Day 2- Android App: Code Starter!

1. Android: Code starter

2. Contents
• Data types and Methods
• Conditional Statements
• Intents
• Java coding in a sign up activity

3. Data types and Methods
• Data types in android? More like data types in java!
• Simple put, data type specifies the type of data you want to put in your variable
Two types of data types
1. Primitive
2. Non-primitive

4. Primitive data types
• They include very basic data types.

5. Non-primitive data types
• Not pre-defined by java (except ‘String’)
• They have attributes and methods associated with them

6. Classes and objects
• Java is an object-oriented programming language.
• Everything in Java is associated with classes and objects, along with its attributes
and methods. For example: in real life, a car is an object. The car has attributes,
such as weight and color, and methods, such as drive and brake.
• A Class is like an object constructor, or a "blueprint" for creating objects.
• Syntax:
<access-modifier> class <class-name> [optional: extends <super-class name>]
[optional: implements <interface name>]
{
….
}

7. Classes and objects
• A class alone is not functional since it is just a blueprint.
• Think of it this way, Just a recipe to make biryani is no good. When you carry out
that recipe and actually cook biryani that is when it is eatable.
• When you make the object its called instantiation of object. The keyword ‘new’ is
used to create an instance of a class in java.
• Syntax: <class-name> <object-name> = new <class-name>()
• E.g. ClassA objectOfA=new ClassA()
• Here ‘ClassA()’ is the constructor of the class

8. A simple java program

9. Simple class

10. Simple class with constructor

11. Methods
• Methods or functions are simple block of code that perform some task
• It’s just a block of code with a name and can be called anywhere.
• Syntax:
<access-modifiers> <return-type> <function-name> ( <parameters> ){
//function definition
}
E.g. public void exFunction(int value){
//definition
}

12. Simple method

13. Conditional Statements
• Statements that get executed based on some condition.
• E.g. if x is equal to 10 print x

14. Simple if-else

15. Simple if-else

16. Okay! Now let
us move on to
something a
little less
boring…

17. Tada!
Intents

18. Intents
• Intents are simply the
messaging objects that enable
activities to communicate
• They can navigate from one
activity to another and even
send data between activities

19. Types of Intents

20. Before moving on…
package com.example.explicitintentdemo;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}

21. Explicit Intents
• Explicit intents specify which application will satisfy the intent, by supplying
either the target app's package name or a fully-qualified component class name.
You'll typically use an explicit intent to start a component in your own app,
because you know the class name of the activity or service you want to start. For
example, you might start a new activity within your app in response to a user
action, or start a service to download a file in the background.

23. MainActivity.java
package com.example.explicitintentdemo;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button=findViewById(R.id.button);
}
public void openSecondActivity(View view){
Intent intent=new Intent(this,SecondActivity.class);
startActivity(intent);
}
}

24. activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="open Second Activity"
android:onClick="openSecondActivity"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.366" />
</androidx.constraintlayout.widget.ConstraintLayout>

25. SecondActivity.java
package com.example.explicitintentdemo;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
public class SecondActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
}
}

26. activity_second.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".SecondActivity">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Congrats you made it to Second Activity"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

28. Implicit Intents
• Implicit intents do not name a specific component, but instead declare a general
action to perform, which allows a component from another app to handle it. For
example, if you want to show the user a location on a map, you can use an
implicit intent to request that another capable app show a specified location on a
map.

29. package com.example.implicitintent;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
Button button;
EditText webAddress;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = findViewById(R.id.button);
webAddress=findViewById(R.id.webAddress);
}
public void openBrowser(View view){
Editable temp=webAddress.getText();
String address=temp.toString();
//Alternate way: String address=webAddress.getText().toString();
Intent intent=new Intent(Intent.ACTION_VIEW, Uri.parse(address));
startActivity(intent);
}
}

30. <?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<EditText
android:id="@+id/webAddress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="https://www.example.com"
android:inputType="textPersonName"
app:layout_constraintBottom_toTopOf="@+id/button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.886" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Browse"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:onClick="openBrowser"/>
</androidx.constraintlayout.widget.ConstraintLayout>