长时间在Android错误中从列表视图删除项目

Question

I want to add items to appear as ListView , and I also want when I long click on a specific item, it should get deleted.

For the adding part, it is working well, but for the deleting part, it doesn't work out.

I think I should add an ArrayList, but I don't know how I can link it with the adapter, so the items that I enter should be put in ArrayList..

package com.example.asus.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         final ArrayList<String> arrayList = new ArrayList<String>();
        final ListView myList = (ListView)findViewById(R.id.listToDo);

        final ArrayAdapter<String> listAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1);
        myList.setAdapter(listAdapter);
        Button addButton = (Button) findViewById(R.id.button);
        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                EditText myItem = (EditText)findViewById(R.id.editText);
                String value = myItem.getText().toString();
                listAdapter.add(value);
                myItem.getText().clear();


            }
        });
        myList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(getApplicationContext(),((TextView)view).getText().toString(),Toast.LENGTH_LONG).show();
            }
        });
        myList.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
                //Adapter adapter = new Adapter(this, listAdapter);


                listAdapter.remove(String.valueOf(position));
                listAdapter.notifyDataSetChanged();
                Toast.makeText(MainActivity.this, "Item deleted", Toast.LENGTH_LONG).show();
                return false;
            }
        });

    }
}

It was working well in the adding part without any error. Update:

I added

listAdapter.remove(String.valueOf(position));

instead of

listAdapter.remove(position);

There is not any error, but when I long click the item, a message appears "Item deleted" as in the toast, but the item still exists on the listview, how can I fix that?

Answer 1

Because listAdapter is an instance of ArrayAdapter . It do not have any APIs which allow you delete an item based on given position. To delete an item you should you remove(T) API.

By the way when init the listAdapter you should pass arrayList into constructor.

final ArrayAdapter<String> listAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);

To delete a selected item

arrayList.remove(position);
listAdapter.notifyDataSetChanged();

or

listAdapter.remove(arrayList.get(position));
listAdapter.notifyDataSetChanged();