Android/Java Lightning Tutorial JULY 30, 2018

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1 Android/Java Lightning Tutorial JULY 30, 2018

Java Android uses java as primary language Resource : https://github.mit.

2 Java Android uses java as primary language Resource : Online Tutorial : x.html

3 JAVA Basics Printing System.out.println("Hello World!"); Types: Unlike python, every variable has a type int age = 22; long bignumber = ; boolean itscold = true; double temperature = 40.5; char firstinitial = 'J'; Simple Types like these are called primitives

4 JAVA Basics More types: Object types String name = "Jennifer"; Standard Operations Apply int a; a = 1 + 1; // Addition a = 2-1; // Subtraction a = 2 * 3; // Multiplication a = 4 / 2; // Division

5 JAVA Basics Static Checking JAVA Checks types before you run your code. Example: Code with hello /42 will not be able start to run. This is different from python. Keywords Static used when declaring a variable that can be accessed without the instantiation of a class. Final used when declaring a variable that can only be assigned once.

6 JAVA Basics: Loops Same as C/C++ IF FOR WHILE if (condition) { // Do something. else if (condition) { // Do something else else { // Default case. for (int i=0; i < 10; i++) { // Do something. int j = 0; while (j < 10) { // Do something. j++;

7 JAVA Basics: Methods Similar to Python functions except include types, modifier public static double ToCelsius(double Fahrenheit) { double tempcelsius; tempcelsius = (Fahrenheit ) * 5.0 / 9.0; return tempcelsius;

8 JAVA Basics: Methods Modifiers Static: Allow running the method without instantiating the whole class Public: Make this method public. Use private to make method only available to the class Types: double in signature for return type and double as type of input parameter.

9 JAVA More Types Arrays: String[] names; Int[] numbers; For non-primitive types use new to instantiate; Int[] numbers = new int[12]; //create an array of 12 ints Use [] indexing to fill in array numbers[0] = 42

10 JAVA : Classes Java is heavily centered around Classes. Typically, in Java you can t write code that is not part of a class A class are like in other languages

11 JAVA : Classes package myproject import java.util.array public class CoolClass { //Other methods and declarations public static void main(string[] args) { //This code runs when the program is run //Other methods and declarations

12 JAVA : Classes and inheritance To have one class inherit from another, use the extends keyword Classes can also implement interfaces. Interfaces are classes that only have method signatures but no implementation. To implement an interface use the implements keyword. Inheriting and implementation are basically the same thing, the key difference is in java you can t inherit multiple classes but can implement many interfaces Use super keyword to refer to superclass, this refers to current

13 JAVA : Inheritance Example class Animal { public String name; public Animal(String name) { this.name = name; public void breathe() { System.out.println("in, out"); class Dog extends Animal { public String breed; public Dog(String name, String breed) { super(name); this.breed = breed; public void bark() { System.out.println("woof!");

14 Android That s a quick intro to java, Lets now get into Android Recall the critical components an Android App: Manifest Activities Resources Intents The hardest part of Android is the studio installation Lets install Android then move on to a Hello World App

15 Android package com.example.dalitsobanda.gsl_hw; import android.support.v7.app.appcompatactivity; import android.os.bundle; import android.view.view; import android.widget.button; import android.widget.toast; public class MainActivity extends AppCompatActivity protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); Button btn = (Button) findviewbyid(r.id.button); btn.setonclicklistener(new View.OnClickListener() public void onclick(view view) { Toast.makeText(MainActivity.this, "hello world",toast.length_long).show(); );

16 Android Challenge Create an app with two activities In the first activity create a button to switch to the second activity

17 Android: Deeper Hopefully, that gives you an understanding of activities There s a lot more to it Fragments: A fragment is a part of an activity Services: For long running processes Storage: Shared Prefs, Internal, External, Content Providers Threading: AsyncTasks, The UI Thread

18 Resources When in doubt, always check The API changes often, so check things frequently

Basic GUI elements - exercises

Basic GUI elements - exercises https://developer.android.com/studio/index.html LIVE DEMO Please create a simple application, which will be used to calculate the area of basic geometric figures. To add