Question

我是Android新手，我正处于学习阶段。我搜索了很多但是找不到合适的解决方案。虽然我添加了findViewById语句，但我在notes.setOnClickListener中得到一个空指针异常

       package com.example.hp.newcalendar;

import android.app.Activity;
import android.support.v4.app.Fragment;
import android.content.Context;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;

import java.text.SimpleDateFormat;
import java.util.ArrayList;

public class PreviouslyCalledFragment extends Fragment {

    ListView students;
    TextView test;
    ImageView notes;
    SimpleDateFormat formatter = new SimpleDateFormat("dd M yyyy hh:mm a");
    String dateInString="23 Dec 2015 18:00 pm";
    View view;
    Context mContext;
    ArrayList<FieldDetails> searchResults;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        view = inflater.inflate(R.layout.activity_previously_called_fragment, container, false);
        students = (ListView) view.findViewById(R.id.alreadyCalled);
        notes=(ImageView)view.findViewById(R.id.notesView);
        searchResults = GetSearchResults();


        students.setAdapter(new CustomAdapter_Notes(mContext, searchResults));
        notes.setOnClickListener(new View.OnClickListener() {       //null pointer exception
            @Override
            public void onClick(View v) {
                Toast.makeText(mContext,"hello", Toast.LENGTH_LONG).show();
            }
        });

        return view;
    }

    @Override
    public void onAttach(final Activity activity) {
        super.onAttach(activity);
        mContext = activity;
    }
    private ArrayList<FieldDetails> GetSearchResults() {
        ArrayList<FieldDetails> results = new ArrayList<FieldDetails>();

        FieldDetails fieldDetails = new FieldDetails();
        fieldDetails.setName("Aman Jain");
        fieldDetails.setTime("Dec 23,18:00 pm");
        results.add(fieldDetails);

        fieldDetails = new FieldDetails();
        fieldDetails.setName("Keshav Sharma");
        fieldDetails.setTime("Dec 23,19:00 pm");
        results.add(fieldDetails);
        return results;
    }


}

xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:padding="5dp"
android:background="#ffffff">

<ListView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/alreadyCalled"
    android:layout_centerHorizontal="true"
    android:clickable="false"
    android:layout_alignParentTop="true" />

Custom_layout xml：

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

>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceSmall"
    android:text="Small Text"
    android:textSize="15dp"
    android:id="@+id/nameOfInterviewee"
    android:textColor="#008080"
    android:layout_marginTop="5dp"
    android:paddingBottom="5dp"
    android:layout_marginLeft="2dp"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceSmall"
    android:text="Small Text"
    android:textSize="12dp"
    android:id="@+id/dateAndTime"
    android:textColor="#008080"
    android:paddingBottom="10dp"
    android:layout_below="@+id/nameOfInterviewee"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="-5dp"
    />

<View
    android:layout_width="match_parent"
    android:layout_height="1dp"
    android:background="#848482"
    android:id="@+id/view"
    android:layout_below="@+id/dateAndTime"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<ImageView
    android:layout_width="30dp"
    android:layout_height="20dp"
    android:id="@+id/notesView"
    android:clickable="true"
    android:layout_marginTop="16dp"
    android:layout_alignParentTop="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:src="@drawable/notes"/>

 </RelativeLayout>

请帮助!!

Answer 1

这很可能是因为您的xml文件R.id.notesView中不存在R.layout.activity_previously_called_fragment id。请检查xml文件或在此处共享。

在片段类中的imageView上设置onClickListener时出现空指针异常

1 个答案: