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Returning nothing instead of NaN

I'm creating a simple app that calculates BMI and I'm struggling with one small problem. I have 2 edit text fields, which are allowed to type numbers only. The point is when one of the text fields are empty the app is to generate a toast message and display nothing. I wrote an if statement to check if an edit text is empty and if not just to calculate further.
All would work fine, but I needed to put return statement and Android Studio suggested me writing "return 0;" so did I.
This is the code responsible for calculations:
/// parse input value from edittext field into double type
private double weight() {
EditText weightInput = (EditText) findViewById(R.id.weight_input);
String sWeightInput = weightInput.getEditableText().toString();
if (sWeightInput.matches("")){
Toast.makeText(this, R.string.noweight, Toast.LENGTH_SHORT).show();
} else {
String weight = sWeightInput;
double weightTyped = Double.parseDouble(weight);
return weightTyped;
}
return 0;
}
private double heigh() {
EditText heightInput = (EditText) findViewById(R.id.height_input);
String sHightInput = heightInput.getEditableText().toString();
if (sHightInput.matches("")){
Toast.makeText(this, R.string.noheight, Toast.LENGTH_SHORT).show();
} else {
String height = sHightInput;
double heightTyped = Double.parseDouble(height);
heightTyped = heightTyped / 100;
heightTyped = heightTyped * heightTyped;
return heightTyped;
}
return 0;
}
//make calculations and return the output value
public void makeCalculations(View view){
double result = weight() / heigh();
String message = String.valueOf(result);
TextView bmiSummaryTextView = (TextView) findViewById(R.id.bmi_calculation);
bmiSummaryTextView.setText(message);
}
This is the interface of the app.
To sum up, all I want to do is to display nothing instead of NaN (not a number).

Return a non-primitive Double rather than a double, and you will be able to use null as a value. Be sure to check for this value though, or you'll run into a NullPointerException.
Alternatively, you could look into using optionals, but since you're using Android you might need an external library for that (unless your minimum SDK version is high enough, then you can use Java 8's Optional).

The problem is probably if in your calculation weight() / height height is 0 it outputs NaN because it is infinity.
Also put your return 0; after Toast.makeText() in the condition. AS grumbles because you are not returning a value in the if branch.
if (sHightInput.matches("")){
Toast.makeText(this, R.string.noheight, Toast.LENGTH_SHORT).show();
return 0;
}
Maybe this will help you also to avoid dividing by zero.
public void makeCalculations(View view) {
String message = "Invalid input!";
if (weight() > 0 && height() > 0) {
double result = weight() / heigh();
String message = String.valueOf(result);
}
TextView bmiSummaryTextView = (TextView) findViewById(R.id.bmi_calculation);
bmiSummaryTextView.setText(message);
}

How to convert double values to string in a text field

I want to do the average of 9 textfields and also the sum of them and place them in 2 other textfields by using a button, currently this code doesnt displays anything in the other textfiels. If i put anything, for example "A" instead of "%.Of" it would display the "A" in the textfield but not the average or the sum. Please i need help with a code that would work, dont mind if i need to change a lot.
This is what im working with:
private void jButton_RankingActionPerformed(java.awt.event.ActionEvent evt) {
double R[] = new double [14];
R[0] = Double.parseDouble(jTextField_Math.getText());
R[1]= Double.parseDouble(jTextField_English.getText());
R[2] = Double.parseDouble(jTextField_Spanish.getText());
R[3] = Double.parseDouble(jTextField_Biology.getText());
R[4] = Double.parseDouble(jTextField_Physics.getText());
R[5] = Double.parseDouble(jTextField_Chemestry.getText());
R[6] = Double.parseDouble(jTextField_PE.getText());
R[7] = Double.parseDouble(jTextField_Humanities.getText());
R[8] = Double.parseDouble(jTextField_Technology.getText());
R[9] = (R[0]+R[1]+R[2]+R[3]+R[4]+R[5]+R[6]+R[7]+R[8])/ 9;
R[10] = R[0]+R[1]+R[2]+R[3]+R[4]+R[5]+R[6]+R[7]+R[8];
String Average = String.format("%.Of",R[9]);
jTextField_Average.setText(Average);
String TotalScore = String.format("%.Of",R[10]);
jTextField_TotalScore.setText(TotalScore);
if(R[10]>=50)
{
jTextField_Ranking.setText("Superior");
}
else if (R[10]>=41){
jTextField_Ranking.setText("Alto");
}
else if (R[10]>=34){
jTextField_Ranking.setText("Basico");
}
else if (R[10]<=33){
jTextField_Ranking.setText("Bajo");

Since you mentioned that an A would print, it follows that jButton_RankingActionPerformed is being called. The issue you have is the format string you are using to print the total and average. You have mistakenly chosen the capital letter O rather than the number zero.
Replace this (which contains a capital letter O):
String.format("%.Of",R[9]);
With
1) No decimal will be printed: i.e. 50.2 would be 50
String.format("%.0f",R[9]);
2) Or perhaps you want to see one decimal place like 50.2
String.format("%.1f",R[9]);
Also a very small optimization is:
R[9] = (R[0]+R[1]+R[2]+R[3]+R[4]+R[5]+R[6]+R[7]+R[8])/ 9;
R[10] = R[0]+R[1]+R[2]+R[3]+R[4]+R[5]+R[6]+R[7]+R[8];
Could be replaced with:
R[10] = R[0]+R[1]+R[2]+R[3]+R[4]+R[5]+R[6]+R[7]+R[8];
R[9] = R[10] / 9;
or use a loop to calculate R[10]. (to add R[0] to R[8])

I want an image to fade out and the another to fade in when it is clicked and after that the other way around

The code below is supposed to fade two ImageViews, one needs to fade in and the other out depending on the value of counter. For some reason when I run the code I get the following log output:
I/Info: One
I/Info Counter:: 1
I/Info: One
I/Info Counter:: 1
...
It never shows:
I/Info: Two
I/Info Counter:: 0
Can someone explain why this is happening?
Here's the code:
public void fade(View view) {
int counter = 0;
ImageView bale = (ImageView) findViewById(R.id.bale);
ImageView pogba = (ImageView) findViewById(R.id.pogba);
if (counter == 0) {
bale.animate().alpha(0f).setDuration(2000);
pogba.animate().alpha(1f).setDuration(2000);
Log.i("Info", "One");
counter = 1;
} else if (counter == 1){
pogba.animate().alpha(1f).setDuration(2000);
bale.animate().alpha(0f).setDuration(2000);
Log.i("Info", "Two");
counter = 0;
}
Log.i("Info Counter: ", String.valueOf(counter));
}

You're making a logical error, there is nothing syntactically wrong with your code. The scope of counter is where you're having trouble. counter is a local variable, it only exists in the fade(...) method. Every time you call fade() you recreate counter and initialize it to 0. Meaning even though you set it to 1 in the if statement, it will be 0 the next time you call fade(). You either need to make it a class variable or use the alternating approach I describe below.
Non If Statement Alternating Approach:
You don't need an if statement, simply get the alpha of pogba and bale and then when you set their alphas use 1f - pogba.getAlpha() and 1f - bale.getAlpha() (using whichever method returns their alphas). Using this approach will alternate between 1 and 0.
So your fade(View view) method would look similar to the following:
public void fade(View view) {
ImageView bale = (ImageView) findViewById(R.id.bale);
ImageView pogba = (ImageView) findViewById(R.id.pogba);
// I'm not familiar with the method to get the alpha
// so it might not be getAlpha()
bale.animate().alpha(1f - bale.getAlpha()).setDuration(2000);
pogba.animate().alpha(1f - pogba.getAlpha()).setDuration(2000);
}
You would of course need to do the following somewhere else in your code, possibly the constructor.
bale.setAlpha(1f); // I'm not familiar with the method to set the alpha
pogba.setAlpha(0f); // it might be setAlpha(), but I'm not sure

textView wont display decimals

I am having an issue with my program, my textveiw will not display any decimals, heres the break down on whats happeneing. The user enters a number in a textEdit (Also how do i make the textedit only accept numbers AND a decimal point?) that number gets converted to a int, sent to my second activity, diveded by 3600, then displayed in a textveiw box. The issue is that when that number is displayed it has no decimal value, for example if its less than 1 it will not display anything, how can i go about fixing this? i need it to at least go to the 1000th place.
Here is my code one activity1:
public void sendMessage(View view) {
// Do something in response to button
Intent intent = new Intent(this, PayTracker.class);
// Gather text from text boxes
EditText editText = (EditText) findViewById(R.id.hourly_wage);
//Create String from text
String message1 = editText.getText().toString();
//Convert String to Int
int HW = 0;
try{
HW = Integer.valueOf(message1);
}
catch(NumberFormatException nfe){
//do something else here
//for e.g. initializing default values to your int variables
}
// Send Integers to PayTracker.java
intent.putExtra(MESSAGE_HW, HW);
// start new activity
startActivity(intent);
And then this is activity2 where the number needs to be displayed:
public void sendMessage(View view) {
// Receive messages from options page
Intent intent = getIntent();
int HW = intent.getIntExtra(Options.MESSAGE_HW, 0);
// Calculate pay per second
int PPS = 0;
PPS = (HW/3600);
// set textView
TextView textView = (TextView) this.findViewById(R.id.yourpay);
textView.setText(String.valueOf(PPS));
}
Any help would be appreciated! thanks!

Use doubles or floats. From what I see, everything should work except that you forgot that 5 divided by 2 as int is 2, and not 2.5.
so do as gtumca said and use doubles; longs are just bigger ints.
in other words...
activity1
try{
HW = Double.valueOf(message1);
}
activity 2
//double HW = intent.getIntExtra(Options.MESSAGE_HW, 0);
double HW = intent.getDoubleExtra(Options.MESSAGE_HW, 0);
// pay is rarely a round number
double PPS = HW / 3600;

that number gets converted to a int
Integers dont have decimals :)
As to the EditText only accepting numbers:
EditText, inputType values (xml)
Set one of those types to your EditText in the Layout xml like:
android:inputType="number"

You are using int as data type so you are getting int values only
double PPS = 0;
^^^^^^
instead of
int PPS = 0;

You shouldn't use float or double to keep numbers with such big precision. Float and double cannot represent decimal fractions exactly due to their internal representations. Please, check BigDecimal if you want 1000-digit precission(or more).

Another Android Activity or an iterative JAVA method?

I am new to Android application development and am trying to find a way to proceed through a series of screens that take in user input. I'm making a small math game where the user would answer basic two integer addition problems. So far the main menu is created. It has a New Game button which launches my GameActivity and it runs just fine for one math problem. However, after the user inputs their answer to the simple math problem, I would like to be able to continue on to another math problem once the user had answered the current problem and the method would return a correct/incorrect value. Initially I thought of doing something like a basic FOR loop from within the GameActivity :
for(int i = 0; i < 10; i++){ gameMethod(); }
gameMethod() is a JAVA method that simply generates 2 random numbers, adds them to get the correct answer and then prompts the user using an EditText field to type in their guess. It displays the random numbers and answer using TextView boxes created in an XML layout file.
Each call to the gameMethod would, at least I think, just re-input the randomized numbers into the TextView fields displayed on the screen each iteration. I really don't care what the previous numbers were so I figured I would just overwrite them. I wan't able to get the code to do that though. I put in a Log.d() statement or two and found that the FOR loop was in fact running through correctly 10 times, but it was not waiting for user input before firing off its next gameMethod().
In doing some looking around, I found the startActivityForResult() and wondered if this was a more appropriate way of approaching this. So in this way, I foresee having three Activities, the Main menu which calls the GameActivity which would then iterate through, say 10 times, each iteration calling yet another activity GameScreenActivity which would actually put the numbers on the screen, read in user input and then return 1 for a correct answer and 0 for an incorrect answer. So far in reading up on StarActivityForResult() I'm getting somewhat confused by the process and wondered if this was even a plausible path to be exploring.
Again, I'm very new at this Android programming and appreciate any and all help that I can get.
Thank you.
Sorry for not including the gameMethod() initially, I've added it below.
// Create and initialize arrays of integers
int[] a = {0,1,2,3,4,5,6,7,8,9,10};
int[] b = {0,1,2,3,4,5,6,7,8,9,10};
// Creates random number generator
Random randy = new Random();
// Generates two random values to add
int r1 = randy.nextInt(10);
int r2 = randy.nextInt(10);
// Calculates correct answer
int an = a[r1] + a[r2];
// Displays 1st number
TextView number1 = (TextView) findViewById(R.id.firstNumber);
number1.setText(Integer.toString(a[r1]));
// Displays 2nd number
TextView number2 = (TextView) findViewById(R.id.secondNumber);
number2.setText(Integer.toString(b[r2]));
// Displays correct answer
TextView answer1 = (TextView) findViewById(R.id.answerNumber);
//hide answer until user puts in theirs
answer1.setVisibility(View.INVISIBLE);
answer1.setText(Integer.toString(an));
//hide the answer place holder value
TextView uAnswerDisplay = (TextView) findViewById(R.id.userAnswerNumber);
uAnswerDisplay.setVisibility(View.INVISIBLE);
//Get the EditText field that the user will input their answer to
EditText inputText = (EditText) findViewById(R.id.userInput);
//set up a listener to run once the ENTER key is hit after their answer has been entered
inputText.setOnKeyListener(new EditText.OnKeyListener(){
public boolean onKey(View v, int keyCode, KeyEvent event){
//only go on the ENTER key when pressed DOWN
if((event.getAction() == KeyEvent.ACTION_DOWN) &&
(keyCode == KeyEvent.KEYCODE_ENTER)){
EditText innerInputText = (EditText) findViewById(R.id.userInput); //get the EditText box reference
TextView innerUAnswerDisplay = (TextView) findViewById(R.id.userAnswerNumber); //get the TextView box that the answer will go in
String inputString = innerInputText.getText().toString(); //capture the user's input
int uAnswer = Integer.parseInt(inputString); //parse user answer to an integer
int cAnswer = Integer.parseInt((((TextView) findViewById(R.id.answerNumber)).getText()).toString());
innerUAnswerDisplay.setText(Integer.toString(uAnswer)); //display the string after converting from integer
//change colors of text based on correctness
if (uAnswer == cAnswer){ innerUAnswerDisplay.setTextColor(Color.GREEN); } //green for correct
else { innerUAnswerDisplay.setTextColor(Color.RED); } //red for incorrect
innerUAnswerDisplay.setVisibility(View.VISIBLE); //make the user input answer visible
TextView innerAnswer1 = (TextView) findViewById(R.id.answerNumber);
innerAnswer1.setVisibility(View.VISIBLE); //hide answer until user puts in theirs
} //end of if
return false; //return false
} //end of onKey
}); //end of setOnKeyListener
Sorry for all the edits, I couldn't get the edits to include the code and post correctly so I broke it up into chunks and added a little at a time.

From what you say, I'd consider two ways of letting the user answer questions:
have an onclick listener on the input EditText that triggers a new loop;
have a dialog activity that gets started in the beginning of the loop, which prompts the user for a new answer, your game activity would receive the answer via its onActivityResult.