空指针Zxing扫描器

Question

我遇到了一些麻烦，试图解决我的空指针错误。
我想在我的应用程序中实现从片段Zxing扫描仪，但我得到以下错误。

错误

10-20 19:17:39.249 4123-4123/? E/AndroidRuntime: FATAL EXCEPTION: main 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime: Process: app.rory.menu, PID: 4123 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'void me.dm7.barcodescanner.zxing.ZXingScannerView.startCamera()' on a null object reference 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at app.rory.pocket_chef.Fragments.scan_Foods_Fragment.onCreateView(scan_Foods_Fragment.java:35) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.Fragment.performCreateView(Fragment.java:2220) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:973) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1148) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.BackStackRecord.run(BackStackRecord.java:793) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1535) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.FragmentManagerImpl$1.run(FragmentManager.java:482) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.os.Handler.handleCallback(Handler.java:739) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.os.Handler.dispatchMessage(Handler.java:95) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.os.Looper.loop(Looper.java:148) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at android.app.ActivityThread.main(ActivityThread.java:5417) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at java.lang.reflect.Method.invoke(Native Method) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
10-20 19:17:39.249 4123-4123/? E/AndroidRuntime:  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
10-20 19:17:39.274 782-2968/? W/ActivityManager: Force finishing activity app.rory.menu/app.rory.pocket_chef.MyActivity 

我跟着这个简单的教程（http://d-codepages.com/barcode-scanner-android-example/），但运行到空指针错误。
我应该采取不同的方法，如果我从片段启动？

片段从那里我正在试图推出扫描仪

import android.app.AlertDialog; 
import android.app.Fragment; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 

import javax.xml.transform.Result; 

import app.rory.slidemenu.R; 
import me.dm7.barcodescanner.zxing.ZXingScannerView; 

/** 
* Created by Rory on 10/22/2014. 
*/ 



public class scan_Foods_Fragment extends Fragment implements ZXingScannerView.ResultHandler{ 

    private ZXingScannerView scannerView; 

    View rootview; 
    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     rootview = inflater.inflate(R.layout.scan_foods_layout, container, false); 
     //return rootview; 

     scannerView = (ZXingScannerView) container.findViewById(R.id.scanner_view); 
     scannerView.startCamera(); //error on this line 
     scannerView.setResultHandler(this); 

     return rootview; 
    } 

    @Override 
    public void handleResult(com.google.zxing.Result result) { 
     AlertDialog.Builder alert = new AlertDialog.Builder(getActivity()); 
     alert.setTitle(result.getBarcodeFormat().toString()); 
     alert.setMessage(result.getText()); 
     alert.show(); 
    } 
} 

XML文件的片段

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" android:layout_height="match_parent" 
    android:gravity="center_horizontal"> 

    <me.dm7.barcodescanner.zxing.ZXingScannerView 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:id="@+id/scanner_view" 
     /> 

    <!--<TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:textAppearance="?android:attr/textAppearanceLarge" 
     android:text="@string/scanFoods" 
     android:id="@+id/textView" />--> 

</RelativeLayout> 

Answer 1

这里有一个错误：

scannerView = (ZXingScannerView) container.findViewById(R.id.scanner_view); 

它必须是

scannerView = (ZXingScannerView) rootView.findViewById(R.id.scanner_view);