Android data storage--sqlite instances, determine whether tables exist in the database

This article mainly records how to determine the existence of tables in the database in Android Sqlitedatabase and the basic operation of testing the Sqlitedatabase database. For a detailed description of SQLite, you can view the reproduced Android data storage--sqlite use detailed

Example :

androidmanifest.xml--did not make any changes to create the project by default

<?xml version= "1.0" encoding= "Utf-8"? ><manifest xmlns:android= "/http Schemas.android.com/apk/res/android "package=" Com.wxl.handlerthread "android:versioncode=" 1 "android:versionname=        "1.0" > <uses-sdk android:minsdkversion= "8" android:targetsdkversion= "/> <application"        Android:allowbackup= "true" android:icon= "@drawable/ic_launcher" android:label= "@string/app_name"            Android:theme= "@style/apptheme" > <activity android:name= "com.wxl.handlerthread.MainActivity" Android:label= "@string/app_name" > <intent-filter> <action android:name= "a            Ndroid.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;        @Override protected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate);                Setcontentview (R.layout.activity_main);                Parameter two is the database file name Mydatabaseutil = new Mydatabaseutil (This, "db1.db", NULL, 1);        DB1 = This.openorcreatedatabase ("Db1.db", context.mode_private, NULL); /*/data/data/com.example.sqlite/databases must exist, otherwise create an error, and finally databases instead of database, do not forget to add ' s ' *///DB2 = Sqlitedatabase.openorcreatedatabase ("/data/data/com.EXAMPLE.SQLITE/DATABASES/DB2.DB3 ", NULL);  /* Create a table and determine if this table already exists, create and initialize the */if (!mydatabaseutil.tabisexist ("person")) {Db1.execsql ("CREATE TABLE"        (_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 ("+++++++++++", "already created, no need to create");        }/* Update database */contentvalues values =new contentvalues ();        Values.put ("name", "WXL");        Db1.update ("person", Values, "_id=1", null);                Db1.update ("person", Values, "_id=", New string[]{"5"});        /* Query data */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", 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}/** * Determine if a table exists * @param tabn AME Table name * @return */public boolean tabisexist (String tabname) {Boolean result = Fals                E                if (tabname = = null) {return false;                } sqlitedatabase db = null;       cursor cursor = NULL;         try {db = This.getreadabledatabase ();//This is inherited from the Sqliteopenhelper class                        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; }        }    }

where the Getreadabledatabase () method is in the Sqliteopenhelper class

Create the table and initialize the resulting table data as follows :

table data from the updated data :

the data for the query data table shows the following results :

Android data storage--sqlite instances, determine whether tables exist in the database