Home > Articles > Mobile Application Development & Programming

  • Print
  • + Share This
This chapter is from the book

Recipe: Displaying and Selecting Numbers Through NumberPicker

In this recipe, you will learn to display a NumberPicker that displays numbers in the specified range. The number that is selected from the NumberPicker is displayed through TextView. Create a new Android project called NumberPickerApp.

You just want to display TextView and NumberPicker in this application. The NumberPicker will display the numbers between the specified range, and the TextView will display the number selected from the NumberPicker. To define the TextView and NumberPicker, write the code shown in Listing 4.3 to the activity layout file activity_number_picker_app.xml.

Listing 4.3. Code Written in the Activity Layout File activity_number_picker_app.xml

<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"
    android:orientation="vertical" >
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="Select a number from NumberPicker"
        android:id="@+id/numberview"
        android:textSize="@dimen/text_size"
        android:textStyle="bold"  />
    <NumberPicker android:id="@+id/numberpicker"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"  />
</LinearLayout>

You can see that the TextView control is assigned the ID numberview and is initialized to display the text Select a number from NumberPicker. The text displayed through TextView will appear in bold and in the size defined by the dimension resource text_size. To access and identify Java code, assign NumberPicker the ID numberpicker.

In the main Java activity file, you need to write the Java code to do the following tasks:

  • Access the TextView and NumberPicker from the layout file, and map them to the respective objects.
  • Set the maximum and minimum numerical values to be displayed through NumberPicker.
  • Associate an event listener to the NumberPicker to listen if the current value in NumberPicker is changed.
  • Display the number selected from the NumberPicker through TextView.

To perform all these tasks, write the code shown in Listing 4.4 to the Java activity file NumberPickerAppActivity.java.

Listing 4.4. Code Written in the Java Activity File NumberPickerAppActivity.java

package com.androidtablet.numberpickerapp;

import android.os.Bundle;
import android.app.Activity;
import android.widget.NumberPicker;
import android.widget.TextView;

public class NumberPickerAppActivity extends Activity {
    TextView numberView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_number_picker_app);
        numberView = (TextView)findViewById(R.id.numberview);
        NumberPicker numberPicker = (NumberPicker) findViewById(R.id.numberpicker);
        numberPicker.setMaxValue(100);       #1
        numberPicker.setMinValue(0);         #2
        numberPicker.setWrapSelectorWheel(true);
        numberPicker.setOnValueChangedListener( new NumberPicker.
            OnValueChangeListener() {
            @Override
            public void onValueChange(NumberPicker picker, int
                oldVal, int newVal) {
                numberView.setText("Selected number is "+
                    newVal);
            }
        });
    }
}

You can see that the TextView control with ID numberview is accessed from the layout file and mapped to the TextView object numberView. Similarly, NumberPicker with ID numberpicker is accessed from the layout file and is mapped to the NumberPicker object numberPicker. The minimum and maximum values to be displayed through NumberPicker are set to 0 and 100, respectively.

The setWrapSelectorWheel() method is set to true to make the selector wheel wrap around the minimum and maximum values that are displayed through NumberPicker. When the range of values (that is, maximum value – minimum values) displayed through NumberPicker is more than the number of numerical shown in the selector wheel, wrapping is enabled by default. (The selector wheel wraps around the maximum and minimum values by default.)

The setOnValueChangedListener is associated with the NumberPicker. When the current value is changed in the NumberPicker, the callback method onValueChange is invoked. In the onValueChange method, the newly selected number in the NumberPicker is displayed through the TextView control.

After you run the application, the TextView will display a text message directing the user to Select a number from NumberPicker. The NumberPicker displays the assigned minimum value in editable form. The lesser value is shown above, and a greater value is shown below (see Figure 4.2 [top]). You can change the number by scrolling up or down and by tapping on the lesser or greater value shown above and below. When you tap a number, it is displayed through the TextView control, as shown in Figure 4.2 (bottom).

Figure 4.2

Figure 4.2. NumberPicker displaying the numbers beginning from the set minimum value (top) and the selected number displayed through TextView (bottom)

You can display any range of values through the NumberPicker. For example, to display odd values from 1 to 19, you can replace the statements #1 and #2 in Listing 4.4 with the following code:

String[] stringArray = new String[10];
int n=1;
for(int i=0; i<10; i++){
    stringArray[i] = Integer.toString(n);
    n+=2;
}
numberPicker.setMaxValue(stringArray.length-1);
numberPicker.setMinValue(0);
numberPicker.setDisplayedValues(stringArray);

You can see that a String array called stringArray is defined and values 1,3,5... 19 are stored in it. The min value of the NumberPicker is set to 0. The max value of NumberPicker is set equal to the length of stringArray -1 because you want to display all the elements of the array stringArray. Thereafter, through the setDisplayedValues() method, the values in the stringArray are displayed through NumberPicker.

Because the current theme in the Android application is derived from Theme_Holo or Theme_Holo_Light, the NumberPicker appears as shown in Figure 4.2 (that is, the current value as editable with lesser and greater value shown above and below the NumberPicker, respectively). If you change the theme of your application, you can change the appearance of the NumberPicker. For example, the following statements applied in the AndroidManifest.xml file will set the current theme of the application to be derived from Theme:

<application
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.Black.NoTitleBar" >

The preceding statements will change the theme of the application to Theme.Black.NoTitleBar and hence the appearance of the NumberPicker widget. In other words, the NumberPicker will display the current value in editable form with an increment and decrement button displayed above and below, respectively (see Figure 4.3 [top]). After you change the current value, it will be displayed through TextView, as shown in Figure 4.3 (bottom).

Figure 4.3

Figure 4.3. NumberPicker with black background, increment, and decrement buttons on changing the theme of the application (top), and the selected number displayed through TextView (bottom)

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020