[Android Studio] Lord Kelvin:
Hi to all the community. I am introducing myself.

I am Mario and I am really a newbie of Android. I am trying to move my first steps through it because I need to build an app. Just a simple calculator. From there I would like to learn more and more with the help of the community.

I am using as a "learning" code, the code below found online (so it is not mine).

I tried it on a win7 computer with the following configuration and no error was given:

Android Studio 3.1.3

Build #AI-173.4819257, built on June 4, 2018

JRE: 1.8.0_152-release-1024-b02 amd64

JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o

Windows 7

I am now in need to run it on my computer with win10, same configuration:

Android Studio 3.1.3

Build #AI-173.4819257, built on June 4, 2018

JRE: 1.8.0_152-release-1024-b02 amd64

JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o

Windows 10 10.0

I am having the following problem after the build: Unexpected metadata type found. I could give more indication if requested here...

The error is with every code, even the very first one it appears on Android Studio as soon as you install it.

So the code is good but I guess there is something wrong around that I am getting crazy and I cannot see. Java? Gradle? I have looked online and I did not find anything to help so I am really asking help even though it might seem an easy question here for most of you guys.

NOTE: schemas_android_com is actually a website I DO NOT know for what but it was blocking me to post my question, sorry if I did something unappropriate here.

Layout:

<RelativeLayout xmlns:android="schemas_android_com/apk/res/android"
xmlns:tools="schemas_android_com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
tools:context="com.example.mario.MainActivity" >

<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="97dp"
android:text="Ratio"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="@dimen/abc_action_bar_default_height_material" />

<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView1"
android:layout_marginLeft="20dp"
android:layout_marginTop="43dp"
android:text="Number One"
android:textAppearance="?android:attr/textAppearanceMedium" />

<EditText
android:id="@+id/txtNumber1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/textView2"
android:layout_alignRight="@+id/textView1"
android:ems="2"
android:singleLine="true"
android:inputType="numberDecimal" >

<requestFocus />
</EditText>

<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView2"
android:layout_below="@+id/textView2"
android:layout_marginTop="47dp"
android:text="Number Two"
android:textAppearance="?android:attr/textAppearanceMedium" />

<Button
android:id="@+id/btnAdd"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView3"
android:layout_alignRight="@+id/textView3"
android:layout_below="@+id/textView3"
android:layout_marginTop="46dp"
android:onClick="onClick"
android:text="Divide" />

<EditText
android:id="@+id/txtNumber2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/btnAdd"
android:layout_alignLeft="@+id/txtNumber1"
android:ems="2"
android:singleLine="true"
android:inputType="numberDecimal" />

<TextView
android:id="@+id/txtResult"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/txtNumber2"
android:layout_alignTop="@+id/btnAdd"
android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>

Java code:

package com.example.mario;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

EditText firstNumber;
EditText secondNumber;
TextView addResult;
Button btnAdd;

double num1,num2,ratio;

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

firstNumber = (EditText)findViewById(R.id.txtNumber1);
secondNumber = (EditText)findViewById(R.id.txtNumber2);
addResult = (TextView)findViewById(R.id.txtResult);
btnAdd = (Button)findViewById(R.id.btnAdd);

btnAdd.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {
num1 = Double.parseDouble(firstNumber.getText().toString());
num2 = Double.parseDouble(secondNumber.getText().toString());
ratio = num1 / num2;
addResult.setText(Double.toString(ratio));
}
});
}

}

I really need to put my head down and learn how to do a simple Android app, so I would really appreciate any sort of help/advice that I will receive from the community.

Many thanks to everyone that will be able to help.

Mario