Ergebnis in einer TextView ausgeben

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
	xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:gravity="center">


	<TextView
		android:layout_width="match_parent"
		android:layout_height="match_parent"
		android:text=""
		android:id="@+id/mainTextView1"/>


</LinearLayout>

package com.mycompany.myapp3;


import android.app.*;
import android.os.*;
import android.widget.TextView;




public class MainActivity extends Activity 
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
		
		int zufallszahl;
		int x;
		x =100;
		
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
		
		TextView text = (TextView) findViewById(R.id.mainTextView1);
		
		zufallszahl = (int)(Math.random()*17)+ 13;
		x = x - zufallszahl;
		text.setText(x); 
		
    }
}

package com.mycompany.myapp2;


import android.app.*; 
import android.os.*; 
import android.view.*; 
import android.widget.*; 
import android.view.View.*;


public class MainActivity extends Activity 
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.startmain);
    }
	public void schwert (View view) {
		TextView y = (TextView) findViewById(R.id.textausgabe);
		y.getText().toString();
		int zufallszahl;
		int x;
		x =100;


		TextView text = (TextView) findViewById(R.id.textausgabe);


		zufallszahl = (int)(Math.random()*4)+ 8;
		x = x - zufallszahl;
		text.setText( Integer.toString(x));
	}
}

package com.mycompany.myapp2;


import android.app.*; 
import android.os.*; 
import android.view.*; 
import android.widget.*; 
import android.view.View.*;


public class MainActivity extends Activity 
{


	int x = 100;
	
	
	
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.startmain);
    }
	public void schwert (View view) {
		
		int zufallszahl;
		
		
		TextView y = (TextView) findViewById(R.id.textausgabe);
		y.getText().toString();


		TextView text = (TextView) findViewById(R.id.textausgabe);


		zufallszahl = (int)(Math.random()*4)+ 8;
		x = x - zufallszahl;
		text.setText( Integer.toString(x));
	}
}