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);
}
Related
Hello I'm trying to make an app that gives you 2 random numbers and the user has to add the 2 random numbers, so my error is that that the random numbers are widgets not integers,
I have tried hundreds of explinations but nothing is working.
public void action(View v){
num1.setText(String.valueOf(randNum1.nextInt(10)));
num2.setText(String.valueOf(randNum2.nextInt(10)));
userAnswer.getText();
if (num1 + num2){
}
}
and this is the error:
bad operand types for binary operator '+' first type: TextView second
type: TextView
The problem you have is well described by the error you are receiving.
From the code snippet you have provided, I am guessing num1 and num2 are references to textview objects.
You CANNOT perform addition on the textview objects themselves, but rather on their content.
So, what you are trying to achieve is this:
public void action(View v){
num1.setText(String.valueOf(randNum1.nextInt(10)));
num2.setText(String.valueOf(randNum2.nextInt(10)));
userAnswer.getText();
String num1String = num1.getText().toString();
String num2String = num2.getText().toString();
int firstNumber = Integer.parseInt(num1String);
int secondNumber = Integer.parseInt(num2String);
if (firstNumber + secondNumber){
// YOUR LOGIC
}
}
Or better yet, you could save the generated random numbers to variables and use them later, like so:
public void action(View v){
int randomNumberOne = randNum1.nextInt(10);
int randomNumberTwo = randNum2.nextInt(10);
num1.setText(String.valueOf(randomNumberOne));
num2.setText(String.valueOf(randomNumberTwo));
userAnswer.getText();
if (randomNumberOne + randomNumberTwo){
// YOUR LOGIC
}
}
You can follow the below steps. i assume randNum1 and randNum2 is random number and num1 and num2 is TextView.
public void action(View v){
num1.setText(String.valueOf(randNum1.nextInt(10)));
num2.setText(String.valueOf(randNum2.nextInt(10)));
userAnswer.getText();
int randNumber1 = Integer.parseInt(num1.getText().toString());
int randNumber2 = Integer.parseInt(num2.getText().toString());
if (randNumber1 + randNumber2 ){
//your logic write here
}else{}
}
I have a simple screen with two EditText Boxes and 1 button. I want users to be able to enter various integers into the boxes and the program will perform different operations based on the specific number entered into the box. I'm trying to have them only enter one number at a time but the code wont seem to execute unless both boxes have something in them. And I'm having the if statements check for nulls on the respective boxes before executing to determine which piece of code to execute.
public void button(View view) {
double x, y;
EditText freq1 = findViewById(R.id.freq1);
EditText freq2 = findViewById(R.id.freq2);
TextView str1 = findViewById(R.id.freqanswer);
TextView str2 = findViewById(R.id.injVolt);
TextView error1 = findViewById(R.id.error1);
String strf1, strf2;
strf1 = freq1.getText().toString();
strf2 = freq2.getText().toString();
try {
f1 = Double.parseDouble(strf1);
f2 = Double.parseDouble(strf2);
if ((f1 >= 225) & (f1 <= 312) & (strf1.isEmpty())) {
x = f1 + 20.6;
y = x / 4;
str1.setText(String.format("%.3f", y));
}
}
catch (Exception e){
error1.setText("splat");
}
finally {
InputMethodManager input = (InputMethodManager)
getSystemService(Context.INPUT_METHOD_SERVICE);
input.hideSoftInputFromWindow(getCurrentFocus().getWindowToken(), InputMethodManager.HIDE_NOT_ALWAYS);
}
I included only 1 formula for the sake of brevity, but I'm going to be putting about 6 if statements, checking for number ranges and nulls on this button and I just need it to run with one box being empty. I know the formula works by having play with various outputs, it just won't run with the strf1.isEmpty(). Something has to be in that second box for the formula to execute.
Would appreciate any help
I think you should check before assigning:
if(strf1.isEmpty()){strf1="0";} //if assuming zero does not change the formula's output
if(strf2.isEmpty()){strf2="0";}
f1 = Double.parseDouble(strf1);
f2 = Double.parseDouble(strf2);
this way you are assured of a default value.
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])
Can someone tell me, why my app keep getting crashed. Cannot find solution for this and why its happening when TextField is empty
public void contanges(View v){
TextView wynik = (TextView)findViewById(R.id.wynik);
double b = Double.parseDouble(wynik.getText().toString());
if(wynik.getText().length() == 0 ){
wynik.setText("Bad opperand!");
}else if(b % 180 ==0){
wynik.setText("Bad opperand!");
}else {
BigDecimal a = new BigDecimal(wynik.getText().toString());
BigDecimal result = new BigDecimal("0");
result = new BigDecimal(1 / Math.tan(Math.toRadians(a.doubleValue())));
wynik.setText(result.toString());
}
}
Don't check for 0 length. Instead use TextTextUtils.isEmpty(). This way, you can check if the TextView actually has text to parse before you parse it.
TextView wynik = (TextView)findViewById(R.id.wynik);
if (TextUtils.isEmpty(wynik.toString().trim())) {
// Do your stuff here
}
Your error is in this line :
Double.parseDouble(wynik.getText().toString());
You are trying to parse an empty string to double which is not valid.
Add this line before that
if(wynik.getText().length() > 0){
Double.parseDouble(wynik.getText().toString());
}
Also it depends what you are passing as a textview value because if it is not been able to parse than also it will throw an exception
Try passing a double value to edittext when not empty.
So, I am messing around with java/android programming and right now I am trying to make a really basic calculator. I am hung up on this issue though. This is the code I have right now for getting the number thats in the textview and making it an int
CharSequence value1 = getText(R.id.textView);
int num1 = Integer.parseInt(value1.toString());
And from what I can tell it is the second line that is causing the error, but im not sure why it is doing that. It is compiling fine, but when it tries to run this part of the program it crashes my app. And the only thing thats in the textview is numbers
Any advice?
I can also provide more of my code if necessary
You can read on the usage of TextView.
How to declare it:
TextView tv;
Initialize it:
tv = (TextView) findViewById(R.id.textView);
or:
tv = new TextView(MyActivity.this);
or, if you are inflating a layout,
tv = (TextView) inflatedView.findViewById(R.id.textView);
To set a string to tv, use tv.setText(some_string) or tv.setText("this_string"). If you need to set an integer value, use tv.setText("" + 5) as setText() is an overloaded method that can handle string and int arguments.
To get a value from tv use tv.getText().
Always check if the parser can handle the possible values that textView.getText().toString() can supply. A NumberFormatException is thrown if you try to parse an empty string(""). Or, if you try to parse ..
String tvValue = tv.getText().toString();
if (!tvValue.equals("") && !tvValue.equals(......)) {
int num1 = Integer.parseInt(tvValue);
}
TextView tv = (TextView)findviewbyID(R.id.textView);
int num = Integer.valueOf(tv.getText().toString());
Here is the kotlin version :
var value = textview.text.toString().toIntOrNull() ?: 0
TextView tv = (TextView)findviewbyID(R.id.textView);
String text = tv.getText().toString();
int n;
if(text.matches("\\d+")) //check if only digits. Could also be text.matches("[0-9]+")
{
n = Integer.parseInt(text);
}
else
{
System.out.println("not a valid number");
}
this code actually works better:
//this code to increment the value in the text view by 1
TextView quantityTextView = (TextView)findViewById(R.id.quantity_text_view);
CharSequence v1=quantityTextView.getText();
int q=Integer.parseInt(v1.toString());
q+=1;
quantityTextView.setText(q +"");
//I hope u like this