1 activity可以继承扩展 ListActivity 比如：class DummyNote extends ListActivity { private String[] note_array = { "gasolin", "crota", "louk", "magicion" }; ListAdapter adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, note_array); setListAdapter(adapter);
}
2 使用sqlite 在新建立工程后，打开模拟器后，在sdk的tools下运行adb shellcd data/data/ls cd 工程名mkdir databasescd databasessqlite3 notes.db （建立了一个notes.db数据库）create talbe notes......;sqlite>.databases (查看当前目录下的数据库列表）sqllite>.tables (查看所有数据表） .schema notes (查看指定表的结构）离开sqllite: .exit
3 CRUD的典型例子 public class NotesDbAdapter { private static final String DATABASE_NAME = "notes.db"; private static final int DATABASE_VERSION = 1;
private static final String DATABASE_TABLE = "notes";
private static final String DATABASE_CREATE = "create table notes(" +"_id INTEGER PRIMARY KEY," +"note TEXT," +"created INTEGER," +"modified INTEGER" +");";
private static class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(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(DATABASE_CREATE); }
@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); }
} private Context mCtx = null; private DatabaseHelper dbHelper ; private SQLiteDatabase db;
/** Constructor */ public NotesDbAdapter(Context ctx) { this.mCtx = ctx; }
public NotesDbAdapter open () throws SQLException { dbHelper = new DatabaseHelper(mCtx); db = dbHelper.getWritableDatabase(); return this; }
public void close() { dbHelper.close(); }
//start query public static final String KEY_ROWID = "_id"; public static final String KEY_NOTE = "note"; public static final String KEY_CREATED = "created";
String[] strCols = new String[] { KEY_ROWID, KEY_NOTE, KEY_CREATED };
/* public Cursor getall() { return db.rawQuery("SELECT * FROM notes", null); } */ /* // get all entries public Cursor getall() { return db.query(DATABASE_TABLE, //Which table to Select strCols,// Which columns to return null, // WHERE clause null, // WHERE arguments null, // GROUP BY clause null, // HAVING clause null //Order-by clause ); } */ // get all entries public Cursor getall() { return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NOTE, KEY_CREATED}, null, null, null, null, null); }
// add an entry public long create(String Note) { Date now = new Date(); ContentValues args = new ContentValues(); args.put(KEY_NOTE, Note); args.put(KEY_CREATED, now.getTime());
return db.insert(DATABASE_TABLE, null, args); }
//remove an entry public boolean delete(long rowId) { return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; } //query single entry public Cursor get(long rowId) throws SQLException { Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NOTE, KEY_CREATED}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; }
//update public boolean update(long rowId, String note) { ContentValues args = new ContentValues(); args.put(KEY_NOTE, note);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; }
}
主程序调用： private NotesDbAdapter mDbHelper; private Cursor mNotesCursor; private void setAdapter() { mDbHelper = new NotesDbAdapter(this); mDbHelper.open(); fillData();
} private void fillData() { mNotesCursor = mDbHelper.getall(); startManagingCursor(mNotesCursor);
String[] from = new String[]{"note"}; int[] to = new int[]{android.R.id.text1};
// Now create a simple cursor adapter SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, mNotesCursor, from, to); setListAdapter(adapter); } 新增记录： public long create(String Note) { Date now = new Date(); ContentValues args = new ContentValues(); args.put(KEY_NOTE, Note); 。。。。。。
return db.insert(DATABASE_TABLE, null, args); }删除记录： public boolean delete(long rowId) { return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; } mDbHelper.delete(getListView().getSelectedItemId());//这里用getListView().getSelectedItemId()获得选定删除哪一条记录
查询记录：//query single entry public Cursor get(long rowId) throws SQLException { Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NOTE, KEY_CREATED}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; }更新记录： //update public boolean update(long rowId, String note) { ContentValues args = new ContentValues(); args.put(KEY_NOTE, note);
return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; }4 activity中的相关，比如选了A中的记录，然后打开B来编辑，B编辑完后，再返回A。 首先在B中，接收BUNDLE： private void showViews(Bundle savedInstanceState) { //mRowId = savedInstanceState != null ? savedInstanceState.getLong(NotesDbAdapter.KEY_ROWID) : null; if (mRowId == null) { Bundle extras = getIntent().getExtras(); mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID) : null; }
//把编辑的数据拿出来 if (mRowId != null) { Cursor note = mDbHelper.get(mRowId); startManagingCursor(note);
field_note.setText(note.getString( note.getColumnIndexOrThrow(NotesDbAdapter.KEY_NOTE) )); } 当编辑成功提交后， public void onClick(View view) { mDbHelper.update(mRowId, field_note.getText().toString()); setResult(RESULT_OK); finish(); 这里的setResult，表示这个activity成功，返回
在调用方中，如果是一个LISTVIEW的列表的话，点某一个列 protected void onListItemClick(ListView l, View v, int position, long id) { super.onListItemClick(l, v, position, id); Intent intent = new Intent(this, NoteEdit.class); intent.putExtra(NotesDbAdapter.KEY_ROWID, id); startActivityForResult(intent, ACTIVITY_EDIT); } 这里的startActivityForResult表示的是要调用另外一个activity，并且要求结果返回同时： protected void onActivityResult(int requestCode, int resultCode, Intent intent) { super.onActivityResult(requestCode, resultCode, intent); fillData(); }
5 长按菜单 A 在oncreate函数中，注册 registerForContextMenu(getListView());//说明点listview时会使用长按菜单 B public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { // TODO Auto-generated method stub menu.add(0, MENU_DELETE, 0, "删除记事"); menu.setHeaderTitle("要怎么处理这个项目"); super.onCreateContextMenu(menu, v, menuInfo); }
本文来自博客，转载请标明出处：http://blog.csdn.net/jackyrongvip/archive/2010/02/09/5303823.aspx
