When Button has Tapped App stops.

import android.content.Intent;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.widget.TextViewCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.text.method.ScrollingMovementMethod;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.example.eleni.interactivestory.R;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {

    private TextView meditCenterText;
    private Button mStartButton;

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

        meditCenterText = (TextView) findViewById(R.id.editCenterText);
        mStartButton = (Button) findViewById(R.id.startButton);

        mStartButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String TextView = meditCenterText.getText().toString();
                startStory(TextView);
            }
        });
    }

    private void startStory(String TextView) {
        Intent intent = new Intent(this, StoryActivity.class);
        intent.putExtra("TextView", TextView);
        startActivity(intent);
    }

    @Override
    protected void onResume() {
        super.onResume();

        meditCenterText.setText("");
    }
}

import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.method.ScrollingMovementMethod;
import android.util.Log;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.eleni.interactivestory.R;
import com.example.eleni.interactivestory.model.Page;
import com.example.eleni.interactivestory.model.Story;

import static android.widget.TextView.*;

public class StoryActivity extends AppCompatActivity {

    public static final String TAG = StoryActivity.class.getSimpleName();


    private Story mStory = new Story();

    private ImageView mImageView;
    private TextView mTextView;
    private Button mChoice1;
    private Button mChoice2;
    private String mName;
    private Page mCurrentPage;
    private Page mPreviousPage;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_story2);


      //Intent intent = getIntent();
       //mName = intent.getStringExtra(getString(R.string.key_name));

        if(mName == null){
            mName = "Friend";
        }

        Log.d(TAG, mName);

        mImageView = (ImageView)findViewById(R.id.storyImageView);
        mTextView = (TextView)findViewById(R.id.storyTextView);
        mChoice1 = (Button)findViewById(R.id.choiceButton1);
        mChoice2 = (Button)findViewById(R.id.choiceButton2);

        loadPage(0);
    }
    private void loadPage(int choice){
     mCurrentPage = mStory.getPage(choice);
        //edw prepei na kanw kati gia to previous
        //mPreviousPage = mStory.getPage(choice);


        Drawable drawable  = getResources().getDrawable(mCurrentPage.getImageId());
        mImageView.setImageDrawable(drawable);

        String pageText = mCurrentPage.getText();
        //add the name if placeholder included.
       // pageText  = String.format(pageText,mName);
        mTextView.setText(pageText);

        if(mCurrentPage.isFinal()){
            mChoice1.setVisibility(View.INVISIBLE);
            mChoice2.setText("Start From The Begining");
            mChoice2.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                   finish();
                }
            });

        }else{

        mChoice1.setText(mCurrentPage.getChoice1().getText());
        mChoice2.setText(mCurrentPage.getChoice2().getText());

       mChoice1.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               mCurrentPage.getChoice1().getNextPage();
               int nextPage = mCurrentPage.getChoice1().getNextPage();
               loadPage(nextPage);
           }
       });

        mChoice2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mPreviousPage.getChoice2().getPreviousPage();
                int previousPage = mPreviousPage.getChoice2().getPreviousPage();
                loadPage(previousPage);
            }
        });


    }
}}

public class Choice {
    private String mText;
    private int mNextPage;
    private int mPreviousPage;


    public Choice(String text, int nextPage) {
        mText = text;
        mNextPage = nextPage;

    }

    public String getText() {

        return mText;
    }

    public void setText(String text) {

        mText = text;
    }

    public int getNextPage() {

        return mNextPage;
    }

    public void setNextPage(int nextPage) {
        mNextPage = nextPage;
    }

 public int getPreviousPage() {

     return mPreviousPage;
   }

   public void setPreviousPage(int previousPage) {
       mPreviousPage = previousPage;

   }
}

public class Page {
    private int mImageId;
    private String mText;
    private Choice mChoice1;
    private Choice mChoice2;
    private boolean mIsFinal = false;

    public Page(int imageId, String text, Choice choice1, Choice choice2){
        mImageId = imageId;
        mText = text;
        mChoice1 = choice1;
        mChoice2 = choice2;


    }
    public Page(int imageId, String text){
        mImageId = imageId;
        mText = text;
        mChoice1 = null;
        mChoice2 = null;
        mIsFinal = true;
    }



    public int getImageId() {
        return mImageId;
    }

    public void setImageId(int imageId) {
        mImageId = imageId;
    }

    public String getText() {
        return mText;
    }

    public void setText(String text) {
        mText = text;
    }

    public Choice getChoice1() {
        return mChoice1;
    }

    public void setChoice1(Choice choice1) {
        mChoice1 = choice1;
    }

    public Choice getChoice2() {
        return mChoice2;
    }

    public void setChoice2(Choice choice2) {
        mChoice2 = choice2;
    }

        public boolean isFinal() {

            return mIsFinal;
        }

        public void setIsFinal(boolean isFinal) {

            mIsFinal = isFinal;
        }
      }