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Android GreenDao 升级 保留旧表数据

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0.2052019.08.05 11:54:36字数 270阅读 363

瓦力和伊娃

GreenDao升级库版本号之后，以前的旧数据没有了，为啥，因为GreenDao在升级的时候会删除旧库，创建新库，就问你，到这里，脑袋是不是嗡嗡的？！

********别着急，有答案！亲测可用，非常完美~********

查阅资料得到了满意的答案！如下：

• 第一项： 新建一个MigrationHelper类，它主要是通过创建一个临时表，将旧表的数据迁移到新表中。

import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.support.annotation.NonNull;
import android.text.TextUtils;
import android.util.Log;import org.greenrobot.greendao.AbstractDao;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.database.StandardDatabase;
import org.greenrobot.greendao.internal.DaoConfig;import java.lang.ref.WeakReference;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;/*** * please call {@link #migrate(SQLiteDatabase, Class[])} or {@link #migrate(Database, Class[])}* */
public final class MigrationHelper {public static boolean DEBUG = false;private static String TAG = "MigrationHelper";private static final String SQLITE_MASTER = "sqlite_master";private static final String SQLITE_TEMP_MASTER = "sqlite_temp_master";private static WeakReference<ReCreateAllTableListener> weakListener;public interface ReCreateAllTableListener{void onCreateAllTables(Database db, boolean ifNotExists);void onDropAllTables(Database db, boolean ifExists);}public static void migrate(SQLiteDatabase db, Class<? extends AbstractDao<?, ?>>... daoClasses) {printLog("【The Old Database Version】" + db.getVersion());Database database = new StandardDatabase(db);migrate(database, daoClasses);}public static void migrate(SQLiteDatabase db, ReCreateAllTableListener listener, Class<? extends AbstractDao<?, ?>>... daoClasses) {weakListener = new WeakReference<>(listener);migrate(db, daoClasses);}public static void migrate(Database database, ReCreateAllTableListener listener, Class<? extends AbstractDao<?, ?>>... daoClasses) {weakListener = new WeakReference<>(listener);migrate(database, daoClasses);}public static void migrate(Database database, Class<? extends AbstractDao<?, ?>>... daoClasses) {printLog("【Generate temp table】start");generateTempTables(database, daoClasses);printLog("【Generate temp table】complete");ReCreateAllTableListener listener = null;if (weakListener != null) {listener = weakListener.get();}if (listener != null) {listener.onDropAllTables(database, true);printLog("【Drop all table by listener】");listener.onCreateAllTables(database, false);printLog("【Create all table by listener】");} else {dropAllTables(database, true, daoClasses);createAllTables(database, false, daoClasses);}printLog("【Restore data】start");restoreData(database, daoClasses);printLog("【Restore data】complete");}private static void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {for (int i = 0; i < daoClasses.length; i++) {String tempTableName = null;DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);String tableName = daoConfig.tablename;if (!isTableExists(db, false, tableName)) {printLog("【New Table】" + tableName);continue;}try {tempTableName = daoConfig.tablename.concat("_TEMP");StringBuilder dropTableStringBuilder = new StringBuilder();dropTableStringBuilder.append("DROP TABLE IF EXISTS ").append(tempTableName).append(";");db.execSQL(dropTableStringBuilder.toString());StringBuilder insertTableStringBuilder = new StringBuilder();insertTableStringBuilder.append("CREATE TEMPORARY TABLE ").append(tempTableName);insertTableStringBuilder.append(" AS SELECT * FROM `").append(tableName).append("`;");db.execSQL(insertTableStringBuilder.toString());printLog("【Table】" + tableName +"\n ---Columns-->"+getColumnsStr(daoConfig));printLog("【Generate temp table】" + tempTableName);} catch (SQLException e) {Log.e(TAG, "【Failed to generate temp table】" + tempTableName, e);}}}private static boolean isTableExists(Database db, boolean isTemp, String tableName) {if (db == null || TextUtils.isEmpty(tableName)) {return false;}String dbName = isTemp ? SQLITE_TEMP_MASTER : SQLITE_MASTER;String sql = "SELECT COUNT(*) FROM `" + dbName + "` WHERE type = ? AND name = ?";Cursor cursor=null;int count = 0;try {cursor = db.rawQuery(sql, new String[]{"table", tableName});if (cursor == null || !cursor.moveToFirst()) {return false;}count = cursor.getInt(0);} catch (Exception e) {e.printStackTrace();} finally {if (cursor != null)cursor.close();}return count > 0;}private static String getColumnsStr(DaoConfig daoConfig) {if (daoConfig == null) {return "no columns";}StringBuilder builder = new StringBuilder();for (int i = 0; i < daoConfig.allColumns.length; i++) {builder.append(daoConfig.allColumns[i]);builder.append(",");}if (builder.length() > 0) {builder.deleteCharAt(builder.length() - 1);}return builder.toString();}private static void dropAllTables(Database db, boolean ifExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {reflectMethod(db, "dropTable", ifExists, daoClasses);printLog("【Drop all table by reflect】");}private static void createAllTables(Database db, boolean ifNotExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {reflectMethod(db, "createTable", ifNotExists, daoClasses);printLog("【Create all table by reflect】");}/*** dao class already define the sql exec method, so just invoke it*/private static void reflectMethod(Database db, String methodName, boolean isExists, @NonNull Class<? extends AbstractDao<?, ?>>... daoClasses) {if (daoClasses.length < 1) {return;}try {for (Class cls : daoClasses) {Method method = cls.getDeclaredMethod(methodName, Database.class, boolean.class);method.invoke(null, db, isExists);}} catch (NoSuchMethodException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}}private static void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {for (int i = 0; i < daoClasses.length; i++) {DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);String tableName = daoConfig.tablename;String tempTableName = daoConfig.tablename.concat("_TEMP");if (!isTableExists(db, true, tempTableName)) {continue;}try {// get all columns from tempTable, take careful to use the columns listList<TableInfo> newTableInfos = TableInfo.getTableInfo(db, tableName);List<TableInfo> tempTableInfos = TableInfo.getTableInfo(db, tempTableName);ArrayList<String> selectColumns = new ArrayList<>(newTableInfos.size());ArrayList<String> intoColumns = new ArrayList<>(newTableInfos.size());for (TableInfo tableInfo : tempTableInfos) {if (newTableInfos.contains(tableInfo)) {String column = '`' + tableInfo.name + '`';intoColumns.add(column);selectColumns.add(column);}}// NOT NULL columns listfor (TableInfo tableInfo : newTableInfos) {if (tableInfo.notnull && !tempTableInfos.contains(tableInfo)) {String column = '`' + tableInfo.name + '`';intoColumns.add(column);String value;if (tableInfo.dfltValue != null) {value = "'" + tableInfo.dfltValue + "' AS ";} else {value = "'' AS ";}selectColumns.add(value + column);}}if (intoColumns.size() != 0) {StringBuilder insertTableStringBuilder = new StringBuilder();insertTableStringBuilder.append("REPLACE INTO `").append(tableName).append("` (");insertTableStringBuilder.append(TextUtils.join(",", intoColumns));insertTableStringBuilder.append(") SELECT ");insertTableStringBuilder.append(TextUtils.join(",", selectColumns));insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");db.execSQL(insertTableStringBuilder.toString());printLog("【Restore data】 to " + tableName);}StringBuilder dropTableStringBuilder = new StringBuilder();dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);db.execSQL(dropTableStringBuilder.toString());printLog("【Drop temp table】" + tempTableName);} catch (SQLException e) {Log.e(TAG, "【Failed to restore data from temp table 】" + tempTableName, e);}}}private static List<String> getColumns(Database db, String tableName) {List<String> columns = null;Cursor cursor = null;try {cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 0", null);if (null != cursor && cursor.getColumnCount() > 0) {columns = Arrays.asList(cursor.getColumnNames());}} catch (Exception e) {e.printStackTrace();} finally {if (cursor != null)cursor.close();if (null == columns)columns = new ArrayList<>();}return columns;}private static void printLog(String info){if(DEBUG){Log.d(TAG, info);}}private static class TableInfo {int cid;String name;String type;boolean notnull;String dfltValue;boolean pk;@Overridepublic boolean equals(Object o) {return this == o|| o != null&& getClass() == o.getClass()&& name.equals(((TableInfo) o).name);}@Overridepublic String toString() {return "TableInfo{" +"cid=" + cid +", name='" + name + '\'' +", type='" + type + '\'' +", notnull=" + notnull +", dfltValue='" + dfltValue + '\'' +", pk=" + pk +'}';}private static List<TableInfo> getTableInfo(Database db, String tableName) {String sql = "PRAGMA table_info(`" + tableName + "`)";printLog(sql);Cursor cursor = db.rawQuery(sql, null);if (cursor == null)return new ArrayList<>();TableInfo tableInfo;List<TableInfo> tableInfos = new ArrayList<>();while (cursor.moveToNext()) {tableInfo = new TableInfo();tableInfo.cid = cursor.getInt(0);tableInfo.name = cursor.getString(1);tableInfo.type = cursor.getString(2);tableInfo.notnull = cursor.getInt(3) == 1;tableInfo.dfltValue = cursor.getString(4);tableInfo.pk = cursor.getInt(5) == 1;tableInfos.add(tableInfo);// printLog(tableName + "：" + tableInfo);}cursor.close();return tableInfos;}}
}

• 第二项： 新建一个UpgradeOpenHelper类，继承DaoMaster.DevOpenHelper，重写onUpgrade(Database db, int oldVersion, int newVersion)方法，在该方法中使用MigrationHelper进行数据库升级以及数据迁移。

public class UpgradeOpenHelper extends DaoMaster.OpenHelper {public UpgradeOpenHelper (Context context, String name, SQLiteDatabase.CursorFactory factory) {super(context, name, factory);}@Overridepublic void onUpgrade(Database db, int oldVersion, int newVersion) {//把需要管理的数据库表DAO作为最后一个参数传入到方法中MigrationHelper.migrate(db, new MigrationHelper.ReCreateAllTableListener() {@Overridepublic void onCreateAllTables(Database db, boolean ifNotExists) {DaoMaster.createAllTables(db, ifNotExists);}@Overridepublic void onDropAllTables(Database db, boolean ifExists) {DaoMaster.dropAllTables(db, ifExists);}},  Test1Dao.class，Test2Dao.class，Test3Dao.class，Test4Dao.class);}
}

• 第三项： 然后使用UpgradeOpenHelper替代DaoMaster.DevOpenHelper来进行创建数据库等操作。

upgradeOpenHelper= new UpgradeOpenHelper(MyApplication.getInstance(), DB_NAME, null);//建库
mDaoMaster = new DaoMaster(mSQLiteOpenHelper.getWritableDatabase());
mDaoSession = mDaoMaster.newSession();

• 第四项：
  修改Module下build.gradle中数据库的版本号schemaVersion ，递增加1即可，最后运行app