Android Discount Calculator App Source Code

"As Knowledge Grows, Experience Increases" . Today in this post we will learn how to create simple "Discount Calculator" Android app. I will post full source code at end of tutorial. As always user can use this code to create their own Discount Calculator app.

In this app we will use only one Activity class and one XML layout. In activity our code part will be carried out and in XML our UI part (I am explaining in this simple way because it will be easy for newbies to understand). 

public class DiscountActivity extends FragmentActivity implements OnClickListener {

private Button btnCalc;
private EditText edtxtSumInput;
private EditText edttxtPercnt;
private EditText edttxtResult;
private EditText edttxtafterdis;

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

btnCalc = (Button) findViewById(R.id.calc);
btnCalc.setOnClickListener(this);

edtxtSumInput = (EditText) findViewById(R.id.sumInput);
edttxtPercnt = (EditText) findViewById(R.id.sumPercnt);
edttxtResult = (EditText) findViewById(R.id.sumResult);
edttxtafterdis = (EditText) findViewById(R.id.afterdiscount);
} 

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.calc:

if (!edtxtSumInput.getText().toString().equals("") && edtxtSumInput.getText().toString() != null && !edttxtPercnt.getText().toString().equals("") && edttxtPercnt.getText().toString() != null ) 
{
double number = Double.parseDouble(edtxtSumInput.getText()
.toString());
double percentage = Double.parseDouble(edttxtPercnt.getText()
.toString());

if (percentage >= 0 && percentage <= 100) {
double savedprice = (percentage / 100.0) * number;
double finalprice = number - savedprice;

String svdPrice = String.valueOf(savedprice);
edttxtResult.setText(svdPrice);

String disprice = String.valueOf(finalprice);
edttxtafterdis.setText(disprice);
} else {

Toast.makeText(this, "Discount must be in between 0 to 100 %",
Toast.LENGTH_LONG).show();
}
}
else {
Toast.makeText(this, "Amount and Discount should not be blank",
Toast.LENGTH_LONG).show();
}
break;

default:
break;
}
}

As usual user are always welcome to leave their precious comment and to participate in discussion, if their is any error in code or if needed some improvement in code.

Image shows how output will look like,

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Unique Random Number Generator in Android

Many of my reader ask how to generate unique random number in android without duplication or repetition. In this post I will show simple code snippet which will use to generate random number without repetition or duplication. The code snippet mentioned in this post is used in SmakAndApp quiz game app. User can download SmakAndApp quiz game app from Google Play. 

Initially, I used Random class to generate random number in given range i.e. upto 50 in this example. But problem is, this generate duplicate entry. To know more about Random class visit developer.android.com/reference/java/util/Random.html 

      Random rndNoGnrt = new Random();
      int rndNo = rndNoGnrt.nextInt(50)+1;

To overcome above problem I used List class to create random number without repetition. Given below code is used for unique random number generation.

List<Integer> NumberList = new ArrayList<Integer>();

for (int i = 1; i <= 50; i++) 

     {

  NumberList.add(i); 

    } 

  Collections.shuffle(NumberList);

  NumberList.get(0)

  NumberList.remove(0); 

Searched Key:

Random number generator example in android.

Generate random numbers without duplication.

Generating a unique random number between given numbers.

Generate random number without repetition

Timer Execption In Android

FATAL EXCEPTION: Timer-1 

"Only the original thread that created a view hierarchy can touch its views."

Above given exception occurred when I used following piece of code in my app.

public void onClick(View v) 

{

SetGlobal.parseQuestCount++;

SetGlobal.titleQuestCount++;

final Timer tmr = new Timer(); 

tmr.schedule(new TimerTask() {

 public void run() {  

setQuestion();

t.cancel(); 

}}, 1000);

}

This is because setQuestion() method (In my case) can only be called from UI thread, but it is called from  tmr.schedule(new TimerTask(){..}) method. So the following error occured.

To overcome the error use runOnUiThread(Runnable action) method. This Runs the specified action on the UI thread.

public void onClick(View v)
{
SetGlobal.parseQuestCount++;
SetGlobal.titleQuestCount++;

final Timer tmr = new Timer();
tmr.schedule(new TimerTask() {
@Override
public void run() {
runOnUiThread(new Runnable() {
@Override
public void run() {
setQuestion();
tmr.cancel();
}
});
}}, 1000);
}