我目前有一个列表视图，它从 SQL Lite 数据库中获取数据。我不知道如何使数据显示在顶部，最新信息在底部，最旧的信息在底部。这是我的主类，它显示列表视图和我的 DBAdapter
主要的：
package com.ArielR.Spot;
import java.util.ArrayList;
import java.util.Arrays;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.content.Intent;
import android.widget.SimpleCursorAdapter;
import android.widget.Toast;
import android.database.Cursor;
import android.view.MenuInflater;
import android.view.MenuItem;
public class main extends Activity {
/** Called when the activity is first created. */
DBAdapter SpotDB;
String Name;
String URL;
String Description;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Bundle extras = getIntent().getExtras();
openDB();
if (extras != null) {
Name= extras.getString("name");
URL= extras.getString("url");
Description= extras.getString("description");
if(Name.equals("") || URL.equals("") || Description.equals("")){
Toast.makeText(this, "Invalid Submission", Toast.LENGTH_LONG).show();
populateListViewfromDB();
}
else{
populateListViewfromDB();
}
}
}
@Override
protected void onDestroy() {
super.onDestroy();
closeDB();
}
private void openDB() {
SpotDB = new DBAdapter(this);
SpotDB.open();
addRow();
populateListViewfromDB();
}
private void closeDB() {
SpotDB.close();
}
public void addRow() {
long newid = SpotDB.insertRow(Name, URL, Description);
populateListViewfromDB();
}
public void AddNew() {
Intent intent = new Intent();
intent.setClass(this, AddNewItem.class);
startActivity(intent);
}
public void populateListViewfromDB() {
Cursor cursor = SpotDB.getAllRows();
startManagingCursor(cursor);
String[] FromFieldNames= new String[]
{DBAdapter.KEY_NAME, DBAdapter.KEY_URL, DBAdapter.KEY_DESCRIPTION};
int[] ToViewIDs= new int[]
{R.id.Name, R.id.URL, R.id.Description};
SimpleCursorAdapter myCursorAdapter =
new SimpleCursorAdapter(
this,
R.layout.row,
cursor,
FromFieldNames,
ToViewIDs
);
ListView list = (ListView) findViewById(R.id.listView);
list.setAdapter(myCursorAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case R.id.action_search:
AddNew();
return true;
}
return true;
}
}
数据库适配器：
package com.ArielR.Spot;
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;
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";
public static final String KEY_URL = "URL";
public static final String KEY_DESCRIPTION = "Description";
// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_NAME = 1;
public static final int COL_URL = 2;
public static final int COL_DESCRIPTION = 3;
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, KEY_URL, KEY_DESCRIPTION};
// DB info: it's name, and the table we are using (just one).
public static final String DATABASE_NAME = "SpotDb";
public static final String DATABASE_TABLE = "main";
// 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, "
+ KEY_URL + " text not null, "
+ KEY_DESCRIPTION + " 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, String url, String description) {
/*
* 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);
initialValues.put(KEY_URL, url);
initialValues.put(KEY_DESCRIPTION, description);
// 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, String url, String description) {
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);
newValues.put(KEY_URL, url);
newValues.put(KEY_DESCRIPTION, description);
// 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);
}
}
}