Android：从数据库填充ListView

Question

我在从sqlite数据库获取ListView时遇到麻烦。 我使用本教程创建了鳕鱼。 http://lecturesnippets.com/android-populating-listview-sqlite-database/

当我单击添加按钮时，ListView中什么也没有显示。

这是我的MainActivity

package com.teamvdb.checklist;

import com.teamvdb.checklist.R;

import android.app.Activity;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;

public class MainActivity extends Activity {


DBAdapter myDB;
EditText etListName;


@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    etListName = (EditText) findViewById(R.id.etListName);
    openDB();
    populateListView();

}



private void openDB() {
    myDB = new DBAdapter(this);
    myDB.open();

}

public void onClick_bAddList(View v) {
    if(!TextUtils.isEmpty(etListName.getText().toString())) {
        myDB.insertRow(etListName.getText().toString());
    }   
    populateListView();

}



private void populateListView() {
    Cursor cursor = myDB.getAllRows();
    String[] fromFieldNames = new String[] {DBAdapter.KEY_ROWID,DBAdapter.KEY_NAME};        
    int[] toViewIDs = new int[] {R.id.name, R.id.dist};
    SimpleCursorAdapter myCursorAdapter;
    myCursorAdapter = new SimpleCursorAdapter(getBaseContext(), R.layout.single_listview_item,           cursor, fromFieldNames, toViewIDs, 0);
    ListView lvCheckLists = (ListView) findViewById(R.id.lvCheckLists);
    lvCheckLists.setAdapter(myCursorAdapter);


}
}

这是DBAdapter。

// ------------------------------------ DBADapter.java ------------------------------------------      

// TODO: Change the package to match your project.
package com.teamvdb.checklist;

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


// TO USE:
// Change the package (at top) to match your project.
// Search for "TODO", and make the appropriate changes.
public class DBAdapter {

/////////////////////////////////////////////////////////////////////
//  Constants & Data
/////////////////////////////////////////////////////////////////////
// For logging:
private static final String TAG = "DBAdapter";

// DB Fields
public static final String KEY_ROWID = "_id";
public static final int COL_ROWID = 0;
/*
 * CHANGE 1:
 */
// TODO: Setup your fields here:
public static final String KEY_NAME = "name";

// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_NAME = 1;


public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME};

// DB info: it's name, and the table we are using (just one).
public static final String DATABASE_NAME = "MyDb";
public static final String DATABASE_TABLE = "mainTable";
// Track DB version if a new version of your app changes the format.
public static final int DATABASE_VERSION = 2;   

private static final String DATABASE_CREATE_SQL = 
        "create table " + DATABASE_TABLE 
        + " (" + KEY_ROWID + " integer primary key autoincrement, "

        /*
         * CHANGE 2:
         */
        // TODO: Place your fields here!
        // + KEY_{...} + " {type} not null"
        //  - Key is the column name you created above.
        //  - {type} is one of: text, integer, real, blob
        //      (http://www.sqlite.org/datatype3.html)
        //  - "not null" means it is a required field (must be given a value).
        // NOTE: All must be comma separated (end of line!) Last one must have NO comma!!
        + KEY_NAME + " text not null, "
        // Rest  of creation:
        + ");";

// Context of application who uses us.
private final Context context;

private DatabaseHelper myDBHelper;
private SQLiteDatabase db;

/////////////////////////////////////////////////////////////////////
//  Public methods:
/////////////////////////////////////////////////////////////////////

public DBAdapter(Context ctx) {
    this.context = ctx;
    myDBHelper = new DatabaseHelper(context);
}

// Open the database connection.
public DBAdapter open() {
    db = myDBHelper.getWritableDatabase();
    return this;
}

// Close the database connection.
public void close() {
    myDBHelper.close();
}

// Add a new set of values to the database.
public long insertRow(String name) {
    /*
     * CHANGE 3:
     */     
    // TODO: Update data in the row with new fields.
    // TODO: Also change the function's arguments to be what you need!
    // Create row's data:
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_NAME, name);

    // Insert it into the database.
    return db.insert(DATABASE_TABLE, null, initialValues);
}

// Delete a row from the database, by rowId (primary key)
public boolean deleteRow(long rowId) {
    String where = KEY_ROWID + "=" + rowId;
    return db.delete(DATABASE_TABLE, where, null) != 0;
}

public void deleteAll() {
    Cursor c = getAllRows();
    long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
    if (c.moveToFirst()) {
        do {
            deleteRow(c.getLong((int) rowId));              
        } while (c.moveToNext());
    }
    c.close();
}

// Return all data in the database.
public Cursor getAllRows() {
    String where = null;
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                        where, null, null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;
}

// Get a specific row (by rowId)
public Cursor getRow(long rowId) {
    String where = KEY_ROWID + "=" + rowId;
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                    where, null, null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;
}

// Change an existing row to be equal to new data.
public boolean updateRow(long rowId, String name, int studentNum, String favColour) {
    String where = KEY_ROWID + "=" + rowId;

    /*
     * CHANGE 4:
     */
    // TODO: Update data in the row with new fields.
    // TODO: Also change the function's arguments to be what you need!
    // Create row's data:
    ContentValues newValues = new ContentValues();
    newValues.put(KEY_NAME, name);

    // Insert it into the database.
    return db.update(DATABASE_TABLE, newValues, where, null) != 0;
}



/////////////////////////////////////////////////////////////////////
//  Private Helper Classes:
/////////////////////////////////////////////////////////////////////

/**
 * Private class which handles database creation and upgrading.
 * Used to handle low-level database access.
 */
private static class DatabaseHelper extends SQLiteOpenHelper
{
    DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase _db) {
        _db.execSQL(DATABASE_CREATE_SQL);           
    }

    @Override
    public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
        Log.w(TAG, "Upgrading application's database from version " + oldVersion
                + " to " + newVersion + ", which will destroy all old data!");

        // Destroy old database:
        _db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);

        // Recreate new database:
        onCreate(_db);
    }
}
}

Answer 1

您只需要创建一次适配器，然后可以调用adapter.notifydatasetchanged或adapter.getCursor（）。requery（）刷新lsit