我在android中学习 RxJava2 。任何人都可以解释我如何使用 RxJava2 将数据插入SQLiteDatabase。 这是我试图使用的代码示例,但它将数据六次插入数据库;
//的OnClick
getCompletableObservable()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(getCompletableObserver());
//可观察
private Completable getCompletableObservable(){
return Completable.create(new CompletableOnSubscribe() {
@Override
public void subscribe(CompletableEmitter emitter) throws Exception {
addData();
if(!emitter.isDisposed())
emitter.onComplete();
}
});
}
//观察
CompletableObserver getCompletableObserver(){
return new CompletableObserver() {
@Override
public void onSubscribe(Disposable d) {
}
@Override
public void onComplete() {
showMessage("Student Added Sucessfully");
}
@Override
public void onError(Throwable e) {
showMessage(e.getMessage()+"");
}
};
}
//添加方法
try {
DatabaseHelper db = new DatabaseHelper(DemoRxJava.this);
db.open();
String c = db.AddData(new Student(random.nextInt(1000)+"",SName.getText().toString(),SContact.getText().toString(),SEmail.getText().toString()));
Log.d("StudentData",c);
db.close();
}catch (Exception e){
}
答案 0 :(得分:1)
使用Room Persistence library。它的创建是为了简化与数据库的交互。它支持使用RxJava和LiveData包装数据。
检查the Documentation开始使用
基本上,您希望创建将抽象表并将表示单个行对象的Entity类。例如,这显示了名为users
的表的用户实体,以及作为PK的表。
@Entity(tableName="users")
public class User {
@PrimaryKey
private int uid;
@ColumnInfo(name = "first_name")
private String firstName;
@ColumnInfo(name = "last_name")
private String lastName;
// Getters and setters are ignored for brevity,
// but they're required for Room to work.
}
然后定义将包含查询定义的DAO类。您将使用此接口的对象进行实际查询。房间将为您制作具体的课程
@Dao
public interface UserDao {
@Query("SELECT * FROM user")
List<User> getAll();
@Query("SELECT * FROM user WHERE uid IN (:userIds)")
List<User> loadAllByIds(int[] userIds);
@Query("SELECT * FROM user WHERE first_name LIKE :first AND "
+ "last_name LIKE :last LIMIT 1")
User findByName(String first, String last);
@Insert
void insertAll(User... users);
@Delete
void delete(User user);
}
最后,您创建了用于实际查询数据库的数据库对象。该类是抽象的,Room也将为您创建具体的类。它包含创建DAO的方法,您可以根据需要命名方法。
@Database(entities = {User.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract UserDao userDao();
}
现在假设我
AppDatabase db = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "databaseName.db").build(); //Most of the time I have used this, it is a Singleton.
List<User> users = db.userDao().getAll();
for(User u : users)
{
Log.d("SQLITE_ROOM_DATA", u.firstName);
}
这里我们返回了简单的List<User>
,但是Room允许你用RxJava Observables包装它们,如Flowable<List<User>>
或Architecture component livedata LiveData<List<User>>
要使用Room,您需要将依赖项添加到您的gradle中,如下所示:
dependencies {
def room_version = "1.1.0" // or, for latest rc, use "1.1.1-rc1"
implementation "android.arch.persistence.room:runtime:$room_version"
annotationProcessor "android.arch.persistence.room:compiler:$room_version"
// optional - RxJava support for Room
implementation "android.arch.persistence.room:rxjava2:$room_version"
// Test helpers
testImplementation "android.arch.persistence.room:testing:$room_version"
}