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;
        }
    }

}