basket"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="18" />
 
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.zing.basket.StartScreen"
            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="com.zing.basket.CityScreen"
            android:label="@string/city_screen"
             android:screenOrientation="portrait"
            android:launchMode="singleTask" >
        </activity>
    </application>
    

</manifest>