我有一个应用程序，用户可以在其中创建事件，将其保存到数据库中，然后显示在 ListView 中。
这是我将事件添加到数据库的活动：
public class AddEvent extends Activity{
DBAdapter DB;
int day;
int month;
int year;
int hour;
int minute;
String date;
String time;
String description;
String name;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.event);
openDB();
DatePicker Date = (DatePicker) findViewById (R.id.DatePicker);
year = Date.getYear();
month = Date.getMonth();
day = Date.getDayOfMonth();
String yearstr = Integer.toString(year);
String monthstr = Integer.toString(month);
String daystr = Integer.toString(day);
date = monthstr+"/"+daystr+"/"+yearstr;
TimePicker Time = (TimePicker) findViewById (R.id.TimePicker);
hour = Time.getCurrentHour();
minute = Time.getCurrentHour();
String hourstr;
if(hour>12){
hourstr = Integer.toString(hour-12);
}
else{
hourstr = Integer.toString(hour);
}
String minutestr = Integer.toString(minute);
time = hourstr+":"+minutestr;
EditText namefield = (EditText) findViewById (R.id.EventNameField);
name = namefield.getText().toString().trim();
EditText descfield = (EditText) findViewById (R.id.editText2);
description = descfield.getText().toString().trim();
}
@Override
protected void onDestroy() {
super.onDestroy();
closeDB();
}
public void Add(View v){
DB.insertRow(name, date, time, description, "event");
Intent move = new Intent (this, main.class);
startActivity(move);
}
public void openDB(){
DB = new DBAdapter(this);
DB.open();
}
public void closeDB(){
DB.close();
}
}
这是我要显示 ListView 的活动：
public class main extends Activity{
DBAdapter DB;
ListView mainList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
openDB();
populateListViewFromDB();
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
closeDB();
}
public void AddEvent(View v){
Intent StartAddNew = new Intent(this, AddNew.class);
startActivity(StartAddNew);
}
public void openDB(){
DB = new DBAdapter(this);
DB.open();
populateListViewFromDB();
}
public void closeDB(){
DB.close();
}
public void populateListViewFromDB(){
Cursor cursor = DB.getAllRows();
startManagingCursor(cursor);
// Setup mapping from cursor to view fields:
String[] fromFieldNames = new String[]
{ DBAdapter.Value_1, DBAdapter.Value_2, DBAdapter.Value_3, DBAdapter.Value_4, DBAdapter.Value_5};
int[] toViewIDs = new int[]
{R.id.itemName,R.id.itemMain,R.id.itemExtra,R.id.itemDescription,R.id.itemType};
// Create adapter to may columns of the DB onto element in the UI.
SimpleCursorAdapter myCursorAdapter =
new SimpleCursorAdapter(this, R.layout.listitem, cursor, fromFieldNames, toViewIDs)
{
@Override
public View getView(int position, View convertView, ViewGroup parent)
{
final View row = super.getView(position, convertView, parent);
if (position % 2 == 0)
row.setBackgroundResource(android.R.color.darker_gray);
else
row.setBackgroundResource(android.R.color.background_light);
return row;
}
};
mainList = (ListView) findViewById (R.id.mainList);
mainList.setAdapter(myCursorAdapter);
}
}
还有我的 DBAdapter：
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 Value_1 = "value1";
public static final String Value_2 = "value2";
public static final String Value_3 = "value3";
public static final String Value_4 = "value4";
public static final String Value_5 = "value5";
// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_NAME = 1;
public static final int COL_1 = 2;
public static final int COL_2 = 3;
public static final int COL_3 = 4;
public static final int COL_4 = 5;
public static final int COL_5 = 6;
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, Value_1, Value_2, Value_3, Value_4, Value_5};
// 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, "
+ Value_1 + " text not null, "
+ Value_2 + " text not null, "
+ Value_3 + " text not null, "
+ Value_4 + " text not null, "
+ Value_5 + " 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 Value1, String Value2, String Value3, String Value4, String Value5) {
/*
* 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(Value_1, Value1);
initialValues.put(Value_2, Value2);
initialValues.put(Value_3, Value3);
initialValues.put(Value_4, Value4);
initialValues.put(Value_5, Value5);
// 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(int rowId, String Value1, String Value2, String Value3, String Value4, String Value5) {
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(Value_1, Value1);
newValues.put(Value_2, Value2);
newValues.put(Value_3, Value3);
newValues.put(Value_4, Value4);
newValues.put(Value_5, Value5);
// 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);
}
}
}
当我运行应用程序时，SimpleCursorAdapter 不会填充 ListView，但是不会引发任何错误。我该怎么做才能让我的数据出现在 ListView 中？