我想开始工作并理解SQlite，这就是为什么我开始尝试在android开发者页面上理解和编程Notepad-Tutorial。但在ListView中，它们只显示您创建的注释的标题，但不显示正文。所以我想在ListView项目中显示标题和正文。这是我的代码：
NoteActivity类：
public class NoteActivity extends ListActivity
{
private static final ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
private static final int ACTIVITY_CREATE=0;
private static final int ACTIVITY_EDIT=1;
private static final int INSERT_ID = Menu.FIRST;
private static final int DELETE_ID = Menu.FIRST + 1;
private NotesDbAdapter mDbHelper;
Context ctx;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ctx = this;
setContentView(R.layout.notepad_list);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
fillData();
registerForContextMenu(getListView());
}
private void fillData() {
Cursor notesCursor = mDbHelper.fetchAllNotes();
// Get all of the rows from the database and create the item list
notesCursor = mDbHelper.fetchAllNotes();
startManagingCursor(notesCursor);
//This code works only to display the title in the ListView:
/*
// Create an array to specify the fields we want to display in the list (only TITLE)
String[] from = new String[]{NotesDbAdapter.KEY_TITLE};
// and an array of the fields we want to bind those fields to (in this case just text1)
int[] to = new int[]{R.id.text1};
// Now create a simple cursor adapter and set it to display
SimpleCursorAdapter notes =new SimpleCursorAdapter(this, R.layout.notes_row, notesCursor, from, to);
setListAdapter(notes);
*/
//Here I want to use a SimpleAdapter to display the title and body of the Note
SimpleAdapter adapter = new SimpleAdapter
(this, list, R.layout.custom_row_view, new String[] {"title","body"}, new int[] {R.id.text11,R.id.text2});
HashMap<String,String> temp = new HashMap<String,String>();
temp.put("title",NotesDbAdapter.KEY_TITLE);
temp.put("body", NotesDbAdapter.KEY_BODY);
list.add(temp);
setListAdapter(adapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
menu.add(0, INSERT_ID,0, R.string.menu_insert);
return true;
}
@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
switch(item.getItemId()) {
case INSERT_ID:
createNote();
return true;
}
return super.onMenuItemSelected(featureId, item);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenu.ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(0,DELETE_ID,0,R.string.menu_delete);
}
@Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()){
case DELETE_ID:
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
mDbHelper.deleteNote(info.id);
fillData();
Toast.makeText(this,"Note deleted",Toast.LENGTH_SHORT).show();
return true;
}
return super.onContextItemSelected(item);
}
private void createNote() {
Intent intent = new Intent(this, NoteEdit.class);
startActivityForResult(intent, ACTIVITY_CREATE);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
super.onListItemClick(l, v, position, id);
Intent i = new Intent(this, NoteEdit.class);
i.putExtra(NotesDbAdapter.KEY_ROWID, id);
startActivityForResult(i, ACTIVITY_EDIT);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
super.onActivityResult(requestCode, resultCode, intent);
fillData();
}
我使用菜单按钮创建注释但您可以忽略它们，importat方法是“fillData（）”。我不明白为什么ListView会显示两个字符串“titl”和“body”，而不是标题和正文的内容。
这是我用来创建/编辑笔记的NoteEdit类：
public class NoteEdit extends Activity {
private EditText mTitleText;
private EditText mBodyText;
private Button confirmButton;
private Long mRowId;
private NotesDbAdapter mDbHelper;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
setContentView(R.layout.note_edit);
setTitle(R.string.edit_note);
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
confirmButton = (Button) findViewById(R.id.confirm);
mRowId = (savedInstanceState == null) ? null :
(Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
if (mRowId == null) {
Bundle extras = getIntent().getExtras();
mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
: null;
}
populateFields();
}
public void confirmButton(View view)
{
switch (view.getId()){
case R.id.confirm:
setResult(RESULT_OK);
finish();
}
}
@Deprecated
private void populateFields() {
if (mRowId != null) {
Cursor note = mDbHelper.fetchNote(mRowId);
startManagingCursor(note);
mTitleText.setText(note.getString(
note.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE)));
mBodyText.setText(note.getString(
note.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY)));
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
saveState();
outState.putSerializable(NotesDbAdapter.KEY_ROWID, mRowId);
}
@Override
protected void onPause() {
super.onPause();
saveState();
}
@Override
protected void onResume() {
super.onResume();
populateFields();
}
private void saveState() {
String title = mTitleText.getText().toString();
String body = mBodyText.getText().toString();
if (mRowId == null) {
long id = mDbHelper.createNote(title, body);
if (id > 0) {
mRowId = id;
}
} else {
mDbHelper.updateNote(mRowId, title, body);
}
}
}
这里是我的NotesDBAdapter类：
/ ** *简单说明数据库访问助手类。定义基本的CRUD操作 *用于记事本示例，并且能够列出所有音符以及 *检索或修改特定的笔记。
* / 公共类NotesDbAdapter {
private static final String DATABASE_NAME = "data";
private static final String DATABASE_TABLE = "notes";
private static final int DATABASE_VERSION = 2;
public static final String KEY_TITLE = "title";
public static final String KEY_BODY = "body";
public static final String KEY_ROWID = "_id";
private static final String TAG = "NotesDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private static final String DATABASE_CREATE =
"create table notes (_id integer primary key autoincrement, "
+ "title text not null, body text not null);";
private final Context mCtx;
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);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS notes");
onCreate(db);
}
}
/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param ctx the Context within which to work
*/
public NotesDbAdapter(Context ctx) {
this.mCtx = ctx;
}
/**
* Open the notes database. If it cannot be opened, try to create a new
* instance of the database. If it cannot be created, throw an exception to
* signal the failure
*
* @return this (self reference, allowing this to be chained in an
* initialization call)
* @throws android.database.SQLException if the database could be neither opened or created
*/
public NotesDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
public void close() {
mDbHelper.close();
}
/**
* Create a new note using the title and body provided. If the note is
* successfully created return the new rowId for that note, otherwise return
* a -1 to indicate failure.
*
* @param title the title of the note
* @param body the body of the note
*/
public long createNote(String title, String body) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_BODY, body);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}
/**
* Delete the note with the given rowId
* @param rowId id of note to delete
* @return true if deleted, false otherwise
*/
public boolean deleteNote(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
/**
* Return a Cursor over the list of all notes in the database
*
* @return Cursor over all notes
*/
public Cursor fetchAllNotes() {
return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE,
KEY_BODY}, null, null, null, null, null);
}
/**
* Return a Cursor positioned at the note that matches the given rowId
* @param rowId id of note to retrieve
* @return Cursor positioned to matching note, if found
* @throws android.database.SQLException if note could not be found/retrieved
*/
public Cursor fetchNote(long rowId) throws SQLException {
Cursor mCursor =
mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
KEY_TITLE, KEY_BODY}, KEY_ROWID + "=" + rowId, null,
null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
/**
* Update the note using the details provided. The note to be updated is
* specified using the rowId, and it is altered to use the title and body
* values passed in
*
* @param rowId id of note to update
* @param title value to set note title to
* @param body value to set note body to
* @return true if the note was successfully updated, false otherwise
*/
public boolean updateNote(long rowId, String title, String body) {
ContentValues args = new ContentValues();
args.put(KEY_TITLE, title);
args.put(KEY_BODY, body);
return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
我没有发布xml文件，因为我认为你不需要它们，主要问题是“fillData”方法，我不知道如何从listView中的数据库中发布2行
我也尝试过其他一些教程，但我无法让它工作
答案 0 :(得分：0)
问题在于我所说的fillData()方法。您将列名称作为值传递，而不是光标中的实际值。
HashMap<String,String> temp = new HashMap<String,String>();
temp.put("title",NotesDbAdapter.KEY_TITLE);
temp.put("body", NotesDbAdapter.KEY_BODY);
list.add(temp);
这似乎是不正确的。相反，你应该按照以下几点做一些事情;
private void fillData() {
// Get all of the rows from the database and create the item list
Cursor notesCursor = mDbHelper.fetchAllNotes();
startManagingCursor(notesCursor);
// The list that will back our table, this could be turned into a member variable.
List<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
// Get the column indexes
int titleColumnIndex = notesCursor.getColumnIndex(NotesDbAdapter.KEY_TITLE);
int bodyColumnIndex = notesCursor.getColumnIndex(NotesDbAdapter.KEY_BODY);
// Iterate through all of the cursor rows to fill the adapter
while (notesCursor.moveToNext()) {
String title = notesCursor.getString(titleColumnIndex);
String body = notesCursor.getString(bodyColumnIndex);
HashMap<String,String> temp = new HashMap<String,String>();
temp.put("title", title);
temp.put("body", body);
list.add(temp);
}
//Here I want to use a SimpleAdapter to display the title and body of the Note
SimpleAdapter adapter = new SimpleAdapter
(this, list, R.layout.custom_row_view, new String[] {"title","body"}, new int[] {R.id.text11,R.id.text2});
setListAdapter(adapter);
}
有关Cursor的更多信息，因为在Android中使用数据库时，您将大量使用它。