Android编程心得-在Assets文件夹中放入.sql文件实现创建SQlite表的操作

当我们在使用SQLiteOpenHelper时，经常使用db.execSQL(String sql)方法写入对应语句实现创建表的操作，这样的确可以实现业务逻辑。与此同时还有一种更灵活的方法，从assets文件夹下读取对应的.sql文件，然后创建表。

1.首先在工程的assets文件夹下，添加对应的.sql文件



2.配置一个Configuration类，用于保存固定路径变量

[java] view plaincopy





public class Configuration {

public static final String DB_PATH = "schema";

public static final String DB_NAME = "test.db";

public static final int DB_VERSION = 1;

public static int oldVersion = -1;

}

3.逻辑实现类，executeAssetsSQL方法用于向Assets文件夹对应的路径读取SQL语句然后执行创建操作

[java] view plaincopy





public class DBHelper extends SQLiteOpenHelper {

private Context mContext;

public DBHelper(Context context, String databaseName,

CursorFactory factory, int version) {

super(context, databaseName, factory, version);

mContext = context;

}

/**

* 数据库第一次创建时调用

* */

@Override

public void onCreate(SQLiteDatabase db) {

executeAssetsSQL(db, "schema.sql");

System.out.println("创建表");

}

/**

* 数据库升级时调用

* */

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

//数据库不升级

if (newVersion <= oldVersion) {

return;

}

Configuration.oldVersion = oldVersion;

int changeCnt = newVersion - oldVersion;

for (int i = 0; i < changeCnt; i++) {

// 依次执行updatei_i+1文件 由1更新到2 [1-2]，2更新到3 [2-3]

String schemaName = "update" + (oldVersion + i) + "_"

+ (oldVersion + i + 1) + ".sql";

executeAssetsSQL(db, schemaName);

}

}

/**

* 读取数据库文件（.sql），并执行sql语句

* */

private void executeAssetsSQL(SQLiteDatabase db, String schemaName) {

BufferedReader in = null;

try {

in = new BufferedReader(new InputStreamReader(mContext.getAssets()

.open(Configuration.DB_PATH + "/" + schemaName)));

System.out.println("路径:"+Configuration.DB_PATH + "/" + schemaName);

String line;

String buffer = "";

while ((line = in.readLine()) != null) {

buffer += line;

if (line.trim().endsWith(";")) {

db.execSQL(buffer.replace(";", ""));

buffer = "";

}

}

} catch (IOException e) {

Log.e("db-error", e.toString());

} finally {

try {

if (in != null)

in.close();

} catch (IOException e) {

Log.e("db-error", e.toString());

}

}

}

}