Android Studio : Layoutofnotification

MainActivity.java

package com.thaiall.www.layoutofnotification;

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.support.v7.widget.Toolbar.LayoutParams;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private void layoutRuntime() {
        LinearLayout linearLayout = new LinearLayout(this);
        TextView ProgrammaticallyTextView = new TextView(this);
        ProgrammaticallyTextView.setText(R.string.runtime);
        ProgrammaticallyTextView.setTextSize(16);
        ProgrammaticallyTextView.setPadding(30, 250, 30, 100);
        linearLayout.addView(ProgrammaticallyTextView);
        this.setContentView(linearLayout, new LinearLayout.LayoutParams(
                LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
        //http://www.android-examples.com/android-create-textview-programmatically-example/
    }

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

        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();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        //if (id == R.id.action_settings) {
        //    return true;
        //}
        //return super.onOptionsItemSelected(item);

        switch (item.getItemId()) {
            case R.id.content1:
                findViewById(R.id.content1).setVisibility(View.VISIBLE);
                findViewById(R.id.content2).setVisibility(View.GONE);
                return true;

            case R.id.content2:
                findViewById(R.id.content1).setVisibility(View.GONE);
                findViewById(R.id.content2).setVisibility(View.VISIBLE);
                return true;
            case R.id.layoutRuntime:
                layoutRuntime();
                return true;
            default:
                // If we got here, the user's action was not recognized.
                // Invoke the superclass to handle it.
                return super.onOptionsItemSelected(item);
        }
    }
}