Button button;

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

    button = (Button) findViewById(R.id.button);
    button.setOnClickListener(this);
   }
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.button:
            Intent intent = new Intent(this, Activity_2.class);
            startActivity(intent);
            break;
        default:
            break;
    }
}