diff --git a/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsAdapter.java b/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsAdapter.java
index 547e2dc..8831fdf 100644
--- a/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsAdapter.java
+++ b/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsAdapter.java
@@ -1,6 +1,9 @@
 package moe.feng.common.view.breadcrumbs;
 
 import android.content.Context;
+import android.support.annotation.IdRes;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.v7.widget.ListPopupWindow;
 import android.support.v7.widget.RecyclerView;
 import android.view.*;
@@ -33,23 +36,23 @@ public BreadcrumbsAdapter(BreadcrumbsView parent, ArrayList<BreadcrumbItem> item
 		DROPDOWN_OFFSET_Y_FIX = parent.getResources().getDimensionPixelOffset(R.dimen.dropdown_offset_y_fix_value);
 	}
 
-	public ArrayList<BreadcrumbItem> getItems() {
+	public @NonNull ArrayList<BreadcrumbItem> getItems() {
 		return this.items;
 	}
 
-	public void setItems(ArrayList<BreadcrumbItem> items) {
+	public void setItems(@NonNull ArrayList<BreadcrumbItem> items) {
 		this.items = items;
 	}
 
-	public void setCallback(BreadcrumbsCallback callback) {
+	public void setCallback(@Nullable BreadcrumbsCallback callback) {
 		this.callback = callback;
 	}
 
-	public BreadcrumbsCallback getCallback() {
+	public @Nullable BreadcrumbsCallback getCallback() {
 		return this.callback;
 	}
 
-	public void setPopupThemeId(int popupThemeId) {
+	public void setPopupThemeId(@IdRes int popupThemeId) {
 		this.mPopupThemeId = popupThemeId;
 	}
 
@@ -100,7 +103,7 @@ public void onClick(View view) {
 		}
 
 		@Override
-		public void setItem(BreadcrumbItem item) {
+		public void setItem(@NonNull BreadcrumbItem item) {
 			super.setItem(item);
 			button.setText(item.getSelectedItem());
 			button.setTextColor(
@@ -136,7 +139,7 @@ public void onClick(View view) {
 		}
 
 		@Override
-		public void setItem(BreadcrumbItem item) {
+		public void setItem(@NonNull BreadcrumbItem item) {
 			super.setItem(item);
 			imageButton.setClickable(item.hasMoreSelect());
 			if (item.hasMoreSelect()) {
@@ -187,7 +190,7 @@ class ItemHolder<T> extends RecyclerView.ViewHolder {
 			super(itemView);
 		}
 
-		public void setItem(T item) {
+		public void setItem(@NonNull T item) {
 			this.item = item;
 		}
 
diff --git a/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsView.java b/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsView.java
index 8729245..df087f4 100644
--- a/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsView.java
+++ b/library/src/main/java/moe/feng/common/view/breadcrumbs/BreadcrumbsView.java
@@ -92,7 +92,10 @@ private void init() {
 	 *
 	 * @return Current item
 	 */
-	public BreadcrumbItem getCurrentItem() {
+	public @Nullable BreadcrumbItem getCurrentItem() {
+		if (mAdapter.getItems().size() <= 0) {
+			return null;
+		}
 		return mAdapter.getItems().get(mAdapter.getItems().size() - 1);
 	}
 
@@ -177,7 +180,7 @@ public void removeLastItem() {
 	 * @see BreadcrumbsCallback
 	 * @see DefaultBreadcrumbsCallback
 	 */
-	public void setCallback(BreadcrumbsCallback callback) {
+	public void setCallback(@Nullable BreadcrumbsCallback callback) {
 		mAdapter.setCallback(callback);
 	}
 
@@ -187,7 +190,7 @@ public void setCallback(BreadcrumbsCallback callback) {
 	 * @return Callback
 	 * @see BreadcrumbsCallback
 	 */
-	public BreadcrumbsCallback getCallback() {
+	public @Nullable BreadcrumbsCallback getCallback() {
 		return mAdapter.getCallback();
 	}
 
diff --git a/library/src/main/java/moe/feng/common/view/breadcrumbs/model/BreadcrumbItem.java b/library/src/main/java/moe/feng/common/view/breadcrumbs/model/BreadcrumbItem.java
index d7f042f..9c8fde2 100644
--- a/library/src/main/java/moe/feng/common/view/breadcrumbs/model/BreadcrumbItem.java
+++ b/library/src/main/java/moe/feng/common/view/breadcrumbs/model/BreadcrumbItem.java
@@ -23,33 +23,64 @@ public BreadcrumbItem(@NonNull List<String> items, int selectedIndex) {
 		}
 	}
 
-	public void setSelectedItem(String selectedItem) {
+	public void setSelectedItem(@NonNull String selectedItem) {
 		this.mSelectedIndex = mItems.indexOf(selectedItem);
 		if (mSelectedIndex == -1) {
 			throw new IllegalArgumentException("This item does not exist in items.");
 		}
 	}
 
+	/**
+	 * Select a item by index
+	 *
+	 * @param selectedIndex The index of the item should be selected
+	 */
 	public void setSelectedIndex(int selectedIndex) {
 		this.mSelectedIndex = selectedIndex;
 	}
 
+	/**
+	 * Get selected item index
+	 *
+	 * @return The index of selected item
+	 */
 	public int getSelectedIndex() {
 		return this.mSelectedIndex;
 	}
 
+	/**
+	 * Get selected item
+	 *
+	 * @return The selected item
+	 */
 	public @NonNull String getSelectedItem() {
 		return this.mItems.get(getSelectedIndex());
 	}
 
+	/**
+	 * Check if there are other items
+	 *
+	 * @return Result
+	 */
 	public boolean hasMoreSelect() {
 		return this.mItems.size() > 1;
 	}
 
+	/**
+	 * Set a new items list
+	 *
+	 * @param items Items list
+	 */
 	public void setItems(@NonNull List<String> items) {
 		this.setItems(items, 0);
 	}
 
+	/**
+	 * Set a new items list with selecting a item
+	 *
+	 * @param items Items list
+	 * @param selectedIndex The selected item index
+	 */
 	public void setItems(@NonNull List<String> items, int selectedIndex) {
 		if (items != null && !items.isEmpty()) {
 			this.mItems = items;
@@ -59,11 +90,23 @@ public void setItems(@NonNull List<String> items, int selectedIndex) {
 		}
 	}
 
-	public List<String> getItems() {
+	/**
+	 * Get items list
+	 *
+	 * @return Items List
+	 */
+	public @NonNull List<String> getItems() {
 		return mItems;
 	}
 
-	public static BreadcrumbItem createSimpleItem(String title) {
+	/**
+	 * Create a simple BreadcrumbItem with single item
+	 *
+	 * @param title Item title
+	 * @return Simple BreadcrumbItem
+	 * @see BreadcrumbItem
+	 */
+	public static BreadcrumbItem createSimpleItem(@NonNull String title) {
 		return new BreadcrumbItem(Collections.singletonList(title));
 	}