application Crashes with Zxing Intent

Question

I'm trying to use zxing application with intent, it works just one time. now, application crashes when the main Activity shows up.

this is the code for the main activity only I have.

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

public class MainActivity extends Activity {

    Button button;
    TextView txtView1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            //Link Activity
            setContentView(R.layout.activity_main);
            //TextView
            txtView1= (EditText) findViewById(R.id.TextView1);
            //Link Button
            button=(Button) findViewById(R.id.button1);
            //Add onClick
            button.setOnClickListener(new Button.OnClickListener() 
            {
                @Override
                public void onClick(View v) {
                        IntentIntegrator integrator =new IntentIntegrator(MainActivity.this);
                        integrator.initiateScan();
                }
            });
    }


    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {
            IntentResult scanResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, intent);

          if (scanResult != null) {
              String sBarcode = scanResult.getContents();
                txtView1.setText(sBarcode);
          }
          //if No Result
          txtView1.setText("Can't Get Data!");
        }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
            getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

I don't know where is the bug. and how can I handle it. I tried to add try catch on every line, app stops crashing but the intent doesn't work.