android sqlLite 及Adapter 自定义和Adapter 改变UI

Android 在运行时（run-time）集成了 SQLite，所以每个 Android 应用程序都可以使用 SQLite 数据库。对于熟悉 SQL 的开发人员来时，在 Android 开发中使用 SQLite 相当简单。但是，由于 JDBC 会消耗太多的系统资源，所以 JDBC 对于手机这种内存受限设备来说并不合适。因此，Android 提供了一些新的 API 来使用 SQLite 数据库，Android 开发中，程序员需要学使用这些 API。

数据库存储在 data/< 项目文件夹 >/databases/ 下。

另推荐一个网站http://www.ibm.com/developerworks/cn/opensource/os-cn-sqlite/

上面这篇文章很不错!

我上网找了些资料! 大部分资料是继承SQLiteDatabase,这样相对来说比较麻烦!

下面是sqllite代码

public class SqlListeHelper {    private final static String DATABASE_NAME = "test.db";  //数据库名    private final static String TABLE_NAME = "sec_pwd";         //表名    public final static String FIELD_ID = "_id";                //字段名    public final static String FIELD_TITLE = "sec_Title";              //字段名    SQLiteDatabase dba ;    Context _context ;    /**     * android.content.Context 中提供了函数 , 注： Activity 是 Context 的子类     * openOrCreateDatabase () 来创建我们的数据库    *db = context .openOrCreateDatabase(String DATABASE_NAME , int Context. MODE_PRIVATE , null );     *String DATABASE_NAME   数据库的名字     *Int  MODE    操作模式   Context.MODE_PRIVATE 等     *CursorFactory 指针工厂 ，本例中传入 null ，暂不用     * @param context     */    public SqlListeHelper(Context context) {        _context = context;        this.dba = _context.openOrCreateDatabase(DATABASE_NAME,Context.MODE_PRIVATE, null);         createTable();        //获取数据的存储路径        System.out.println("------path["+dba.getPath()+"]--------------");    }    /**     * 创建表     */    public void createTable() {        // TODO Auto-generated method stub        String sql = "Create table " + TABLE_NAME + "(" + FIELD_ID + " integer primary key autoincrement,"                + FIELD_TITLE + " text )";        System.out.println("--------onCreate---------" +sql);        try {            dba.execSQL(sql);   //执行sql语句 无 返回结果        } catch (Exception e) {            System.out.println("table already exists (表已存在)");        }    }    /**     * 查询表数据     * @return     */    public List select() {        String sql = "select * from "+TABLE_NAME +" t where 1=1";        Cursor cursor = dba.rawQuery(sql, new String[]{});        int size = 0;        List list= null;        UserInfo user = null;        if(cursor !=null)            size = cursor.getCount();  //获取数据大小        list = new ArrayList();        //将指针移到第一条        cursor.moveToFirst();        //cursor.isAfterLast() 指是否到最后一条        while (!cursor.isAfterLast()){            user = new UserInfo();            user.setId(cursor.getInt(cursor.getColumnIndex(FIELD_ID)));            user.setPwd(cursor.getString(cursor.getColumnIndex(FIELD_TITLE)));            list.add(user);            //移到下条数据            cursor.moveToNext();        }        cursor.close();        return list;    }    public void insert(int id, String Title) {            //   new Object[]{id,Title}; 类似 key ,value            Object[] params = new Object[]{id,Title};            String sql = "insert into " + TABLE_NAME + "("+FIELD_ID+","+FIELD_TITLE+") VALUES(?,?)";            System.out.println("addsql = " + sql);        //执行sql语句            this.dba.execSQL(sql,params);    }}

注意的是 cursor.getColumnIndex 其实类似字符串中的indexOf 作用也就是获取字段位置

至于cursor.getInt () 和cursor.getString() 我想连

接过数据库的都知道!就不多解释!

大概的就写这两个比较代表性的方法,相对来说,查询比较麻烦点! 而添加与删除和修改差不多!就不多写了!

==================Adapter 的使用 ===============

---------------------------- Adapter 重写 start--------------------------------------------------------

要想更好的使用 Adapter或者想在listview中更好的添加自己的UI ,用重写 Adapter就更好不过了如下代码:

//重写Adapter    class MyArrayAdapter extends ArrayAdapter{        private Context _context;        private List<UserInfo> item;        public MyArrayAdapter(Context context, int textViewResourceId,List _item) {            super(context, textViewResourceId);    //To change body of overridden methods use File | Settings | File Templates.            this.item = _item;            this._context = context;        }        public void add(UserInfo user) {            if(user == null)                item = new ArrayList();            item.add(user);        }        @Override        public int getCount() {            try {                if(item == null)                    return  0;                else                    return item.size();            } catch (Exception e) {                return 0;            }        }        @Override        public Object getItem(int position) {            if(item != null)                return item.get(position) ;            else                return null;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            View _convertView = convertView;            if (convertView == null) {                LayoutInflater factory = LayoutInflater.from(_context);                final View textEntryView = factory.inflate(                        R.layout.listview_item, null);                _convertView = textEntryView;            }            UserInfo userInfo = item.get(position);            if(userInfo != null){                TextView id_tv =  (TextView)_convertView.findViewById(R.id.item_idet);                if(id_tv != null)                    id_tv.setText(userInfo.getId()+"");                TextView title_tv =(TextView) _convertView.findViewById(R.id.item_titileet);                if(title_tv != null)                    title_tv.setText(userInfo.getPwd());            }            return _convertView;        }    }

还有,就是在写activity的事实要继承ListActivity 因为这样更加方便使用 Adapter, 注意的是,有的人,习惯了直接用 findViewById(R.id.item_idet),而不是 _convertView.findViewById(R.id.item_idet) ,如果你这样操作,会导致错误产生!出现空!原因就在于你加载的Layout 的xml配置文件! 其他的都好理解,就是怎么使用List集合!
---------------------------- Adapter 重写 end --------------------------------------------------------

---------------------------- Adapter 改变UI start--------------------------------------------------------
我是用sqllite和此demo一起使用的!有数据才方便测试学习!还有在配置文件中,添加的主配置文件中要添加红线部分(内置ID) 如下图:

private SqlListeHelper helper; private static MyArrayAdapter myArrayAdapter = null;         setContentView(R.layout.main);           //new MyArrayAdapter(this, R.layout.main, getData()) 可以看重写 就知道原因        setListAdapter(new MyArrayAdapter(this, R.layout.main, getData()));      myArrayAdapter = (MyArrayAdapter)getListAdapter(); //此处 myArrayAdapter  为全局 方便UI改变        if(myArrayAdapter != null)            System.out.println("getCount["+myArrayAdapter.getCount()+"]"); private List<Map<String,Object>> getData(){        List<Map<String,Object>> list = new ArrayList<Map<String, Object>>();        List data = helper.select();  //查询sqllite表中数据        Map userMap = null;        if(data == null)            return  null;        return data;    }

注意,UI改变的时候要用到Message ,以及handler不然会出现异常,导致系统崩溃! 如下!

Message ms = Message.obtain(updateUIHandler);                 ms.what = UPDATEUIADAPTER;                ms.obj = u;                ms.sendToTarget();

//下面最为关键的是myArrayAdapter.notifyDataSetChanged(); 此行代码为改变UI关键

Handler updateUIHandler = new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what){                case UPDATEUIADAPTER:                    UserInfo user = (UserInfo)msg.obj;                    if(user != null && myArrayAdapter != null){                       myArrayAdapter.add(user);                       myArrayAdapter =(MyArrayAdapter) getListAdapter();                       myArrayAdapter.notifyDataSetChanged();                    }                    break;                default:                    break;            }        }    }   ;

---------------------------- Adapter 改变UI end--------------------------------------------------------

下面例子是我与sqllite一起使用的demo代码!sqllite中代码已经在上面贴出与大家分享!

public class MyActivity extends ListActivity{    private final int UPDATEUIADAPTER = 1;    private static EditText addEt = null;    private static Button addbtn = null;    private static Button querybtn = null;    private static EditText queryet = null;    private static Context _context ;    private ListView listView = null;    private SimpleAdapter adapter = null  ;    private static MyArrayAdapter myArrayAdapter = null;    private SQLiteDatabase base ;    private SqlListeHelper helper;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState)    {        _context = this;        helper = new SqlListeHelper(_context);//        base = helper.getWritableDatabase();        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        listView = new ListView(_context);//        setListAdapter(new MyArrayAdapter(this, R.layout.main, getData()));        myArrayAdapter = (MyArrayAdapter)getListAdapter();        if(myArrayAdapter != null)            System.out.println("getCount["+myArrayAdapter.getCount()+"]");        addEt = (EditText)findViewById(R.id.addet);        queryet = (EditText)findViewById(R.id.queryet);        addbtn = (Button)findViewById(R.id.addbtn);        querybtn = (Button)findViewById(R.id.querybtn);        addbtn.setOnClickListener(addBtnOnClickListener);        querybtn.setOnClickListener(queryBtnOnClickListener);    }    private List<Map<String,Object>> getData(){        List<Map<String,Object>> list = new ArrayList<Map<String, Object>>();        List data = helper.select();        Map userMap = null;        if(data == null)            return  null;        return data;    }    View.OnClickListener addBtnOnClickListener = new View.OnClickListener(){        public void onClick(View view) {            Toast.makeText(_context,"你好哈!",Toast.LENGTH_LONG).show();            if(addEt.getText().toString().equals(""))                return;            else{                String addStr = addEt.getText().toString();                UserInfo u = new UserInfo();                u.setPwd("hi![" + addStr + "]");                u.setId(Integer.parseInt(addStr.trim()));                helper.insert(Integer.parseInt(addStr.trim()), "hi![" + addStr + "]");                Message ms = Message.obtain(updateUIHandler);                ms.what = UPDATEUIADAPTER;                ms.obj = u;                ms.sendToTarget();            }        }    } ;    Handler updateUIHandler = new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what){                case UPDATEUIADAPTER:                    UserInfo user = (UserInfo)msg.obj;                    if(user != null && myArrayAdapter != null){                       myArrayAdapter.add(user);                       myArrayAdapter =(MyArrayAdapter) getListAdapter();                       myArrayAdapter.notifyDataSetChanged();                    }                    break;                default:                    break;            }        }    }   ;    View.OnClickListener queryBtnOnClickListener = new View.OnClickListener(){        public void onClick(View view) {            List list = helper.select();            System.out.println("count :"+list.size());        }    };    //重写Adapter    class MyArrayAdapter extends ArrayAdapter{        private Context _context;        private List<UserInfo> item;        public MyArrayAdapter(Context context, int textViewResourceId,List _item) {            super(context, textViewResourceId);    //To change body of overridden methods use File | Settings | File Templates.            this.item = _item;            this._context = context;        }        public void add(UserInfo user) {            if(user == null)                item = new ArrayList();            item.add(user);        }        @Override        public int getCount() {            try {                if(item == null)                    return  0;                else                    return item.size();            } catch (Exception e) {                return 0;            }        }        @Override        public Object getItem(int position) {            if(item != null)                return item.get(position) ;            else                return null;        }        @Override        public View getView(int position, View convertView, ViewGroup parent) {            View _convertView = convertView;            if (convertView == null) {                LayoutInflater factory = LayoutInflater.from(_context);                final View textEntryView = factory.inflate(                            R.layout.listview_item, null);                _convertView = textEntryView;            }            UserInfo userInfo = item.get(position);            if(userInfo != null){                TextView id_tv =  (TextView)_convertView.findViewById(R.id.item_idet);                if(id_tv != null)                    id_tv.setText(userInfo.getId()+"");                TextView title_tv =(TextView) _convertView.findViewById(R.id.item_titileet);                if(title_tv != null)                    title_tv.setText(userInfo.getPwd());            }            return _convertView;        }    }}

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