Android 从listview中删除给定任务

android新手。这里有一点关于应用程序的情况，因为log cat给出了一个空指针异常。 申请流程是这样的；给定的[标题和注释]是通过从listview_活动到不同布局的意图获得的；单击“删除”按钮应删除的位置 从数据库中获取给定的数据并关闭当前活动，然后返回列出活动

package com.example.tasklist;

import java.util.HashMap;
import java.util.List;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

public class DisplayTask extends Activity {

TextView TiTv, Latv;
Button btnEdit, btnDelete;

List<Task> ntsk;
private static int position;

final Task tkks = ntsk.get(position);

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.title_layout);

    Intent intent = getIntent();

    TiTv = (TextView) findViewById(R.id.TitleTV);
    String title = intent.getStringExtra("etra1");
    TiTv.setText(title);

    Latv = (TextView) findViewById(R.id.NotesTV);
    String task = intent.getStringExtra("etra2");
    Latv.setText(task);

    btnDelete = (Button) findViewById(R.id.DeleteBtn);
    btnDelete.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            DbHandler dbht = new DbHandler(DisplayTask.this);
            dbht.DeleteTask(tkks);

            Toast.makeText(DisplayTask.this, tkks.getTitle() + "Deleted",
                    Toast.LENGTH_SHORT).show();

        }
    });

}

空指针异常=>post stacktrace.close当前活动=>finish