Android Sqlite 数据库升级

将每个版本的升级语句按版本顺序放在一个LIST中，这样在数据库版本升级的时候就不用做版本号判断了。List中的INDEX就是每个版本的SQL语句。这里只是做了一个简单的DEMO，没有考虑数据迁移。

如果是第一次安装，会调用onCreate，在onCreate里直接调用execUpgradSql(db, 0, 3)执行所有的SQL语句。

如果是从其它版本升级来的，比如从V2升到V3,则会调用onUpgrade,oldVersion是2，newVersion是3，这里调用execUpgradeSql(db, 2, 3),它只会执行V3新增的SQL语句。V1升到V3也是如此，它执行的是V2,V3的SQL。

以后每升级数据库，只要把这个版本对应的新增SQL放在LIST中就可以了。

package com.gouhao.databaseupdate;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.util.Log;import java.util.ArrayList;import java.util.List;/** * Created by GouHao on 2017/9/16. */public class DatabaseHelper extends SQLiteOpenHelper {    private static final String TAG = DatabaseHelper.class.getSimpleName();    public static final String DB_NAME = "test.db";    public static final String TABLE_USER_OLD = "user";    public static final String TABLE_USER = "table_user";    public static final String TABLE_STUDENT = "table_student";    public static final int VERSION_CODE = 3;    private List<List<String>> upgradeSqlList;    public DatabaseHelper(Context context) {        super(context, DB_NAME, null, VERSION_CODE);        upgradeSqlList = new ArrayList<>();        addUpgradeSqlVersion1();        addUpgradeSqlVersion2();        addUpgradeSqlVersion3();    }    @Override    public void onCreate(SQLiteDatabase db) {        Log.d(TAG, "onCreate");        execUpgradeSql(db, 0, VERSION_CODE);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        Log.d(TAG, "onUpgrade: oldVersion=" + oldVersion + ", newVersion=" + newVersion);        execUpgradeSql(db, oldVersion, newVersion);    }    private void addUpgradeSqlVersion1() {        List<String> sqlListVersion1 = new ArrayList<>();        String userSql = "CREATE TABLE IF NOT EXISTS " + TABLE_USER_OLD + "(id INTEGER PRIMARY KEY AUTOINCREMENT, username VARCHAR);";        sqlListVersion1.add(userSql);        upgradeSqlList.add(sqlListVersion1);    }    private void addUpgradeSqlVersion2() {        List<String> sqlListVersion2 = new ArrayList<>();        String userAlter = "ALTER TABLE " + TABLE_USER_OLD + " ADD COLUMN age INTEGER;";        sqlListVersion2.add(userAlter);        upgradeSqlList.add(sqlListVersion2);    }    private void addUpgradeSqlVersion3() {        List<String> sqlListVersion3 = new ArrayList<>();        String alterUserTableName = "ALTER TABLE user RENAME TO " + TABLE_USER + ";";        String tableStudent = "CREATE TABLE IF NOT EXISTS " + TABLE_STUDENT + "(id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR);";        sqlListVersion3.add(alterUserTableName);        sqlListVersion3.add(tableStudent);        upgradeSqlList.add(sqlListVersion3);    }    private void execUpgradeSql(SQLiteDatabase db, int oldVersion, int newVersion) {        Log.d(TAG, "execUpgradeSql: oldVersion=" + oldVersion + ", newVersion=" + newVersion);        for (int i = oldVersion; i < newVersion; i++) {            List<String> sqlListVersion = upgradeSqlList.get(i);            int size = sqlListVersion.size();            for (int j = 0; j < size; j++) {                try {                    db.execSQL(sqlListVersion.get(j));                    Log.d(TAG, "execUpgradeSql: version" + (i + 1) + " exec success:" + sqlListVersion.get(j));                } catch (Exception e) {                    e.printStackTrace();                    Log.e(TAG, "execUpgradeSql: version" + (i + 1) + " exec failed: " + sqlListVersion.get(j));                }            }            Log.d(TAG, "execUpgradeSql: version" + (i + 1) + " exec success");        }    }    @Override    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {        Log.d(TAG, "onDowngrade: oldVersion: " + oldVersion + ", newVersion=" + newVersion);    }}