Android Application Tutorial - AppyWare: March 2015

Saturday 14 March 2015

Simple Calculator Application

Simple Calculator :

To make a simple calculator first make a basic app(Don't know? Follow this).

Android consists of Xml(for layout) and Java(for code) files. We need to set up both as per our application requirements.

We will use OnClickListener to get button clicks and perform tasks. We need to implement the class View.OnClickListener within our MainActivity class, then import unimplemented methods.

**We implement this class as to avoid setting up individual OnClickListener for each button we use.

Now the onClick() method is used to get button view which can be used to get button id that we will declare in layout(xml) file.

Follow these steps to set up files :

1) We need to first create a layout of the calculator.

Paste this code into you activity_main.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:layout_margin="16dp"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Basic Calculator"
        android:textSize="30dp" />

    <EditText
        android:id="@+id/edittext"
        android:layout_width="wrap_content"
        android:ems="10"
        android:inputType="numberDecimal"
        android:layout_margin="10dp"
        android:layout_gravity="center_horizontal"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/edittext2"
        android:layout_width="wrap_content"
        android:ems="10"
        android:layout_margin="10dp"
        android:inputType="numberDecimal"
        android:layout_gravity="center_horizontal"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Result"
        android:layout_margin="10dp"
        android:textSize="30dp" />
    <Button
        android:id="@+id/butadd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        android:ems="9"
        android:layout_gravity="center_horizontal"
        />
    <Button
        android:id="@+id/butsub"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Subtract"
        android:ems="9"
        android:layout_gravity="center_horizontal"
        />
    <Button
        android:id="@+id/butmul"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Multiply"
        android:ems="9"
        android:layout_gravity="center_horizontal"
        />
    <Button
        android:id="@+id/butdiv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Divide"
        android:ems="9"
        android:layout_gravity="center_horizontal"
        />
</LinearLayout>

Paste this code into you MainActivity.java :

package com.appyware.myfirstapp;

import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


//implement View.OnClickListener for button clicks
public class MainActivity extends Activity implements View.OnClickListener {

    Button butadd, butsub, butmul, butdiv;
    EditText editText, editText2;
    TextView textView;

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

        //definition
        butadd = (Button) findViewById(R.id.butadd);
        butsub = (Button) findViewById(R.id.butsub);
        butmul = (Button) findViewById(R.id.butmul);
        butdiv = (Button) findViewById(R.id.butdiv);

        editText = (EditText) findViewById(R.id.edittext);
        editText2 = (EditText) findViewById(R.id.edittext2);

        textView = (TextView)findViewById(R.id.textview);

        //setting onClickListener for buttons
        butadd.setOnClickListener((View.OnClickListener) this);
        butsub.setOnClickListener(this);
        butmul.setOnClickListener(this);
        butdiv.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {

        //declare variables
        float num1 = 0;
        float num2 = 0;
        float result = 0;

        //checking if the input is empty
        if (TextUtils.isEmpty(editText.getText().toString())
                || TextUtils.isEmpty(editText2.getText().toString())) {
            return;
        }

        // reading EditText and storing the value into variables
        num1 = Float.parseFloat(editText.getText().toString());
        num2 = Float.parseFloat(editText2.getText().toString());

        // task to perform by buttons when clicked
        switch (v.getId()) {
            case R.id.butadd:
                result = num1 + num2;
                break;
            case R.id.butsub:
                result = num1 - num2;
                break;
            case R.id.butmul:
                result = num1 * num2;
                break;
            case R.id.butdiv:
                if(num2 != 0)
                result = num1 / num2;
                break;
            default:
                break;
        }

        // to display the result
        textView.setText("Result = " + result);

    }
}

2) Save and Run the application.

Complete Source Code : Simple Calculator

For any doubts you can comment below, i'll respond ASAP.

Monday 9 March 2015

Your First Android Application!

Your First Android Application :

Let's begin by creating a basic Android App with your name on it!

1) Start Android Studio(Don't have? Follow this link).

2) In the main window select Start a new Android Studio project.

3) Type the name of the app you want(I take MyFirstApp).

4) Change your Company Domain(You can't use default to upload apps to playstore).

5) Choose your project location.

6) Select next > next(we won't change platform or min SDK level for now) > next( we will use Blank Activity for now) > Finish.

7) You will see a window like this, don't worry we will learn about everything.

8) Now to Run the app either choose Run 'app' from menu bar or press SHIFT + F10 (Win) and CTRL + R (Mac).

9) You will see this popup either Use a device(Follow this link to learn) or Create AVD(Follow this link to learn). Select the choice and press OK.

10) You have successfully made your app!

To replace your name instead of Hello World! text :

1) In your activity_main.xml and in the text part of the code browse to TextView and android:text="@string/hello_world".

2) Replace this line by android:text="Your name".

3) Now run the app.

Enable USB Debugging

Enable USB Debugging :

To use a device to run android apps we need to configure your Android Device.

1) Open Settings in your Android Device, and goto About Phone option and tap 7 times on Build Number until you see a message "Now you are a developer", it enables Developer Options in settings.

2) Open Developer Options in Settings and Check USB Debugging option, click OK in the popup.

3) Now connect your device to your system via USB cable and run the app, it will show
your device in the available devices.

Create Android Virtual Device

Create Android Virtual Device(AVD) :

1) Start Android Studio(Don't have? Follow this link).

2) Goto Tools > Android > AVD Manager and select it.

3) Select Create Virtual Device > choose the device you want to emulated(I choose Nexus 6) and click next.

4) Select the system image as per your OS(32bit/64bit) and click next.

5) Click Finish and you have created AVD, double click on the AVD to run it.

Sunday 8 March 2015

Setting up Android Studio

Setting up Android Studio :

1)Before this you need to setup Java SDK(skip this step if already done).

2) You need to download Android Studio from this link(http://developer.android.com/sdk/index.html).

3) While installing the setup you can install the Android SDK updates at the time of installation or later manually.

Tip : To cancel the automatic update close the setup and check Do no not Re-run the Setup option.

Manual Update :

1) Open Android Studio > Tools > Android > Android SDK and open it.

2) Download and Install the latest updates(It will automatically select for you).

3) Once the download is finished you are all set to make your first app.

Home