Learning Android Java - application fails

Question

I have been trying to learn Java for Android development, so I decided to try to make a simple converter application to learn from. At the moment i have a simple UI and I am trying to convert from Celsius to Fahrenheit. the converter will, when working, convert betweem Celsius, Fahrenheit and Kelvin.

When I click the button that is supposed to run the calculation method, i get the error "Unfortunately, Converter has stopped." Below is my code, I have also included the XML for the view as well.


    package com.michaelmurphy.converter;

    import android.app.Activity;
    import android.os.Bundle;
    import android.widget.EditText;
    import android.widget.Spinner;

    public class Temperature extends Activity {

        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) 
        {

            super.onCreate(savedInstanceState);
            setContentView(R.layout.temperature_view);

            // TODO Auto-generated method stub
        }

        public void tempCalc()
        {
            //define variables
            float value = 0;
            String from = "";//for spinner
            String to = "";//for spinner

            //get entered value
            EditText input = (EditText) findViewById(R.id.editText1);
            //convert to string
            String enteredValue = input.getText().toString();
            //convert string into float
            float num = Float.valueOf(enteredValue);

            //retrieve the from spinner value
            final Spinner fromSpinner = (Spinner) findViewById(R.id.spinner1);
            from = fromSpinner.getSelectedItem().toString();    
            //retrieve the to spinner value
            final Spinner toSpinner = (Spinner) findViewById(R.id.spinner1);
            to = toSpinner.getSelectedItem().toString();

            EditText output = (EditText) findViewById(R.id.textView2);

            /*if(from.equals(to)) //the same conversion type
            {
                //error
            }*/

            if(from.equals("Celcius"))
            {
                if(to.equals("Fahrenheit"))
                {
                    value = celToFar(num);
                } 
                else 
                {
                    //value = celToKel(num);
                }
            }
            else if(from.equals("Fahrenheit"))
            {
                if(to.equals("Celcius"))
                {
                    //value = fahToCel(num);
                } 
                else 
                {
                    //value = fahToKel(num);
                }
            }
            else //kelvin
            {
                if(to.equals("Celcius"))
                {
                    //value = kelToCel(num);
                }
                else 
                {
                    //value = kelToFah(num);
                }
            }

            //set the label to variable value
            String valueStr = Float.toString(value);//cast float to string
            output.setText(valueStr);
        }

        public float celToFar(float cel)
        {
            float fah = cel * 9/5 + 32;
            return fah;
        }

    }

View XML code:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/app_name"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="numberDecimal" >

        <requestFocus />
    </EditText>

    <Spinner
        android:id="@+id/spinner1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:entries="@array/temp_arr" />

    <Spinner
        android:id="@+id/spinner2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:entries="@array/temp_arr" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/convertBtn"
        android:onClick="tempCalc" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceLarge" />

</LinearLayout>

Is anyone able to point out where I am going wrong, I have no idea. Thanks

Well, you posted everything except exception stack, which is key thing to understand issue. Please post stack trace from logcat. — kosa

Raghav Sood Raghav Sood · Accepted Answer · 2013-01-18T21:38:04

Change:

public void tempCalc()

To

public void tempCalc(View v)

Any onClick method expects a View parameter. As you don't pass one, the method signatures don't match, and your app throws an exception.

Learning Android Java - application fails

1 Answers