Android入门04 -- RecyclerView

作者: YanZi_33 | 来源:发表于2022-01-27 17:46 被阅读0次

Android入门04 -- RecyclerView
Recyclerview简单效果(水平方向第一个和最后一个加间距
RecyclerView性能优化
【Android 基础】 RecyclerView
Android 控件 RecyclerView
Android教程2020 - RecyclerView使用入门
Android基础__RecyclerView入门
Android实现RecyclerView自定义列表、点击事件以
BRVAH配合ConcatAdapter轻松实现多type布局
万能适配器BaseQuickAdapter简单使用

RecycleView的简单使用

第一步：在activity_main.xml文件中创建RecyclerView，如下所示：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/rv"/>

</LinearLayout>

第二步：创建自定义适配器MainAdapter，实现相关的接口方法，并创建item的布局文件item_main.xml，代码如下：

package com.example.recycleview;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class MainAdapter extends RecyclerView.Adapter {

    private Context context;

    public MainAdapter(Context context) {
        this.context = context;
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_main,parent,false);
        return new MainViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {

    }

    @Override
    public int getItemCount() {
        return 50;
    }

    public class MainViewHolder extends RecyclerView.ViewHolder {
        public MainViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_width="match_parent"
    android:layout_height="50dp"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/black"
        android:text="左侧的文字"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="15dp"
        android:textSize="18sp"
        android:layout_weight="1"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/black"
        android:text="右侧的文字"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="15dp"
        android:textSize="14sp"
        android:layout_marginRight="15dp"/>
</LinearLayout>

第三步：在Activity中根据id获取RecyclerView，然后创建LinearLayoutManager实例对象layoutManager，其决定了RecyclerView列表中item的布局方向，默认为垂直方向，设置为水平方向可通过layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

package com.example.recycleview;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView rv = findViewById(R.id.rv);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        //设置布局
        rv.setLayoutManager(layoutManager);
        //创建适配器
        MainAdapter adapter = new MainAdapter(this);
        //设置适配器
        rv.setAdapter(adapter);
    }
}

显示效果如下所示：

image.png

RecyclerView添加分割线

方案一：在item的布局文件item_main.xml文件中，添加一个View，作为分割线，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_width="match_parent"
    android:layout_height="50dp"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="49dp"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="@color/black"
            android:text="左侧的文字"
            android:layout_gravity="center_vertical"
            android:layout_marginLeft="15dp"
            android:textSize="18sp"
            android:layout_weight="1"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="@color/black"
            android:text="右侧的文字"
            android:layout_gravity="center_vertical"
            android:layout_marginLeft="15dp"
            android:textSize="14sp"
            android:layout_marginRight="15dp"/>
    </LinearLayout>

    <!-- 分割线view -->
    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="#F40303"/>
</LinearLayout>

方案二：自定义RecyclerView.ItemDecorationitem的装饰类RecyclerViewDivider，详细代码如下：

package com.example.recycleview;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.view.View;

import androidx.core.content.ContextCompat;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

public class RecyclerViewDivider extends RecyclerView.ItemDecoration {

    private Paint mPaint;

    private Drawable mDivider;

    private int mDividerHeight = 1;//分割线高度，默认为1px
    private int mOrientation;//列表的方向：LinearLayoutManager.VERTICAL或LinearLayoutManager.HORIZONTAL

    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

    private final Rect mBounds = new Rect();


    /**
     * 默认分割线：高度为2px，颜色为灰色
     * @param context
     * @param orientation 列表方向
     */
    public RecyclerViewDivider(Context context, int orientation) {
        if (orientation != LinearLayoutManager.VERTICAL && orientation != LinearLayoutManager.HORIZONTAL) {
            throw new IllegalArgumentException("请输入正确的参数！");
        }
        mOrientation = orientation;
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    /**
     * 自定义分割线
     * @param context
     * @param orientation 列表方向
     * @param drawableId  分割线图片
     */
    public RecyclerViewDivider(Context context, int orientation, int drawableId) {
        this(context, orientation);
        mDivider = ContextCompat.getDrawable(context, drawableId);
        mDividerHeight = mDivider.getIntrinsicHeight();
    }

    /**
     * 自定义分割线
     * @param context
     * @param orientation   列表方向
     * @param dividerHeight 分割线高度
     * @param dividerColor  分割线颜色
     */
    public RecyclerViewDivider(Context context, int orientation, int dividerHeight, int dividerColor) {
        this(context, orientation);
        mDividerHeight = dividerHeight;
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(dividerColor);
        mPaint.setStyle(Paint.Style.FILL);
    }


    //获取分割线尺寸
    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        outRect.set(0, 0, 0, mDividerHeight);
    }

    //绘制分割线
    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        if (mOrientation == LinearLayoutManager.VERTICAL) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }

    //绘制横向 item 分割线
    private void drawHorizontal(Canvas canvas, RecyclerView parent) {
        canvas.save();
        final int top;
        final int bottom;
        //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
        if (parent.getClipToPadding()) {
            top = parent.getPaddingTop();
            bottom = parent.getHeight() - parent.getPaddingBottom();
            canvas.clipRect(parent.getPaddingLeft(), top,
                    parent.getWidth() - parent.getPaddingRight(), bottom);
        } else {
            top = 0;
            bottom = parent.getHeight();
        }

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            parent.getLayoutManager().getDecoratedBoundsWithMargins(child, mBounds);
            final int right = mBounds.right + Math.round(child.getTranslationX());
            final int left = right - mDivider.getIntrinsicWidth();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        canvas.restore();
    }

    //绘制纵向 item 分割线
    private void drawVertical(Canvas canvas, RecyclerView parent) {
        canvas.save();
        final int left;
        final int right;
        //noinspection AndroidLintNewApi - NewApi lint fails to handle overrides.
        if (parent.getClipToPadding()) {
            left = parent.getPaddingLeft();
            right = parent.getWidth() - parent.getPaddingRight();
            canvas.clipRect(left, parent.getPaddingTop(), right,
                    parent.getHeight() - parent.getPaddingBottom());
        } else {
            left = 0;
            right = parent.getWidth();
        }

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            parent.getDecoratedBoundsWithMargins(child, mBounds);
            final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
            final int top = bottom - mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        canvas.restore();
    }
}

分割线的资源文件为divider.xml，放在Drawable文件夹中，代码如下：

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="#F40303"/>
    <size android:height="1dp"/>
</shape>

然后在themes.xml文件中，设置用系统中的android.R.attr.listDivider来作为分割线，如下所示：

Snip20220127_16.png

最后创建item装饰类RecyclerViewDivider，设置给RecyclerView，代码如下：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView rv = findViewById(R.id.rv);
        //创建布局管理器
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        //设置布局
        rv.setLayoutManager(layoutManager);

        //创建item装饰类 可设置分割线
        RecyclerViewDivider divider = new RecyclerViewDivider(this,LinearLayoutManager.VERTICAL);
        rv.addItemDecoration(divider);

        //创建适配器
        MainAdapter adapter = new MainAdapter(this);
        //设置适配器
        rv.setAdapter(adapter);
    }
}

效果如下：

image.png

RecyclerView横向滚动，item设置水平间距

方案一：自定义继承自RecyclerView.ItemDecoration类的HorizontalItemDecoration，代码如下：

package com.example.recycleview;

import android.content.Context;
import android.graphics.Rect;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class HorizontalItemDecoration extends RecyclerView.ItemDecoration {

    //定义2个Item之间的距离
    private int space;
    //首尾两个item距离 RecyclerView的内边距
    private int firstAndLastSpace;
    private Context context;

    public HorizontalItemDecoration(Context context,float space,float firstAndLastSpace) {
        this.context = context;
        this.space = dip2px(space,context);
        this.firstAndLastSpace = dip2px(firstAndLastSpace,context);
    }

    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        //获取item的位置position
        int position = parent.getChildAdapterPosition(view);
        //获取item的总数量
        int totalCount = parent.getAdapter().getItemCount();
        if (position == 0) { //第一个
            outRect.left = firstAndLastSpace;
            outRect.right = space / 2;
        } else if (position == totalCount - 1) { //最后一个
            outRect.left = space / 2;
            outRect.right = firstAndLastSpace;
        } else { //中间的
            outRect.left = space / 2;
            outRect.right = space / 2;
        }
    }

    public int dip2px(float dpValue, Context context) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }
}

item的布局文件item_main_horizontal.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout android:layout_width="wrap_content"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="文本文案"
        android:textSize="16sp"
        android:textColor="@color/black"
        android:background="#F40303"
        android:layout_gravity="center_vertical"/>

</LinearLayout>

最后调用如下：

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView rv = findViewById(R.id.rv);
        //创建布局管理器
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        //设置布局
        rv.setLayoutManager(layoutManager);

        HorizontalItemDecoration decoration = new HorizontalItemDecoration(this,10,10);
        rv.addItemDecoration(decoration);

        //创建适配器
        MainAdapter adapter = new MainAdapter(this);
        //设置适配器
        rv.setAdapter(adapter);
    }
}

效果图如下：

image.png

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