Хотя можно оставить вид заголовка внутри RecyclerView
и сделать его статическим, я предлагаю альтернативный подход.
Заголовок может по-прежнему отображаться внутри RecyclerView
, но отображение будет вынесено наружу в верхнюю часть RecyclerView
следующим образом:
- Title (C) <-- We want that to be still
- Recycler View (A)
- - Cell (parent) (B)
- - - Content
RecyclerView.OnScrollListener
будет прослушивать появление новых элементов и соответствующим образом изменять заголовок. Таким образом, по мере появления новых элементов заголовок, который является TextView
, будет отображать новый заголовок. Это демонстрирует следующее.
(Это простая реализация для демонстрационных целей. Полное приложение будет отображать изображения пород собак и какое-то осмысленное описание.)
Вот код, который реализует этот эффект:
MainActivity.java
public class MainActivity extends AppCompatActivity {
private LinearLayoutManager mLayoutManager;
private RecyclerViewAdapter mAdapter;
private TextView mBreedNameTitle;
private int mLastBreedTitlePosition = RecyclerView.NO_POSITION;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
List<String> breedList = createBreedList();
// This is where the breed title is displayed.
mBreedNameTitle = findViewById(R.id.breedNameTitle);
// Set up the RecyclerView.
mLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
RecyclerView recyclerView = findViewById(R.id.recyclerView);
mAdapter = new RecyclerViewAdapter(breedList);
recyclerView.setLayoutManager(mLayoutManager);
recyclerView.setAdapter(mAdapter);
// Add the OnScrollListener so we know when to change the breed title.
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int lastVisible = mLayoutManager.findLastVisibleItemPosition();
if (lastVisible == RecyclerView.NO_POSITION) {
return;
}
if (lastVisible != mLastBreedTitlePosition) {
mBreedNameTitle.setText(mAdapter.getItems().get(lastVisible));
mLastBreedTitlePosition = lastVisible;
}
}
});
}
private List<String> createBreedList() {
List<String> breedList = new ArrayList<>();
breedList.add("Affenpinscher");
breedList.add("Afghan Hound");
breedList.add("Airedale Terrier");
breedList.add("Akita");
breedList.add("Alaskan Malamute");
breedList.add("American Cocker Spaniel");
breedList.add("American Eskimo Dog (Miniature)");
breedList.add("American Eskimo Dog (Standard)");
breedList.add("American Eskimo Dog (Toy)");
breedList.add("American Foxhound");
breedList.add("American Staffordshire Terrier");
breedList.add("American Eskimo Dog (Standard)");
return breedList;
}
@SuppressWarnings("unused")
private final static String TAG = "MainActivity";
}
class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private final List<String> mItems;
RecyclerViewAdapter(List<String> items) {
mItems = items;
}
@Override
@NonNull
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view;
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false);
return new RecyclerViewAdapter.ItemViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
RecyclerViewAdapter.ItemViewHolder vh = (RecyclerViewAdapter.ItemViewHolder) holder;
vh.mBreedImage.setImageDrawable(holder.itemView.getResources().getDrawable(R.drawable.no_image));
vh.mBreedName = mItems.get(position);
}
@Override
public int getItemCount() {
return mItems.size();
}
public List<String> getItems() {
return mItems;
}
static class ItemViewHolder extends RecyclerView.ViewHolder {
private ImageView mBreedImage;
private String mBreedName;
ItemViewHolder(View itemView) {
super(itemView);
mBreedImage = itemView.findViewById(R.id.breedImage);
}
}
}
activity_main.xml
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="@dimen/activity_horizontal_margin"
android:orientation="vertical">
<TextView
android:id="@+id/breedNameTitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:fontFamily="sans-serif"
android:textColor="@android:color/black"
android:textSize="16sp"
tools:text="Breed name" />
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" />
</LinearLayout>
item_layout.xml
<android.support.constraint.ConstraintLayout
android:id="@+id/cont_item_root"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/white">
<ImageView
android:id="@+id/breedImage"
android:layout_width="64dp"
android:layout_height="64dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:contentDescription="Dog breed image"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0"
tools:ignore="HardcodedText" />
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginEnd="16dp"
android:layout_marginStart="16dp"
android:text="@string/large_text"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/breedImage"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
Обновление. Вот еще один подход, который устанавливает левый отступ TextView
, чтобы сделать заголовок липким. Отрицательное x-смещение TextView
используется в качестве заполнения для заголовка, чтобы заставить его скользить вправо в пределах TextView
и прикрепляться к левой стороне экрана.
Вот результат:
MainActivity.java
public class MainActivity extends AppCompatActivity {
private LinearLayoutManager mLayoutManager;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
List<String> breedList = createBreedList();
// Set up the RecyclerView.
mLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
RecyclerView recyclerView = findViewById(R.id.recyclerView);
RecyclerViewAdapter adapter = new RecyclerViewAdapter(breedList);
recyclerView.setLayoutManager(mLayoutManager);
recyclerView.setAdapter(adapter);
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// Pad the left of the breed name so it stays aligned with the left side of the display.
int firstVisible = mLayoutManager.findFirstVisibleItemPosition();
View firstView = mLayoutManager.findViewByPosition(firstVisible);
firstView.findViewById(R.id.itemBreedName).setPadding((int) -firstView.getX(), 0, 0, 0);
// Make sure the other breed name has zero padding because we may have changed it.
int lastVisible = mLayoutManager.findLastVisibleItemPosition();
View lastView = mLayoutManager.findViewByPosition(lastVisible);
lastView.findViewById(R.id.itemBreedName).setPadding(0, 0, 0, 0);
}
});
}
private List<String> createBreedList() {
List<String> breedList = new ArrayList<>();
breedList.add("Affenpinscher");
breedList.add("Afghan Hound");
breedList.add("Airedale Terrier");
breedList.add("Akita");
breedList.add("Alaskan Malamute");
breedList.add("American Cocker Spaniel");
breedList.add("American Eskimo Dog (Miniature)");
breedList.add("American Eskimo Dog (Standard)");
breedList.add("American Eskimo Dog (Toy)");
breedList.add("American Foxhound");
breedList.add("American Staffordshire Terrier");
breedList.add("American Eskimo Dog (Standard)");
return breedList;
}
@SuppressWarnings("unused")
private final static String TAG = "MainActivity";
}
class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private final List<String> mItems;
RecyclerViewAdapter(List<String> items) {
mItems = items;
}
@Override
@NonNull
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view;
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false);
return new RecyclerViewAdapter.ItemViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
RecyclerViewAdapter.ItemViewHolder vh = (RecyclerViewAdapter.ItemViewHolder) holder;
vh.mBreedImage.setImageDrawable(holder.itemView.getResources().getDrawable(R.drawable.no_image));
vh.mBreedName.setPadding(0, 0, 0, 0);
vh.mBreedName.setText(mItems.get(position));
}
@Override
public int getItemCount() {
return mItems.size();
}
static class ItemViewHolder extends RecyclerView.ViewHolder {
private ImageView mBreedImage;
private TextView mBreedName;
ItemViewHolder(View itemView) {
super(itemView);
mBreedImage = itemView.findViewById(R.id.breedImage);
mBreedName = itemView.findViewById(R.id.itemBreedName);
}
}
}
activity_main.xml
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="@dimen/activity_horizontal_margin"
android:orientation="vertical">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" />
</LinearLayout>
item_layout.xml
<android.support.constraint.ConstraintLayout
android:id="@+id/cont_item_root"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@android:color/white">
<TextView
android:id="@+id/itemBreedName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:ellipsize="none"
android:fontFamily="sans-serif"
android:singleLine="true"
android:textColor="@android:color/black"
android:textSize="16sp"
tools:text="Breed name" />
<ImageView
android:id="@+id/breedImage"
android:layout_width="64dp"
android:layout_height="64dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:contentDescription="Dog breed image"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/itemBreedName"
app:layout_constraintVertical_bias="1.0"
tools:ignore="HardcodedText" />
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginEnd="16dp"
android:layout_marginStart="16dp"
android:text="@string/large_text"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/breedImage"
app:layout_constraintTop_toBottomOf="@+id/itemBreedName" />
</android.support.constraint.ConstraintLayout>
person
Cheticamp
schedule
09.04.2018