我的水平RecyclerView上有很长的单元格,
并且我希望他们有一个标题,当用户水平滚动时它仍然保持不动.
并且我希望他们有一个标题,当用户水平滚动时它仍然保持不动.
- Recycler View (A) - - Cell (parent) (B) - - - Header (C) <-- We want that to be still - - - Content (D)
这是它在视觉上的样子：
因此,我正在寻找一种方法：
1)当用户在RecyclerView(A)上拖动手指时,停止标题(C)更改位置
要么
2)像正常一样滚动单元格(B),但是将它的子项(C)的位置改变到相反的方向,以使标题即使在移动时也显示为静止(在父项的相反方向上(B) .
这是我正在尝试构建的内容：
有任何想法吗？
p.s 1：我注意到很多SO答案,建议使用Itemdecoration,但所有可能的答案都有VERTICAL实现的代码,这与HORIZONTAL实现非常不同.
p.s 2我正在以编程方式创建所有视图内容,因此我不会使用布局文件. (那是因为内容将是反应原生视图,我无法创建具有布局文件的内容).
p.s 3：我还注意到Itemdecoration是旧策略,更新的第三方库扩展了LayoutManager.
请稍微说清楚,谢谢.
解决方法
虽然可以将标题视图保留在RecyclerView中并使其静态,但我建议采用另一种方法.
标题可以继续在RecyclerView内部表示,但显示将被带到RecyclerView的顶部,如下所示：
- Title (C) <-- We want that to be still - Recycler View (A) - - Cell (parent) (B) - - - Content
RecyclerView.OnScrollListener将侦听新项目的外观并相应地更改标题.这样,当出现新项目时,作为TextView的标题将显示新标题.以下说明了这一点.
(这是一个用于演示目的的简单实现.一个完整的应用程序将显示狗品种图像和某种有意义的描述.)
以下是实现此效果的代码：
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中
<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>
更新：这是另一种设置TextView的左边距以使标头粘滞的方法. TextView的负x偏移量被视为标题的填充,使其在TextView中向右滑动并粘贴到屏幕的左侧.
结果如下：
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,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,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);
// 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);
}
});
}
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 position) {
RecyclerViewAdapter.ItemViewHolder vh = (RecyclerViewAdapter.ItemViewHolder) holder;
vh.mBreedImage.setimageDrawable(holder.itemView.getResources().getDrawable(R.drawable.no_image));
vh.mBreedname.setPadding(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中
<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>