添加/删除 SQLite 列表视图不更新

Question

我有一个列表视图，它从 SQLite 数据库中获取信息并显示它。有一个 EditText 和一个 addButton。当按下 addButton 时，EditText 中的文本被放入数据库，之后列表视图应该更新。添加到数据库是可行的，但是在您暂停活动并再次恢复之前，列表视图不会更新。

在这个布局中还有一个eraseButton，所有带有选中复选框的文本视图都应从数据库中删除并从列表视图中删除。在这个问题中，按钮不会删除选定的文本视图（可能是由于数据库中的一些 rowid 问题。我相信它不会在删除后更新列表视图，因为 addButton 的方法相同。

感谢任何帮助。

这是 MainActivity

package net.ddns.introzen.jagharaldrig;

import android.app.ListFragment;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.SparseBooleanArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckedTextView;
import android.widget.CursorAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.Toast;

import java.lang.reflect.Array;
import java.util.ArrayList;



public class Main3Activity extends AppCompatActivity {

    //ArrayList<String> questions = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);


        //SQLite Database
        final DatabaseHandler db = new DatabaseHandler(this);


        //listview

        //add items
        /*questions.add("Jag har aldrig");
        questions.add("Jag har aldrig varit");
        questions.add("Jag har aldrig2");

        //Checkboxadapters
        final ListView questionList = (ListView) findViewById(R.id.questionList);
        final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list_item, questions);
        if(questionList != null) {
            questionList.setAdapter(adapter);
            questionList.setItemsCanFocus(false);
            questionList.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
        }*/

        final ListView questionList = (ListView) findViewById(R.id.questionList);
        final Cursor cursor = db.getData();
        final SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.list_item, cursor, new String[] { DatabaseHandler.COL_QUESTION }, new int[] { R.id.checkedTextView1 },0);
        assert questionList != null;
        questionList.setAdapter(adapter);
        questionList.setItemsCanFocus(false);
        questionList.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);

        //Erasebutton listener
        final Button eraseButton = (Button) findViewById(R.id.eraseButton);
        assert eraseButton != null;
        eraseButton.setOnClickListener(new View.OnClickListener() { //erasebutton onclick
            public void onClick(View eraseButton) {
                SparseBooleanArray checked = questionList.getCheckedItemPositions();
                for(int i = questionList.getCount() - 1; i >= 0; i--)
                {
                    if(checked.get(i)) {
                        //What to do with selected listitems
                        db.removeData(i);
                    }
                }
                checked.clear();
                Cursor newCursor = db.getData();
                adapter.swapCursor(newCursor);
            }
        });


        //addbutton listener
        final Button addButton = (Button) findViewById(R.id.addButton);
        assert addButton != null;
        addButton.setOnClickListener(new View.OnClickListener() { //Nextbutton onclick
            public void onClick(View addButton) {
                EditText addText = (EditText) findViewById(R.id.addText);
                assert addText != null;
                String text = addText.getText().toString();
                db.insertData(text);
                Cursor newCursor = db.getData();
                adapter.swapCursor(newCursor);
            }
        });


        //Nextbutton listener
        final Button returnButton = (Button) findViewById(R.id.returnButton);
        assert returnButton != null;
        returnButton.setOnClickListener(new View.OnClickListener() { //Nextbutton onclick
            public void onClick(View returnButton) {
                Intent mainMenu = new Intent(Main3Activity.this, Main2Activity.class);
                Main3Activity.this.startActivity(mainMenu);
            }
        });


    }


}  

这是数据库处理程序

package net.ddns.introzen.jagharaldrig;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;



public class DatabaseHandler extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "questions.db";
    public static final String TABLE_NAME = "questions";
    public static final String COL_ID = "ID";
    public static final String COL_QUESTION = "question";


    public DatabaseHandler(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("CREATE TABLE " + TABLE_NAME + " ( " + COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COL_QUESTION + " TEXT);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
        onCreate(db);

    }


    public boolean insertData(String question) {

        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(COL_QUESTION, question);
        db.insert(TABLE_NAME, null, cv);
        return true;
    }

    public boolean removeData(int position) {

        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_NAME, COL_ID+"="+position, null);
        return true;
    }

    public Cursor getData() {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor res = db.rawQuery("SELECT "+COL_ID+" AS _id, "+COL_QUESTION+" FROM " + TABLE_NAME, null);
        return res;
    }

}

Answer 1

您能否尝试将项目添加到适配器，然后调用适配器。 notifyDataSetChanged 之后。

原来是这样的

db.insertData(text)
adapter.add()//the item;
adapter.notifyDataSetChanged();

或者将 notify 方法放在 swapCursor 之后

Answer 2

更新数据库后添加新游标解决了问题。感谢 user3431672 的回答。

adapter.swapCursor(newCursor);