Question

我有一个填充了本地存储数据库的ListView。当您单击列表项时，它会将您带到viewArtist活动，该活动根据您单击的项目的ROW_ID填充带有行条目信息的textView框。这是使用putExtra（）完成的。 viewArtist活动有一个删除条目的按钮。当您删除某个条目时，该列表不会刷新，因此您必须关闭该应用并重新登录。

但我的主要问题是删除某个项目后，该列表不再显示该条目，但是当您点击该项目代替已删除的项目时，下一个editText视图中不会显示任何信息屏幕。除此之外，当您单击此列表后面的任何列表条目时，它会使用上一个列表条目的信息填充textViews。

这是一张图片，用于说明我试图解释的内容。

图片1：http://i.imgur.com/RsXyygF.jpg

好像删除了行，但列表仍然将每个ROW_ID与列表项匹配，并且没有自动增量。

任何帮助都会非常感激，因为我已经试图解决这个问题了好几天！提前谢谢！

以下是调用viewArtist类的mainActivity类：

package com.example.msdproject;

import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.content.Intent;
import android.widget.ListView;  
import android.widget.Button;
import android.widget.ArrayAdapter;
import android.view.View;
import java.sql.SQLException;
import java.util.ArrayList;


public class MainActivity extends ListActivity {

public ArrayList<String> data_list=new ArrayList<String>();

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

    Button btn = (Button)findViewById(R.id.addConcertButton);
    btn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivity.this, AddArtist.class);
            startActivity(i);
        }
    });

    DBManager db =  new DBManager(this);

    try {
        db.open();
    } catch (SQLException e) {
        e.printStackTrace();
    }

    ListView listView = (ListView) findViewById(android.R.id.list);
    Cursor c = db.getAllConcerts();
    if (c.moveToFirst())
    {
        do {
            data_list.add(c.getString(0));
        } while (c.moveToNext());
    }
    ArrayAdapter<String> concertList=new ArrayAdapter<String>(getApplicationContext(),       android.R.layout.simple_list_item_1, data_list);
    listView.setAdapter(concertList);
    concertList.notifyDataSetChanged();

    db.close();
}

protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

    Intent i =  new Intent(MainActivity.this, ViewArtist.class);
    String strLong = Long.toString(id);
    //String idString = Objects.toString(id, null);

    if(strLong == "null")
    {
        id = id + 1;
        i.putExtra("id", id);
        startActivity(i);

    }

    else
    {
        i.putExtra("id", id);
        startActivity(i);
    }


}

}

这是我的ViewArtist类：

package com.example.msdproject;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.sql.SQLException;


public class ViewArtist extends Activity {

    DBManager db = new DBManager(this);

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

        Intent intent = getIntent();
        final long num = intent.getLongExtra("id", 1);

        Button btn = (Button)findViewById(R.id.updateConcertButton);
        btn.setOnClickListener(new View.OnClickListener()
        {

            @Override
            public void onClick(View v)
            {
                Intent i = new Intent(ViewArtist.this, UpdateArtist.class);
                i.putExtra("id", num);
                startActivity(i);
            }
        });

        String name;
        String venue;
        String date;
        String comments;

        try {
            db.open();
            Cursor c = db.getConcert(num + 1);
            //The reason I have num + 1 is because List Item 1 has a ROW_ID of 0
            if (c.moveToFirst())
            {
                do
                {
                    name = (c.getString(1));
                    venue = (c.getString(2));
                    date = (c.getString(3));
                    comments = (c.getString(4));

                    TextView nameTxt = (TextView)findViewById(R.id.viewName);
                    TextView titleTxt = (TextView)findViewById(R.id.viewTitle);
                    TextView venueTxt = (TextView)findViewById(R.id.viewVenue);
                    TextView dateTxt = (TextView)findViewById(R.id.viewDate);
                    TextView commentsTxt = (TextView)findViewById(R.id.viewComments);

                    nameTxt.setText(name);
                    titleTxt.setText("ROW_ID: " + String.valueOf(num));
                    venueTxt.setText(venue);
                    dateTxt.setText(date);
                    commentsTxt.setText(comments);

                    Button btn2 = (Button)findViewById(R.id.deleteConcertButton);
                    btn2.setOnClickListener(new View.OnClickListener()
                    {

                        @Override
                        public void onClick(View v) {
                            db.deleteConcert(num);

                        }
                    });

                } while (c.moveToNext());
            }
        }

        catch (SQLException e)
        {
            e.printStackTrace();
        }

        db.close();

    }
}

这是我的DBManager类：

package com.example.msdproject;

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

import java.sql.SQLException;


public class DBManager {

    public static final String COL_ROWID = "_id";
    public static final String COL_NAME = "name";
    public static final String COL_VENUE = "venue";
    public static final String COL_DATE = "date";
    public static final String COL_COMMENTS = "comments";

    private static final String DB_NAME = "Concerts";
    private static final String DB_TABLE = "Concert_Info";
    private static final int DB_VERSION = 1;

    private static final String DB_CREATE =
            "create table " + DB_TABLE + 
    " (_id integer primary key autoincrement, " +
            "name text not null, " +
            "venue text not null, " +
            "comments text not null, " +
            "date text not null);";

    private final Context context;

    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public DBManager(Context ctx)
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }

    //embedded class
    public static class DatabaseHelper extends SQLiteOpenHelper
    {
        DatabaseHelper(Context context)
        {
            super(context, DB_NAME, null, DB_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db)
        {
            db.execSQL(DB_CREATE);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
        {
            /*
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("drop table if exists Concert_Info");
            onCreate(db);*/
        }
    }

    public DBManager open() throws SQLException
    {
        db = DBHelper.getWritableDatabase();
        //db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE + ";");
        return this;
    }

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

    public long getId(String name)
    {
        long x = 10;
        return x;
    }
    public long insertConcert(String name, String venue, String date, String comments)
    {
        ContentValues initialValues = new ContentValues();
        initialValues.put(COL_NAME, name);
        initialValues.put(COL_VENUE, venue);
        initialValues.put(COL_DATE, date);
        initialValues.put(COL_COMMENTS, comments);
        return db.insert(DB_TABLE, null, initialValues);
    }

    public boolean deleteConcert(long ROW_ID)
    {
        return db.delete(DB_TABLE, COL_ROWID + "=" + ROW_ID, null) > 0;
    }

    public Cursor getAllConcerts() {
        return db.query(DB_TABLE, new String[]
                        {
                                COL_NAME,
                                COL_VENUE,
                                COL_DATE,
                                COL_COMMENTS
                        },
                        null,
                        null,
                        null,
                        null,
                        null
                );
    }

    public Cursor getConcert(long ROW_ID) throws SQLException
    {
        Cursor mCursor =
                db.query(DB_TABLE, new String[]
                        {
                                COL_ROWID,
                                COL_NAME,
                                COL_VENUE,
                                COL_DATE,
                                COL_COMMENTS
                        },
                        COL_ROWID + "=" + ROW_ID,
                        null,
                        null,
                        null,
                        null
                );
        if (mCursor != null)
        {
            mCursor.moveToFirst();
        }

        return mCursor;

    }


    public boolean updateConcert(long ROW_ID, String name, String venue, String date, String comments)
    {
        ContentValues args = new ContentValues();
        args.put(COL_NAME, name);
        args.put(COL_VENUE, venue);
        args.put(COL_DATE, date);
        args.put(COL_COMMENTS, comments);
        return db.update(DB_TABLE, args, COL_ROWID  + "=" + ROW_ID, null) > 0;

    }

}

Answer 1

您需要在片段或活动中向onResume添加代码，以使列表更新光标，因此还需要更新列表视图以删除已删除的值

似乎您可能正在向现有列表添加新列表。在OnResume中你需要做的是更新data_list并调用concertList.notifyDataSetChanged（）;.对于来自DB的列表，我使用CursorAdapter而不是数组适配器，因为实际的机制不是100％熟悉

Answer 2

两件事，关于db id与列表位置的评论是正确的。您将需要查询数据库不是基于列表中的位置，而是基于列表中的值。（即，如果它是唯一的），以便从数据库中获取详细视图/记录。

第二个/第一个是当你选择列表并进入详细视图时列表活动没有消失/没有被销毁，所以当你回到列表时它仍然会显示之前查询过的值。

您需要在片段或活动中向onResume添加代码，以使列表更新光标，因此还需要更新列表视图以删除已删除的值

Android数据库：从数据库填充的ListView中删除项目需要帮助

2 个答案: