Android课程设计 ToDoList备忘录 SQLite，高分课程设计，可一键运行

package com.reigns.todolist; import androidx.annotation.Nullable; import androidx.appcompat.app.AppCompatActivity; import android.content.Intent; import android.os.Bundle; import android.view.ContextMenu; import android.view.MenuItem; import android.view.View; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.ListView; import android.widget.Toast; import java.util.ArrayList; public class MainActivity extends AppCompatActivity { private ArrayAdapter<String> adapter; private Button addBtn; public ArrayList<String> list = new ArrayList(); private ListView mlv; private TodoListDatabaseHelper db; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mlv = findViewById(R.id.listView); addBtn = findViewById(R.id.addbtn); mlv.setOnCreateContextMenuListener(MainActivity.this); db = new TodoListDatabaseHelper(this); if (db.queryAll() != null) { list = db.queryAll(); adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, list); mlv.setAdapter(adapter); } addBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(MainActivity.this, AddPage.class); startActivityForResult(intent, 1); } }); } @Override protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) { super.onActivityResult(requestCode, resultCode, data); if (requestCode == 1) { String add = data.getStringExtra("editTextValue"); if (!add.equals("null")) { if (db.queryAll() != null) { list = db.queryAll(); adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, list); adapter.add(add); db.insert(add); adapter.notifyDataSetChanged(); mlv.setAdapter(adapter); } else { list = new ArrayList<>(); adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, list); adapter.add(add); db.insert(add); adapter.notifyDataSetChanged(); mlv.setAdapter(adapter); } } } } public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) { super.onCreateContextMenu(menu, v, menuInfo); menu.add(0, 1, 0, "删除"); } @Override public boolean onContextItemSelected(MenuItem item) { AdapterView.AdapterContextMenuInfo menuInfo = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo(); int pos = (int) mlv.getAdapter().getItemId(menuInfo.position); String remove = list.remove(pos); db.delete(remove); adapter.notifyDataSetChanged(); Toast.makeText(this, "删除成功", Toast.LENGTH_SHORT).show(); return super.onContextItemSelected(item); } }