MainActivity

package com.example.test;

import com.example.test.listen_fragment.onSelectedListener;

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

public class MainActivity extends Activity implements onSelectedListener {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.twopane);
    }

    @Override
    public void onSelected(int index) {
        TextView text = (TextView) findViewById(R.id.text_content);
        text.setText(content_fragment.TextQuellen[index]);
    }

}