Im trying to make an app that converts the value that the user inputs into the editText. But when I run the program it shuts down and won't show the input the user inputted or the input divided by 2. I tried putting btCalculate.setText("Hi" + convert); and that displayed hi and the user input but when I get rid of the string and just have convert it shuts down. Can someone help me or make sense of what I'm trying to do?
Here is my code:
btCalculate.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v) {
int convert = Integer.parseInt(editText.getText().toString());
if (btCopper1.isPressed());
btCopper2.isPressed();{
btCalculate.setText(convert);
}
if (btCopper1.isPressed());
btSilver2.isPressed();
btCalculate.setText(convert/2);
}
});
}
}
Is a good practice to code as simple as possible. It will be easier to found and fix issues.
Exemple:
if(expression == true) {
// do this instructions
}
In your code, start fixing the {}, making it easier to understand:
if (btCopper1.isPressed()) {
btCalculate.setText(convert);
}
Think about it, it seems the error is in your logic.
Related
I am pulling data from a Website to my application. I want the TextView to display the result I want from the website immediately as the user launches the app. However html codes make the result look weird some times and I am trying to correct it. I have the codes that will do what I am trying to do. I just can't figure out how to get it to do everything automatically at app launch. It needs to pull the code from the website and if it receives any special symbols within the string I want it to correct it as soon as the app launches. Here is an example...
TextView tv = (TextView) findViewbyId(R.id.my_textview_result);
tv.setText(resultFromWebsite);
The result it pulled: You u0026 Me Forever!
The result I want: You & Me Forever! My app should correct that.
Here is my correction code...
public void symbolTextFilter(TextView myTv) {
String getData = tv.getText().toString();
if (getData.contains("u0026") {
String replace = getData.replace("u0026", "&");
myTv.setText(replace);
}
Now on my onCreate Method
TextView tv = (TextView) findViewbyId(R.id.my_textview_result);
tv.setText(resultFromWebsite);
symbolTextFilter(tv);
It will not make that correction. It will if I put the symbolTextFilter(tv) in a onClickListener button though. I don't want to assign the correction in a button. I want it automatically. My guess is, everything that I have in the onCreate is happening too fast for corrections to be made. How do I fix that? Thanks in advance!
Try this:
tv.setText(symbolTextFilter(resultFromWebsite))
You should use the method symbolTextFilter to handle the string only:
public void symbolTextFilter(String input) {
if (input.contains("u0026") {
return input.replace("u0026", "&");
} else {
return input
}
Nevermind, I got it! I'm not sure where the "\" came from because it wasn't in the original string that it pulled before the correction. I fixed it with this...
public String symbolTextFilter(String input) {
if (input.contains("u0026") {
return input.replace("\\" + "u0026", "&");
} else {
return input
}
I have to do a little program based in a shop, I have to add new clients to the shop customer collection, new items to the shop stock, edit them etc, so I use user input(scanner) to create this new objects. I have all the methods I need for this already without exceptions.
I would like some simple java exception handling for when the user introduces a string were he is supposed to enter a integer or viceversa.
For example if I'm executing a method to create a item for the shop and when I ask the user to introduce the stock(integer) the user types hello instead of a number the program crashes, I would like to handle the exception, show a error message, don't create the object and relaunch the item creation method from the beggining(or relaunch the submenu it was right before)
should I use try and catch? the method in try, when it fails catch throws message of error and relaunches the item creation menu? How should i do this? I've been searching and found a interesting method for integers here:
Exception Handling for no user input in Java
The problem is I don't know how I could handle possible exceptions for when introducing the ID for the user(which would be a string composed of 8 numbers and a letter like for example: 13234354A, so how could I show a error if a user introduces "sjadsjasdj" as a ID instead of something sort of realistic ) or some other things like handling exceptions for a few enum or boolean variables I use when creating this objects.
I've been looking in this site and searching google but I haven't found what I need or are more complex than what I understand with my little knowledge, also English is not my native language so my searches may be a little off.
Thanks for your time!
When you are reading the input just read in the the entire ID 123A for example and verify that each character is valid using for example Character.isDigit() and Character.isLetter(). With a 4 letter case
import java.util.Scanner;
public class Test {
public static void main(String[]args) {
boolean flag = false;
Scanner kb = new Scanner(System.in);
while(!flag) {
String id = kb.next();//To get the next word
flag = true;//by default its assumed to be valid input
if(id.length() == 4) {
for(int i = 0; i < 3; i++) {
if(!Character.isDigit(id.charAt(i))) {
flag = false;
}
}
if(!Character.isLetter(id.charAt(3))) {
flag = false;
}
}
else {
flag = false;
}
System.out.println("ID is "+ (flag == true?"Valid":"Invalid"));
}
}
}
Output
1234
ID is Invalid
123A
ID is Valid
You could throw your own error at the end if you want or just loop back to the beginning to take a new input.
I have a registration page where the user has to enter personal information about themselves, if something entered is invalid then error notifications should pop up
if (!PhoneNumber.startsWith("055") || !PhoneNumber.startsWith("050") || !PhoneNumber.startsWith("056") || !PhoneNumber.startsWith("052")) {
// does not match
contact_number.setError("Please enter a valid phone number");
return;
}
if (TextUtils.isEmpty(password) )
{
VendorRegPassword.setError("Please enter your password");
return;
}
else if (password.length() < 6)
{
VendorRegPassword.setError("Please use more than 6 characters");
return;
}
if (TextUtils.isEmpty(email) || !email.contains("#") )
{
VendorRegEmail.setError("Please enter a valid email address");
}
Independently they work on their own but when put together it does not work properly, also the phone number error does not work properly, can somebody help me with this?
The other answer is correct; the return statement simply prevents all checks to be executed. And in this case, you want all validations to take place, as each validation has a different way of informing the user about the problem.
Beyond that: from a "clean code" perspective you should be careful to simply stuff all validations into the same poor method. Instead: structure your code so that it clearly expresses what is going on, like:
private void validateAll(PhoneNumber number, Email email, Password password) {
validatePhoneNumber(number);
validateEmail(email);
...
and separate helpers like
private void validatePhoneNumber(number) {
boolean validPrefix = false;
for (String validPrefix : PREFEIXES) {
if (phoneNumber.startsWith(validPrefix) {
validPrefix = true;
}
}
if (!validPrefix) {
contact_number.setError("Please enter a valid phone number");
}
}
for example. And please note - I fixed another bad practice (your idea to simply hard-code all valid prefixes). You always want to put such information into some constant set/list; so that you have exactly one place in your code that knows what those prefixes are.
They are not working together properly because you are returning from the method in if or else ifconditions. Remove return statements from if and else. Because return will terminate the execution of method, so further code will never be executed due to return.
They are working separately because, there is no need to execute further conditions (no further conditions at all), so returning from method seems correct solution.
I am working on a program that allows me to move a pen, making a mark on a canvas. At the moment, I have a method called convertToInteger in class "MyInput" (which in the class with my methods I've referred to as "reader"), which converts a string into an integer.
public int convertToInteger(String word)
{
return Integer.parseInt(word);
}
I've then tied this into my method, converting a string input into an integer.
case "move":
int distance = reader.convertToInteger(command.get(1));
brush.move(distance);
break;
Thus, in my program I can type "move 100" and the brush move 100 pixels. The code, in its current state, crashes with an exception error if I tried typing a non-integer; e.g. "move here".
In "MyInput" class, I created a boolean method that checks to see if it's a integer or not using 'try' and 'catch':
public boolean isAnInteger(String word)
{
boolean ok;
try {
Integer.parseInt(word);
ok = true;
}
catch(NumberFormatException ex) {
// Non-integer string.
ok = false;
}
return ok;
}
Then tried implementing it in my code:
case "move":
int distance = reader.convertToInteger(command.get(1));
if (reader.isAnInteger(command.get(1)) == true){
brush.move(distance);
}
else {
printError();
}
break;
When I run the code and type something like "move here" in the terminal, it throws an exception so clearly its bypassing my code - but typing "move 100" or any other valid integer works.
Any suggestions? Thanks in advance.
Your instructions are in the wrong order. Your are attempting to parse, then checking if it can be parsed. You should really check first, then try to parse.
This is an assignment i have to complete.
Can someone lead me in the right direction?
The program compiles but wont run correctly.
The error is InputMissmatch exception.
The error you are getting means that you are trying to use some kind of data as another one, in your case, you are probably trying to use a String as a float.
When using any of the next methods in the Scanner class you should first be sure that there's an appropiate input from the user.
In order to do so, you need to use the has methods.
Your problem is that you are not checking wether the input is a correct float or not before using your Scanner.nextFloat();
You should do something like this:
if (hope.hasNextFloat())
{
// Code to execute when you have a proper float,
// which you can retrieve with hope.nextFloat()
}
else
{
// Code to execute when the user input is not a float
// Here you should treat it properly, maybe asking for new input
}
That should be enough to point you in the right direction.
Also, check the Scanner api documentation for further details.
EDIT
Also, you are asking the user to input characters (or strings): "A", "B", etc..., but you are trying to compare them with a float. That's wrong, you should compare them with a string or character, like this:
if (hope.hasNextString())
{
if (hope.nextString().equals("A"))
{
// Code for option "A"
}
else if (hope.nextString().equals("B"))
{
// Code for option "B"
}
else ...
}
You could use a switch there, but it seems that you are not yet very fammiliar with java, so I'll leave it for another time.
Your problem is that you are entering a letter into a float field.
In your program you're asking the user to enter a float:
A = hope.nextFloat();
But if you enter the letter "A", you're going to get an exception because "A" is not a float, it's a string.
A simpler way to solve your problem is instead of having all the choices fields, you just read the input the user enters from the scanner like:
String choice = hope.next();
Next in the if statement, you check if the value from the string choice is equal to a specific letter, for example
if (choice.equals("A")) {
number4 = (number1 + number2 + number3);
System.out.printf("Your results are:" + (number4));
}
And you can do the same thing for the other choices you have.