Center a CardView in a RecyclerView with only one element
1.Try set LayoutParams CENTER_IN_PARENT when recyclerview has 1 child
2.Or Use a FrameLayout as parent of recyclerView and set layout_gravity
3.Or just compute the space above cardview and set marginTop to recyclerView or setTranslationY to recyclerView
4.Or add a itemDecaration with space'height at Recylerview.
RelativeLayout.LayoutParams rLp = (RelativeLayout.LayoutParams) recyclerView.getLayoutParams();
if(data != null || data.size()>1){
rLp.removeRule(RelativeLayout.CENTER_IN_PARENT);
}else{
rLp.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);
}
recyclerView.setLayoutParams(rLp);
When recyclerView has only one child use this LayoutManager:
import android.content.Context;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
public class FullyLinearLayoutManager extends LinearLayoutManager {
private static final String TAG = FullyLinearLayoutManager.class.getSimpleName();
private MeasureEndListener mMeasureEndListener;
public FullyLinearLayoutManager(Context context) {
super(context);
}
private float divHeight =0;
public FullyLinearLayoutManager(Context context,float height) {
super(context);
divHeight = height;
}
public FullyLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
private int[] mMeasuredDimension = new int[2];
@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state,
int widthSpec, int heightSpec) {
final int widthMode = View.MeasureSpec.getMode(widthSpec);
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);
Log.i(TAG, "onMeasure called. \nwidthMode " + widthMode
+ " \nheightMode " + heightSpec
+ " \nwidthSize " + widthSize
+ " \nheightSize " + heightSize
+ " \ngetItemCount() " + getItemCount());
int width = 0;
int height = 0;
for (int i = 0; i < getItemCount(); i++) {
measureScrapChild(recycler, i,
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(i, View.MeasureSpec.UNSPECIFIED),
mMeasuredDimension);
if (getOrientation() == HORIZONTAL) {
width = width + mMeasuredDimension[0];
if (i == 0) {
height = mMeasuredDimension[1];
}
} else {
// LogUtils.e(mMeasuredDimension[1]);
height = height + mMeasuredDimension[1];
if(i!= getItemCount()-1){
height += divHeight;
// LogUtils.e(divHeight + "xxx add"+DensityUtils.dp2px(divHeight));
}else{
height += 2*divHeight;
// LogUtils.e(divHeight+ "xxx no add"+ DensityUtils.dp2px(divHeight));
}
if (i == 0) {
width = mMeasuredDimension[0];
}
}
}
switch (widthMode) {
case View.MeasureSpec.EXACTLY:
width = widthSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
switch (heightMode) {
case View.MeasureSpec.EXACTLY:
height = heightSize;
case View.MeasureSpec.AT_MOST:
case View.MeasureSpec.UNSPECIFIED:
}
if(mMeasureEndListener!=null){
mMeasureEndListener.onMeasureEnd(width,height);
// new Thread().interrupt();
}
setMeasuredDimension(width, height);
}
private void measureScrapChild(RecyclerView.Recycler recycler, int position, int widthSpec,
int heightSpec, int[] measuredDimension) {
try {
View view = recycler.getViewForPosition(0);//fix 动态添加时报IndexOutOfBoundsException
if (view != null) {
RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) view.getLayoutParams();
int childWidthSpec = ViewGroup.getChildMeasureSpec(widthSpec,
getPaddingLeft() + getPaddingRight(), p.width);
int childHeightSpec = ViewGroup.getChildMeasureSpec(heightSpec,
getPaddingTop() + getPaddingBottom(), p.height);
view.measure(childWidthSpec, childHeightSpec);
measuredDimension[0] = view.getMeasuredWidth() + p.leftMargin + p.rightMargin;
measuredDimension[1] = view.getMeasuredHeight() + p.bottomMargin + p.topMargin;
recycler.recycleView(view);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
}
}
public interface MeasureEndListener{
void onMeasureEnd(int width,int height);
}
public void setMeasureEndListener(MeasureEndListener mMeasureEndListener){
this.mMeasureEndListener = mMeasureEndListener;
}
}
I've implemented simple HelloWorld app, which shows list of cities and based on how many museums it has - shows full-sized city-card or the centered, wrapped version of it.
(Yes, I'm not exactly good at arts :-) )
Here's how I did it.
TL;DR:
The crucial part is ItemDecoration: set proper items offset and you'll get what you need; Here's how I've done it:
RecyclerView recyclerViewMuseum = (RecyclerView)findViewById(R.id.recyclerViewMuseum);
recyclerViewMuseum.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
recyclerViewMuseum.setAdapter(adapter);
recyclerViewMuseum.addItemDecoration(new RecyclerView.ItemDecoration() {
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (view instanceof CityWithOneMuseumCardView) {
int totalWidth = parent.getWidth();
int cardWidth = getResources().getDimensionPixelOffset(R.dimen.small_card_width);
int sidePadding = (totalWidth - cardWidth) / 2;
sidePadding = Math.max(0, sidePadding);
outRect.set(sidePadding, 0, sidePadding, 0);
}
}
});
Here's my model - City and Museum classes:
public class Museum {
public String title;
public Museum(String title) {
this.title = title;
}
}
public class City {
public String title;
public int imageRes;
public List<Museum> museums = new ArrayList<>();
public City(String title, int imageRes) {
this.title = title;
this.imageRes = imageRes;
}
}
Then Views: CityWithManyMuseumsCardView and CityWithOneMuseumCardView. Both of them are using helper-interface IItemDisplayer.
public class CityWithOneMuseumCardView extends CardView implements IItemDisplayer<City> {
public CityWithOneMuseumCardView(Context context) {
super(context);
LayoutInflater.from(context).inflate(R.layout.one_museum_layout, this);
}
@Override
public void displayItem(City city) {
TextView cityTitleTextView = (TextView)findViewById(R.id.cityTitleTextView);
cityTitleTextView.setText(city.title);
}
}
public class CityWithManyMuseumsCardView extends CardView implements IItemDisplayer<City> {
public CityWithManyMuseumsCardView(Context context) {
super(context);
LayoutInflater.from(context).inflate(R.layout.many_museums_layout, this);
}
@Override
public void displayItem(City city) {
ImageView cityBackgroundImageView = (ImageView)findViewById(R.id.cityBackgroundImageView);
cityBackgroundImageView.setImageResource(city.imageRes);
TextView cityTitleTextView = (TextView)findViewById(R.id.cityTitleTextView);
cityTitleTextView.setText(city.title);
TextView cityNumberOrMuseumsTextView = (TextView)findViewById(R.id.cityNumberOrMuseumsTextView);
cityNumberOrMuseumsTextView.setText(String.valueOf(city.museums.size()));
}
}
public interface IItemDisplayer<TItem> {
public void displayItem(TItem item);
}
And their layouts :
<!-- One Museum card -->
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#BB2050AB"
android:layout_width="@dimen/small_card_width"
android:layout_height="200dp">
<TextView
android:background="#AA000000"
android:textColor="#FFFFFF"
android:text="Only one museum available"
android:textSize="16sp"
android:padding="4dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/cityTitleTextView"
android:layout_gravity="bottom"
android:background="#AAFFFFFF"
android:textColor="#000000"
android:textSize="24sp"
android:paddingStart="16dp"
android:paddingEnd="16dp"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="48dp" />
</FrameLayout>
<!-- Many museums card -->
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="240dp">
<ImageView
android:id="@+id/cityBackgroundImageView"
android:scaleType="fitXY"
android:layout_width="500dp"
android:layout_height="match_parent" />
<TextView
android:id="@+id/cityNumberOrMuseumsTextView"
android:layout_gravity="top|end"
android:background="#AA000000"
android:textColor="#FFFFFF"
android:textSize="16sp"
android:padding="4dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/cityTitleTextView"
android:layout_gravity="bottom"
android:background="#AA000000"
android:textColor="#FFFFFF"
android:textSize="24sp"
android:paddingStart="16dp"
android:paddingEnd="16dp"
android:gravity="center_vertical"
android:layout_width="match_parent"
android:layout_height="48dp" />
</FrameLayout>
Then we need to create an adapter for our RecyclerView
CityAdapter.java
public class CityAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
final static int ITEM_TYPE_MANY_MUSEUMS = 0;
final static int ITEM_TYPE_ONE_MUSEUM = 1;
private List<City> items;
public CityAdapter(List<City> items) {
this.items = items;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
switch (viewType) {
case ITEM_TYPE_MANY_MUSEUMS:
return new ViewHolder(new CityWithManyMuseumsCardView(viewGroup.getContext()));
case ITEM_TYPE_ONE_MUSEUM:
return new ViewHolder(new CityWithOneMuseumCardView(viewGroup.getContext()));
default:
throw new IllegalArgumentException(String.format("Unexpected viewType: %d", viewType));
}
}
@Override
public int getItemViewType(int position) {
if (items == null || items.size() < position) {
throw new IllegalArgumentException("Wrong position!");
}
if (items.get(position).museums.size() > 1) {
return ITEM_TYPE_MANY_MUSEUMS;
} else if (items.get(position).museums.size() == 1){
return ITEM_TYPE_ONE_MUSEUM;
}
throw new IllegalArgumentException("Wrong number of museums!");
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
((IItemDisplayer<City>) holder.itemView).displayItem(items.get(position));
}
@Override
public int getItemCount() {
return items.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(View itemView) {
super(itemView);
}
}
}
I've uploaded this project to my dropbox - feel free to check it out! Hope, it helps.
Try set height of RecyclerView when have only one item or more.
Refer this topic for to do that. When have only one item, set RecyclerView to WRAP_CONTENT. And when have more one item, set RecyclerView to MATCH_CONTENT. Good luck!
Can you try this:
import android.content.Context;
import android.graphics.Rect;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import java.lang.reflect.Field;
/**
* {@link android.support.v7.widget.LinearLayoutManager} which wraps its content. Note that this class will always
* wrap the content regardless of {@link android.support.v7.widget.RecyclerView} layout parameters.
* <p/>
* Now it's impossible to run add/remove animations with child views which have arbitrary dimensions (height for
* VERTICAL orientation and width for HORIZONTAL). However if child views have fixed dimensions
* {@link #setChildSize(int)} method might be used to let the layout manager know how big they are going to be.
* If animations are not used at all then a normal measuring procedure will run and child views will be measured during
* the measure pass.
*/
public class WrapContentLinearLayoutManager extends android.support.v7.widget.LinearLayoutManager {
private static boolean canMakeInsetsDirty = true;
private static Field insetsDirtyField = null;
private static final int CHILD_WIDTH = 0;
private static final int CHILD_HEIGHT = 1;
private static final int DEFAULT_CHILD_SIZE = 100;
private final int[] childDimensions = new int[2];
private final RecyclerView view;
private int childSize = DEFAULT_CHILD_SIZE;
private boolean hasChildSize;
private int overScrollMode = ViewCompat.OVER_SCROLL_ALWAYS;
private final Rect tmpRect = new Rect();
@SuppressWarnings("UnusedDeclaration")
public WrapContentLinearLayoutManager(Context context) {
super(context);
this.view = null;
}
@SuppressWarnings("UnusedDeclaration")
public WrapContentLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
this.view = null;
}
@SuppressWarnings("UnusedDeclaration")
public WrapContentLinearLayoutManager(RecyclerView view) {
super(view.getContext());
this.view = view;
this.overScrollMode = ViewCompat.getOverScrollMode(view);
}
@SuppressWarnings("UnusedDeclaration")
public WrapContentLinearLayoutManager(RecyclerView view, int orientation, boolean reverseLayout) {
super(view.getContext(), orientation, reverseLayout);
this.view = view;
this.overScrollMode = ViewCompat.getOverScrollMode(view);
}
public void setOverScrollMode(int overScrollMode) {
if (overScrollMode < ViewCompat.OVER_SCROLL_ALWAYS || overScrollMode > ViewCompat.OVER_SCROLL_NEVER)
throw new IllegalArgumentException("Unknown overscroll mode: " + overScrollMode);
if (this.view == null) throw new IllegalStateException("view == null");
this.overScrollMode = overScrollMode;
ViewCompat.setOverScrollMode(view, overScrollMode);
}
public static int makeUnspecifiedSpec() {
return View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
}
@Override
public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec, int heightSpec) {
final int widthMode = View.MeasureSpec.getMode(widthSpec);
final int heightMode = View.MeasureSpec.getMode(heightSpec);
final int widthSize = View.MeasureSpec.getSize(widthSpec);
final int heightSize = View.MeasureSpec.getSize(heightSpec);
final boolean hasWidthSize = widthMode != View.MeasureSpec.UNSPECIFIED;
final boolean hasHeightSize = heightMode != View.MeasureSpec.UNSPECIFIED;
final boolean exactWidth = widthMode == View.MeasureSpec.EXACTLY;
final boolean exactHeight = heightMode == View.MeasureSpec.EXACTLY;
final int unspecified = makeUnspecifiedSpec();
if (exactWidth && exactHeight) {
// in case of exact calculations for both dimensions let's use default "onMeasure" implementation
super.onMeasure(recycler, state, widthSpec, heightSpec);
return;
}
final boolean vertical = getOrientation() == VERTICAL;
initChildDimensions(widthSize, heightSize, vertical);
int width = 0;
int height = 0;
// it's possible to get scrap views in recycler which are bound to old (invalid) adapter entities. This
// happens because their invalidation happens after "onMeasure" method. As a workaround let's clear the
// recycler now (it should not cause any performance issues while scrolling as "onMeasure" is never
// called whiles scrolling)
recycler.clear();
final int stateItemCount = state.getItemCount();
final int adapterItemCount = getItemCount();
// adapter always contains actual data while state might contain old data (f.e. data before the animation is
// done). As we want to measure the view with actual data we must use data from the adapter and not from the
// state
for (int i = 0; i < adapterItemCount; i++) {
if (vertical) {
if (!hasChildSize) {
if (i < stateItemCount) {
// we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items
// we will use previously calculated dimensions
measureChild(recycler, i, widthSize, unspecified, childDimensions);
} else {
logMeasureWarning(i);
}
}
height += childDimensions[CHILD_HEIGHT];
if (i == 0) {
width = childDimensions[CHILD_WIDTH];
}
if (hasHeightSize && height >= heightSize) {
break;
}
} else {
if (!hasChildSize) {
if (i < stateItemCount) {
// we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items
// we will use previously calculated dimensions
measureChild(recycler, i, unspecified, heightSize, childDimensions);
} else {
logMeasureWarning(i);
}
}
width += childDimensions[CHILD_WIDTH];
if (i == 0) {
height = childDimensions[CHILD_HEIGHT];
}
if (hasWidthSize && width >= widthSize) {
break;
}
}
}
if (exactWidth) {
width = widthSize;
} else {
width += getPaddingLeft() + getPaddingRight();
if (hasWidthSize) {
width = Math.min(width, widthSize);
}
}
if (exactHeight) {
height = heightSize;
} else {
height += getPaddingTop() + getPaddingBottom();
if (hasHeightSize) {
height = Math.min(height, heightSize);
}
}
setMeasuredDimension(width, height);
if (view != null && overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS) {
final boolean fit = (vertical && (!hasHeightSize || height < heightSize))
|| (!vertical && (!hasWidthSize || width < widthSize));
ViewCompat.setOverScrollMode(view, fit ? ViewCompat.OVER_SCROLL_NEVER : ViewCompat.OVER_SCROLL_ALWAYS);
}
}
private void logMeasureWarning(int child) {
if (BuildConfig.DEBUG) {
Log.w("LinearLayoutManager", "Can't measure child #" + child + ", previously used dimensions will be reused." +
"To remove this message either use #setChildSize() method or don't run RecyclerView animations");
}
}
private void initChildDimensions(int width, int height, boolean vertical) {
if (childDimensions[CHILD_WIDTH] != 0 || childDimensions[CHILD_HEIGHT] != 0) {
// already initialized, skipping
return;
}
if (vertical) {
childDimensions[CHILD_WIDTH] = width;
childDimensions[CHILD_HEIGHT] = childSize;
} else {
childDimensions[CHILD_WIDTH] = childSize;
childDimensions[CHILD_HEIGHT] = height;
}
}
@Override
public void setOrientation(int orientation) {
// might be called before the constructor of this class is called
//noinspection ConstantConditions
if (childDimensions != null) {
if (getOrientation() != orientation) {
childDimensions[CHILD_WIDTH] = 0;
childDimensions[CHILD_HEIGHT] = 0;
}
}
super.setOrientation(orientation);
}
public void clearChildSize() {
hasChildSize = false;
setChildSize(DEFAULT_CHILD_SIZE);
}
public void setChildSize(int childSize) {
hasChildSize = true;
if (this.childSize != childSize) {
this.childSize = childSize;
requestLayout();
}
}
private void measureChild(RecyclerView.Recycler recycler, int position, int widthSize, int heightSize, int[] dimensions) {
final View child;
try {
child = recycler.getViewForPosition(position);
} catch (IndexOutOfBoundsException e) {
if (BuildConfig.DEBUG) {
Log.w("LinearLayoutManager", "LinearLayoutManager doesn't work well with animations. Consider switching them off", e);
}
return;
}
final RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) child.getLayoutParams();
final int hPadding = getPaddingLeft() + getPaddingRight();
final int vPadding = getPaddingTop() + getPaddingBottom();
final int hMargin = p.leftMargin + p.rightMargin;
final int vMargin = p.topMargin + p.bottomMargin;
// we must make insets dirty in order calculateItemDecorationsForChild to work
makeInsetsDirty(p);
// this method should be called before any getXxxDecorationXxx() methods
calculateItemDecorationsForChild(child, tmpRect);
final int hDecoration = getRightDecorationWidth(child) + getLeftDecorationWidth(child);
final int vDecoration = getTopDecorationHeight(child) + getBottomDecorationHeight(child);
final int childWidthSpec = getChildMeasureSpec(widthSize, hPadding + hMargin + hDecoration, p.width, canScrollHorizontally());
final int childHeightSpec = getChildMeasureSpec(heightSize, vPadding + vMargin + vDecoration, p.height, canScrollVertically());
child.measure(childWidthSpec, childHeightSpec);
dimensions[CHILD_WIDTH] = getDecoratedMeasuredWidth(child) + p.leftMargin + p.rightMargin;
dimensions[CHILD_HEIGHT] = getDecoratedMeasuredHeight(child) + p.bottomMargin + p.topMargin;
// as view is recycled let's not keep old measured values
makeInsetsDirty(p);
recycler.recycleView(child);
}
private static void makeInsetsDirty(RecyclerView.LayoutParams p) {
if (!canMakeInsetsDirty) {
return;
}
try {
if (insetsDirtyField == null) {
insetsDirtyField = RecyclerView.LayoutParams.class.getDeclaredField("mInsetsDirty");
insetsDirtyField.setAccessible(true);
}
insetsDirtyField.set(p, true);
} catch (NoSuchFieldException e) {
onMakeInsertDirtyFailed();
} catch (IllegalAccessException e) {
onMakeInsertDirtyFailed();
}
}
private static void onMakeInsertDirtyFailed() {
canMakeInsetsDirty = false;
if (BuildConfig.DEBUG) {
Log.w("LinearLayoutManager", "Can't make LayoutParams insets dirty, decorations measurements might be incorrect");
}
}
}
Put this WrapContentLinearLayoutManager in your recyclerview
mRecyclerView.setLayoutManager(new WrapContentLinearLayoutManager(activity));
And this in the xml (with the relative in parent)
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:id="@+id/recyclerViewMuseum"
android:scrollbars="vertical"
android:scrollIndicators="none"/>
This should work :)