数据存储之SQLite

dbHelper.java

package com.terry;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.util.Log;public class dbHelper extends SQLiteOpenHelper {private final static String DATABASE_NAME="sec_db";private final static int DATABASE_VERSION=1;private final static String TABLE_NAME="sec_pwd";public final static String FIELD_ID="_id"; public final static String FIELD_TITLE="sec_Title";public dbHelper(Context context){   /** * 通过构造函数来创建数据库,如果进入此函数，不存在此数据库则创建，如果存在此数据库则打开连接， * 只要进入此方法就可以用打开的连接获得getWritableDatabase()或getReadableDatabase()这两个方法。 */super(context, DATABASE_NAME,null, DATABASE_VERSION);} /**  * 一个数据库中可以包含多个表，每一条数据都存在指定的表中，要创建可以通过 execSQL 方法来执行一条 SQL 语句。  */@Overridepublic void onCreate(SQLiteDatabase db) {// TODO Auto-generated method stub//创建了表名为“sec_pwd” 的数据表，表内存在一个 integer 类型的主键和一个 text 类型的字段，并执行创建该表。String sql="Create table "+TABLE_NAME+"("+FIELD_ID+" integer primary key autoincrement,"+FIELD_TITLE+" text );";db.execSQL(sql); }@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stubString sql=" DROP TABLE IF EXISTS "+TABLE_NAME;db.execSQL(sql);onCreate(db);}    /** * 查询数据 * @return */public Cursor select(){SQLiteDatabase db=this.getReadableDatabase();Cursor cursor=db.query(TABLE_NAME, null, null, null, null, null,  " _id desc");   return cursor;}/** * 添加数据 * @param Title * @return */public long insert(String Title){   /** * 封装了一个使用SQLite 的 insert 方法，向表中添加数据，但是insert 方法要求把数据都打包到 ContentValues 中， *  ContentValue 其实可就是一个 HashTable，Key值是字段名称，Value 值是字段的值。 * 通过 ContentValues 的put 方法就可以把数据库放到 ContentValue 对象中，然后插入到表中去。 */SQLiteDatabase db=this.getWritableDatabase();ContentValues cv=new ContentValues(); cv.put(FIELD_TITLE, Title);long row=db.insert(TABLE_NAME, null, cv);return row;}/** * 删除数据 * @param id */public void delete(int id){SQLiteDatabase db=this.getWritableDatabase();String where=FIELD_ID+"=?";String[] whereValue={Integer.toString(id)};db.delete(TABLE_NAME, where, whereValue);}/** * 修改数据 * @param id * @param Title */public void update(int id,String Title){SQLiteDatabase db=this.getWritableDatabase();String where=FIELD_ID+"=?";String[] whereValue={Integer.toString(id)};ContentValues cv=new ContentValues(); cv.put(FIELD_TITLE, Title);db.update(TABLE_NAME, cv, where, whereValue);}}

这里用到了Menu做功能按钮，实例代码如下：

package com.terry;

import android.app.Activity;import android.database.Cursor;import android.database.sqlite.SQLiteCursor;import android.os.Bundle; import android.view.Menu;  import android.view.MenuItem;import android.view.View;import android.widget.AdapterView;import android.widget.EditText;import android.widget.ListAdapter;import android.widget.ListView;import android.widget.SimpleCursorAdapter;import android.widget.AdapterView.OnItemClickListener;import android.widget.AdapterView.OnItemSelectedListener;public class testDbActivity extends Activity {private dbHelper db;private Cursor myCursor;private ListView myListView;private EditText myEditText;private int _id;protected final static int MENU_ADD=Menu.FIRST;protected final static int MENU_EDIT=Menu.FIRST+1;protected final static int MENU_DELETE=Menu.FIRST+2;   @Overridepublic boolean onCreateOptionsMenu(Menu menu) {// TODO Auto-generated method stub   super.onCreateOptionsMenu(menu);menu.add(Menu.NONE, MENU_ADD, 0, R.string.ADD);menu.add(Menu.NONE, MENU_EDIT, 0,R.string.EDIT);menu.add(Menu.NONE, MENU_DELETE, 0,R.string.DELETE); return true;}   @Overridepublic boolean onOptionsItemSelected(MenuItem item) {// TODO Auto-generated method stubsuper.onOptionsItemSelected(item); switch (item.getItemId()) {case MENU_ADD:operation("add");break;case MENU_EDIT:operation("edit");break;case MENU_DELETE:operation("delete");break;default:break;}return true;}             /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        myEditText=(EditText)findViewById(R.id.EditText1);        myListView=(ListView)findViewById(R.id.ListView1);        db=new dbHelper(testDbActivity.this);        myCursor=db.select();        SimpleCursorAdapter adpater=new SimpleCursorAdapter(this        , R.layout.test, myCursor,        new String[]{dbHelper.FIELD_TITLE},        new int[]{R.id.topTextView});        myListView.setAdapter(adpater);                myListView.setOnItemClickListener(new OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> arg0, View arg1, int arg2,long arg3) {// TODO Auto-generated method stubmyCursor.moveToPosition(arg2);_id=myCursor.getInt(0);myEditText.setText(myCursor.getString(1));}});                        myListView.setOnItemSelectedListener(new OnItemSelectedListener() {@Overridepublic void onItemSelected(AdapterView<?> arg0, View arg1,int arg2, long arg3) {// TODO Auto-generated method stubSQLiteCursor sc=(SQLiteCursor)arg0.getSelectedItem();_id=sc.getInt(0);myEditText.setText(sc.getString(1));}@Overridepublic void onNothingSelected(AdapterView<?> arg0) {// TODO Auto-generated method stub}});    }    private void operation(String cmd)    {    if(myEditText.getText().toString().equals(""))    return;    if(cmd=="add")    db.insert( myEditText.getText().toString());    if(cmd=="edit")    db.update(_id,  myEditText.getText().toString());    if(cmd=="delete")    db.delete(_id);    myCursor.requery();    myListView.invalidateViews();    myEditText.setText("");    _id=0;        }                                   }

更多相关文章

随机推荐