如何将 Recyclerview 中的项目居中？

Question

我正在规划一个带有 recyclerviews 的小应用程序。\n有时我只需加载 4 个项目，有时甚至超过 200 个。\n现在我不明白，如何将自定义 recyclerviews 项目居中！

\n\n

我有一个自定义的 recyclerview （网格），我希望其中有 4 (2x2) 个项目居中。

\n\n

我拥有的：

\n\n

\n\n

我想要的是：

\n\n

\n\n

那么我下面的代码错误在哪里呢？

\n\n

fragment_single_pokemon.xml

\n\n

<?xml version="1.0" encoding="utf-8"?>\n<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"\n    xmlns:app="http://schemas.android.com/apk/res-auto"\n    xmlns:tools="http://schemas.android.com/tools"\n    android:layout_width="match_parent"\n    android:layout_height="match_parent"\n    app:layout_behavior="@string/appbar_scrolling_view_behavior"\n    tools:context=".MainActivity">\n\n\n    <android.support.constraint.ConstraintLayout\n        android:id="@+id/cLayTypOne"\n        android:layout_width="50dp"\n        android:layout_height="25dp"\n        android:layout_marginBottom="8dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:background="@drawable/customborder_typ"\n        app:layout_constraintBottom_toTopOf="@+id/cLayTypTwo"\n        app:layout_constraintEnd_toStartOf="@+id/civSprite"\n        app:layout_constraintStart_toStartOf="parent">\n\n        <TextView\n            android:id="@+id/txtTypOne"\n            android:layout_width="wrap_content"\n            android:layout_height="wrap_content"\n            android:text="TextView"\n            android:textColor="#FFFFFF"\n            android:textSize="8sp"\n            android:textStyle="bold"\n            app:layout_constraintBottom_toBottomOf="parent"\n            app:layout_constraintEnd_toEndOf="parent"\n            app:layout_constraintStart_toStartOf="parent"\n            app:layout_constraintTop_toTopOf="parent" />\n    </android.support.constraint.ConstraintLayout>\n\n    <View\n        android:id="@+id/vLine2"\n        android:layout_width="50dp"\n        android:layout_height="1dp"\n        android:layout_marginBottom="8dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="8dp"\n        android:background="#000000"\n        app:layout_constraintBottom_toBottomOf="@+id/civSprite"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toEndOf="@+id/civSprite"\n        app:layout_constraintTop_toTopOf="@+id/civSprite">\n\n    </View>\n\n    <TextView\n        android:id="@+id/txtPokemonName"\n        android:layout_width="wrap_content"\n        android:layout_height="wrap_content"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="8dp"\n        android:text="Pok\xc3\xa9ball"\n        android:textAlignment="center"\n        android:textSize="24sp"\n        android:textStyle="bold"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toStartOf="parent"\n        app:layout_constraintTop_toTopOf="parent" />\n\n    <de.hdodenhof.circleimageview.CircleImageView\n        android:id="@+id/civSprite"\n        android:layout_width="148dp"\n        android:layout_height="148dp"\n        android:layout_alignParentTop="true"\n        android:layout_centerHorizontal="true"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="16dp"\n        android:src="@mipmap/ic_launcher"\n        app:civ_border_width="2dp"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toStartOf="parent"\n        app:layout_constraintTop_toBottomOf="@+id/txtPokemonName" />\n\n    <View\n        android:id="@+id/vLine"\n        android:layout_width="50dp"\n        android:layout_height="1dp"\n        android:layout_marginBottom="8dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="8dp"\n        android:background="#000000"\n        app:layout_constraintBottom_toBottomOf="@+id/civSprite"\n        app:layout_constraintEnd_toStartOf="@+id/civSprite"\n        app:layout_constraintStart_toStartOf="parent"\n        app:layout_constraintTop_toTopOf="@+id/civSprite">\n\n    </View>\n\n    <ImageView\n        android:id="@+id/imgIsRaidBoss"\n        android:layout_width="50dp"\n        android:layout_height="50dp"\n        android:layout_marginBottom="8dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        app:layout_constraintBottom_toTopOf="@+id/vLine2"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toEndOf="@+id/civSprite"\n        app:srcCompat="@drawable/raid_sprite" />\n\n    <ImageView\n        android:id="@+id/imgShinyExists"\n        android:layout_width="50dp"\n        android:layout_height="50dp"\n        android:layout_marginBottom="4dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        app:layout_constraintBottom_toTopOf="@+id/imgIsRaidBoss"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toEndOf="@+id/civSprite"\n        app:srcCompat="@drawable/ic_shiny" />\n\n    <android.support.constraint.ConstraintLayout\n        android:id="@+id/cLayTypTwo"\n        android:layout_width="50dp"\n        android:layout_height="25dp"\n        android:layout_marginBottom="8dp"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:background="@drawable/customborder_typ"\n        app:layout_constraintBottom_toTopOf="@+id/vLine"\n        app:layout_constraintEnd_toStartOf="@+id/civSprite"\n        app:layout_constraintStart_toStartOf="parent">\n\n        <TextView\n            android:id="@+id/txtTypTwo"\n            android:layout_width="wrap_content"\n            android:layout_height="wrap_content"\n            android:text="TextView"\n            android:textColor="#FFFFFF"\n            android:textSize="8sp"\n            android:textStyle="bold"\n            app:layout_constraintBottom_toBottomOf="parent"\n            app:layout_constraintEnd_toEndOf="parent"\n            app:layout_constraintStart_toStartOf="parent"\n            app:layout_constraintTop_toTopOf="parent" />\n    </android.support.constraint.ConstraintLayout>\n\n    <Button\n        android:id="@+id/btnPokeDexEnty"\n        android:layout_width="match_parent"\n        android:layout_height="wrap_content"\n        android:layout_marginEnd="48dp"\n        android:layout_marginStart="48dp"\n        android:layout_marginTop="16dp"\n        android:background="@drawable/boarder_shape"\n        android:text="Pok\xc3\xa9dex Eintrag"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toStartOf="parent"\n        app:layout_constraintTop_toBottomOf="@+id/civSprite" />\n\n    <TextView\n        android:id="@+id/txtPokeDexEntry"\n        android:layout_width="wrap_content"\n        android:layout_height="wrap_content"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="8dp"\n        android:text="TextView"\n        android:textAlignment="center"\n        android:visibility="gone"\n        app:layout_constraintEnd_toEndOf="@+id/btnPokeDexEnty"\n        app:layout_constraintStart_toStartOf="@+id/btnPokeDexEnty"\n        app:layout_constraintTop_toBottomOf="@+id/btnPokeDexEnty" />\n\n    <android.support.v7.widget.RecyclerView\n        android:id="@+id/rViewPokeInfo"\n        android:layout_width="wrap_content"\n        android:layout_height="wrap_content"\n        android:layout_gravity="center_vertical"\n        android:layout_marginEnd="8dp"\n        android:layout_marginStart="8dp"\n        android:layout_marginTop="16dp"\n        android:foregroundGravity="center_vertical"\n        android:orientation="vertical"\n        android:textAlignment="center"\n        app:layout_constraintEnd_toEndOf="parent"\n        app:layout_constraintStart_toStartOf="parent"\n        app:layout_constraintTop_toBottomOf="@+id/txtPokeDexEntry" />\n\n\n</android.support.constraint.ConstraintLayout>\n

\n\n

gridview_pokedex_pokeinfo.xml

\n\n

<?xml version="1.0" encoding="utf-8"?>\n\n<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"\n    xmlns:app="http://schemas.android.com/apk/res-auto"\n    android:id="@+id/rLayMainContainer"\n    android:layout_width="wrap_content"\n    android:layout_height="wrap_content"\n    android:layout_marginBottom="8dp"\n    android:layout_marginEnd="8dp"\n    android:layout_marginStart="8dp"\n    android:layout_marginTop="8dp"\n    android:gravity="center"\n    android:orientation="vertical">\n\n    <TextView\n        android:id="@+id/txtPokeInfoTitle"\n        android:layout_width="wrap_content"\n        android:layout_height="wrap_content"\n        android:layout_alignParentTop="true"\n        android:layout_centerHorizontal="true"\n        android:text="TextView"\n        android:textStyle="bold" />\n\n    <TextView\n        android:id="@+id/txtPokeInfoText"\n        android:layout_width="wrap_content"\n        android:layout_height="wrap_content"\n        android:layout_below="@+id/txtPokeInfoTitle"\n        android:layout_centerHorizontal="true"\n        android:text="TextView" />\n</RelativeLayout>\n

\n\n

回收者查看代码

\n\n

RecyclerView recyclerViewPokeInfo = (RecyclerView)rLayout_mainFragment.findViewById(R.id.rViewPokeInfo);\nRecyclerView.LayoutManager layoutManager = new GridLayoutManager(getActivity(),2);\nrecyclerViewPokeInfo.setLayoutManager(layoutManager);\n\nCustomRecyclerAdapterPokeInfoGrid adapter = new CustomRecyclerAdapterPokeInfoGrid(getActivity(), db.getPokeInfo(intPokemonID));\nrecyclerViewPokeInfo.setAdapter(adapter);\n

\n\n

回收者视图适配器

\n\n

package com.spicysoftware.goexpert;\n\nimport android.content.Context;\nimport android.support.constraint.ConstraintLayout;\nimport android.support.v7.widget.RecyclerView;\nimport android.util.Log;\nimport android.view.LayoutInflater;\nimport android.view.View;\nimport android.view.ViewGroup;\nimport android.widget.TextView;\n\nimport java.util.ArrayList;\n\npublic class CustomRecyclerAdapterPokeInfoGrid extends RecyclerView.Adapter<CustomRecyclerAdapterPokeInfoGrid.ViewHolder> {\n    private final ArrayList<String> strPokeInfo;\n    private Context context;\n    MySQLiteHelper db;\n    int locationSpriteNo;\n    String strCatchRate = "";\n    String strEscapeRate = "";\n    String strInEggs = "";\n    String strKmAsFriend = "";\n\n    public CustomRecyclerAdapterPokeInfoGrid(Context context, ArrayList<String> strPokeInfo) {\n        this.strPokeInfo = strPokeInfo;\n        this.context = context;\n    }\n\n\n    @Override\n    public CustomRecyclerAdapterPokeInfoGrid.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {\n        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.gridview_pokedex_pokeinfo, viewGroup, false);\n\n        return new ViewHolder(view);\n    }\n\n    @Override\n    public void onBindViewHolder(final CustomRecyclerAdapterPokeInfoGrid.ViewHolder viewHolder, final int i) {\n\n\n        viewHolder.setClickListener(new ItemClickListener() {\n            @Override\n            public void onClick(View view, int position, boolean isLongClick) {\n\n            }\n        });\n\n        // load image\n        try {\n            db = new MySQLiteHelper(context);\n\n            String currentString = strPokeInfo.get(i);\n\n            if(i == 0){\n                viewHolder.txtPokeInfoTitle.setText("Fangchance");\n            }else if(i == 1){\n                viewHolder.txtPokeInfoTitle.setText("Fluchtchance");\n            }else if(i == 2){\n                viewHolder.txtPokeInfoTitle.setText("In Eiern");\n            }else if(i == 3){\n                viewHolder.txtPokeInfoTitle.setText("Distanz als Kumpel");\n            }\n\n            viewHolder.txtPokeInfoText.setText(currentString);\n\n\n        }\n        catch(Exception ex) {\n            Log.v("Error: ", "-> "+ex);\n        }\n\n    }\n\n    @Override\n    public int getItemCount() {\n        return strPokeInfo.size();\n    }\n\n    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener{\n        private TextView txtPokeInfoTitle,txtPokeInfoText;\n        private ItemClickListener clickListener;\n        private ConstraintLayout cLayoutSingleItem;\n\n        public ViewHolder(View view) {\n            super(view);\n\n            txtPokeInfoTitle = (TextView)view.findViewById(R.id.txtPokeInfoTitle);\n            txtPokeInfoText = (TextView)view.findViewById(R.id.txtPokeInfoText);\n\n\n            cLayoutSingleItem = (ConstraintLayout)view.findViewById(R.id.cLayoutSingleItem);\n            itemView.setOnClickListener(this);\n            itemView.setOnLongClickListener(this);\n\n        }\n\n        public void setClickListener(ItemClickListener itemClickListener) {\n            this.clickListener = itemClickListener;\n        }\n\n        @Override\n        public void onClick(View view) {\n            clickListener.onClick(view, getPosition(), false);\n        }\n\n        @Override\n        public boolean onLongClick(View view) {\n            clickListener.onClick(view, getPosition(), true);\n            return true;\n        }\n    }\n}\n

\n

Answer 1

将列表项布局设置为 match_parent，如下所示：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rLayMainContainer"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:gravity="center"
    android:orientation="vertical">

    <TextView
        android:id="@+id/txtPokeInfoTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="TextView"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/txtPokeInfoText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/txtPokeInfoTitle"
        android:layout_centerHorizontal="true"
        android:text="TextView" />
</RelativeLayout>