我正在尝试使用SimpleCursorAdapter使用从SQLite数据库检索的数据填充ListView。我们用于表的KEY是;
_ROWID - 表示行号（在ListView中不可见）
_NAME - 我们数据库中的食品名称（如面包或奶酪）
_AMOUNT - 您对此食品的数量
_DATE - 产品的失效日期
另一个小组成员为数据库编写了代码，大约一半时间有一个名为getData的公共String。代码看起来像这样;
public class DatabaseCustom {
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "name";
public static final String KEY_AMOUNT = "amount";
public static final String KEY_DATE = "expiration_date";
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_NAME, KEY_AMOUNT, KEY_DATE};
private static final String DATABASE_NAME = "customDb";
private static final String DATABASE_TABLE = "customTable";
private static final int DATABASE_VERSION = 1;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
+ " INTEGER PRIMARY_KEY, " + KEY_NAME + " TEXT NOT NULL, "
+ KEY_AMOUNT + " TEXT NOT NULL, " + KEY_DATE
+ "TEXT NOT NULL);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public DatabaseCustom(Context c) {
ourContext = c;
}
public DatabaseCustom open() {
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
ourHelper.close();
}
public long createEntry(String name, String amount, String date) {
// TODO Auto-generated method stub
ContentValues cv = new ContentValues();
cv.put(KEY_NAME, name);
cv.put(KEY_AMOUNT, amount);
cv.put(KEY_DATE, date);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
public String getData() {
// TODO Auto-generated method stub
String[] columns = new String[] { KEY_ROWID, KEY_NAME, KEY_AMOUNT,
KEY_DATE };
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null,
null, null);
String result = "";
int iRow = c.getColumnIndex(KEY_ROWID);
int iName = c.getColumnIndex(KEY_NAME);
int iAmount = c.getColumnIndex(KEY_AMOUNT);
int iDate = c.getColumnIndex(KEY_DATE);
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
result = result + c.getString(iRow) + " " + c.getString(iName)
+ " " + c.getString(iAmount) + " " + c.getString(iDate)
+ "\n";
}
return result;
}
public String getName(long l) {
// TODO Auto-generated method stub
String[] columns = new String[] { KEY_ROWID, KEY_NAME, KEY_AMOUNT,
KEY_DATE };
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
+ l, null, null, null, null);
if (c != null) {
c.moveToFirst();
String name = c.getString(1);
return name;
}
return null;
}
public String getAmount(long l) {
// TODO Auto-generated method stub
String[] columns = new String[] { KEY_ROWID, KEY_NAME, KEY_AMOUNT,
KEY_DATE };
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
+ l, null, null, null, null);
if (c != null) {
c.moveToFirst();
String name = c.getString(2);
return name;
}
return null;
}
public String getDate(long l) {
// TODO Auto-generated method stub
String[] columns = new String[] { KEY_ROWID, KEY_NAME, KEY_AMOUNT,
KEY_DATE };
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
+ l, null, null, null, null);
if (c != null) {
c.moveToFirst();
String name = c.getString(3);
return name;
}
return null;
}
public void updateEntry(long lRow, String mName, String mAmount,
String mDate) {
// TODO Auto-generated method stub
ContentValues cvUpdate = new ContentValues();
cvUpdate.put(KEY_NAME, mName);
cvUpdate.put(KEY_AMOUNT, mAmount);
cvUpdate.put(KEY_DATE, mDate);
ourDatabase.update(DATABASE_TABLE, cvUpdate, KEY_ROWID + "=" + lRow,
null);
}
public void deleteEntry(long lRow1) {
// TODO Auto-generated method stub
ourDatabase.delete(DATABASE_TABLE, KEY_ROWID + "=" + lRow1, null);
}
从我收集的内容中，我需要在显示此ListView的Activity的代码中使用SimpleCursorAdapter设置populateListView方法。这是我到目前为止的代码（省略了一些与我的问题无关的代码）;
public class Products extends Activity implements OnClickListener{
DatabaseCustom ourDb;
final Context context = this;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.products);
openDb();
initiate();
populateListView();
}
public void onClick(View v) {
switch (v.getId()){
//A few different buttons for this activity here
}
}
private void initiate(){
//Link all the java variables to the corresponding xml elements here
}
private void openDb(){
ourDb = new DatabaseCustom(this);
ourDb.open();
}
private void populateListView(){
Cursor cursor = ourDb.getData();
String[] fromFieldNames = new String[] {DatabaseCustom.KEY_NAME, DatabaseCustom.KEY_AMOUNT, DatabaseCustom.KEY_DATE};
int[] toViewIDs = new int[] {R.id.tvProductNameList, R.id.tvAmountList, R.id.tvDateList};
SimpleCursorAdapter ourCursorAdapter;
ourCursorAdapter = new SimpleCursorAdapter(getBaseContext(),R.layout.item_layout, cursor, fromFieldNames, toViewIDs, 0);//Put text from KEYS into TVs
ListView ourList = (ListView) findViewById(R.id.lvProducts);
ourList.setAdapter(ourCursorAdapter);
}
在populateListView方法中，我尝试创建一个游标，在我们的数据库中查找getData方法并逻辑地给出错误，因为此数据库中的getData方法是公共String而不是公共游标，所以我尝试创建一个而是公共Cursor，我编码如下;
public Cursor getData() {
String where = null;
Cursor c = ourDatabase.query(true, DATABASE_TABLE, ALL_KEYS, where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
在为private void populateListView和公共Cursor添加代码之后，获取数据Eclipse并不显示任何错误，但应用程序在加载应该显示ListView的活动时崩溃。
在关注了SQL数据库，ListViews，CursorAdapters和String Arrays的大量教程之后，我已经到了我不知道在哪里寻找答案的地步，所以任何帮助都会非常受欢迎。