Problem casting variables in Java: NumberFormatException: For input string: ""
I was starting with Android, but when performing something that in Java has never given me problems and when launching it in an Android App, I have skipped quite a few errors when running it, because compiling does it without problems.
The exercise I'm trying to perform is a very simple calculator, I take two values from two different TextViews, sum them up and display the result on a screen.
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void calcularResultado(View view) {
TextView cuadroNum1, cuadroNum2, resultado;
cuadroNum1 = (TextView) findViewById(R.id.tNum1);
cuadroNum2 = (TextView) findViewById(R.id.tNum2);
resultado = (TextView) findViewById(R.id.resultado);
int num1 = 0, num2 = 0, aux;
num1 = Integer.parseInt(cuadroNum1.getText().toString());
num2 = Integer.parseInt(cuadroNum2.getText().toString());
resultado.setText(String.format(""+ (num1 + num2) ));
}
}
After doing several tests I realized that the application is it closed by emulating it with casteos, as you can see in the code.
I don't know if on Android castings can't be done like this, because TextViews return "Char Sequences", but passing them to String gives no errors until I try to pass them to variables of type int, or if I should use another alternative element to the TextView if I want to work with digits.
Code the error:
--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.pabloperezaradros.calculadora, PID: 2740
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22260)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22260)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NumberFormatException: For input string: ""
at java.lang.Integer.parseInt(Integer.java:533)
at java.lang.Integer.parseInt(Integer.java:556)
at com.pabloperezaradros.calculadora.MainActivity.calcularResultado(MainActivity.java:26)
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5610)
at android.view.View$PerformClick.run(View.java:22260)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
3 answers
You have this problem when calling the method onClick() having the following as the main problem:
Caused by: java.lang.NumberFormatException: For input string: ""
And occurs when you try to convert a non-numeric string value to int, in this case an empty string, "".
You can use a function to first check if the value is numeric and then use Integer.parseInt() to perform the conversion:
public static boolean isNumeric(String valor) {
try {
double d = Double.parseDouble(valor);
} catch(NumberFormatException e) {
return false;
}
return true;
}
En based on the above method we can use a ternary operation to perform the conversion:
int num1 = 0, num2 = 0, aux;
num1 = isNumeric(cuadroNum1.getText().toString())? Integer.parseInt(cuadroNum1.getText().toString()):0 ;
num2 = isNumeric(cuadroNum2.getText().toString())? Integer.parseInt(cuadroNum2.getText().toString()):0 ;
When the value is not numeric the result will be 0, you can define the default value.
Inner operations with integers should be in parentheses, as in Java. you must also declare your components in the onCreate{[2] method]}
TextView cuadroNum1, cuadroNum2, resultado;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cuadroNum1 = (TextView) findViewById(R.id.tNum1);
cuadroNum2 = (TextView) findViewById(R.id.tNum2);
resultado = (TextView) findViewById(R.id.resultado);
}
public void calcularResultado(View view) {
int num1 = 0, num2 = 0, aux;
num1 = Integer.parseInt(cuadroNum1.getText().toString());
num2 = Integer.parseInt(cuadroNum2.getText().toString());
resultado.setText(String.format(""+ (num1 + num2) ));
}
Add this good I'm using 2 EditText, 1 TextView (result) and 1 button
public class ejemplo extends AppCompatActivity {
private EditText editorTexto1, editorTexto2;
private TextView vistaTexto;
private Button boton;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.ejemplo_activity);
editorTexto1 = (EditText)findViewById(R.id.editText1);
editorTexto2 = (EditText)findViewById(R.id.editText1);
vistaTexto = (TextView)findViewById(R.id.textView);
boton = (Button)findViewById(R.id.button);
}
@Override
protected void onResume() {
super.onResume();
boton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
calcularResultado();
}
});
}
public void calcularResultado() {
int num1 = 0, num2 = 0, resultado = 0;
num1 = Integer.parseInt(editorTexto1.getText().toString());
num2 = Integer.parseInt(editorTexto1.getText().toString());
resultado = num1 + num2;
vistaTexto.setText(String.valueOf(resultado));
}}