Develop Reference

How to validate decimal input not allowing alone "." and empty field?

I'm writing a calculator on Android Studio, in Java, and the app crashes if the user call the result with a dot "." alone or let the EditText field in blank.
I'm looking for a solution for not allowing these two conditions happening, together or individualy, in each of the three fields.
I've already tried TextWatcher and if/else but without success.
The .xml file where the editText field are designed is already set for decimalNumber.
I've already tried this:
if(myfieldhere.getText().toString().equals(".")){myfieldhere.setText("0");}
For each "valor line" and else for the "finalresult" line if everything is fine. Both inside the setOnClickListener block. This is my code:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.peso_layout);
result = findViewById(R.id.layresult);
conc = findViewById(R.id.layconc);
dose = findViewById(R.id.laydose);
peso = findViewById(R.id.laypeso);
calc = findViewById(R.id.laycalcpeso);
calc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
float valor1 = Float.parseFloat(peso.getText().toString());
float valor2 = Float.parseFloat(conc.getText().toString());
float valor3 = Float.parseFloat(dose.getText().toString());
float finalresult = valor1 * valor2 * valor3;
result.setText("The result is: " + finalresult);
}
});
}
The ideal output should be the app not crashing if these two conditions happen and sending an error message to the user that input is invalid.
What i'm receiving is the app crashing.
Thank you very much. I'm very beginner in Java and I'm few days struggling with this.

Dear Friend, Your directly trying to convert string input into float and then after your check value but do your code like Below.
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
EditText edt1,edt2;
TextView txtans;
Button btnsum;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edt1=findViewById(R.id.edt1);
edt2=findViewById(R.id.edt2);
txtans=findViewById(R.id.txtans);
btnsum=findViewById(R.id.btnsum);
btnsum.setOnClickListener(this);
}
#Override
public void onClick(View v) {
if(v.getId()==R.id.btnsum){
float n1,n2;
String value1=edt1.getText().toString();
String value2=edt2.getText().toString();
if(value1.equals("") || value1.equals(".")){
n1=0;
}else {
n1= Float.parseFloat(value1);
}
if(value2.equals("")|| value2.equals(".")){
n2=0;
}else{
n2= Float.parseFloat(value2);
}
float ans=n1+n2;
txtans.setText(ans+"");
}
}
}
See In above code, First get value from edittext and then check wheather it contain null or "." inside it. if it contains then store 0.0 value in some variable. then after make sum and display in textbox.

calc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String myvalor = myfieldhere.getText().toString();
if(myvalor.equals(".") || myvalor.isEmpty())
{
// toast error : incorrect value
return;
}
try
{
float valor1 = Float.parseFloat(peso.getText().toString());
float valor2 = Float.parseFloat(conc.getText().toString());
float valor3 = Float.parseFloat(dose.getText().toString());
float finalresult = valor1 * valor2 * valor3;
result.setText("The result is: " + finalresult);
}
catch(Exception exp){// toast with exp.toString() as message}
}
});

use TextUtils for check empty String its better
if(TextUtils.isEmpty(peso.getText().toString())||
TextUtils.isEmpty(conc.getText().toString())||
TextUtils.isEmpty(dose.getText().toString())){
return;
}

How do i make a button take text from an edittext and compare it to a random number?

I'm trying to make my button compare the number in the edit text to the random number I'm generating and make a toast if they're the same. the code runs but no matter what i set the bound to the number in the edit text never equals the random number.
Here is my code
Button submit;
EditText etcode;
Random random = new Random();
String generatedPassword = String.format(String.valueOf(random.nextInt(1)));
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
mFlower = findViewById(R.id.ivImage);
mDescription = findViewById(R.id.tvDescription);
submit = (Button) findViewById(R.id.btn_submit);
etcode = findViewById(R.id.et_code);
Bundle mBundle = getIntent().getExtras();
submit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (etcode.getText().toString().equals(generatedPassword)){
Toast.makeText(getApplicationContext(), "CONGRATS", Toast.LENGTH_SHORT).show();
}
else {
Toast.makeText(getApplicationContext(), "TRY AGAIN", Toast.LENGTH_SHORT).show();
}
}
});

Change this line
String generatedPassword = String.format(String.valueOf(random.nextInt(1)));
Because generatePassword is always 0 . That's why it works with zero.
random.nextInt(1);
Above code will always generate number less than 1.
You should change it to any other number.
Suppose you writerandom.nextInt(5);
Then above line will generate number between 0 to 5 means it can be 0,1,2,3,4.
Check this link https://www.geeksforgeeks.org/java-util-random-nextint-java/

Android app crashes when trying to use variable [duplicate]

#Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.screenlocked);
//Retrieve stored ID
final String STORAGE = "Storage";
SharedPreferences unique = getSharedPreferences(STORAGE, 0);
LoginID = unique.getString("identifier", "");
//Retrieve stored phone number
final String phoneNumber = unique.getString("PhoneNumber", "");
phoneView = (TextView) findViewById(R.id.phone);
phoneView.setText(phoneNumber.toString());
//Retrieve user input
input = (EditText) findViewById(R.id.editText1);
userInput = input.getText().toString();
//Set login button
login = (Button) findViewById(R.id.login);
login.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
compareID();
}
});
}
public void compareID(){
if (userInput.equals(LoginID)){
//phone screen unlocked
//continue
Toast.makeText(ScreenLockActivity.this, "Success!", Toast.LENGTH_SHORT).show();
}
else{
count += 1;
input.setText("");
Toast.makeText(ScreenLockActivity.this, count, Toast.LENGTH_SHORT).show();
}
}
I am developing a login activity and I would like to record down how many times the user tried to login, so every time there is a login attempt the count will increment by one... but when i run the activity, this error appears in my logcat:
android.content.res.Resources$NotFoundException: String resource ID #0x1,
Can someone help me solve this problem?

Here is your mistake:
Toast.makeText(ScreenLockActivity.this, count, Toast.LENGTH_SHORT).show();
the makeText you are trying to invoke here, is the makeText that takes as second parameter a resId. See here for more info. Since you want to print the count value, you have to convert it in a String.
String value = String.valueOf(count);
Toast.makeText(ScreenLockActivity.this, value, Toast.LENGTH_SHORT).show();

This line should be inside onClick() or compareID():
userInput = input.getText().toString();

Popup Error on blank EditText

How do I require the user to input data into an EditText and not allow the application to proceed until the EditText is populated?
Right now, my application continues to progress even after the user acknowledges the error message stating the EditText is empty and is required.
private final static int EMPTY_TEXT_ALERT = 0;
protected Dialog onCreateDialog(int id) {
switch(id) {
case EMPTY_TEXT_ALERT: {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("oops!!")
.setPositiveButton("ok", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
return builder.create();
}
}
return null;
}
public void sends(View v) {
DatePicker datePicker = (DatePicker) findViewById(R.id.datePicker1);
int year = datePicker.getYear();
int month = datePicker.getMonth();
int day = datePicker.getDayOfMonth();
final EditText phone = (EditText) findViewById(R.id.editText2);
final EditText nameplate = (EditText) findViewById(R.id.editText3);
final EditText issue = (EditText) findViewById(R.id.editText4);
String ph = phone.getText().toString();
if(ph.trim().equals("")) {
// text is empty
showDialog(EMPTY_TEXT_ALERT);
}
String np = nameplate.getText().toString();
if(np.trim().equals("")) {
// text is empty
showDialog(EMPTY_TEXT_ALERT);
}
String i = issue.getText().toString();
if(i.trim().equals("")) {
// text is empty
showDialog(EMPTY_TEXT_ALERT);
}
else
{StringBuilder s= new StringBuilder(100);
s.append(year);
s.append(". ");
s.append(month+1);// month starts from 0 in this
s.append(". ");
s.append(day);
s.append(". ");
s.append(". ");
s.append(ph);
s.append(". ");
s.append(np);
s.append(". ");
s.append(i);
String st=s.toString();
Intent emailIntentt = new Intent(android.content.Intent.ACTION_SEND);
emailIntentt.setType("plain/text");
String aEmailList[] = { "shreyas.t#gmail.com" };
emailIntentt.putExtra(android.content.Intent.EXTRA_EMAIL, aEmailList);
emailIntentt.putExtra(android.content.Intent.EXTRA_SUBJECT, "Feedback");
emailIntentt.putExtra(android.content.Intent.EXTRA_TEXT, st);
startActivity(emailIntentt);
}
}}

You can add return statement after showing the dialog as shown below.
if(i.trim().equals("")) {
// text is empty
showDialog(EMPTY_TEXT_ALERT);
return;
}
It would be better to use Toast messages than showDialog though.

I don't know how you are calling your sends() method, but after any empty error you can just add a return statement immediately after the showDialog(). It means that somehow the sends() method has to get re-invoked via the UI after the user has put in text.
If your sends() method is called from a button via onClick(), then it means the user will see dialog with error, input some text and then, hit the button to send again.

Shreyas Tallani
how to validate the phone number... enters more than 10 digits the
error message should be displayed
If you are just wanting to test the length of the String, just get the String and compare the length to the max length of 10.
In your validate(...) method do something similar to the following:
String ph = phone.getText().toString();
if(ph.trim().equals("")) {
showDialog(EMPTY_TEXT_ALERT);
} else if (ph.length() > 10) {
showDialog(TEXT_TOO_LONG_ALERT);
}
You could also make your EditText only allow numeric values. This would help you validate the numbers. You can do this in the xml file or in code.
xml
android:inputType="TYPE_NUMBER_VARIATION_NORMAL"
code
EditText.setInputType(InputType.TYPE_NUMBER_VARIATION_NORMAL);
First thing you can do, is add a validate(...) method. Inside validate(...), you need to validate all the fields and if anything is left blank then show the error message and stop app progression.
If all the fields are fine, then call your send method. And send(...) should only be sending your data, not checking validation.

Caught in an infinite loop

I'm trying to perform a check on some information in a database. If i run the following code without it being in a loop it runs fine, but only checking the first row, what i need it to do is to check the names and dates for each row.
If i understand the while loop correctly it would move my cursor to the next row then just run the code again. Can anyone see why this is looping until my program crashes?
while (cursor.moveToNext()) {
String titlefromdb = cursor.getString(3);
if (strTitle.equals(titlefromdb)&& cursor.getString(1).equals(dateselforap)) {
Log.d("insidematch", "date and title matched");
final Dialog matchdiag = new DialogCW2Organisor.this);
matchdiag.setContentView(R.layout.apptmatch);
matchdiag.setTitle("View/Edit Appointment");
matchdiag.setCancelable(true);
TextView matchtxt = (TextView) matchdiag.findViewById(R.id.matchtxt);
matchtxt.setText("Appointment \""+ titlefromdb + "\" already exists, please choose a different event title");
Button btnmatchok = (Button) matchdiag.findViewById(R.id.btnmatch);
btnmatchok.setOnClickListener(new OnClickListener() {
//on click for cancel button
#Override
public void onClick(View v) {
matchdiag.dismiss();}
});
matchdiag.show();
} else {
addAppt(strTime, strTitle, strDet);
cursor = getAppts();
dialog.dismiss();
}
}

Try moving to the first record before calling moveToNext().
Move your functionality into a do/while loop so you can still grab the first record
if (!cursor.moveToFirst())
return; //nothing to do since the cursor is empty
do
{
String titlefromdb = cursor.getString(3);
if (strTitle.equals(titlefromdb)&& cursor.getString(1).equals(dateselforap)) {
Log.d("insidematch", "date and title matched");
final Dialog matchdiag = new DialogCW2Organisor.this);
matchdiag.setContentView(R.layout.apptmatch);
matchdiag.setTitle("View/Edit Appointment");
matchdiag.setCancelable(true);
TextView matchtxt = (TextView) matchdiag.findViewById(R.id.matchtxt);
matchtxt.setText("Appointment \""+ titlefromdb + "\" already exists, please choose a different event title");
Button btnmatchok = (Button) matchdiag.findViewById(R.id.btnmatch);
btnmatchok.setOnClickListener(new OnClickListener() {
//on click for cancel button
#Override
public void onClick(View v) {
matchdiag.dismiss();
}
});
matchdiag.show();
} else {
addAppt(strTime, strTitle, strDet);
cursor = getAppts();
dialog.dismiss();
}
} while (cursor.moveToNext());

I have also run into the infinite loop problem, which really baffled me as well, since a while !moveToNext() loop should definitely finish.
However, the workaround is to use a for loop over the length of the cursor, and process each cursor.moveToPosition(i).
for (int i = 0; i <= cursorLen; i++) {
if (!cursor.moveToPosition(i)) {
return;
}
// process your cursor
}
I feel like this must be a bug with the Cursor implementation, because a while loop over cursor.moveToNext() should always finish.