Create android app with java

How to Make Android Apps for Beginners

Are you a new developer learning Java? Read ahead to learn how to make your first Java Android app as a beginner.

Creating a mobile application is a big step towards turning your idea into reality. But the primary concern among new developers is how to make an Android app with all the resources at their disposal. If you’re a beginner, you won’t know the purpose of many of them. So it’s important to begin from the basics and know the starting point.

This guide will walk you through the basics of building an Android app and answer your questions about how to make an app with Java. We’ll be creating a Java Android app using Android Studio as our Integrated Development Environment (IDE).

How to Make an App in Java

To start making a Java Android app, you have to start with an IDE. There are several options for IDEs, but two of the most efficient ones are Eclipse and Android Studio.

For this guide, we are using Android Studio 3.1.3. Android Studio is a complete IDE that offers tools to make app development very simple and easy. It has an advanced code editor and several app design templates. There are tools for development, debugging, and testing as well.

You can learn how to install Android Studio in our post on how to get started making Android apps.

Run Android Studio

Let’s begin with a new project on Android Studio. It gives the option to Create New Project on the welcome screen. You can also continue with your current project if you have one.

Once you choose to create a new project, the next step is choosing your activity. You will be provided with several options, but we’ll begin with an Empty Activity for this tutorial on creating a Java app.

The next step is configuring your activity by giving it a name. Let’s name our app MyBasicApp. From the drop-down menu, choose the Java language. Click Finish.

Now we are ready to start creating our app!

Start Working on Java App Development

At this stage, Android Studio has created two folders that are visible in the left corner. They are:

• A folder for MyBasicApp—this folder carries the code for your app.
• A folder of Gradle scripts—Gradle is a free and open-source tool used by Android Studio to turn the code into an .apk file for your app.

Since we selected the Basic Activity template, Android Studio has created some preset files for our project. You can expand the folders to view them.

Clicking on the app folder will give a drop-down menu with three to four subfolders: manifests, Java, Java (generated), and res. Expanding each one of them will open more folders. Each folder stores a separate component of your project.

In the MyBasicApp folder, go to the Java folder and click on com.example.mybasicapp. This folder contains the source code of your Java Android app.

Now, click the res folder and open the layout folder. It contains a file activity_main.xml. It is the layout of your app. Click to open it.

Now your project view has opened the source code and the layout in two separate tabs. It looks like this:

The .xml file gives you a layout where you can drag and drop elements to build your file. You can also change it to code editor by clicking on text at the bottom left corner. Now you can edit the source code instead of adding elements to the design layout.

In the layout editor, the left pane contains all the elements that you can add to the layout. If you see the component tree, there is just one element—Hello World—in our app.

The elements we add to our layout will be shown in the component tree and how they are added in relation to each other.

Here, ConstraintLayout is the root of the view hierarchy (it is the dimensions of the page on which components will be added).

The ConstraintLayout has a TextView called Hello World.

The TextView is the component that came with a blank activity. The layout at this stage looks like this:

The XML code for this layout will be this:

It has one root hierarchy with just one text element.

Note that this is the basic layout that Android Studio generated itself. We haven’t made any modifications to it yet.

Modify the App Layout

The next step is to modify the layout by adding components of your choice and associating activities with them.

Here you can either start with this ConstraintLayout with TextView in it, or you can clear the ConstraintLayout and begin with a clean slate in terms of layout.

Let’s say you want to change the text on the TextView . You can go to the code editor and view the properties of the TextView element. The code will be like this:

Change the string to whatever you like. For now, I’ll stick with Hello World.

If you have set up an Android Virtual Device (AVD) in the Studio, the app will run on the simulator like this:

This is the basic TextView with Hello World! as its string. You can modify the attributes of this text component. Edit the text, font, size, and color to give a new look to TextView .

The XML code for these changes would be this:

We have changed the font to Sans Serif and made the color darker gray . The font size is also increased to 30sp , and the text is made bold.

The changes as visible in the AVD:

Add Constraints

Up to now, we’ve just modified the stock Empty Activity set up by Android Studio. Now, we will see how to add constraints and views to the user interface.

In the Layout Editor, there is a palette on the right side from where you can choose the constraints you’d like to add.

You can add more than one view and constrain them to top, bottom, left, or right. These views have attributes that can be edited to modify them.

To better understand what an attribute is, select textView in the Component Tree and look at the Constraint Widget in the Attributes panel.

The square represents the constraints.

The rectangular box and each of the four dots represent a constraint. You can increase or decrease their value based on the point where you want to place the view.

Here is how it looks in the Layout Editor.

You can drag and drop the Views from the left palette to add them in the ConstraintLayout . After adding them, you can apply constraints to determine their position. Each new button added to the layout is given a unique identity.

Here is how your layout will look after adding the constraints to the views:

Here is the XML code for the finished layout:

Assigning Activity to the Button

The layout design is the meat of your app. You have added a Button , but it doesn’t do anything when pressed. To make it interactive and responsive to users’ actions, we have to assign activity to it.

Let’s say this is the last step on your app, and upon clicking Next you want people to see the message Finish. Here’s how to do it.

The Next button has an id called @+id/next . Since no other element is using this id, we can use it to find the button and add it to the Java code so that the activity doesn’t get associated with another button.

The id for a view helps you identify it as each id differs from other viewers’ id. With the findViewByID() function, next can be found through its id, R.id.next .

Here is the final code that will display the finish message:

Run the app to see how the Button works.

Conclusion

This guide covered everything from setting up the Android Studio to coding and testing a Button . It’s not hard to get started coding an app—Java mobile app development has become easier since a lot of elements are drag and drop.

Android App Templates and UI Kits From CodeCanyon

You may have noticed that our app looks very plain and simple. That’s because we’re using the default theme, without applying any styles to our views. CodeCanyon is full of Android UI kits that offer beautiful, hand-crafted styles you can apply to your views.

The kits generally also have several custom views and layouts. You can refer to the following articles to learn more about them:

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Tutorial: Create your first Android application

In this tutorial, we will create a simple yet fully-functional Android application that counts how many times you tap a droid image. After that, we will run it on an Android virtual device.

This tutorial covers a simple scenario to help you get started with Android development in IntelliJ IDEA. For comprehensive how-to guides and reference documentation, visit the Android Studio user guide.

Create a new Android project

Create a project

Launch IntelliJ IDEA. On the Welcome screen, click New Project . If you already have a project open, from the main menu select File | New | Project .

In the New Project wizard, select Android on the left.

If you don’t have the Android SDK configured, IntelliJ IDEA will detect this and prompt you to download it:

Select the components you want to install. If you haven’t installed the Android SDK tools before, all the required components will be preselected.

Optionally, modify the location for the Android SDK, and click Next :

Review the installation settings and click Finish to start the download:

When all components have been downloaded and installed, click Finish :

Select Empty Activity as the project template:

On the last step, type HelloDroid as the project name and select Java as the language:

Configure project JDK

Now that we have created our first project, let’s make sure it uses the correct JDK.

From the main menu, choose File | Project Structure and go to Platform Settings | SDKs . Select the Android SDK and make sure that the correct Java version is selected in the Java SDK field.

We recommend that you use Java SE 11 or Java SE 8 for Android development in IntelliJ IDEA. If you don’t have the correct JDK installed, in the Project Structure dialog, click the Add New SDK button on the toolbar and select Download JDK :

In the Settings/Preferences dialog ( Ctrl+Alt+S ), go to Build, Execution, Deployment | Build Tools | Gradle and select the correct Java version (8.x or 11.x).

Explore the project structure

For Android projects, there’s a dedicated view in the IntelliJ IDEA Project tool window: click Project in the top-left corner and select Android .

This view doesn’t reflect the actual hierarchy of files on your disk — it is organized by modules and file types to ease navigation between source files of your project. Note that it hides project files and directories that you don’t commonly use (to see them, choose the Project view):

The app folder consists of the following subfolders:

manifests : contains the AndroidManifest.xml file, which holds general information about the application processed by the Android operating system. Among other things, it declares the package name that serves as a unique identifier for your application and the minimum version of the Android SDK required for the device where the application will run. It also declares the entry points of the application, along with permissions the application requires. For details, see App Manifest Overview.

java : contains the Java source code files grouped by packages, including JUnit tests.

res : contains all non-code resources, such as XML layout files, UI strings, images, and so on.

The Gradle Scripts folder contains all the project’s build-related configuration files.

Edit the UI layout

At this stage, the user interface of our sample HelloDroid application is based on a very simple layout defined in the activity_main.xml file located in the res/layout folder.

Let us modify the auto-generated user interface and see how the application layout is rendered without running it on any physical or virtual device.

Open the UI designer

In the Android project view, go to the app/res/layout and double-click the activity_main.xml file to open it. Note that since IntelliJ IDEA downloads the components required to render layout files, opening it may take a few seconds.

If the UI designer fails to open, and you get the Design editor is unavailable until after a successful project sync error, press Ctrl+Shift+A , search for the Sync Project with Gradle Files action, and wait for the sync to finish.

By default, IntelliJ IDEA provides a graphical view of the layout file, but you can also switch to the source code view, or view the text and the graphical representation side by side — use the icons in the top-right corner of the UI Designer pane:

This pane shows a rectangular canvas that is synchronized with the layout definition and with the Component Tree , so any changes to the canvas are reflected there accordingly.

Normally, layout files have a layout manager as their root element (for example, LinearLayout , FrameLayout , ConstraintLayout , and so on). In our example, the root element in activity_main.xml is ConstraintLayout that is responsible for positioning the elements of the application interface. For the purpose of this tutorial, we are not going to modify it, but you can learn more about designing interfaces from Build a Responsive UI with ConstraintLayout.

To eliminate distraction and only see how your layout is represented, click the Select Design Surface icon in the top-left corner and choose Design :

Now let’s delete the existing text element. To do this, right-click the text label and choose Delete from the context menu.

Now the UI layout looks like the following, and we are ready to start designing the layout of our application:

Add image to the UI layout

Now let’s add a droid image to our layout.

In the Android project view, expand the app/res folder and drag the image you want to use into the drawable folder. For this tutorial, we’ve downloaded a Hello Droid image from the Internet and saved it with the dimensions 50×50 px.

Return to the activity_main.xml file opened in the Designer pane, from the Palette choose the ImageView element, and drag it to the canvas to the position where you want the image to appear.

In the Pick a Resource dialog that opens, choose the resource file you’ve added and click OK :

Next, we need to modify the default id of the imageView element to be able to reference it later.

Select it in the Component Tree and in the Attributes pane on the right, enter the new identifier in the id field: droidImage . Press Enter ; in the dialog that opens, confirm that you want to update all references to the image element id:

Add text to the UI layout

Now let’s add some text to our layout.

In the Palette pane, pick the TextView element and drag it to the canvas below the image.

The widget displays some default text: TextView . To change it and link it to a string, we need to create a new text resource.

Select the textView element in the Component Tree on the left. In the Attributes pane on the right, click the Pick a Resource icon next to the text attribute:

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose String Value .

In the New String Value dialog, enter the resource name ( welcome_text ) and the resource value ( Hello! I’m a droid. ):

Click OK to save the value and then click OK in the Pick a Resource dialog.

Now let’s modify the textView element id the same way we did with imageView .

Select textView in the Component Tree on the left, and in the Attributes pane set the id to a new value: clickCounter .

Add style to text

Now let’s add some style to the text to make it look more appealing.

Pad the text a bit: locate the padding attribute, and set all values to 10dp :

Change the font color: locate the textColor attribute, and click the Pick a Resource icon next to it.

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose Color Value .

Enter the resource name ( text_color ) and the value ( #9C27B0 ):

Change the font size: locate the TextSize property and click the Pick a Resource icon next to it.

In the dialog that opens, click the Add resource to the module icon in the top left corner and choose Dimension Value .

Enter the resource name ( text_size ) and the value ( 24sp ):

As a result, your user interface now looks like the following:

To check what your application UI looks like in landscape orientation, click the Orientation for Preview icon on the Designer toolbar and choose Landscape :

To preview what your layout looks like on different devices, select another device from the device list:

Make the application interactive

Although our sample application is fully functional at this point, it does not support any form of interaction yet. Let’s modify it to support tap events.

In the Android project view, locate the MainActivity file under app\java\com.example.hellodroid and double-click to open it.

MainActivity is not a very meaningful class name, so let’s rename it.

Right-click this file in the Android project view and choose Refactor | Rename from the context menu or press Shift+F6 . In the dialog that opens, change the class name HelloDroidActivity and click Refactor :

All references to this class will be updated automatically, and your application’s source code will look as follows:

Replace the code in HelloDroid.java with the following:

Note that the identifiers we’ve used in the source code correspond to those we’ve set in our layout definition file, otherwise our code would not work.

Build and run the application

Now let’s build our application and run it on a virtual device.

Configure Android virtual device

First of all, to be able to run our application, we need to configure a virtual device.

In the main IntelliJ IDEA toolbar, click the devices list and choose AVD Manager :

On the first step of the wizard, click Create Virtual Device :

On the next step, we need to select the hardware that our virtual device will emulate.

Let’s select Phone on the left, and choose Pixel 2 as the target device:

Choose the system image you want to mimic on the virtual device, that is the OS version, the Android API level, the application binary interface (ABI), and the target SDK version:

Click the Download link next to the system image you want to mimic on the virtual device. For this tutorial, we’ve chosen to download the R system image.

In the License Agreement dialog that opens, read the license agreement and accept it, then click Next and wait for the download to finish. When the system image has been downloaded, select it and click Next in the System Image step of the wizard.

On the last step, you can modify your virtual device name and select the startup size and orientation of the screen. Choose the portrait layout and click Finish :

The newly configured device appears in the Android Virtual Device Manager .

Run the application

On the main IntelliJ IDEA toolbar, make sure the automatically created Run configuration and the virtual device we’ve just configured are selected and click :

The Android emulator will launch after the build has successfully finished, with our application started:

Click the droid image and see how the application processes the tap events, counts them and returns the corresponding message:

For information on how to run the app on a hardware device, refer to Android Studio: Run apps on a hardware device.

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