My QRcode scanner function is not working - android-studio

Question

I'm setting up a QRcode scanner function in my TrackActivity. The code seems fine but when I run the apps and click the scan button, nothing happens.
I have tried QRcode scanner function in a new project and it works fine.
This is my TrackActivity.class
package com.example.majugoscreen;
import android.content.Intent;
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.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class TrackActivity extends AppCompatActivity {
public static TextView resultTExtview;
Button scan_btn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_track);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = 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();
resultTExtview = (TextView) findViewById(R.id.result_text);
scan_btn = (Button) findViewById(R.id.btn_scan);
scan_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
startActivity(new
Intent(getApplicationContext(),ScanCodeActivity.class));
}
});
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Bundle bundle = getIntent().getExtras();
if(bundle != null){
if(bundle.getString("Track") !=null){
Toast.makeText(getApplicationContext(),
"Activity" + bundle.getString("Track"),
Toast.LENGTH_SHORT).show();
}
}
}
});
}
}
This is my ScanCodeActivity.class
package com.example.majugoscreen;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import com.google.zxing.Result;
import me.dm7.barcodescanner.zxing.ZXingScannerView;
class ScanCodeActivity extends AppCompatActivity implements
ZXingScannerView.ResultHandler{
ZXingScannerView ScannerView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ScannerView = new ZXingScannerView(this);
setContentView(ScannerView);
}
#Override
public void handleResult(Result result) {
TrackActivity.resultTExtview.setText(result.getText());
onBackPressed();
}
#Override
protected void onPause(){
super.onPause();
ScannerView.stopCamera();
}
#Override
protected void onResume(){
super.onResume();
ScannerView.setResultHandler(this);
ScannerView.startCamera();
}
}
This is my activity_track.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity='center'
tools:context=".TrackActivity">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<include layout="#layout/content_track" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/fab_margin"
app:srcCompat="#android:drawable/ic_dialog_email" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Scan QR and Code "
android:layout_gravity="center_horizontal"
android:layout_marginTop="290dp"
android:textSize="16sp"
android:id="#+id/btn_scan"
/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Result"
android:gravity="center"
android:textSize="22sp"
android:layout_marginTop="350dp"
android:id="#+id/result_text"
/>
</android.support.design.widget.CoordinatorLayout>