我的代码有什么问题，它无法识别位置？

Question

我正在制作一个简单的规划器应用程序，其中包含一个 xml 和一个活动。这是MainActivity，基本上我在其中输入editText，将其转换为带有onClick按钮的listView项目，然后保存。唯一的问题是我的警告对话框，当您要删除项目时出现错误 - 它无法识别“位置”一词。我觉得这只是一些愚蠢的错字..？谢谢你。

package com.kass.planner2;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

import java.util.ArrayList;

public class MainActivity extends Activity {

    EditText et;
    ListView lv;
    ArrayAdapter<String> adapter;
    Button btn;
    ArrayList<String> list = new ArrayList<String>();
    final Context context = this;

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

        et = (EditText) findViewById(R.id.editText);
        lv = (ListView) findViewById(R.id.listView);
        btn = (Button) findViewById(R.id.button);
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
        lv.setAdapter(adapter);
        LoadPreferences();
        btn.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                String task = et.getText().toString();


                adapter.add(task);
                adapter.notifyDataSetChanged();
                SavePreferences("LISTS", task);
            }
        });

    // set ListView item listener
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view; final int position, long id) {
            AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);
            alertDialogBuilder.setTitle("Confirm Delete");
            alertDialogBuilder.setMessage("Sure you want to delete?");
            alertDialogBuilder.setCancelable(false);
            alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    adapter.remove(adapter.getItem(position));
                }
            });
            alertDialogBuilder.setNegativeButton("No", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    dialogInterface.cancel();
                }
            });
            AlertDialog alertDialog = alertDialogBuilder.create();
            alertDialog.show();
        }
    });}

    protected void SavePreferences(String key, String value) {
        // TODO Auto-generated method stub
        SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
        SharedPreferences.Editor editor = data.edit();
        editor.putString(key, value);
        editor.commit();


    }

    protected void LoadPreferences(){
        SharedPreferences data = PreferenceManager.getDefaultSharedPreferences(this);
        String dataSet = data.getString("LISTS", " ");

        adapter.add(dataSet);
        adapter.notifyDataSetChanged();
    }

    }`

Answer 1

试试这个方法：

 ArrayAdapter<String> adapter = (ArrayAdapter<String>)getListView().getAdapter();
            adapter.remove(adapter.getItem(info.position));
            adapter.notifyDataSetChanged();

Answer 2

position 变量必须是 final，如果您想在那里访问它。

按如下方式进行：

final int p = position; // just before setPositiveButton
alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    adapter.remove(adapter.getItem(p));
                }
            });

Answer 3

可能，这需要.... adapter.notifyDataSetChanged();删除时..

 alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    adapter.remove(adapter.getItem(position));
                    adapter.notifyDataSetChanged(); 
                }
            });