LiveData class that counts how many times it has delivered updated values to Observers.

CountingLiveData.java

/*
 * Copyright (C) 2020 Glowworm Software
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package mobi.glowworm.lib.lifecycle;

import androidx.annotation.NonNull;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MediatorLiveData;

/**
 * {@link LiveData} wrapper that counts the number of times results have been delivered to observers.
 * <p>
 * i.e. how many times {@link androidx.lifecycle.Observer#onChanged(Object)} is called on the wrapped data.
 */
public class CountingLiveData<T> extends MediatorLiveData<T> {
    private int count = 0;

    public CountingLiveData(@NonNull LiveData<T> source) {
        super();
        addSource(source, changedValue -> {
            count++;
            setValue(changedValue);
        });
    }

    public int getCount() {
        return count;
    }

    public boolean isFirstValue() {
        return count == 1;
    }
}

lgtm