//activitymain
package com.example.porcentaje;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;


public class MainActivity extends Activity {
	double cantconsumo, total, porcentaje;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

	}

	@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;
	}
	  public void calcDesc(View view){
		    
	        Intent i = new Intent(this, porcen.class);
	        
        	EditText cannum1 =(EditText) findViewById(R.id.editText1);
	        String num1=cannum1.getText().toString();
	        i.putExtra("cantidad", num1);
	        int cantconsumo = Integer.parseInt(num1);
	        
	        EditText cannum2 =(EditText) findViewById(R.id.editText2);
	        String num2=cannum2.getText().toString();
			i.putExtra("porcent", num2);
			int porcentaje = Integer.parseInt(num2);
			
			total = cantconsumo-(cantconsumo*(porcentaje/100));
			
	     	        
	        startActivity(i);
	        
	       
	  }
	  
	    public void cerrar(View view) {
	    	finish();
	    }
}

//segunactividad
package com.example.porcentaje;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;


public class porcen extends Activity {

	Bundle b;
	String s;
	TextView t;

    /** Called when the activity is first created. */

    @Override 
    public void onCreate(Bundle savedInstanceState) {
    	super.onCreate(savedInstanceState);
        setContentView(R.layout.venta);
        
        t=(TextView)findViewById(R.id.textView1);
        b=getIntent().getExtras();
        s=b.getString("cantidad");
        
        t.setText(s);
    }
}

//xml actvitymain
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Ingresa el total de la venta:"
        android:textSize="20sp"
        android:textStyle="bold" />

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


    <TextView
        android:id="@+id/textView2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Porcentaje de descuento:"
        android:textSize="20sp"
        android:textStyle="bold"/>

    <EditText
        android:id="@+id/editText2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:numeric="integer" />

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="calcDesc"
        android:text="Calcular" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="cerrar"
        android:text="Salir" />

</LinearLayout>