[英]How to show exact number of items in RecyclerView?
我試圖在 RecyclerView 中顯示精確(例如 3 個項目)。 我們的 Web 應用程序顯示如下:
如果我移動項目:
在 Android 中,我使用 RecyclerView 顯示圖像:
如何在 RecyclerView 的可見區域中准確顯示 3 個項目? 如何避免顯示“一半”項目? 這可能嗎?
回收者視圖:
<android.support.v7.widget.RecyclerView
android:layout_width="wrap_content"
android:layout_height="130dp"
android:id="@+id/rvProducts" />
回收商視圖中的一項:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:layout_width="100dp"
android:layout_height="wrap_content"
android:padding="10dp"
android:id="@+id/ivProduct"
android:src="@drawable/noimage"/>
</LinearLayout>
代碼:
LinearLayoutManager layoutManager
= new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
RecyclerView productImageList = (RecyclerView) view.findViewById(R.id.rvProducts);
productImageList.setLayoutManager(layoutManager);
GalleryRecyclerAdapter adapter = new GalleryRecyclerAdapter(images);
productImageList.setAdapter(adapter);
一種解決方案是以編程方式設置每個孩子的width
。
view.getLayoutParams().width = getScreenWidth() / VIEWS_COUNT_TO_DISPLAY;
屏幕尺寸是這樣的:
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics).widthPixels;
我已經按照以下方法完成了上述任務,請參考以下代碼
在我的RecycleView Adapter
onCreateViewHolder()
方法中,我找出了屏幕的寬度,然后將其分為3 個部分。請檢查一次。
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.MY_ITEM_TO_INFALTE, parent, false);
itemView.getLayoutParams().width = (int) (getScreenWidth() / NUMBERS_OF_ITEM_TO_DISPLAY); /// THIS LINE WILL DIVIDE OUR VIEW INTO NUMBERS OF PARTS
return new MyCreationItemAdapter.MyViewHolder(itemView);
}
從上面的代碼中,我們在上面使用的getScreenWidth()
方法如下,請檢查它。
public int getScreenWidth() {
WindowManager wm = (WindowManager) activity.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();
Point size = new Point();
display.getSize(size);
return size.x;
}
在實現這一點的一般方法中,回收者視圖沒有直接的屬性。
實現這一點的方法是將父寬度發送到適配器。
以一種麂皮的方式..
Parent width = parent container width;
InitialiseRecyclerAdapter(parent width) {
on create view holder {
Set the width of ur item layout with a width that divides ur parent width in equal parts;
}
}
這個解決方案對我有用:
private lateinit var productImageList: RecyclerView
override fun onAttachedToRecyclerView(recyclerView: RecyclerView)
{
super.onAttachedToRecyclerView(recyclerView)
productImageList = recyclerView
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ProductViewHolder {
val viewHolder = LayoutInflater.from(parent.context).inflate(R.layout.ITEM_TO_INFALTE, parent, false)
viewHolder.layoutParams.width = productImageList.measuredWidth / NUMBERS_OF_ITEM_TO_DISPLAY
return ProductViewHolder(viewHolder)
}
代碼在 kotlin 中,希望對您有所幫助。
我在下面提供的解決方案有助於在屏幕上的 recyclerView 中顯示預定義數量的子項目(' numOfCardViewItemsOnScreen '),還計算這些項目之間的邊距以均勻間隔它們,通過考慮之間提供的邊距items & recyclerView 的結束邊距(即,' marginAtRecyclerViewsEnds ')
請注意,我已經在 5.0" 到 7.0" 英寸設備之間進行了測試,並獲得了一致的結果。
private fun configureCardViewLayoutParams(cardView: CardView, numOfCardViewItemsOnScreen: Int, marginAtRecyclerViewsEnds: Float, marginLeftParam: Float, marginRightParam: Float, marginTopParam: Float, marginBottomParam: Float): ViewGroup.MarginLayoutParams {
val numOfGapsInBetweenItems = numOfCardViewItemsOnScreen - 1
var combinedGapWidth = ((marginLeftParam + marginRightParam) * numOfGapsInBetweenItems) + (marginAtRecyclerViewsEnds * 2)
//Provided approx. adjustment of 2dp to prevent the extreme edges of the card from being cut-off
combinedGapWidth += 2
val combinedGapWidthDp = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, combinedGapWidth, cardView.resources.displayMetrics).toInt()
//Since margins/gaps are provided in-between the items, these have to be taken to account & subtracted from the width in-order to obtain even spacing
cardView.layoutParams.width = (getScreenWidth(cardView.context as MainActivity) - combinedGapWidthDp) / numOfCardViewItemsOnScreen
//Margins in-between the items
val marginLeftOfItem = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, marginLeftParam, cardView.resources.displayMetrics).toInt()
val marginRightOfItem = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, marginRightParam, cardView.resources.displayMetrics).toInt()
val marginTopOfItem = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, marginTopParam, cardView.resources.displayMetrics).toInt()
val marginBottomOfItem = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, marginBottomParam, cardView.resources.displayMetrics).toInt()
//Providing the above margins to the CardView
val cardViewMarginParams: ViewGroup.MarginLayoutParams = cardView.layoutParams as ViewGroup.MarginLayoutParams
cardViewMarginParams.setMargins(marginLeftOfItem, marginTopOfItem, marginRightOfItem, marginBottomOfItem)
return cardViewMarginParams
}
顧名思義,以下方法有助於計算 screenWidth
private fun getScreenWidth(activity: MainActivity): Int {
var width: Int = 0
val size = Point()
val windowManager = activity.getSystemService(Context.WINDOW_SERVICE) as WindowManager
width = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
val bounds = windowManager.currentWindowMetrics.bounds
bounds.width()
} else {
val display: Display? = windowManager.defaultDisplay
display?.getSize(size)
size.x
}
return width
}
最后在 onCreateViewHolder 中,利用上面描述的 configureCardViewLayoutParams 方法並傳入所需的參數
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyRecyclerViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.row_item_layout, parent, false)
view.layoutParams = configureCardViewLayoutParams(view as CardView, 4, 12f, 4f, 4f, 8f, 8f)
return MyRecyclerViewHolder(view)
}
為了便於理解,我還提供了子項的xml布局(row_item_layout.xml),所以從下面的xml可以看出,我們子項布局的根視圖是一個CardView。
<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:elevation="5dp"
android:foregroundGravity="center">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imageView1"
android:layout_width="30dp"
android:layout_height="28dp"
android:layout_marginTop="22dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:src="@tools:sample/avatars" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="7dp"
android:layout_marginTop="18dp"
android:layout_marginEnd="7dp"
android:layout_marginBottom="16dp"
android:ellipsize="end"
android:gravity="center"
android:maxLines="2"
android:text="@{accountOptionsModel.title}"
android:textSize="14sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/imageView1"
tools:text="@tools:sample/full_names" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
getCount() 中沒有特殊邏輯,只返回整個列表大小
override fun getItemCount(): Int = myList.size
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