main java.lang.RuntimeException

Question

I'm new to Android Studios and I had around a week or two with tutorials, although most tutorials are outdated I still try to pursue learning Android Studios. First time asking a question on stackoverflow, anyways I have been trying to create an app that is addition of two numbers. I was suggested to run my app, it failed and gave me a error FATAL EXCEPTION:mainjava.lang.RuntimeException.

My main java file is:

package com.website.addition;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
Button button ;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    button = (Button)findViewById(R.id.button);
}

public void onButtonClick(View v) {
    EditText e1=(EditText)findViewById(R.id.editText);
    EditText e2=(EditText)findViewById(R.id.editText2);
    TextView t1=(TextView)findViewById(R.id.textView2);
    int num1=Integer.parseInt(e1.getText().toString());
    int num2=Integer.parseInt(e2.getText().toString());
    int sum=num1+num2;
    t1.setText(Integer.toString(sum));
}

}

activity main xml is:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.website.addition.MainActivity">

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:ems="10"
    android:id="@+id/editText"
    android:hint="@string/number1"
    android:layout_alignParentTop="true"
    android:layout_alignRight="@+id/editText2"
    android:layout_alignEnd="@+id/editText2"
    android:layout_marginRight="13dp"
    android:layout_marginEnd="13dp"
    android:layout_marginTop="60dp" />

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:ems="10"
    android:layout_marginTop="31dp"
    android:id="@+id/editText2"
    android:hint="@string/number2"
    android:layout_below="@+id/editText"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<Button
    android:text="Sum"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/button"
    android:textSize="30sp"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:onClick="onButtonClick (MainActivity)"
    tools:ignore="HardcodedText" />

<TextView
    android:text="@string/result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:id="@+id/textView2"
    android:textSize="30sp" />

i am getting the same error in every application which i am going to develop. please help me out of this.

Answer 1

You should change

android:onClick="onButtonClick (MainActivity)"

to

android:onClick="onButtonClick"

It probably causes an issue to resolve what function it refers to.