Activity mit Button wechseln

package com.example.apollow.firstapp;


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


public class MainActivity extends Activity {


    private Button button1;


    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button = (Button)findViewById(R.id.button1);    }


    @Override        public boolean onCreateOptionsMenu(Menu menu) {


        Button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intentSeite2 = new Intent(MainActivity.this, Seite2.class);


                startActivity(intentSeite2);            }        });        return true;    }


}

package com.example.apollow.firstapp;


import android.os.Bundle;import android.support.design.widget.FloatingActionButton;import android.support.design.widget.Snackbar;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.view.View;


public class Seite2 extends AppCompatActivity {


    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_seite2);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);


        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)                        .setAction("Action", null).show();            }        });        getSupportActionBar().setDisplayHomeAsUpEnabled(true);    }


}

package com.example.apollow.nextapp;




import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;




public class MainActivity extends AppCompatActivity {


private Button button1;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button1 = (Button)findViewById(R.id.button1);


        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intentSeite2 = new Intent(MainActivity.this, Seite2.class);


                startActivity(intentSeite2);


            }
        });