Updating the javadoc for MediatorLiveData.
Bug:37567539
Test: NA
Change-Id: Ie3c97932173041801ca14b4ef6e2b5cd7c11355c
diff --git a/lifecycle/extensions/src/main/java/android/arch/lifecycle/MediatorLiveData.java b/lifecycle/extensions/src/main/java/android/arch/lifecycle/MediatorLiveData.java
index 672b3a3..718c79e 100644
--- a/lifecycle/extensions/src/main/java/android/arch/lifecycle/MediatorLiveData.java
+++ b/lifecycle/extensions/src/main/java/android/arch/lifecycle/MediatorLiveData.java
@@ -24,11 +24,43 @@
import java.util.Map;
/**
- * {@link LiveData} subclass which may observer other {@code LiveData} objects and react on
+ * {@link LiveData} subclass which may observe other {@code LiveData} objects and react on
* {@code OnChanged} events from them.
* <p>
* This class correctly propagates its active/inactive states down to source {@code LiveData}
* objects.
+ * <p>
+ * Consider the following scenario: we have 2 instances of {@code LiveData}, let's name them
+ * {@code liveData1} and {@code liveData2}, and we want to merge their emissions in one object:
+ * {@code liveDataMerger}. Then, {@code liveData1} and {@code liveData2} will become sources for
+ * the {@code MediatorLiveData liveDataMerger} and every time {@code onChanged} callback
+ * is called for either of them, we set a new value in {@code liveDataMerger}.
+ *
+ * <pre>
+ * LiveData<Integer> liveData1 = ...;
+ * LiveData<Integer> liveData2 = ...;
+ *
+ * MediatorLiveData<Integer> liveDataMerger = new MediatorLiveData<>();
+ * liveDataMerger.addSource(liveData1, value -> liveDataMerger.setValue(value));
+ * liveDataMerger.addSource(liveData2, value -> liveDataMerger.setValue(value));
+ * </pre>
+ * <p>
+ * Let's consider that we only want 10 values emitted by {@code liveData1}, to be
+ * merged in the {@code liveDataMerger}. Then, after 10 values, we can stop listening to {@code
+ * liveData1} and remove it as a source.
+ * <pre>
+ * liveDataMerger.addSource(liveData1, new Observer<Integer>() {
+ * private int count = 1;
+ *
+ * {@literal @}Override public void onChanged(@Nullable Integer s) {
+ * count++;
+ * liveDataMerger.setValue(s);
+ * if (count > 10) {
+ * liveDataMerger.removeSource(liveData1);
+ * }
+ * }
+ * });
+ * </pre>
*
* @param <T> The type of data hold by this instance
*/