ANDROID：SQLite-ListView 2行

Question

我想开始工作并了解SQlite，所以这就是为什么我开始尝试在android开发人员页面上理解和编写Notepad-Tutorial的原因。 但是在ListView中，它们仅显示您创建的Note的标题，而不显示正文。 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，但是您可以忽略它们，importat方法是“ fillData（）”。 我不明白为什么ListView显示两个字符串“ titl”和“ body”，而不显示标题和正文的内容。

这是我的NoteEdit类，可用于创建/编辑注释：

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);
        }
    }
}

这是我的NotesDBAdapter类：

/ ** *简单的Notes数据库访问帮助程序类。 定义记事本示例的基本CRUD操作，并提供列出所有注释以及检索或修改特定注释的功能。

* /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，因为我认为您不需要它们，主要问题是“ fillData”方法，我不知道如何在listView中从数据库发布2行

我也尝试了其他一些教程，但无法成功

Answer 1

问题出在我所知道的你的fillData()方法中。 您将列名作为值而不是游标的实际值传递。

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，您应该按照以下步骤进行操作；

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更多信息，您将在使用Android中的数据库时对其进行相当广泛的使用。

有关使用游标的更清晰答案，请查阅本教程的 第4节 。