RxAndroid之操作数据库SqlBrite（RXAndroid实现数据库的增、删、改、查）

来源：互联网发布：杭州sql培训班编辑：程序博客网时间：2024/06/05 12:04

一、查询

1.创建SqlBrite

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SqlBrite sqlBrite = SqlBrite.create();

2.将SQLiteOpenHelper的一个实例和一个Scheduler作为参数创建BriteDatabase,正确地传入Scheduler可以防止线程被阻塞

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BriteDatabase db = sqlBrite.wrapDatabaseHelper(openHelper, Schedulers.io());

3.通过BriteDatabase.createQuery方法来进行查询，它需要两个参数，一个是所要查询的表，一个是sql语句，这个方法与SQLiteDatabase.rawQuery类似Observable<Query> users = db.createQuery("users", "SELECT * FROM users");

4.通过返回的Observable来进行订阅，并通过query.run()方法获取数据

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users.subscribe(new Action1<Query>() {
@Override public void call(Query query) {
Cursor cursor = query.run();
// TODO parse data...
}
});

二、增加、删除、更新表后所有订阅的数据都会马上进行更新

所有的增、删、改、查操作都必须通过对象BriteDatabase来正确地通知订阅者

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final AtomicInteger queries = new AtomicInteger();
users.subscribe(new Action1<Query>() {
@Override public void call(Query query) {
queries.getAndIncrement();
}
});
System.out.println("Queries: " + queries.get()); // Prints 1
db.insert("users", createUser("jw", "Jake Wharton"));
db.insert("users", createUser("mattp", "Matt Precious"));
db.insert("users", createUser("strong", "Alec Strong"));
System.out.println("Queries: " + queries.get()); // Prints 4

三、Unsubscribe from the returned Subscription to stop getting updates.

Unsubscribe from the returned Subscription to stop getting updates.

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final AtomicInteger queries = new AtomicInteger();
Subscription s = users.subscribe(new Action1<Query>() {
@Override public void call(Query query) {
queries.getAndIncrement();
}
});
System.out.println("Queries: " + queries.get()); // Prints 1
db.insert("users", createUser("jw", "Jake Wharton"));
db.insert("users", createUser("mattp", "Matt Precious"));
s.unsubscribe();
db.insert("users", createUser("strong", "Alec Strong"));
System.out.println("Queries: " + queries.get()); // Prints 3

四、数据改变较大时使用transactions

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final AtomicInteger queries = new AtomicInteger();
users.subscribe(new Action1<Query>() {
@Override public void call(Query query) {
queries.getAndIncrement();
}
});
System.out.println("Queries: " + queries.get()); // Prints 1
Transaction transaction = db.newTransaction();
try {
db.insert("users", createUser("jw", "Jake Wharton"));
db.insert("users", createUser("mattp", "Matt Precious"));
db.insert("users", createUser("strong", "Alec Strong"));
transaction.markSuccessful();
} finally {
transaction.end();
}
System.out.println("Queries: " + queries.get()); // Prints 2

五、使用操作符

queries只是普通的RxJava 的Observable对象，所有的操作符都可以用来控制所要发给订阅者的数据

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users.debounce(500, MILLISECONDS).subscribe(new Action1<Query>() {
@Override public void call(Query query) {
// TODO...
}
});

六、监测从其它app查询的数据

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BriteContentResolver resolver = sqlBrite.wrapContentProvider(contentResolver, Schedulers.io());
Observable<Query> query = resolver.createQuery(/*...*/);

创建数据库和表的类：

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public class RxDatabaseHelper extends SQLiteOpenHelper{
private String TAG = "RX";
private Context context;
private static RxDatabaseHelper rxDatabaseHelper = null;
private RxDatabaseHelper(Context context) {
super(context, "rxdb.sqlite", null, 1); //创建数据库rxdb.sqlite
this.context = context;
}
public static RxDatabaseHelper getInstance(Context context){
if(rxDatabaseHelper == null){
synchronized (RxDatabaseHelper.class){
if(rxDatabaseHelper == null){
rxDatabaseHelper = new RxDatabaseHelper(context);
}
}
}
return rxDatabaseHelper;
}
@Override
public void onCreate(SQLiteDatabase db) {
//创建表rx_db_test,表中的字段：_id,name,gender,age
db.execSQL("create table if not exists rx_db_test (_id integer primary key,name text, gender text, age long)");
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
}

测试增删改查的类：

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public class RxDatabaseActivity extends Activity{
private String TAG = "RX";
private RxDatabaseHelper rxDatabaseHelper;
private SQLiteOpenHelper sqLiteOpenHelper;
private SQLiteDatabase sqLiteDatabase;
private BriteDatabase briteDatabase;
private SqlBrite sqlBrite;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.rx_widget_layout);
sqLiteOpenHelper = RxDatabaseHelper.getInstance(getApplicationContext());
sqLiteDatabase = sqLiteOpenHelper.getWritableDatabase();
sqlBrite = SqlBrite.create();
briteDatabase = sqlBrite.wrapDatabaseHelper(sqLiteOpenHelper,Schedulers.io());
// testInser(); //增
// testDelete(); //删
// testUpdate(); //改
testQuery(); //查
}
//查询数据
private void testQuery() {
Observable<SqlBrite.Query> rxDbTest = briteDatabase.createQuery("rx_db_test", "SELECT * FROM rx_db_test");
rxDbTest.subscribe(new Action1<SqlBrite.Query>() {
@Override
public void call(SqlBrite.Query query) {
Cursor cursor = query.run();
while (cursor.moveToNext()){
Log.e(TAG,"["+cursor.getString(cursor.getColumnIndex("name"))+","+cursor.getString(cursor.getColumnIndex("gender"))+","
+cursor.getLong(cursor.getColumnIndex("age"))+"]");
}
}
});
}
//修改数据
private void testUpdate() {
ContentValues contentValues = new ContentValues();
contentValues.put("age",10);
//将姓名为zhangsan19的人的年龄改为10
briteDatabase.update("rx_db_test",contentValues,"name=?","zhangsan19");
}
//删除数据
private void testDelete() {
//删除age=10的那条数据
//第一个参数是表名，第二个参数是所要匹配的字段的名字，第三个参数是所要匹配的字段值
briteDatabase.delete("rx_db_test","age=?","10");
}
//添加数据
private void testInser() {
ContentValues contentValues = new ContentValues();
//第一个参数是表名，第二个参数是所要添加的数据的键值对
// db.execSQL("create table if not exists rx_db_test (_id integer primary key,name text, gender text, age long)");
for(int i=1;i<20;i++){
contentValues.put("name","zhangsan"+i);
if(i%2 == 0) {
contentValues.put("gender", "女");
}else{
contentValues.put("gender", "男");
}
contentValues.put("age", i);
briteDatabase.insert("rx_db_test", contentValues);
}
}
}

增加数据运行结果：

删除数据运行结果（将age=10的那条数据删除了）：

修改数据后运行的结果（将姓名为zhangsan19的人的年龄改为10):

查询运行的结果：

注：1.需要在build.gradle中添加compile 'com.squareup.sqlbrite:sqlbrite:0.7.0'

2.参考资料：https://github.com/ReactiveX/RxAndroid/wiki#removed

https://github.com/square/sqlbrite

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