Android tutorials7 calculator_javaprogramming
Upcoming SlideShare
Loading in...5
×
 

Like this? Share it with your network

Share

Android tutorials7 calculator_javaprogramming

on

  • 261 views

 

Statistics

Views

Total Views
261
Views on SlideShare
249
Embed Views
12

Actions

Likes
0
Downloads
8
Comments
0

2 Embeds 12

http://uclu-techsoc.github.io 8
http://localhost 4

Accessibility

Upload Details

Uploaded via as OpenOffice

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Android tutorials7 calculator_javaprogramming Presentation Transcript

  • 1. Basic Java programming in Android
  • 2. All java programming relatively to functionality of your app is done in MainActivity.java type of files.
  • 3. I am not going to explain the way functions work here in detail yet. (they are generated automatically) All we need to know is that all code inside onCreate is running when program first starts.As a first step we need to create variables which will represent the value of input numbers and the final result.
  • 4. Hence, create three integer numbers. In java each variable has a type. Integer number has a type of int. E.g. integer number with name firstVar: int firstVar;
  • 5. Hence, create 4 buttons variables, 2 EditText and 1 TextView for each layout item. As well as to represent numbers we should set a type for Button, TextView and EditText. E.g. Button with name 'plus': Button plus; TextView with name 'answer': TextView answer; and so on...
  • 6. As you noticed Button, TextView and EditText are underlined this mean that they have an error. Eclipse/Android Studio doesn't understand what does they mean until we import library.You can do it by navigating your mouse on it and pressing import. Or you can import them all on Eclipse by running <ctrl> <shift> <all>➪ ➪
  • 7. It is easy to give a value to int variable, just e.g. firstVar=0; Now we need to initialized our variables, give them value. We have to do it inside onCreate function, so we will have them initialized when app is just created. In order to initialize Button, EditText e.g. for button variable 'add': add = (Button) findViewById(R.id.plus); where 'plus' is id we set it up in layout file.
  • 8. Create onClickListener for all buttons. Now let's set button click listener for all buttons. You can do it by adding .setOnClickListner attribute which creates implemented method onClick, which is running when the button (e.g. plus) is clicked
  • 9. plus.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View arg0) { // TODO Auto-generated method stub } }); minus.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { // TODO Auto-generated method stub } }); mult.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub } }); div.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub } }); Next step is to add functionality when buttons will be pressed
  • 10. Firstly lets get the value of our variables from the EditText form. We are getting the text inside EditText in type String(type for text) by writing: firstInput.getText().toString() In order to translate string value into type int(type for math arithmetics) we write: Integer.parseInt(<code which gives us string variable>) plus.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View arg0) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); } });
  • 11. This line makes in this case addition of 2 variables and put it into the result variable. result = firstVar + secondVar; This line sets the result value translated into String type within EditText form <answer> plus.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View arg0) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); result = firstVar + secondVar; } }); answer.setText(String.valueOf(result)); answer.setText(String.valueOf(result));
  • 12. Now change each onClickListener action relatively to the button arithmetical operation and you can run the app. plus.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View arg0) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); result = firstVar + secondVar; } }); minus.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); result = firstVar - secondVar; } }); mult.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); result = firstVar * secondVar; } }); div.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub firstVar = Integer.parseInt(firstInput.getText().toString()); secondVar = Integer.parseInt(secondInput.getText().toString()); result = firstVar / secondVar; } }); answer.setText(String.valueOf(result)); answer.setText(String.valueOf(result)); answer.setText(String.valueOf(result)); answer.setText(String.valueOf(result));
  • 13. Put numbers and click on +,-,/ or *. Does it work only if you put numbers first? Can you fix it? Can you make the code shorter?