Android之SQLite
作者:互联网
一、介绍
SQLite是一个软件库,实现了自给自足的、无服务器的、零配置的、事务性的 SQL 数据库引擎。SQLite是一个增长最快的数据库引擎,这是在普及方面的增长,与它的尺寸大小无关。SQLite 源代码不受版权限制。
二、使用
1、创建
首先SqliteHelper继承SQLiteOpenHelper重写onCreate与onUpgrade方法。其中onCreate是用来创建数据库表的,onUpgrade是用来更新数据库表与数据库表字段,SqliteHelper方法需传入数据库名称与数据库版本。实例代码如下:
public interface DBStructure {
// 数据库名称
public static final String DB_NAME = "temperature.db";
// 数据库版本
public static final int DB_VERSION = 1;
//表名称
public static final String SURFACE_NAME_OPEN_DOOR = "openDoor";
//表字段
public static final String OPEN_DOOR_RECORD =
"CREATE TABLE " + SURFACE_NAME_OPEN_DOOR + " (_id INTEGER PRIMARY KEY AUTOINCREMENT," +
"TYPE TEXT," +
"IDINFO TEXT," +
"QRTYPE TEXT," +
"QRINFO TEXT," +
"NUCLEATEINFO TEXT," +
"VACCINATIONINFO TEXT," +
"STATUS TEXT," +
"OPERATETIME Long," +
"IMAGE TEXT," +
"VIDEO TEXT," +
"TEMPERATURE TEXT)";
public static final String SURFACE_NAME_FACE_FEATURES = "faceFeatures";
public static final String FACE_FEATURES_MD5 = "CREATE TABLE faceFeatures (_id INTEGER PRIMARY KEY AUTOINCREMENT," +
"featuresName TEXT," +
"featuresMD5 TEXT)";
public static final String SURFACE_NAME_CARD = "card";
public static final String CARD_CARDNO = "CREATE TABLE card (_id INTEGER PRIMARY KEY AUTOINCREMENT," +
"RID int," +
"CARDNO Long)";
}
public SqliteHelper(Context context) {
super(context, DBStructure.DB_NAME, null, DBStructure.DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
sqLiteDatabase.execSQL(DBStructure.OPEN_DOOR_RECORD);
if (DBStructure.DB_VERSION == 2) {
sqLiteDatabase.execSQL(DBStructure.CARD_CARDNO);
} else if (DBStructure.DB_VERSION == 4) {
sqLiteDatabase.execSQL(DBStructure.FACE_FEATURES_MD5);
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (DBStructure.DB_VERSION == 2 && newVersion > oldVersion) {
db.execSQL(DBStructure.CARD_CARDNO);
} else if (DBStructure.DB_VERSION == 3 && newVersion > oldVersion) {
db.execSQL("ALTER TABLE openDoor ADD VACCINATIONINFO TEXT;");
} else if (DBStructure.DB_VERSION == 4 && newVersion > oldVersion) {
db.execSQL(DBStructure.FACE_FEATURES_MD5);
}
}
2、CRUD
使用Android系统提供的增删改查,代码如下:
public class OpenDoorSqlistHelper {
private SqliteHelper mSqliteHelper;
public OpenDoorSqlistHelper(SqliteHelper mSqliteHelper) {
this.mSqliteHelper = mSqliteHelper;
}
/**
* 新增
* @param TYPE
* @param IDINFO
* @param QRTYPE
* @param QRINFO
* @param NUCLEATEINFO
* @param VACCINATIONINFO
* @param STATUS
* @param OPERATETIME
* @param IMAGE
* @param VIDEO
* @param TEMPERATURE
*/
public void add(String TYPE, String IDINFO, String QRTYPE, String QRINFO, String NUCLEATEINFO,
String VACCINATIONINFO, String STATUS, long OPERATETIME, String IMAGE, String VIDEO,
String TEMPERATURE) {
SQLiteDatabase writableDatabase = mSqliteHelper.getWritableDatabase();
ContentValues mContentValues = new ContentValues();
mContentValues.put("TYPE", TYPE);
mContentValues.put("IDINFO", IDINFO);
mContentValues.put("QRTYPE", QRTYPE);
mContentValues.put("QRINFO", QRINFO);
mContentValues.put("NUCLEATEINFO", NUCLEATEINFO);
mContentValues.put("VACCINATIONINFO", VACCINATIONINFO);
mContentValues.put("STATUS", STATUS);
mContentValues.put("OPERATETIME", OPERATETIME);
mContentValues.put("IMAGE", IMAGE);
mContentValues.put("VIDEO", VIDEO);
mContentValues.put("TEMPERATURE", TEMPERATURE);
writableDatabase.insert(DBStructure.SURFACE_NAME_OPEN_DOOR, null, mContentValues);
}
/**
* 查询所有
* @return
*/
public Cursor findAll() {
return mSqliteHelper.getReadableDatabase().query(DBStructure.SURFACE_NAME_OPEN_DOOR, null, null, null, null, null, null);
}
/**
* 条件查询
*
* @param columns 需要查询字段
* @param selection 条件语句
* @param selectionArgs 占位符内容
* @return
*/
public Cursor findCondition(String[] columns, String selection, String[] selectionArgs) {
return mSqliteHelper.getReadableDatabase().query(DBStructure.SURFACE_NAME_OPEN_DOOR, columns, selection, selectionArgs, null, null, null);
}
/**
* 修改
* @param values 需要修改的字段
* @param whereClause 修改条件语句
* @param whereArgs 占位符内容
*/
public void update(ContentValues values, String whereClause, String[] whereArgs) {
mSqliteHelper.getWritableDatabase().update(DBStructure.SURFACE_NAME_OPEN_DOOR, values, whereClause, whereArgs);
}
/**
* 条件删除
*
* @param whereClause 条件语句
* @param whereArgs 占位符内容
*/
public void delete(String whereClause, String[] whereArgs) {
mSqliteHelper.getWritableDatabase().delete(DBStructure.SURFACE_NAME_OPEN_DOOR, whereClause, whereArgs);
}
/**
* 删除所有
*/
public void deleteAll() {
mSqliteHelper.getWritableDatabase().delete(DBStructure.SURFACE_NAME_OPEN_DOOR, null, null);
}
}
新增
insert的构造方法
public long insert (String table, String nullColumnHack, ContentValues values)
table
要插入数据的表的名称
values
ContentValues对象,类似一个map通过键值对的形式存储值。
nullColumnHack
当values参数为空或者里面没有内容的时候,insert是会失败的(底层数据库不允许插入一个空行),为了防止这种情况,要在这里指定一个列名,到时候如果发现将要插入的行为空行时,就会将你指定的这个列名的值设为null,然后再向数据库中插入。通过观察源码的insertWithOnConflict方法可以看到当ContentValues类型的数据initialValues为null或size<=0时,就会在sql语句中添加nullColumnHack的设置。
删除
delete的构造方法
public int delete(String table, String whereClause, String[] whereArgs)
table
要插入数据的表的名称
whereClause
删除条件,可以为null。
whereArgs
占位符,可以为null。
修改
update的构造方法
public int update(String table, ContentValues values, String whereClause, String[] whereArgs)
table
要插入数据的表的名称
values
ContentValues对象,类似一个map通过键值对的形式存储值。
whereClause
修改条件。
whereArgs
占位符。
查询
query的构造方法
public Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
table
要插入数据的表的名称 。
columns
要查询的列名,可以是多个,可以为null,表示查询所有列。
selection
查询条件,比如id=? and name=? 可以为null。
selectionArgs
对查询条件赋值,一个问号对应一个值,按顺序 可以为null。
having
语法have,可以为null。
orderBy
语法,按xx排序,可以为null。
3、调用
调用没有什么好说的主要是对应传参即可,代码如下:
public class MainActivity extends AppCompatActivity {
static String TAG = "MainActivity";
SqliteHelper mSqliteHelper;
OpenDoorSqlistHelper mOpenDoorSqlistHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSqliteHelper = new SqliteHelper(this);
mOpenDoorSqlistHelper = new OpenDoorSqlistHelper(mSqliteHelper);
mSqliteHelper.getWritableDatabase().beginTransaction(); //开启事件
try {
mOpenDoorSqlistHelper.add("1", "11111", "11111", "11111", "11111", "11111", "T", System.currentTimeMillis(), "11111", "11111", "11111");
mOpenDoorSqlistHelper.add("2", "2222222", "2222222", "2222222", "2222222", "2222222", "T", System.currentTimeMillis(), "2222222", "2222222", "2222222");
Cursor condition = mOpenDoorSqlistHelper.findCondition(new String[]{"IDINFO", "QRTYPE", "QRINFO", "OPERATETIME"}, "TYPE=?", new String[]{"1"});
if (condition.moveToFirst()) {
do {
String idinfo = condition.getString(condition.getColumnIndex("IDINFO"));
String qrtype = condition.getString(condition.getColumnIndex("QRTYPE"));
String qrinfo = condition.getString(condition.getColumnIndex("QRINFO"));
long operatetime = condition.getLong(condition.getColumnIndex("OPERATETIME"));
Log.d(TAG, "onCreate: 条件查询 idinfo: " + idinfo + "\tqrtype: " + qrtype + "\tqrinfo: " + qrinfo + "\toperatetime: " + operatetime);
} while (condition.moveToNext());
}
condition.close();
ContentValues mContentValues = new ContentValues();
mContentValues.put("IDINFO", "321");
mContentValues.put("QRTYPE", "321");
mContentValues.put("QRINFO", "321");
mContentValues.put("STATUS", "F");
mContentValues.put("OPERATETIME", System.currentTimeMillis());
mOpenDoorSqlistHelper.update(mContentValues, "TYPE=?", new String[]{"1"});
Cursor all = mOpenDoorSqlistHelper.findAll();
if (all.moveToFirst()) {
do {
String idinfo = all.getString(all.getColumnIndex("IDINFO"));
String qrtype = all.getString(all.getColumnIndex("QRTYPE"));
String qrinfo = all.getString(all.getColumnIndex("QRINFO"));
all.getString(all.getColumnIndex("NUCLEATEINFO"));
all.getString(all.getColumnIndex("VACCINATIONINFO"));
String status = all.getString(all.getColumnIndex("STATUS"));
all.getString(all.getColumnIndex("IMAGE"));
all.getString(all.getColumnIndex("VIDEO"));
all.getString(all.getColumnIndex("TEMPERATURE"));
long operatetime = all.getLong(all.getColumnIndex("OPERATETIME"));
Log.d(TAG, "onCreate: 查询所有 idinfo: " + idinfo + "\tqrtype: " + qrtype + "\tqrinfo: " + qrinfo + "\tstatus: " + status+"\toperatetime: " + operatetime);
} while (all.moveToNext());
}
all.close();
mOpenDoorSqlistHelper.delete("TYPE=?",new String[]{"1"});
Cursor all1 = mOpenDoorSqlistHelper.findAll();
if (all1.moveToFirst()) {
do {
String idinfo = all1.getString(all1.getColumnIndex("IDINFO"));
String qrtype = all1.getString(all1.getColumnIndex("QRTYPE"));
String qrinfo = all1.getString(all1.getColumnIndex("QRINFO"));
all1.getString(all1.getColumnIndex("NUCLEATEINFO"));
all1.getString(all1.getColumnIndex("VACCINATIONINFO"));
String status = all1.getString(all1.getColumnIndex("STATUS"));
all1.getString(all1.getColumnIndex("IMAGE"));
all1.getString(all1.getColumnIndex("VIDEO"));
all1.getString(all1.getColumnIndex("TEMPERATURE"));
long operatetime = all1.getLong(all1.getColumnIndex("OPERATETIME"));
Log.d(TAG, "onCreate: 查询所有 all1 idinfo: " + idinfo + "\tqrtype: " + qrtype + "\tqrinfo: " + qrinfo + "\tstatus: " + status+"\toperatetime: " + operatetime);
} while (all1.moveToNext());
}
all1.close();
mOpenDoorSqlistHelper.deleteAll();
} catch (Exception e) {
} finally {
mSqliteHelper.getWritableDatabase().endTransaction(); //结束事件
}
}
}
需要注意的是查询的时候返回的游标处理,以及游标关闭,同时操作数据库CRUD的时候需要开启事件,结束的时候关闭事件,分别是函数beginTransaction()开启事件,endTransaction()关闭事件。
补充
上述所有的是的Android API所支持的数据库CRUD,若是sql语句掌握很好更建议使用sql语句进行数据库操作,使用更灵活。
以上仅限于个人理解操作,若是有更好方法可以留言分享。
标签:SQLite,String,getString,getColumnIndex,all1,Android,null,public 来源: https://blog.csdn.net/duanchuanzhi/article/details/120503242