读ActiveAndroid源码（二）

　　上一次粗略地读了一下TableInfo这个类，了解了一下ActiveAndroid中注解的使用方法，算是一个预热，这一篇，从正常的顺序开始。

　　所以，这次从ActiveAndroid的初始化开始阅读。

public class Application extends android.app.Application {
    @Override
    public void onCreate() {
        super.onCreate();
        ActiveAndroid.initialize(this);
    }
    
    @Override
    public void onTerminate() {
        super.onTerminate();
        ActiveAndroid.dispose();
    }
}

　　先看ActiveAndroid.initialize(this);。

　　

public final class ActiveAndroid {
    //////////////////////////////////////////////////////////////////////////////////////
    // PUBLIC METHODS
    //////////////////////////////////////////////////////////////////////////////////////

    public static void initialize(Context context) {
        initialize(new Configuration.Builder(context).create());
    }
　　……
}

　　只能先看看Configuration这个类。

　　

public class Configuration {

    public final static String SQL_PARSER_LEGACY = "legacy";
    public final static String SQL_PARSER_DELIMITED = "delimited";
……
    public static class Builder {
        //////////////////////////////////////////////////////////////////////////////////////
        // PRIVATE CONSTANTS
        //////////////////////////////////////////////////////////////////////////////////////

        private static final String AA_DB_NAME = "AA_DB_NAME";
        private static final String AA_DB_VERSION = "AA_DB_VERSION";
        private final static String AA_MODELS = "AA_MODELS";
        private final static String AA_SERIALIZERS = "AA_SERIALIZERS";
        private final static String AA_SQL_PARSER = "AA_SQL_PARSER";

        private static final int DEFAULT_CACHE_SIZE = 1024;
        private static final String DEFAULT_DB_NAME = "Application.db";
        private static final String DEFAULT_SQL_PARSER = SQL_PARSER_LEGACY;

        //////////////////////////////////////////////////////////////////////////////////////
        // PRIVATE MEMBERS
        //////////////////////////////////////////////////////////////////////////////////////

        private Context mContext;

        private Integer mCacheSize;
        private String mDatabaseName;
        private Integer mDatabaseVersion;
        private String mSqlParser;
        private List<Class<? extends Model>> mModelClasses;
        private List<Class<? extends TypeSerializer>> mTypeSerializers;

        //////////////////////////////////////////////////////////////////////////////////////
        // CONSTRUCTORS
        //////////////////////////////////////////////////////////////////////////////////////

        public Builder(Context context) {
            mContext = context.getApplicationContext();
            mCacheSize = DEFAULT_CACHE_SIZE;
        }
        ……
        public Configuration create() {
            Configuration configuration = new Configuration(mContext);
            configuration.mCacheSize = mCacheSize;

            // Get database name from meta-data
            if (mDatabaseName != null) {
                configuration.mDatabaseName = mDatabaseName;
            } else {
                configuration.mDatabaseName = getMetaDataDatabaseNameOrDefault();
            }

            // Get database version from meta-data
            if (mDatabaseVersion != null) {
                configuration.mDatabaseVersion = mDatabaseVersion;
            } else {
                configuration.mDatabaseVersion = getMetaDataDatabaseVersionOrDefault();
            }

            // Get SQL parser from meta-data
            if (mSqlParser != null) {
                configuration.mSqlParser = mSqlParser;
            } else {
                configuration.mSqlParser = getMetaDataSqlParserOrDefault();
            }
            
            // Get model classes from meta-data
            if (mModelClasses != null) {
                configuration.mModelClasses = mModelClasses;
            } else {
                final String modelList = ReflectionUtils.getMetaData(mContext, AA_MODELS);
                if (modelList != null) {
                    configuration.mModelClasses = loadModelList(modelList.split(","));
                }
            }

            // Get type serializer classes from meta-data
            if (mTypeSerializers != null) {
                configuration.mTypeSerializers = mTypeSerializers;
            } else {
                final String serializerList = ReflectionUtils.getMetaData(mContext, AA_SERIALIZERS);
                if (serializerList != null) {
                    configuration.mTypeSerializers = loadSerializerList(serializerList.split(","));
                }
            }

            return configuration;
        }
……
}

 　　其中，最关键的就是create()这个方法。

　　我们来逐行分析：

　　首先，configuration获得application的context和缓存大小，默认的缓存大小为1024;

            Configuration configuration = new Configuration(mContext);
            configuration.mCacheSize = mCacheSize;

　　第二步，获得database的name;

            // Get database name from meta-data
            if (mDatabaseName != null) {
                configuration.mDatabaseName = mDatabaseName;
            } else {
                configuration.mDatabaseName = getMetaDataDatabaseNameOrDefault();
            }

　　其中,

        // Meta-data methods

        private String getMetaDataDatabaseNameOrDefault() {
            String aaName = ReflectionUtils.getMetaData(mContext, AA_DB_NAME);
            if (aaName == null) {
                aaName = DEFAULT_DB_NAME;
            }

            return aaName;
        }

    @SuppressWarnings("unchecked")
    public static <T> T getMetaData(Context context, String name) {
        try {
            final ApplicationInfo ai = context.getPackageManager().getApplicationInfo(context.getPackageName(),
                    PackageManager.GET_META_DATA);

            if (ai.metaData != null) {
                return (T) ai.metaData.get(name);
            }
        }
        catch (Exception e) {
            Log.w("Couldn't find meta-data: " + name);
        }

        return null;
    }

　　用java动态取出Androidmanifest中，关于数据库的信息。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.dream.fishbonelsy.baseonlsy" >

    <application
        android:name=".MyApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <meta-data android:name="AA_DB_NAME" android:value="Longsiyang.db" />
        <meta-data android:name="AA_DB_VERSION" android:value="2" />
　　　　……

　通过以上代码获得了数据库的name:Longsiyang.db

　　第三步获得数据库版本号;

            // Get database version from meta-data
            if (mDatabaseVersion != null) {
                configuration.mDatabaseVersion = mDatabaseVersion;
            } else {
                configuration.mDatabaseVersion = getMetaDataDatabaseVersionOrDefault();
            }

　　与第二步原理相同，获得版本号。

　　第四步获得

            // Get SQL parser from meta-data
            if (mSqlParser != null) {
                configuration.mSqlParser = mSqlParser;
            } else {
                configuration.mSqlParser = getMetaDataSqlParserOrDefault();
            }

        private String getMetaDataSqlParserOrDefault() {
            final String mode = ReflectionUtils.getMetaData(mContext, AA_SQL_PARSER);
            if (mode == null) {
                return DEFAULT_SQL_PARSER;
            }
            return mode;
        }

　　默认情况下，mode==null，所以

        public final static String SQL_PARSER_LEGACY = "legacy";
        private static final String DEFAULT_SQL_PARSER = SQL_PARSER_LEGACY;            

　至此，Conguration的默认初始化已经完成。总结一下，Conguration类存储了数据库的：缓存大小、数据库名称、数据库版本号、数据库parser。有了这些信息，我们就可以建数据库了。

===============================================================================================================================================

public final class ActiveAndroid {
    //////////////////////////////////////////////////////////////////////////////////////
    // PUBLIC METHODS
    //////////////////////////////////////////////////////////////////////////////////////

    public static void initialize(Context context) {
        initialize(new Configuration.Builder(context).create());
    }
　　……
}

　　回到这里，我们继续读initialize方法。进入initialize：

    public static synchronized void initialize(Configuration configuration) {
        if (sIsInitialized) {
            Log.v("ActiveAndroid already initialized.");
            return;
        }

        sContext = configuration.getContext();
        sModelInfo = new ModelInfo(configuration);
        sDatabaseHelper = new DatabaseHelper(configuration);

        // TODO: It would be nice to override sizeOf here and calculate the memory
        // actually used, however at this point it seems like the reflection
        // required would be too costly to be of any benefit. We'll just set a max
        // object size instead.
        sEntities = new LruCache<String, Model>(configuration.getCacheSize());

        openDatabase();

        sIsInitialized = true;

        Log.v("ActiveAndroid initialized successfully.");
    }

　　　在这里，将Conguration信息传入ModelInfo，并打开数据库，将标志位sIsInitialized打开。

　　　接下来的一篇，将继续阅读打开数据库的相关代码。

　　Done!