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[英]RxJava. Observable.OnSubscribe cannot be resolved to a type
[英]RxJava. Read file to observable
我是RxJava和反應式編程的新手。 我有一個作業,我必須讀取文件並將其存儲到Observable。 我曾嘗試在內部使用BufferedReader創建一個Callable,並使用Observable.fromCallable(),但它沒有多大用處。
你能告訴我我該怎么辦?
我正在使用RxJava 2.0。
一個基本的解決方案,我使用嵌套類FileObservableSource
生成數據,然后推遲創建Observable直到Observer訂閱:
import io.reactivex.Observable;
import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
public class StackOverflow {
public static void main(String[] args) {
final Observable<String> observable = Observable.defer(() -> new FileObservableSource("pom.xml"));
observable.subscribe(
line -> System.out.println("next line: " + line),
Throwable::printStackTrace,
() -> System.out.println("finished")
);
}
static class FileObservableSource implements ObservableSource<String> {
private final String filename;
FileObservableSource(String filename) {
this.filename = filename;
}
@Override
public void subscribe(Observer<? super String> observer) {
try {
Files.lines(Paths.get(filename)).forEach(observer::onNext);
observer.onComplete();
} catch (IOException e) {
observer.onError(e);
}
}
}
}
對於Java 8,BufferedReader有一個文件流和迭代器,可以與RxJava一起使用。 https://dzone.com/articles/java-8-stream-rx-java
您可以使用以下代碼獲取Flowable
Flowable.fromIterable(bufferedReader.lines()::iterator)
我使用Flowable和Single更簡潔,它仍然適用於Observable。 代碼片段是我如何從緩沖的閱讀器中讀取每一行的示例。
try (
FileReader fr = new FileReader("./folder1/source.txt");
BufferedReader br = new BufferedReader(fr);
//e.g. i write the output into this file
FileWriter fw = new FileWriter("./folder1/destination.txt");
BufferedWriter bw = new BufferedWriter(fw)
) {
//=========================================
//calling br.lines() gives you the stream.
//br.lines()::iterator returns you the iterable
//=========================================
Flowable.fromIterable(br.lines()::iterator)
//at this point you can do what you want for each line
//e.g. I split long strings into smaller Flowable<String> chunks.
.flatMap(i -> splitLine(i))
//e.g. I then use the output to query an external server with retrofit.
// which returns me a Single<String> result
.flatMapSingle(i -> handlePinyin(pr, i))
.subscribe(
//I save the results from server to destination.txt
py -> appendToFile(bw, py),
//print and quit if error
err -> print("ERROR " + err),
() -> print("Completed!"));
}catch (IOException e) {
print("Error " + e);
}
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