Question

我确定，我错过了一些非常简单的东西，但由于某种原因，运行这段代码后我得到Null指针异常。有人知道为什么吗？

11-27 20:27:30.568: E/AndroidRuntime(32479): FATAL EXCEPTION: main
11-27 20:27:30.568: E/AndroidRuntime(32479): Process: com.example.makemyday, PID: 32479
11-27 20:27:30.568: E/AndroidRuntime(32479): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.makemyday/com.example.makemyday.ActionDetailActivity}: java.lang.NullPointerException
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.app.ActivityThread.access$700(ActivityThread.java:135)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.os.Handler.dispatchMessage(Handler.java:102)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.os.Looper.loop(Looper.java:137)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.app.ActivityThread.main(ActivityThread.java:4998)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at java.lang.reflect.Method.invokeNative(Native Method)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at java.lang.reflect.Method.invoke(Method.java:515)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at dalvik.system.NativeStart.main(Native Method)
11-27 20:27:30.568: E/AndroidRuntime(32479): Caused by: java.lang.NullPointerException
11-27 20:27:30.568: E/AndroidRuntime(32479):    at com.example.makemyday.EventDetailsFragment.onCreateView(EventDetailsFragment.java:34)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
11-27 20:27:30.568: E/AndroidRuntime(32479):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)

fragment_event_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="132dp" >

        <EditText
            android:id="@+id/event_description"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:hint="@string/hint_description"
            android:inputType="text"
            android:padding="16dp"
            android:textIsSelectable="true"
            android:scrollbars = "vertical"
            android:lines="4"
            android:textSize="14sp" />
    </ScrollView>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingLeft="0dip"
        android:paddingRight="0dip" >

        <EditText
            android:id="@+id/quantity"
            android:layout_width="166dp"
            android:layout_height="wrap_content"
            android:padding="16dp"
            android:textIsSelectable="true" 
            />

        <Spinner
            android:id="@+id/category_quantity"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="0.01"
            android:textSize="14dip" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:paddingLeft="0dip"
        android:paddingRight="0dip" >

        <Spinner
            android:id="@+id/category_query"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="0.01"
            android:textSize="14dip" />
    </LinearLayout>
</LinearLayout>

EventDetailsFragment

 package com.example.makemyday;

    import android.os.Bundle;
    import android.support.v4.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AdapterView;
    import android.widget.ArrayAdapter;
    import android.widget.EditText;
    import android.widget.Spinner;
    import android.widget.TextView;

import android.widget.AdapterView.OnItemSelectedListener;

public class EventDetailsFragment extends Fragment implements OnItemSelectedListener{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_action_detail,
                container, false);

        // Show the dummy content as text in a TextView.

            Spinner category=(Spinner)rootView.findViewById(R.id.category_query);
            ArrayAdapter<CharSequence> adapterCategory = ArrayAdapter.createFromResource(this.getActivity().getBaseContext(),R.array.category_names, android.R.layout.simple_spinner_item);
            adapterCategory.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            category.setAdapter(adapterCategory);
            category.setOnItemSelectedListener(this);

            Spinner quantity=(Spinner)rootView.findViewById(R.id.category_quantity);
            ArrayAdapter<CharSequence> adapterQuantity = ArrayAdapter.createFromResource(this.getActivity().getBaseContext(),R.array.quantity_names, android.R.layout.simple_spinner_item);
            adapterQuantity.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            quantity.setAdapter(adapterQuantity);
            quantity.setOnItemSelectedListener(this);   

            EditText description = (EditText)rootView.findViewById(R.id.event_description);
            description.setText("this");

        return rootView;
    }


    public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
            long arg3) {
        // TODO Auto-generated method stub

    }

    public void onNothingSelected(AdapterView<?> arg0) {
        // TODO Auto-generated method stub

    }
}

Answer 1

您展示了名为fragment_event_detail.xml的布局，但您夸大了名为R.layout.fragment_action_detail的布局。检查onCreate()

的以下行

View rootView = inflater.inflate(R.layout.fragment_action_detail,
            container, false);

替换下面的布局，

 View rootView = inflater.inflate(R.layout.fragment_event_detail,
                container, false);

片段布局中的Nullpointerexception

1 个答案: