Question

我在尝试修复空指针错误时遇到了一些麻烦我试图在我的应用程序中从片段实现Zxing扫描仪，但是我收到以下错误。

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

我遵循了这个简单的教程（http://d-codepages.com/barcode-scanner-android-example/），但遇到了空指针错误如果我从片段中发布，我应该采取不同的方法吗？

从我尝试启动扫描程序的位置

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();
    }
}

片段的XML文件

<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);

一定是

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

空指针Zxing Scanner

1 个答案: