"Android Interface Effect 49" Recyclerview Height with item adaptive

When writing recyclerview.itemdecoration, in the OnDraw method, the height of the drawable is equal to the height of the recyclerview minus recyclerview up and down padding.

@Override Public voidOnDraw (Canvas C, Recyclerview parent, state state) {inttop =Parent.getpaddingtop (); intBottom = Parent.getheight ()-Parent.getpaddingbottom (); intChildCount =Parent.getchildcount ();  for(intI=0;i < childcount;i++) {View child=Parent.getchildat (i); Recyclerview.layoutparams Layoutparams=(Recyclerview.layoutparams) child.getlayoutparams (); intleft = Child.getright () +Layoutparams.rightmargin; intright = left +mdivider.getintrinsicwidth ();            Mdivider.setbounds (left, top, right, bottom);        Mdivider.draw (c); }    }

But the performance after the run is quite different from what I expected.

As you can see, the itemdecoration height is full screen, then check the XML layout file:

Activity_main.xml

<relativelayout xmlns:android= "http://schemas.android.com/apk/res/android"    xmlns:tools= "http// Schemas.android.com/tools "    android:layout_width=" Match_parent "    android:layout_height = "Match_parent"    tools:context= "Com.xmy.recylerviewdemo.MainActivity" >    <  Android.support.v7.widget.RecyclerView        Android:id= "@+id/recyclerview"        android:layout_width = "Wrap_content"        android:layout_height= "Wrap_content"/>        </RelativeLayout>

Item.xml

<?xml version= "1.0" encoding= "Utf-8"? ><linearlayout xmlns:android= "Http://schemas.android.com/apk/res/android"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"android:gravity= "Center"android:padding= "10.0dip"android:orientation= "Vertical" > <ImageView Android:id= "@+id/item_iv"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:scaletype= "Center"android:src= "@drawable/img"Android:adjustviewbounds= "true"/> <TextView Android:id= "@+id/item_tv"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"/> </LinearLayout>

The height of Recyclerview and item in the XML layout file is set to Wrap_content, which is well adapted to item height? Look at the Android document, did not find about the Recyclerview height related instructions, it seems that only self-clothed.

According to Android-recylerview , Recyclerview is not responsible for the display of the item, and adapter is responsible for the data warehouse and item view, so it eventually locks the target to On the Recyclerview.layoutmanager. So try to inherit Linearlayoutmanager, found that there are onmeasure methods:

 Public void int widthspec,int heightspec)

Recyclerview.recycler can be obtained in the onmeasure. Recycler is responsible for managing the reuse of the item view, so we can get an instance of the item view through Recycler, and then, like the other ViewGroup, Use Measurechild to get the height of the child view and use the Setmeasureddimension setting to Recyclerview the same height.

 Public classMylayoutmanagerextendsLinearlayoutmanager { PublicMylayoutmanager (Context context) {Super(context); //TODO auto-generated Constructor stub} @Override Public voidOnmeasure (recycler recycler, state State,intWidthspec,intHeightspec) {View View= Recycler.getviewforposition (0); if(View! =NULL) {measurechild (view, Widthspec, Heightspec); intMeasuredwidth =measurespec.getsize (WIDTHSPEC); intMeasuredheight =view.getmeasuredheight ();        Setmeasureddimension (Measuredwidth, measuredheight); }    }}

run after the modification:


Finally, the GitHub link is on the sample program.

"Android Interface Effect 49" Recyclerview Height with item adaptive