简单记事本app5

List View部分相关代码

package db;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import com.example.text002.R;

import java.util.ArrayList;
import java.util.List;

public class NoteAdapter extends BaseAdapter {

    Context context;
    List<NoteBean> notes = new ArrayList<>();
    public NoteAdapter(Context context, List<NoteBean> notes){
        this.context = context;
        this.notes = notes;
    }
    //用于获取数据集的数量大小
    @Override
    public int getCount() {
        return notes.size();
    }
    //用于返回指定位置position的那一个item
    @Override
    public Object getItem(int position) {
        return notes.get(position);
    }
    //获取item的下标
    @Override
    public long getItemId(int position) {
        return position;
    }
    //用于获取item的布局
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;
        if(convertView == null){
            //实例化
            viewHolder = new ViewHolder();
            convertView = View.inflate(context, R.layout.item_note,null);
            viewHolder.item_note_title = convertView.findViewById(R.id.item_note_title);
            viewHolder.item_note_key = convertView.findViewById(R.id.item_note_key);
            viewHolder.item_note_contents = convertView.findViewById(R.id.item_note_contents);
            viewHolder.item_note_daytime = convertView.findViewById(R.id.item_note_daytime);
            //用于传输viewHolder
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        //获取当前item的数据
        NoteBean note = notes.get(position);
        //对viewHolder进行赋值
        viewHolder.item_note_title.setText(note.getTitle());
        viewHolder.item_note_key.setText(note.getKeywords());
        viewHolder.item_note_contents.setText(note.getContents());
        viewHolder.item_note_daytime.setText(note.getDaytime());
        return convertView;
    }
    //static静态内部类没有对外部有引用，避免内存泄露
    static class ViewHolder{
        TextView item_note_title, item_note_daytime, item_note_contents, item_note_key;
    }
}