不幸的是，应用在Android的AVD上停止了

Question

I am trying to build a simple calculator app having:

3 EditText for 2 numbers and for result.

6 Buttons + - * / = clear.

When running this app on the AVD it is flashing "Unfortunately app stopped!"

That means there would be some sort of exception being encountered but i am not able to understand what.

When i checked on Logcat, there was something "EditText cannot be typecast to String" .

Please help me out to debug this exception.

package com.example.calci_ver1;

import android.os.Bundle;
import android.app.Activity;
import android.view.*;
import android.widget.*;

public class MainActivity extends Activity {

Button badd, bsub, bmul, bdiv, beq, bclr;
static EditText et1, et2, et3;

static int i=0, n1, n2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    badd = (Button)findViewById(R.id.button1);
    bsub = (Button)findViewById(R.id.button2);
    bmul = (Button)findViewById(R.id.button3);
    bdiv = (Button)findViewById(R.id.button4);
    beq = (Button)findViewById(R.id.button5);
    bclr = (Button)findViewById(R.id.button6);

    et1 = (EditText)findViewById(R.id.editText1);
    et2 = (EditText)findViewById(R.id.editText2);
    et3 = (EditText)findViewById(R.id.editText3);

    badd.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            i = 1;
        }
    });

    bsub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            i = 2;
        }
    });

    bmul.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            i = 3;
        }
    });

    bdiv.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            i = 4;
        }
    });

    beq.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub


            String s1, s2;

            s1 = et1.getText().toString();
            s2 = et2.getText().toString();

            n1 = Integer.parseInt(s1);
            n2 = Integer.parseInt(s2);

            calculation();

            i = 0;
        }
    });

    bclr.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            et1.setText("");
            et2.setText("");
            et3.setText("");
        }
    });
}

public static void calculation() {

    switch(i)
    {
        case 1: et3.setText(n1+n2);
        break;

        case 2: et3.setText(n1-n2);
        break;

        case 3: et3.setText(n1*n2);
        break;

        case 4: et3.setText(n1/n2);
        break;
    }
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

}

Answer 1

I found problem that may cause application crash..

Remove the code what you written in calculation() method.

Actually your problem is that you pass the result of two numbers its give the numeric value and android has method on edittext setText(int resid) so its means its searching text of resid in string.xml which is not present. So its crashing your application. So you need to convert the result in String .

Use this.

public static void calculation() {

    switch(i)
    {
        double result = 0;
        case 1: 
            result = n1+n2;
            et3.setText(String.valueOf(result));
        break;

        case 2: 
            result = n1-n2;
            et3.setText(String.valueOf(result));
        break;

        case 3: 
            result = n1*n2;
            et3.setText(String.valueOf(result));
        break;

        case 4: 
            result = n1/n2;
            et3.setText(String.valueOf(result));
        break;
    }
}

Answer 2

I've found AVD occasionally throws those errors when you call a .setText() command, I have never encountered the error on a real life device though, so just reinstall the program on your AVD. I'll look around a bit because I had this problem and I know I have seen it on SO before.

Answer 3

Use android:inputType="number" to force it to be numeric.

Convert the resulting string into an integer (eg, Integer.parseInt(myEditText.getText().toString())).