android中sqlite数据库操作

1. android中sqlite数据库操作， 首先将操作sqlite数据库的DAO层及数据库信息进入封装， 如下：

(1) MyDbHelper.java代码如下：

package com.gditc.notepad.db;


import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
 * sqlite数据库的创建/打开/关闭， 及对数据的增、 删、 改、 查
 * @author Cryhelyxx
 *
 */
public class MyDbHelper {

	//SQLiteOpenHelper实例对象
	private DatabaseHelper myDbHelper;
	//数据库实例对象
	private SQLiteDatabase myDb;
	//数据库调用实例
	private static MyDbHelper openHelper = null;
	//定义数据库名称
	private static final String DATABASE_NAME = "notepad.db3";
	//定义数据库版本
	private static int DATABASE_VERSION = 1;
	//表名
	private static String TableNames[];
	//字段名
	private static String FieldNames[][];
	//字段类型
	private static String FieldTypes[][];
	//上下文实例
	private final Context mCtx;
	
	public MyDbHelper(Context ctx) {
		this.mCtx = ctx;
	}
	
	public static MyDbHelper getInstance(Context context){
		if(openHelper == null){
			openHelper = new MyDbHelper(context);
			TableNames = MyDbInfo.getTableNames();
			FieldNames = MyDbInfo.getFieldNames();
			FieldTypes = MyDbInfo.getFieldTypes();
		}
		return openHelper;
	}

	//数据库辅助类
	private static class DatabaseHelper extends SQLiteOpenHelper{
		
		//构造方法
		public DatabaseHelper(Context context) {
			
			super(context, DATABASE_NAME, null, DATABASE_VERSION);
		}

		/**
		 * 创建数据库后，对数据库的操作
		 */
		@Override
		public void onCreate(SQLiteDatabase db) {
			if(TableNames == null){
				return;
			}
			for(int i = 0; i < TableNames.length; i++){
				String sql = "CREATE TABLE " + TableNames[i] + " (";
				for(int j = 0; j < FieldNames[i].length; j++){
					sql += FieldNames[i][j] + " " + FieldTypes[i][j] + ",";
				}
				sql = sql.substring(0, sql.length() - 1);		//去年最后的","
				sql += ")";
				db.execSQL(sql);
			}
		}

		/**
		 * 更改数据库版本的操作
		 */
		@Override
		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
			for(int i = 0; i < TableNames[i].length(); i++){
				String sql = "DROP TABLE IF EXISTS " + TableNames[i];
				db.execSQL(sql);
			}
			onCreate(db);
		}

		/**
		 * 打开数据库后首先被执行
		 */
		@Override
		public void onOpen(SQLiteDatabase db) {
			
			super.onOpen(db);
		}
	}

	/**
	 * 打开数据库
	 * @return
	 * @throws SQLException
	 */
	public MyDbHelper open() throws SQLException {
		myDbHelper = new DatabaseHelper(mCtx);
		myDb = myDbHelper.getWritableDatabase();
		return this;
	}
	
	/**
	 * 关闭数据库
	 */
	public void close() {
		myDbHelper.close();
	}
	
	public void execSQL(String sql) throws java.sql.SQLException {
		myDb.execSQL(sql);
	}
	
	/**
	 * sql查询语句
	 * @param sql
	 * @param selectionArgs
	 * @return
	 */
	public Cursor rawQuery(String sql, String[] selectionArgs) {
		Cursor cursor = myDb.rawQuery(sql, selectionArgs);
		return cursor;
	}
	
	/**
	 * 查询数据
	 * @param table
	 * @param columns
	 * @param selection
	 * @param selectionArgs
	 * @param groupBy
	 * @param having
	 * @param orderBy
	 * @return
	 */
	public Cursor select(String table, String[] columns,
			String selection, String[] selectionArgs, String groupBy,
			String having, String orderBy) {
		Cursor cursor = myDb.query(
				table, columns, selection, selectionArgs,
				groupBy, having, orderBy);
		return cursor;
	}
	
	/**
	 * 添加数据
	 * @param table
	 * @param fields
	 * @param values
	 * @return
	 */
	public long insert(String table, String fields[], String values[]) {
		ContentValues cv = new ContentValues();
		for (int i = 0; i < fields.length; i++) {
			cv.put(fields[i], values[i]);
		}
		return myDb.insert(table, null, cv);
	}
	
	/**
	 * 删除数据
	 * @param table
	 * @param whereClause
	 * @param whereArgs
	 * @return
	 */
	public int delete(String table, String whereClause, String[] whereArgs) {
		return myDb.delete(table, whereClause, whereArgs);
	}
	
	/**
	 * 更新数据
	 * @param table
	 * @param updateFields
	 * @param updateValues
	 * @param whereClause
	 * @param whereArgs
	 * @return
	 */
	public int update(String table, String updateFields[], String updateValues[],
			String whereClause, String[] whereArgs) {
		ContentValues cv = new ContentValues();
		for (int i = 0; i < updateFields.length; i++) {
			cv.put(updateFields[i], updateValues[i]);
		}
		return myDb.update(table, cv, whereClause, whereArgs);
	}
}

(2) MyDbInfo.java代码如下：

package com.gditc.notepad.db;
/**
 * sqlite数据库信息
 * @author Cryhelyxx
 *
 */
public class MyDbInfo {
	//表名， 使用一维数组， 使用全局变量(static)
	private static String TableNames[] = {
		"tbl_type", 
		"tbl_note"
	};
	
	//字段名， 为表示每个表table的字段， 使用二维数组， 使用全局变量(static)
	private static String FieldNames[][] = {
		{"_id", "type_name", "note_num"},
		{"_id", "note_title", "note_type", "note_content"}
	};
	
	//字段类型
	private static String FieldTypes[][] = {
		{"INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL", "TEXT CONSTRAINT UC1 UNIQUE"
			, "INTEGER"},
		{"INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL", "TEXT CONSTRAINT FK1 "
				+  "REFERENCES " + TableNames[0]
				+ "(" + FieldNames[0][1]
				+ ") ON DELETE CASCADE ON UPDATE CASCADE", "TEXT", "TEXT"}
	};

	public static String[] getTableNames() {
		return TableNames;
	}

	public static String[][] getFieldNames() {
		return FieldNames;
	}

	public static String[][] getFieldTypes() {
		return FieldTypes;
	}
}

2. 接着在Activity类调用上面的方法对sqlite数据库进入增、 删、 改、 查， 实例如下：

package com.gditc.notepad;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.KeyEvent;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.Toast;

import com.gditc.notepad.db.MyDbHelper;
import com.gditc.notepad.db.MyDbInfo;
import com.gditc.notepad.util.MyApplication;
import com.gditc.notepad.util.PlayAnimActivity;

public class MainActivity extends PlayAnimActivity {

	private Button btn_mainInterface = null;
	private Button btn_addnote = null;
	private Button btn_search = null;
	private Button btn_addType = null;

	private TextView tvNum_allnotes = null;

	private long firstTime = 0; 

	private ListView lv01 = null;
	private List> list = null;
	private Map map = null;
	private SimpleAdapter sa = null;

	private MyDbHelper db = null;	//数据库对象
	private Cursor  cursor = null;	//游标
	private String sql = "";		//sql语句

	private String value = "0";		//新建分类时， 该分类笔记的初始数量

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		this.setContentView(R.layout.activity_main);
		MyApplication.getInstance().addActivity(this);
		loadingFormation();
		initInfo();
	}

	/**
	 * 加载组件
	 */
	private void loadingFormation() {
		lv01 = (ListView) this.findViewById(R.id.lv01);
		btn_mainInterface = (Button) this.findViewById(R.id.btn_mainInterface);
		btn_addnote = (Button) this.findViewById(R.id.btn_addnote);
		btn_search = (Button) this.findViewById(R.id.btn_search);
		btn_addType = (Button) this.findViewById(R.id.btn_addType);
		tvNum_allnotes = (TextView) this.findViewById(R.id.tvNum_allnotes);
	}

	/**
	 * 初始化信息
	 */
	private void initInfo() {
		//实例化数据库对象
		db = MyDbHelper.getInstance(this.getApplicationContext());
		//打开数据库
		db.open();

		//设置拖动之后是否再次显示背景，也就是说设为true后，拖动listview，就不会显示背景图片了
		lv01.setAlwaysDrawnWithCacheEnabled(false); 

		//查询是否存在"默认分类", 且"默认分类"不能被删除
		String defaultNoteType = "默认分类";
		sql = "SELECT * FROM tbl_type WHERE type_name='" + defaultNoteType + "'";
		cursor = db.rawQuery(sql, null);
		if (cursor.getCount() == 0) {
			//插入"默认分类"
			int tableIndex = 0;
			String[] fieldNames = new String[2];
			String[] values = null;
			for (int i = 1; i < MyDbInfo.getFieldNames()[tableIndex].length; i++) {
				fieldNames[i-1] = MyDbInfo.getFieldNames()[tableIndex][i];
			}
			values = new String[]{
					defaultNoteType,
					value
			};
			long reVal = 0;
			reVal = db.insert(MyDbInfo.getTableNames()[tableIndex], fieldNames, values);
			if(!(reVal > 0)){
				refresh();
			}
		}

		sql = "SELECT * FROM tbl_type";
		cursor = db.rawQuery(sql, null);
		//为ListView类型的lv01注册上下文菜单
		registerForContextMenu(lv01);
		//创建数据源
		list = new ArrayList>();	//涉及知识：多态、泛型
		while (cursor.moveToNext()) {	//加载所有分类
			map = new HashMap();
			map.put("image", R.drawable.img30);
			map.put("category", cursor.getString(1));
			sql = "SELECT COUNT(*) FROM tbl_note WHERE note_type='" + cursor.getString(1) +"'";
			Cursor c = db.rawQuery(sql, null);
			if (c.moveToNext()) {
				map.put("num", c.getInt(0));
			}else{
				map.put("num", cursor.getInt(2));
			}
			c.close();
			list.add(map);
		}
		//获取所有笔记的数量总和
		sql = "SELECT count(*) FROM tbl_note";
		cursor = db.rawQuery(sql, null);
		if(cursor.moveToNext()){
			tvNum_allnotes.setText(String.valueOf(cursor.getInt(0)));
		}

		//创建from数组
		String[] from = {"image", "category", "num"};
		//创建to数组
		int[] to = {R.id.iv01, R.id.tvCategory, R.id.tvNum};

		sa = new SimpleAdapter(getApplicationContext(), list, R.layout.listview01, from, to);
		lv01.setAdapter(sa);

		lv01.setOnItemClickListener(new AdapterView.OnItemClickListener() {
			/**
			 * 匿名内部类
			 */
			@Override
			public void onItemClick(AdapterView parent, View view,
					int position, long id) {
				map = new HashMap();
				map = list.get(position);
				Integer image = Integer.parseInt(map.get("image").toString());
				String category = map.get("category").toString();
				//创建一个Bundle对象
				Bundle bundle = new Bundle();
				bundle.putInt("image", image);
				bundle.putString("category", category);
				//创建一个Intent
				Intent intent = new Intent(MainActivity.this, NotesActivity.class);
				intent.putExtra("data", bundle);
				//启动intent对应的Activity
				startActivity(intent);
				playAnim();
			}
		});
		btn_mainInterface.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				//暂时不必处理
			}
		});
		btn_addnote.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				//处理新增笔记操作
				sql = "SELECT COUNT(*) FROM tbl_type";
				cursor = db.rawQuery(sql, null);
				if (cursor.getCount() == 0) {
					Toast.makeText(getApplicationContext(), "笔记分类不存在， 请先创建分类",
							Toast.LENGTH_LONG).show();
				}else{
					Intent intent = new Intent();
					intent.setClass(MainActivity.this, AddNoteActivity.class);
					startActivity(intent);
					playAnim();		//播放动画
				}
			}
		});
		btn_search.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				//处理查询操作
				Intent intent = new Intent();
				intent.setClass(MainActivity.this, SearchNotesActivity.class);
				startActivity(intent);
				playAnim();
			}
		});
		btn_addType.setOnClickListener(new View.OnClickListener() {

			@SuppressWarnings("deprecation")
			@Override
			public void onClick(View v) {
				//处理创建分类操作， 弹出创建分类对话框
				Bundle args = new Bundle();
				//调用 onCreateDialog(int id, Bundle args) 方法
				showDialog(1, args);
			}
		});
	}

	//创建上下文菜单时触发该方法
	@Override
	public void onCreateContextMenu(ContextMenu menu, View v,
			ContextMenuInfo menuInfo) {
		MenuInflater inflator = new MenuInflater(this);
		//装填R.menu.context对应的菜单， 并添加到menu中
		inflator.inflate(R.menu.context01, menu);
	}

	//上下文菜单中菜单项被单击时触发该方法
	@Override
	public boolean onContextItemSelected(MenuItem item) {
		AdapterContextMenuInfo menuInfo = (AdapterContextMenuInfo) item.getMenuInfo();
		switch (item.getItemId()) {
		case R.id.mainInterface_update:
			editNoteType(menuInfo.position);
			break;

		case R.id.mainInterface_delete:
			deleteNoteType(menuInfo.position);
			break;
		}
		//return super.onContextItemSelected(item);
		return true;
	}

	/**
	 * 编辑笔记类别名称
	 * @param position
	 */
	private void editNoteType(int position) {
		map = new HashMap();
		/**
		 * ListView点击的时候会有一个position, 可以通过position来获取你listView绑定的数据源中的数据的 
		 * 如果是List