Android ADT: Extending android.widget.EditText - runtime class cast exception

Question

I have a simple app which will have a bunch of EditTexts taking numeric values, and various calculations between them. Like a unit conversion tool.

So I've defined CalcField as a subclass of EditText to serve as a field that contains only float values, with some extra methods, for example:

package com.example.ex1;
import android.content.Context;
import android.widget.*;
public class CalcField extends EditText {

// no idea why this is needed.  without it i'm told an explicit constructor needed.
public CalcField(Context c) {
    super(c);
}

public void setValue(float d) {
    setText(String.valueOf(d));
}
public float getValue() {
    return Float.valueOf(getText().toString());
}
}

==

In my layout I have a field X defined like this:

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

And in my main activity I try to grab this field from my layout, like this:

    CalcField fieldX = (CalcField) findViewById(R.id.X);

Which gives a class cast exception that I don't understand:

07-16 21:23:49.049: E/AndroidRuntime(1429): FATAL EXCEPTION: main
07-16 21:23:49.049: E/AndroidRuntime(1429): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ex1/com.example.ex1.MainActivity}: java.lang.ClassCastException: android.widget.EditText cannot be cast to com.example.ex1.CalcField
07-16 21:23:49.049: E/AndroidRuntime(1429):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)

Can anyone tell me why I can't do this simple typecast?

Thanks in advance

Andro Selva · Accepted Answer · 2012-07-16 13:27:21Z

4

Change this

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

to

        <com.example.ex1.CalcField
        android:id="@+id/X"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="numberDecimal" />

answered Jul 16, 2012 at 13:27

Andro Selva

54.4k53 gold badges195 silver badges244 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

AMerle Over a year ago

Yes, add add the constructor (Context, AttributeSet) I think.

user1526826 Over a year ago

Thanks a lot, I'll try that. Any suggestion for the best place/way to learn about this stuff?

Collectives™ on Stack Overflow

Android ADT: Extending android.widget.EditText - runtime class cast exception

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related