本文主要记录一下Android SQLiteDatabase中如何判断数据库中表是否存在，以及测试SQLiteDatabase数据库的基本操作。有关SQLite的详细说明，，可以查看转载的Android 数据存储——SQLite使用详解
例子：
AndroidManifest.xml——没有做任何修改，创建工程默认
<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android=""package="com.wxl.handlerthread"android:versionCode="1"android:versionName="1.0" ><uses-sdkandroid:minSdkVersion="8"android:targetSdkVersion="19" /><applicationandroid:allowBackup="true"android:icon="@drawable/ic_launcher"android:label="@string/app_name"android:theme="@style/AppTheme" ><activityandroid:name="com.wxl.handlerthread.MainActivity"android:label="@string/app_name" ><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity></application></manifest>MainActivity.java
package com.example.sqlite;import android.os.Bundle;import android.util.Log;import android.app.Activity;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class MainActivity extends Activity {private SQLiteDatabase db1;//private SQLiteDatabase db2;private MyDatabaseUtil myDatabaseUtil;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//参数二是数据库文件名myDatabaseUtil = new MyDatabaseUtil(this, "db1.db", null, 1);db1 = this.openOrCreateDatabase("db1.db", Context.MODE_PRIVATE, null);/*/data/data/com.example.sqlite/databases必须存在，否则创建出错，最后是databases而不是database，不要忘了加's'*///db2 = SQLiteDatabase.openOrCreateDatabase("/data/data/com.example.sqlite/databases/db2.db3",null);/*创建表，并判断是否已经存在此表，没创建，则创建并初始化*/if (!myDatabaseUtil.tabIsExist("person")) {db1.execSQL("CREATE TABLE person (_id integer primary key autoincrement, name varchar(20))");ContentValues values =new ContentValues();for(int i=0;i<10;i++){values.put("name", "name "+ i);db1.insert("person", "_id", values);}}else {Log.i("+++++++++++", "已经创建了，无需再创建");}/*更新数据库*/ContentValues values =new ContentValues();values.put("name", "wxl");db1.update("person", values, "_id=1", null);db1.update("person", values, "_id=?", new String[]{"5"});/*查询数据*/Cursor c = db1.query("person", null, null, null, null, null, null);c.moveToFirst();while(!c.isAfterLast()){int index = c.getColumnIndex("name");Log.d("SQLite", c.getString(index));c.moveToNext();}c = db1.rawQuery("select * from person", null);c.moveToFirst();while(!c.isAfterLast()){int index = c.getColumnIndex("name");Log.d("SQLite", c.getString(index));c.moveToNext();}}public class MyDatabaseUtil extends SQLiteOpenHelper{public MyDatabaseUtil(Context context, String name,CursorFactory factory, int version) {super(context, name, factory, version);// TODO Auto-generated constructor stub}@Overridepublic void onCreate(SQLiteDatabase arg0) {// TODO Auto-generated method stub}@Overridepublic void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {// TODO Auto-generated method stub}/*** 判断某张表是否存在* @param tabName 表名* @return*/public boolean tabIsExist(String tabName){boolean result = false;if(tabName == null){return false;}SQLiteDatabase db = null;Cursor cursor = null;try {db = this.getReadableDatabase();//此this是继承SQLiteOpenHelper类得到的String sql = "select count(*) as c from sqlite_master where type ='table' and name ='"+tabName.trim()+"' ";cursor = db.rawQuery(sql, null);if(cursor.moveToNext()){int count = cursor.getInt(0);if(count>0){result = true;}}} catch (Exception e) {// TODO: handle exception}return result;}}}其中getReadableDatabase()方法是SQLiteOpenHelper类中的
创建表并初始化得到的表数据如下：
更新数据得到的表数据：
查询数据表的数据显示结果如下：
即使爬到最高的山上，一次也只能脚踏实地地迈一步。
