getView（）不会在ListView的自定义适配器中调用

Question

我正在Android中制作便笺应用。我想在主活动的ListFragment中显示ListView。但是，由于未在自定义适配器中调用getView方法，因此未显示该列表。我阅读了很多SO帖子并尝试了很多解决方案，但它们似乎都不适合我。 getCount（）方法工作正常并返回正确的数据大小而不是0，但它被调用大约3到4次。

我检查了getAllNotes（），getCount（），notesListView，notesList，adapter的值，它们都返回正确的值。我在代码中设置了断点并对其进行了调试，但执行并没有停止在getView（）方法中设置的断点处，所以我知道问题出在哪里。

我的列表片段（NotesListFragment.java）：

package com.example.sriramkailasam.notes;

import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v4.app.ListFragment;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import java.util.ArrayList;

public class NotesListFragment extends ListFragment {
    private Context context;
    private ArrayList<Note> notesList = new ArrayList<>();

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        this.context = context;
        System.out.println("notes list fragment attached");
    }


    @Override
    public View onCreateView(
             LayoutInflater inflater,
             ViewGroup container,
             Bundle savedInstanceState) {

        System.out.println("fragment going to inflate layout");
        return inflater.inflate(R.layout.fragment_notes_list, container);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        System.out.println("fragment view created");
        NotesAdapter adapter = new NotesAdapter(context,
                        R.layout.notes_list_item,
                        R.id.list_no_items,
                        getAllNotes());
        ListView notesListView = getListView();
        notesListView.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

    private ArrayList<Note> getAllNotes() {
        openAndQueryDatabase();
        return notesList;
    }

    private void openAndQueryDatabase() {
        DatabaseHelper helper = new DatabaseHelper(context);
        SQLiteDatabase database = helper.getReadableDatabase();

        String selectQuery =
                "SELECT title, body FROM " + DatabaseContract.NotesEntry.TABLE_NAME;

        Cursor cursor = database.rawQuery(selectQuery, null);
        if (cursor != null) {
            cursor.moveToFirst();
            do {
                Note note = new Note();
                note.setTitle(cursor.getString(cursor.getColumnIndex("title")));
                note.setBody(cursor.getString(cursor.getColumnIndex("body")));

                notesList.add(note);
            } while (cursor.moveToNext());

            cursor.close();
        }
        else {
            System.out.println("cursor is null");
        }
    }
}

自定义适配器（NotesAdapter.java）：

package com.example.sriramkailasam.notes;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import java.util.List;

public class NotesAdapter extends ArrayAdapter<Note> {
    private int resourceId;
    private List<Note> notes;

    public NotesAdapter(Context context,
                        int resource,
                        int textViewResourceId,
                        List<Note> notesList) {
        super(context, resource,textViewResourceId, notesList);
        resourceId = resource;
        notes = notesList;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public int getCount() {
        System.out.println("getCount called: " + notes.size());
        return notes.size();
    }

    @Override
    public Note getItem(int position) {
        return notes.get(position);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        System.out.println("getView called");
        LayoutInflater inflater = LayoutInflater.from(getContext());
        if (convertView == null) {
            convertView = inflater.inflate(resourceId, parent, true);
        }

        TextView titleTextView =(TextView) convertView.findViewById(R.id.note_title);
        TextView bodyTextView = (TextView) convertView.findViewById(R.id.note_body);
        titleTextView.setText((getItem(position)).getTitle());
        bodyTextView.setText((getItem(position)).getBody());

        return convertView;
    }
}

行布局（notes_list_item.xml）：

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

    <TextView
        android:id="@+id/note_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textStyle="bold"/>
    <TextView
        android:id="@+id/note_body"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

片段布局（fragment_notes_list.xml）：

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:context="com.example.sriramkailasam.notes.NotesListFragment">

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <TextView
        android:id="@+id/list_no_items"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/empty_list" />

</LinearLayout>

Logcat输出：

    06-19 15:35:45.466 14513-14524/com.example.sriramkailasam.notes I/art: Background sticky concurrent mark sweep GC freed 14374(578KB) AllocSpace objects, 0(0B) LOS objects, 38% free, 5MB/8MB, paused 6.269ms total 27.655ms
06-19 15:35:45.686 14513-14513/com.example.sriramkailasam.notes W/System: ClassLoader referenced unknown path: /data/app/com.example.sriramkailasam.notes-1/lib/arm
06-19 15:35:45.700 14513-14513/com.example.sriramkailasam.notes I/InstantRun: starting instant run server: is main process
06-19 15:35:45.792 14513-14513/com.example.sriramkailasam.notes W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
06-19 15:35:46.001 14513-14513/com.example.sriramkailasam.notes I/System.out: notes list fragment attached
06-19 15:35:46.002 14513-14513/com.example.sriramkailasam.notes I/System.out: fragment going to inflate layout
06-19 15:35:46.008 14513-14513/com.example.sriramkailasam.notes I/System.out: fragment view created
06-19 15:35:46.018 14513-14513/com.example.sriramkailasam.notes I/System.out: getCount called: 30
06-19 15:35:46.018 14513-14513/com.example.sriramkailasam.notes I/System.out: getCount called: 30
06-19 15:35:46.018 14513-14513/com.example.sriramkailasam.notes I/System.out: getCount called: 30
06-19 15:35:46.018 14513-14513/com.example.sriramkailasam.notes I/System.out: getCount called: 30
06-19 15:35:46.018 14513-14513/com.example.sriramkailasam.notes I/System.out: getCount called: 30
06-19 15:35:46.086 14513-14550/com.example.sriramkailasam.notes I/Adreno: QUALCOMM build                   : 48a5bf5, I15255e4b4a
                                                                          Build Date                       : 02/22/17
                                                                          OpenGL ES Shader Compiler Version: XE031.09.00.03
                                                                          Local Branch                     : 
                                                                          Remote Branch                    : refs/tags/AU_LINUX_ANDROID_LA.UM.5.5.R1.07.00.00.269.019
                                                                          Remote Branch                    : NONE
                                                                          Reconstruct Branch               : NOTHING
06-19 15:35:46.092 14513-14550/com.example.sriramkailasam.notes I/OpenGLRenderer: Initialized EGL, version 1.4
06-19 15:35:46.092 14513-14550/com.example.sriramkailasam.notes D/OpenGLRenderer: Swap behavior 1
06-19 15:35:46.125 14513-14513/com.example.sriramkailasam.notes W/art: Before Android 4.1, method int android.support.v7.widget.ListViewCompat.lookForSelectablePosition(int, boolean) would have incorrectly overridden the package-private method in android.widget.ListView

Answer 1

您尚未初始化listView。

@Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_notes_list,
                    container, false);
            notesListView = (ListView) rootView.findViewById(android.R.id.yourListView);

            return rootView;
        }

然后

 @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        System.out.println("fragment view created");
        NotesAdapter adapter = new NotesAdapter(context,
                        R.layout.notes_list_item,
                        R.id.list_no_items,
                        getAllNotes());
        notesListView.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

修改

 private ArrayList<Note> getAllNotes() {
        DatabaseHelper helper = new DatabaseHelper(context);
    SQLiteDatabase database = helper.getReadableDatabase();

    String selectQuery =
            "SELECT title, body FROM " + DatabaseContract.NotesEntry.TABLE_NAME;

    Cursor cursor = database.rawQuery(selectQuery, null);
    if (cursor != null) {
        cursor.moveToFirst();
        do {
            Note note = new Note();
            note.setTitle(cursor.getString(cursor.getColumnIndex("title")));
            note.setBody(cursor.getString(cursor.getColumnIndex("body")));

            notesList.add(note);
        } while (cursor.moveToNext());

        cursor.close();
    }
    else {
        System.out.println("cursor is null");
    }
        return noteList;
}
    }