RxJava2 / RxAndroid2的過濾器filter

RxJava2 / RxAndroid2的過濾器filter

filter完成一個條件過濾和篩選，從Observable的輸出資料中，經過filter篩選一層，如果filter判斷的值為真，則交給觀察者，否則跳過，例如代碼：

package zhangphil.app;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.CompositeDisposable;
import io.reactivex.functions.Predicate;
import io.reactivex.observers.DisposableObserver;
import io.reactivex.schedulers.Schedulers;

public class MainActivity extends AppCompatActivity {
    private final String TAG = getClass().getSimpleName();
    private CompositeDisposable mCompositeDisposable = new CompositeDisposable();

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        test();
    }

    private void test() {
        DisposableObserver disposableObserver = new DisposableObserver<Integer>() {
            @Override
            public void onNext(Integer i) {
                Log.d(TAG, "#####開始#####");
                Log.d(TAG + "資料", String.valueOf(i));
                Log.d(TAG, "#####結束#####");
            }

            @Override
            public void onComplete() {
                Log.d(TAG, "onComplete");
            }

            @Override
            public void onError(Throwable e) {
                Log.e(TAG, e.toString(), e);
            }
        };

        mCompositeDisposable.add(
                getObservable().filter(new Predicate<Integer>() {
                    @Override
                    public boolean test(Integer integer) throws Exception {
                        int result = integer % 10;
                        boolean b = (result == 0);
                        return b; // 此處傳回的條件若為true，則資料交給觀察者 ,否則跳過
                    }
                })
                        .subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribeWith(disposableObserver));
    }

    private Observable<Integer> getObservable() {
        return Observable.range(0, 100);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // 如果退出程式，就清除背景任務
        mCompositeDisposable.clear();
    }
}
           

代碼輸出：

05-15 17:15:49.664 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.664 29872-29872/zhangphil.app D/MainActivity資料: 0
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 10
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 20
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 30
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 40
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 50
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 60
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 70
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 80
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####開始#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity資料: 90
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: #####結束#####
05-15 17:15:49.665 29872-29872/zhangphil.app D/MainActivity: onComplete