自定义Simplecursoradapter不会填充Listview

Question

SimpleCustomAdapter工作并填充了我的ListView，但后来我想在ListView中实现删除ImageButton。为了实现这一点，我必须制作一个自定义适配器。现在它没有在ListView中显示数据。

这是我的MainActivity.java，我也放置了MyListAdapter类（在底部）。我是初学者所以我知道代码可能到处都是。 MainAcitivty调用了适配器，一个用于listview的setonclicklistener，它也在sharedpreferences中发送item的id，所以我可以在适配器中的deleteNotes中捕获它。此外，删除按钮工作得很好，我可以删除笔记，但唯一的问题是标题和日期不会在ListView中显示，而在他们之前。感谢

package com.example.android.notepad2;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.media.Image;
import android.preference.PreferenceManager;
import android.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Layout;
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.Button;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

import static com.example.android.notepad2.R.id.parent;
import static com.example.android.notepad2.R.layout.listtemplate;

public class MainActivity extends AppCompatActivity {

    NDb mydb;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mydb = new NDb(this);
        ListView listview;

//        listview
           listview = (ListView) findViewById(R.id.listview);
        String[] array = new String[] {mydb.name, mydb.date};
        int[] display = new int[] {R.id.title, R.id.date};
        Cursor c = mydb.fetchAll();

        MyListAdapter adapter = new MyListAdapter(this, listtemplate, c, array, display, 0);
        listview.setAdapter(adapter);


        listview.setOnItemClickListener(new AdapterView.OnItemClickListener(){
           @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
               Bundle dataBundle = new Bundle();
               dataBundle.putInt("id", (int)l);

               SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
               SharedPreferences.Editor editor = sp.edit();
               editor.putInt("ajdi", (int)l);
               editor.apply();

               Intent intent = new Intent(MainActivity.this, NoteDisplay.class);
               intent.putExtras(dataBundle);
               MainActivity.this.startActivity(intent);
           }
        });




    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){
            case R.id.add_note:
                Bundle dataBundle = new Bundle();
                dataBundle.putInt("id", 0);
                Intent intent = new Intent(MainActivity.this,NoteDisplay.class);
                intent.putExtras(dataBundle);
                MainActivity.this.startActivity(intent);
                finish();
                return true;
        }

        return super.onOptionsItemSelected(item);
    }






 public class MyListAdapter extends SimpleCursorAdapter{

        private LayoutInflater mInflater;
        private Context context;
        private int layout;

        public MyListAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags){
            super(context, layout, c, from, to, flags);
            this.context = context;
            this.layout = layout;
            mInflater = LayoutInflater.from(context);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup par){
          ViewHolder holder;

            if(convertView==null){

                mInflater = LayoutInflater.from(getBaseContext());
                convertView = mInflater.inflate(R.layout.listtemplate, null);

                holder = new ViewHolder();
                holder.btn = (ImageButton) convertView.findViewById(R.id.delete_note);
                holder.title = (TextView) convertView.findViewById(R.id.title);
                holder.date = (TextView) convertView.findViewById(R.id.date);
                holder.btn.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
                        int l = sp.getInt("ajdi", 0);
                        if (l != 0) {
                            mydb.deleteNotes(l);
                            Toast.makeText(MainActivity.this, "Deleted", Toast.LENGTH_SHORT).show();
                            finish();
                            startActivity(getIntent());
                        }
                    }
                });
                convertView.setTag(holder);
            }else{
                holder= (ViewHolder) convertView.getTag();
            }


            return convertView;
        }


 }

    public class ViewHolder{
        ImageButton btn;
        TextView title;
        TextView date;
    }

}

这是我的数据库java文件。

package com.example.android.notepad2;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by DelicAnte on 04.10.2017..
 */

public class NDb extends SQLiteOpenHelper {

    public static final String dbname = "mydb";
    public static final String mynotes = "mynotes";
    public static final String _id = "_id";
    public static final String name = "name";
    public static final String content = "content";
    public static final String date = "date";
    SQLiteDatabase db;

    public NDb(Context context){
        super(context,dbname,null,1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table mynotes"
        +"(_id integer primary key, name text, content text, date text)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
        db.execSQL("DROP TABLE IF EXISTS" + mynotes);
        onCreate(db);
    }

    public boolean insertNotes(String name, String content, String date){
    db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put("name", name);
        contentValues.put("content", content);
        contentValues.put("date", date);
        db.insert(mynotes, null, contentValues);
        return true;
    }

    public Cursor fetchAll(){
    db = this.getReadableDatabase();
        Cursor mCursor = db.query(mynotes, new String[] {"_id", "name", "content", "date"}, null, null, null, null, null);
        if(mCursor!=null){
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    public Integer deleteNotes(Integer id){
        db = this.getWritableDatabase();
        return db.delete(mynotes, "_id=?", new String[] {Integer.toString(id)});
    }

    public Cursor getData(int id){
        db = this.getReadableDatabase();
        Cursor c = db.rawQuery("select * from " + mynotes +" where _id=" + id + "", null);
        return c;
    }
}

这是我的listtemplate.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="match_parent"
    android:descendantFocusability="blocksDescendants"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:weightSum="2"
        >
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:id="@+id/title"
        android:textSize="22sp"
        android:layout_weight="1"
        android:paddingBottom="15dp"
        />
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:id="@+id/date"
        android:textSize="14sp"
        android:layout_weight="0.5"
        />
    <ImageButton
            android:layout_width="0dp"
            android:layout_height="match_parent"
           android:layout_gravity="right"
            android:src="@drawable/delete_note"
            android:layout_weight="0.5"
        android:focusable="false"
        android:id="@+id/delete_note"
        />
     <!--       android:focusable="false"
           android:focusableInTouchMode="false"
           android:clickable="false"-->

    </LinearLayout>


</LinearLayout>

Answer 1

如果有人可能感兴趣。我通过在mainactivity.java中添加adapter.bindView解决了这个问题。在该方法中，您可以为标题，内容和最后一个按钮setonclicklistener设置文本。