小贝子编程

Using Listview and Sqlite



我从以下链接下载了sqlite的示例 http://www.codegod.com/android-listview-with-dynamic-images-aid590.aspx

sqlitelistactivity.java：

package com.codegod.android;
import java.util.ArrayList;
import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.AdapterView.OnItemClickListener;
public class SQLiteListActivity extends ListActivity implements View.OnClickListener {
    private StockAdapter tableRowAdapter;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        try {
            StocksManager stockMgr = new StocksManager(getApplicationContext());
            // clear the table
            stockMgr.clear();
            // Add values to database
            stockMgr.insert("APPL", "Apple Inc.");
            stockMgr.insert("GOOG", "Google Inc.");
            stockMgr.insert("LTSB", "Let's drink some beer");
            // get the values from database
            ArrayList<Stock> stocks = stockMgr.getStocks(); 
            tableRowAdapter = new StockAdapter(
                    getApplicationContext(), R.layout.table_row, stocks);
            setListAdapter(tableRowAdapter);

        } catch (Exception ex) {
            Log.e(ex.toString(), ex.toString());
        }
    }
    @Override
    public void onClick(View v) {
        ImageButton button = (ImageButton) v;
        Stock row = (Stock) button.getTag();
        tableRowAdapter.deleteRow(row);
        tableRowAdapter.notifyDataSetChanged();
    }
}

stock.java 

package com.codegod.android;
public class Stock {
    private String id;
    private String description;
    public Stock(String id, String description) {
        this.id = id;
        this.description = description;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getId() {
        return id;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public String getDescription() {
        return description;
    }
}

Stockadapter.java 

package com.codegod.android;
import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageButton;
import android.widget.TextView;
/**
 * Adapter for Stock-objects 
 *
 */
public class StockAdapter extends BaseAdapter {
    private final List<Stock> rows;
    public StockAdapter(final Context context, final int itemResId,
            final List<Stock> items) {
        this.rows = items;
    }
    public int getCount() {
        return this.rows.size();
    }
    public Object getItem(int position) {
        return this.rows.get(position);
    }
    public long getItemId(int position) {
        return position;
    }
    /**
     * Set the content for a row here
     */
    public View getView(int position, View convertView, ViewGroup parent) {
        final Stock row = this.rows.get(position);
        View itemView = null;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) parent.getContext()
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            itemView = inflater.inflate(R.layout.table_row, null);
        } else {
            itemView = convertView;
        }
        // Set the text of the row
        TextView txtId = (TextView) itemView.findViewById(R.id.rowId);
        txtId.setText(row.getId());
        TextView txtDesc = (TextView) itemView.findViewById(R.id.rowDesc);
        txtDesc.setText(row.getDescription());
        // Remember the row for each button so that we can refer to
        // it when the button is clicked
        ImageButton imgButton = (ImageButton) itemView.findViewById(R.id.icon);
        imgButton.setTag(row);
        return itemView;
    }
    /**
     * Delete a row from the list of rows
     * @param row row to be deleted
     */
    public void deleteRow(Stock row) {
        if(this.rows.contains(row)) {
            this.rows.remove(row);
        }
    }
}

stocksmanager.java 

package com.codegod.android;
import java.util.ArrayList;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import com.codegod.android.db.OpenDbHelper;
public class StocksManager {
    private OpenDbHelper dbHelper;
    private static final String STOCK_TABLE = "Stock";
    private static final String STOCK_ID = "stock_id";
    private static final String STOCK_DESC = "stock_desc";
    private static final String SELECT_STOCKS = "SELECT * FROM " + STOCK_TABLE;
    public StocksManager(Context context) {
        dbHelper = new OpenDbHelper(context, STOCK_TABLE, STOCK_ID + " TEXT,"
                + STOCK_DESC + " TEXT");
    }
    /**
     * Insert a Stock-value into database
     * @param stockId id of the stock
     * @param stockDesc description of the stock
     * @return success or fail
     */
    public boolean insert(String stockId, String stockDesc) {
        try {
            SQLiteDatabase sqlite = dbHelper.getWritableDatabase();
            ContentValues initialValues = new ContentValues();
            initialValues.put(STOCK_ID, stockId);
            initialValues.put(STOCK_DESC, stockDesc);
            sqlite.insert(STOCK_TABLE, null, initialValues);
        } catch (SQLException sqlerror) {
            Log.v("Insert into table error", sqlerror.getMessage());
            return false;
        }
        return true;
    }
    /**
     * Get all available stocks
     * @return List of stocks
     */
    public ArrayList<Stock> getStocks() {
        ArrayList<Stock> stocks = new ArrayList<Stock>();
        SQLiteDatabase sqliteDB = dbHelper.getReadableDatabase();
        Cursor crsr = sqliteDB.rawQuery(SELECT_STOCKS, null);
        crsr.moveToFirst();
        for (int i = 0; i < crsr.getCount(); i++)
        {
            stocks.add(new Stock(crsr.getString(0), crsr.getString(1)));
            crsr.moveToNext();
        }
        return stocks;
    }
    /**
     * Clear the table
     */
    public void clear() {
        try {
            SQLiteDatabase sqlite = dbHelper.getWritableDatabase();
            sqlite.delete(STOCK_TABLE, "", null);
        } catch (SQLException sqlerror) {
            Log.v("delete from table error", sqlerror.getMessage());
        }   
    }
}

opendbhelper.java 

package com.codegod.android.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class OpenDbHelper extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 2;
    private String createStatement = "";
    /**
     * Creates the OpenDbHelper 
     * 
     * @param context app-context
     * @param tableName name of the table to open/create
     * @param fields fields of the table to create
     */
    public OpenDbHelper(Context context, String tableName, String fields) {
        super(context, tableName, null, DATABASE_VERSION);
        this.createStatement  = "CREATE TABLE ";
        this.createStatement += tableName + " (";
        this.createStatement += fields + ");";
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(this.createStatement);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int neVersion) {
        // TODO Auto-generated method stub
    }
}

layout.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="?android:attr/listPreferredItemHeight"
    android:padding="4dip">
    <TextView android:id="@+id/rowId" android:layout_width="fill_parent"
        android:layout_height="26dip" android:singleLine="true"
        android:textSize="20dip" android:textColor="#ffffff" android:text="Id..." />
    <TextView android:id="@+id/rowDesc" android:layout_width="fill_parent"
        android:text="Descr..." android:layout_height="20dip"
        android:textSize="12dip" android:layout_below="@+id/rowId"
        android:layout_alignParentBottom="true" android:textColor="#ffffff" />
    <ImageButton android:id="@+id/icon" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:src="@drawable/delete"
        android:gravity="right" android:layout_alignParentRight="true"
        android:onClick="onClick" />
</RelativeLayout>

哪个列表视图连接到数据库，也有一个图像按钮来删除行，但是我想更改它以将删除结果保存在数据库中，我的意思是，删除后的更改无法保存。现在，在这个项目中，即使我从文件资源管理器中提取它时，数据库中仍然有三行，我应该如何更改它？请在这个问题上帮助我。

您需要编写数据库方法才能从SQLITE数据库中删除行。这是一些代码段

public void RemoveRow(String id){
    SQLiteDatabase sqliteDB = dbHelper.getReadableDatabase();
    String query = "DELETE FROM Stock WHERE stock_id='"+id+"'";
    sqliteDB.execSQL(query);
}

并在listView onclick方法

上调用此方法 
@Override
public void onClick(View v) {
    StocksManager.RemoveRow();
}

您需要初始化Stockmanager方法;

编辑：

这样做，StocksManager.java将是

package com.codegod.android;
import java.util.ArrayList;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import com.codegod.android.db.OpenDbHelper;
public class StocksManager {
    private OpenDbHelper dbHelper;
    private static final String STOCK_TABLE = "Stock";
    private static final String STOCK_ID = "stock_id";
    private static final String STOCK_DESC = "stock_desc";
    private static final String SELECT_STOCKS = "SELECT * FROM " + STOCK_TABLE;
    public StocksManager(Context context) {
        dbHelper = new OpenDbHelper(context, STOCK_TABLE, STOCK_ID + " TEXT,"
                + STOCK_DESC + " TEXT");
    }
    /**
     * Insert a Stock-value into database
     * @param stockId id of the stock
     * @param stockDesc description of the stock
     * @return success or fail
     */
    public boolean insert(String stockId, String stockDesc) {
        try {
            SQLiteDatabase sqlite = dbHelper.getWritableDatabase();
            ContentValues initialValues = new ContentValues();
            initialValues.put(STOCK_ID, stockId);
            initialValues.put(STOCK_DESC, stockDesc);
            sqlite.insert(STOCK_TABLE, null, initialValues);
        } catch (SQLException sqlerror) {
            Log.v("Insert into table error", sqlerror.getMessage());
            return false;
        }
        return true;
    }
    /**
     * Get all available stocks
     * @return List of stocks
     */
    public ArrayList<Stock> getStocks() {
        ArrayList<Stock> stocks = new ArrayList<Stock>();
        SQLiteDatabase sqliteDB = dbHelper.getReadableDatabase();
        Cursor crsr = sqliteDB.rawQuery(SELECT_STOCKS, null);
        crsr.moveToFirst();
        for (int i = 0; i < crsr.getCount(); i++)
        {
            stocks.add(new Stock(crsr.getString(0), crsr.getString(1)));
            crsr.moveToNext();
        }
        return stocks;
    }
    /**
     * Remove selected stock
     * @return Void
     */
    public void RemoveRow(String id){
        SQLiteDatabase sqliteDB = dbHelper.getReadableDatabase();
        String query = "DELETE FROM Stock WHERE stock_id='"+id+"'";
        sqliteDB.execSQL(query);
    }
    /**
     * Clear the table
     */
    public void clear() {
        try {
            SQLiteDatabase sqlite = dbHelper.getWritableDatabase();
            sqlite.delete(STOCK_TABLE, "", null);
        } catch (SQLException sqlerror) {
            Log.v("delete from table error", sqlerror.getMessage());
        }   
    }
}

和SQLiteListActivity.java：

package com.codegod.android;
import java.util.ArrayList;
import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.AdapterView.OnItemClickListener;
public class SQLiteListActivity extends ListActivity implements View.OnClickListener {
    private StockAdapter tableRowAdapter;
    private StocksManager stockMgr;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        try {
            //Initialize StockManager Database class
            stockMgr = new StocksManager(getApplicationContext());
            // clear the table
            stockMgr.clear();
            // Add values to database
            stockMgr.insert("APPL", "Apple Inc.");
            stockMgr.insert("GOOG", "Google Inc.");
            stockMgr.insert("LTSB", "Let's drink some beer");
            // get the values from database
            ArrayList<Stock> stocks = stockMgr.getStocks(); 
            tableRowAdapter = new StockAdapter(
                    getApplicationContext(), R.layout.table_row, stocks);
            setListAdapter(tableRowAdapter);

        } catch (Exception ex) {
            Log.e(ex.toString(), ex.toString());
        }
    }
    @Override
    public void onClick(View v) {
        ImageButton button = (ImageButton) v;
        Stock row = (Stock) button.getTag();
        tableRowAdapter.deleteRow(row);
        tableRowAdapter.notifyDataSetChanged();
        //Call DB Method to remove stock from database
        stockMgr.RemoveRow(row.getId());
    }
}

我没有机会对其进行测试，但我确定它可以正常工作。

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