The Android implementation executes statements when it creates or upgrades a database

  • 2020-06-07 05:17:06
  • OfStack

The example in this article describes the statement that Android executes when it creates or upgrades a database. If it is creating or upgrading a database, use the constructor with the List parameter, which executes when the database is created or upgraded.

The specific program code is as follows:


import java.util.List;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class SimpleSQLiteOpenHelper extends SQLiteOpenHelper {
 private static final int INIT_VERSION = 1;
 /**
 *  The statement executed when a database is created or upgraded. 
 */
 private List<String> sqlStatementExed;
 /**
 *  If you are creating or upgrading a database, use the tape List A constructor for a parameter. 
 * 
 * @param context
 *      to use to open or create the database
 * @param name
 *      of the database file, or null for an in-memory database
 * @param factory
 *      to use for creating cursor objects, or null for the default
 * @param version
 *      number of the database (starting at 1); if the database is
 *      older, onUpgrade(SQLiteDatabase, int, int) will be used to
 *      upgrade the database; if the database is newer,
 *      onDowngrade(SQLiteDatabase, int, int) will be used to
 *      downgrade the database
 */
 public SimpleSQLiteOpenHelper(Context context, String name,
  CursorFactory factory, int version) {
 super(context, name, factory, version);
 sqlStatementExed = null;
 }
 /**
 *  with SQL The constructor of the statement. this SQL The statement is executed when the database is created or upgraded. 
 * 
 * @param context
 *      to use to open or create the database
 * @param name
 *      of the database file, or null for an in-memory database
 * @param factory
 *      to use for creating cursor objects, or null for the default
 * @param version
 *      number of the database (starting at 1); if the database is
 *      older, onUpgrade(SQLiteDatabase, int, int) will be used to
 *      upgrade the database; if the database is newer,
 *      onDowngrade(SQLiteDatabase, int, int) will be used to
 *      downgrade the database
 * @param sqlStatementExed
 *       Statement that will be executed when a database is created or upgraded. 
 */
 public SimpleSQLiteOpenHelper(Context context, String name,
  CursorFactory factory, int version, List<String> sqlStatementExed) {
 super(context, name, factory, version);
 this.sqlStatementExed = sqlStatementExed;
 }
 /**
 *  If you are creating or upgrading a database, use the tape List A constructor for a parameter. 
 * @param context
 *      to use to open or create the database
 * @param name
 *      of the database file, or null for an in-memory database
 * @param version
 *      number of the database (starting at 1); if the database is
 *      older, onUpgrade(SQLiteDatabase, int, int) will be used to
 *      upgrade the database; if the database is newer,
 *      onDowngrade(SQLiteDatabase, int, int) will be used to
 *      downgrade the database
 */
 public SimpleSQLiteOpenHelper(Context context, String name, int version) {
 super(context, name, null, version);
 sqlStatementExed = null;
 }
 /**
 *  If you are creating or upgrading a database, use the tape List A constructor for a parameter. 
 * @param context
 *      to use to open or create the database
 * @param name
 *      of the database file, or null for an in-memory database
 */
 public SimpleSQLiteOpenHelper(Context context, String name) {
 super(context, name, null, INIT_VERSION);
 sqlStatementExed = null;
 }
 /**
 *  If you are creating or upgrading a database, use the tape List A constructor for a parameter. 
 * 
 * @param context
 *      to use to open or create the database
 * @param name
 *      of the database file, or null for an in-memory database
 * @param version
 *      number of the database (starting at 1); if the database is
 *      older, onUpgrade(SQLiteDatabase, int, int) will be used to
 *      upgrade the database; if the database is newer,
 *      onDowngrade(SQLiteDatabase, int, int) will be used to
 *      downgrade the database
 * @param sqlCreateStatement
 *       Statement to execute when creating or upgrading a database. 
 */
 public SimpleSQLiteOpenHelper(Context context, String name, int version,
  List<String> sqlCreateStatement) {
 super(context, name, null, version);
 this.sqlStatementExed = sqlCreateStatement;
 }
 /**
 * @param context
 * @param name
 * @param sqlCreateStatement
 *       Statement to execute when creating or upgrading a database. 
 */
 public SimpleSQLiteOpenHelper(Context context, String name,
  List<String> sqlCreateStatement) {
 super(context, name, null, INIT_VERSION);
 this.sqlStatementExed = sqlCreateStatement;
 }
 /*
 * (non-Javadoc)
 * @see
 * android.database.sqlite.SQLiteOpenHelper#onCreate(android.database.sqlite
 * .SQLiteDatabase)
 */
 @Override
 @Deprecated
 public void onCreate(SQLiteDatabase db) {
 exeSqlStatementExed(db);
 }
 /*
 * (non-Javadoc)
 * @see
 * android.database.sqlite.SQLiteOpenHelper#onUpgrade(android.database.sqlite
 * .SQLiteDatabase, int, int)
 */
 @Override
 @Deprecated
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 if (newVersion > oldVersion) {
  exeSqlStatementExed(db);
 }
 }
 /**
 *  Performed when the database is initialized or upgraded SQL Statement.. 
 */
 private void exeSqlStatementExed(SQLiteDatabase db) {
 if (sqlStatementExed != null) {
  for (String statement : sqlStatementExed) {
  db.execSQL(statement);
  }
 }
 }
}

It is hoped that the method described in this article will be helpful for you to develop Android program.


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