Question

我试图从数据库中删除一个条目已经失败。这是我的代码，以显示我在做什么。我创建了一个ContextMenu，它会打开一个名为“删除”的新菜单，但是当我点击此删除时，它不会删除所选项目。它只是没有做任何事情。

main.java：

import java.util.List;
import java.util.Random;

import android.app.ListActivity;
import android.os.Bundle;
import android.text.Editable;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.MenuInflater;
import android.view.View;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
import android.view.MenuItem;


public class Announce extends ListActivity{
    private CommentsDataSource datasource;
    EditText edit;      


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.announce);

        datasource = new CommentsDataSource(this);
        datasource.open();      

        List<Comment> values = datasource.getAllComments();

        ArrayAdapter<Comment> adapter = new ArrayAdapter<Comment>(this,
                android.R.layout.simple_list_item_1, values);
        setListAdapter(adapter);
        registerForContextMenu(getListView());
    }


    public void onClick(View view) {
        @SuppressWarnings("unchecked")
        ArrayAdapter<Comment> adapter = (ArrayAdapter<Comment>) getListAdapter();
        Comment comment = null;
        switch (view.getId()) {
        case R.id.add:  
            edit = (EditText)findViewById(R.id.editTxt);            
            Editable txt=(Editable)edit.getText();
            String insert = txt.toString();         
            comment = datasource.createComment(insert);
            adapter.add(comment);
            edit.setText("");
            break;      
        }
        adapter.notifyDataSetChanged();
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo){
        super.onCreateContextMenu(menu, v, menuInfo);
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.context_menu, menu);
    }


    @Override
    public boolean onContextItemSelected(MenuItem item){
        AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();          
        if(item.getTitle() == "Delete") {
            datasource.deleteCommentById(info.id);          
            return true;
        }
        return super.onContextItemSelected(item);
    }

    @Override
    protected void onResume() {
        datasource.open();
        super.onResume();
    }

    @Override
    protected void onPause() {
        datasource.close();
        super.onPause();
    }

}

这是我的SQLHelper，我要求删除。

import java.util.ArrayList;
import java.util.List;

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

public class CommentsDataSource {

    // Database fields
    private SQLiteDatabase database;
    private MySQLiteHelper dbHelper;
    private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
            MySQLiteHelper.COLUMN_COMMENT };

    public CommentsDataSource(Context context) {
        dbHelper = new MySQLiteHelper(context);
    }

    public void open() throws SQLException {
        database = dbHelper.getWritableDatabase();
    }

    public void close() {
        dbHelper.close();
    }

    public Comment createComment(String comment) {
        ContentValues values = new ContentValues();
        values.put(MySQLiteHelper.COLUMN_COMMENT, comment);
        long insertId = database.insert(MySQLiteHelper.TABLE_COMMENTS, null,
                values);
        Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
                allColumns, MySQLiteHelper.COLUMN_ID + " = " + insertId, null,
                null, null, null);
        cursor.moveToFirst();
        Comment newComment = cursorToComment(cursor);
        cursor.close();
        return newComment;
    }

    public void deleteComment(Comment comment) {
        long id = comment.getId();
        System.out.println("Comment deleted with id: " + id);
        database.delete(MySQLiteHelper.TABLE_COMMENTS, MySQLiteHelper.COLUMN_ID
                + " = " + id, null);
    }

    public void deleteCommentById(long id) {
        System.out.println("Comment deleted with id: " + id);
        database.delete(MySQLiteHelper.TABLE_COMMENTS, MySQLiteHelper.COLUMN_ID
                + " = " + id, null);
    }

    public List<Comment> getAllComments() {
        List<Comment> comments = new ArrayList<Comment>();

        Cursor cursor = database.query(MySQLiteHelper.TABLE_COMMENTS,
                allColumns, null, null, null, null, null);

        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            Comment comment = cursorToComment(cursor);
            comments.add(comment);
            cursor.moveToNext();
        }
        // Make sure to close the cursor
        cursor.close();
        return comments;
    }

    private Comment cursorToComment(Cursor cursor) {
        Comment comment = new Comment();
        comment.setId(cursor.getLong(0));
        comment.setComment(cursor.getString(1));
        return comment;
    }
}

我做错了什么？它只是不删除我选择的项目。

Answer 1

尝试更改

if(item.getTitle() == "Delete") {

到

if(item.getTitle().equals("Delete")) {

Answer 2

我认为你应该称之为

 adapter.notifyDataSetChanged();

这部分代码之后..

  datasource.deleteCommentById(info.id);

从数据库中删除，不成功

2 个答案: