blocks|key|3182395|text|如果您编写一个类来扩展SQLiteOpenHelper并在onCreate方法中创建表，那么它将只执行一次。仅当您从设备中完全删除数据/应用程序时，帮助器才会重新创建数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3182396|来自第一次创建数据库时调用的developer.android.com:。这是创建表和初始表填充的地方。|offset|length|3182397|给你更多的信息。在用于扩展SQLiteOpenHelper的类的构造函数中，调用超级构造函数，它接受一些参数。其中之一是数据库版本。|3182398|如果传递给超级构造函数的这个db_version与最后传递的那个不同，就会调用onUpgrade方法，在onUpgrade()方法中可以调用onCreate()|3182399|所以：|3182400|3182401|delete+data/app|ordered-list-item|3182402|导致调用onUpgrade，后者调用onCreate()|3182403|3182404|是创建/续订/删除数据库的方法|3182405|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html#onCreate%2528android.database.sqlite.SQLiteDatabase%2529^0|0|E|M|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@$D|14|E|15|1|16]]|A|$]]|$1|F|3|G|5|6|7|17|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|18|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|19|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|O|7|1B|8|@]|9|@]|A|$]]|$1|P|3|Q|5|O|7|1C|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1E|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

If you write a class to extend SQLiteOpenHelper and create your tables in the onCreate method it will only be executed once. The helper will only recreate the data if you completely remove the data/application from the device.

From <a href="http://developer.android.com/reference/android/database/sqlite/SQLiteOpenHelper.html#onCreate%28android.database.sqlite.SQLiteDatabase%29" rel="nofollow">developer.android.com:</a> Called when the database is created for the first time. This is where the creation of tables and the initial population of the tables should happen.

To give you some more info.
In the constructor of the class that you use to extend SQLiteOpenHelper, call the super constructor, which accepts a few parameters. One of them being the database version.

If this db_version passed to the super constructor is different then the last passed one, the onUpgrade method is called, in the onUpgrade() method you can call onCreate()

so:

<ol>
<li>delete data/app</li>
<li>cause onUpgrade to be called which calls onCreate()</li>
</ol>

are the ways to create/renew/delete your database

blocks|key|1029143|text|您可以在主活动中创建数据库和表|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1029144|但在创建数据库之前，您可以检查|1029145|if(exits())
{
+++//+do+not+create
}
else
{
+++//+create+here
}|code-block|syntax|javascript|1029146|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can create database and tables in main activity

But before creating database you can check 

<pre><code>if(exits())
{
 // do not create
}
else
{
 // create here
}
</code></pre>

blocks|key|4650172|text|就个人而言，我使用选项：CREATE+TABLE+IF+NOT+EXISTS。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4650173|所以这个打开的帮助器有这个参数：|4650174|+private+static+final+int+VERSION_BDD+=+1;|code-block|syntax|javascript|4650175|我认为openHelper不会在每次启动时重新创建每个表。|4650176|entityMap^0|C|Q|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|V|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

Personnaly, I use the option : <code>CREATE TABLE IF NOT EXISTS</code>.

So th open helper have this param : 

<pre><code> private static final int VERSION_BDD = 1;
</code></pre>

I think the openHelper don't recreate each table at each launch.

blocks|key|866926|text|您可以使用内部类扩展SQLiteOpenHelper，并覆盖公共空onCreate(SqLiteDatabase+sqlLiteDatabase)和公共空onUpgrade(SQLiteDatabase+sqLiteDatabase，int+oldVersion，int+newVersion)方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|866927|当磁盘中不存在数据库并且帮助器类需要创建新数据库时，将调用onCreate|866928|当存在数据库版本不匹配时，将调用onUpgrade。磁盘上的db版本需要升级到newVersion|866929|private+static+final+class+PatientDatabaseHelper+extends+SQLiteOpenHelper+{

++++private+static+final+String+TAG+=+"PatientProvider";

++++private+static+final+String+DATABASE_NAME+=+"myPatient.db";
++++private+static+final+int+DATABASE_VERSION+=+1;
++++private+static+final+String+PATIENT_TABLE+=+"PATIENT";

++++private+static+final+String+CREATE_TABLE_PATIENT+=
++++++++++++"create+table+"+%2B+PATIENT_TABLE+%2B+"+("
++++++++++++++++++++%2B+PATIENT_KEY_ID+%2B+"+integer+primary+key+autoincrement,+"
++++++++++++++++++++%2B+PATIENT_NAME+%2B+"+TEXT+NOT+NULL,+"
++++++++++++++++++++%2B+PATIENT_FIRST_NAME+%2B+"+TEXT+NOT+NULL,+"
++++++++++++++++++++%2B+PATIENT_TEL+%2B+"+TEXT,+"
++++++++++++++++++++%2B+PATIENT_GSM1+%2B+"+TEXT,+"
++++++++++++++++++++%2B+PATIENT_GSM2+%2B+"+TEXT,+"
++++++++++++++++++++%2B+PATIENT_BIRTHDATE+%2B+"+DATE);+";



++++public+PatientDatabaseHelper(Context+context,+String+name,+SQLiteDatabase.CursorFactory+factory,+int+version)+{
++++++++super(context,+name,+factory,+version);
++++}

++++@Override
++++public+void+onCreate(SQLiteDatabase+sqLiteDatabase)+{
++++++++sqLiteDatabase.execSQL(CREATE_TABLE_PATIENT);
++++}

++++@Override
++++public+void+onUpgrade(SQLiteDatabase+sqLiteDatabase,+int+oldVersion,+int+newVersion)+{
++++++++Log.w(TAG,+"Upgrading+database+from+version+"+%2B+oldVersion+%2B+"+to+"
++++++++++++++++%2B+newVersion+%2B+",+which+will+destroy+all+old+data");
+++++++//simple+case+sample+-+droppin+the+table
+++++++sqLiteDatabase.execSQL("DROP+TABLE+IF+IT+EXISTS+"+%2B+PATIENT_TABLE);


++++++//Create+a+new+One
++++++onCreate(sqLiteDatabase);

++++}
}|code-block|syntax|javascript|866930|取决于android的目标版本，但我认为一个好的方法是使用ContentProvider+http://developer.android.com/guide/topics/providers/content-provider-creating.html。|offset|length|866931|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/guide/topics/providers/content-provider-creating.html^0|0|0|0|0|19|2A|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|Z|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|9|@$M|11|N|12|1|13]]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

You can use an inner class extendings the SQLiteOpenHelper and override the methods public void onCreate(SqLiteDatabase sqlLiteDatabase) and public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion)

The onCreate is called when no database exists in disk and the helper class needs to create a new one

The onUpgrade is called when there is a db version mismatch. The version of db on disks needs to be upgraded to the newVersion

<pre><code>private static final class PatientDatabaseHelper extends SQLiteOpenHelper {

 private static final String TAG = "PatientProvider";

 private static final String DATABASE_NAME = "myPatient.db";
 private static final int DATABASE_VERSION = 1;
 private static final String PATIENT_TABLE = "PATIENT";

 private static final String CREATE_TABLE_PATIENT =
 "create table " + PATIENT_TABLE + " ("
 + PATIENT_KEY_ID + " integer primary key autoincrement, "
 + PATIENT_NAME + " TEXT NOT NULL, "
 + PATIENT_FIRST_NAME + " TEXT NOT NULL, "
 + PATIENT_TEL + " TEXT, "
 + PATIENT_GSM1 + " TEXT, "
 + PATIENT_GSM2 + " TEXT, "
 + PATIENT_BIRTHDATE + " DATE); ";



 public PatientDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
 super(context, name, factory, version);
 }

 @Override
 public void onCreate(SQLiteDatabase sqLiteDatabase) {
 sqLiteDatabase.execSQL(CREATE_TABLE_PATIENT);
 }

 @Override
 public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
 Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
 + newVersion + ", which will destroy all old data");
 //simple case sample - droppin the table
 sqLiteDatabase.execSQL("DROP TABLE IF IT EXISTS " + PATIENT_TABLE);


 //Create a new One
 onCreate(sqLiteDatabase);

 }
}
</code></pre>

Depends of the target version of android but i think a good approach is to use with that a ContentProvider <a href="http://developer.android.com/guide/topics/providers/content-provider-creating.html" rel="nofollow">http://developer.android.com/guide/topics/providers/content-provider-creating.html</a>

I have to create nearly 5-6 tables in my android application. What is the best place to create SQLite database and 5-6 tables? I can write all these logic(Using SQLite open helper methods) when initial activity launch, but if i do that it will be called every time initial activity launches. Which means these creation logic of database and tables will be executes every time application launches.Can any body tell the best practice to do this.

Android: What is the best place to create SQLite database and tables

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我必须在我的android应用程序中创建近5-6个表。创建SQLite数据库和5-6个表的最佳位置是什么？我可以在初始活动启动时编写所有这些逻辑(使用SQLite打开助手方法)，但如果我这样做，它将在每次初始活动启动时被调用。这意味着这些数据库和表的创建逻辑将在每次应用程序launches.Can时执行，任何主体都会告诉最佳实践这样做。

问安卓:创建SQLite数据库和表的最佳位置是什么？
EN

回答 4

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