Problem when casting variables in Java (Android): NumberFormatException: For input string: ""

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Problem when casting variables in Java (Android): NumberFormatException: For input string: ""

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#1 by (4 votes)
#2 by (1 votes)
#3 by (0 votes)

2

I was starting with Android, but when doing something that in Java has never given me problems and launching it in an Android App, I have missed a lot of errors when executing it, because compiling does it without problems.

The exercise I try to perform is a very simple calculator, I take two values from two different TextViews, add them and show 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 was closed when emulating it with the casteos, as you can see in the code.

I do not know if in Android the casteos can not be done, because the TextView returns "Char Sequences", but passing them to String does not give 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)

java android

asked by Pablo Pérez-Aradros 09.10.2016 в 01:22

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3 answers

1

Internal operations with integers must be enclosed in parentheses, as in Java. you must also declare your components in the onCreate 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) ));


 }

answered by 09.10.2016 в 01:48

0

Add this well 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));
}}

answered by 09.10.2016 в 08:33

The program skips the IF and goes straight to the ELSE [closed] Delete Row according to text in a Java Txt

score 4 · Accepted Answer

You have this problem when calling the onClick() method with 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;
 }

Based on the previous 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.