简介
RecyclerView已经出来相当长一段时间了，现在目前开发过程中大部分的列表数据使用的RecyclerView。为什么广泛使用此控件呢，相比ListView的区别在哪里？因为这个控件自身有优化处理，你只需要设置布局填入数据即可，这点比Listview好很多。在布局管理方面，有三种，比listView强太多了。但是也有部分仍旧在使用listview，毕竟listview优化处理好了，简单的数据也是很好的处理的。
RecyclerView涉及到的知识：
1.三种布局管理器：LinearLayoutManager,GridLayoutManager,StaggeredGridLayoutManager；
2.设置item之间的分割线 ItemDecoration；
3.item的添加和删除动画ItemAnimator。
1. 基本用法和三种布局管理器的使用和效果
recyclerView = (RecyclerView) findViewById(R.id.rc_photo);
recyclerView.setLayoutManager(new GridLayoutManager(this,4));//设置布局管理器
recyclerView.setItemAnimator(new DefaultItemAnimator());//设置item动画效果
recyclerView.addItemDecoration(new DividerGridItemDecoration(this));//设置item的分割线
recyclerView.setAdapter(new FirstAdapter());//设置recyclerview的适配器。
适配器的代码;
public class FirstAdapter extends RecyclerView.Adapter{
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(MainActivity.this).inflate(R.layout.rcv_item_layout, parent, false);
MyViewHolder holder=new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {
if(holder instanceof MyViewHolder)
{
MyViewHolder mholder= (MyViewHolder) holder;
mholder.tv.setText("第 "+list.get(position)+" item");
mholder.tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(MainActivity.this,"点击了"+position,Toast.LENGTH_SHORT).show();
}
});
}
}
@Override
public int getItemCount() {
return list.size();
}
}
public class MyViewHolder extends RecyclerView.ViewHolder
{
public TextView tv;
public MyViewHolder(View itemView) {
super(itemView);
tv = (TextView) itemView.findViewById(R.id.tv_itemcount);
}
}
1）.
LinearLayoutManager的使用，效果和listview是一样的，只需要执行下面的代码就可以实现
recyclerView.setLayoutManager(new LinearLayoutManager(this));
2）.GridLayoutManager的使用，效果和GridView效果类似。
recyclerView.setLayoutManager(new GridLayoutManager(this,4));//第二个参数是列数
3）.StaggeredGridLayoutManager的使用
recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,StaggeredGridLayoutManager.VERTICAL));//第一个是列数，第二个是方向
1）.线性布局管理器LinearLayoutManager。系统的分割线如下
DividerItemDecoration dividerItemDecoration = new DividerItemDecoration(this, DividerItemDecoration.VERTICAL);
qRecycleView.addItemDecoration(dividerItemDecoration);
这是系统的分割线，但是如果不满意，想自己定义的话也是可以实现的。 DividerItemDecoration 该实现类可以看到通过读取系统主题中的 Android.R.attr.listDivider作为Item间的分割线
先定义一个shape
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#F00"
android:endColor="#0F0"
android:centerColor="#00f"
android:type="linear">
</gradient>
<size android:height="4px">
</size>
</shape>在把这个shape设置到主题中
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="android:listDivider">@drawable/shape_itemdecoration</item>
</style>
2）.但是自定义的这种不能使用到GridLayoutManager上，为了适配，我们必须重写android的
DividerItemDecoration这个类，动态的区划item的边界
package com.zwg.xjkb.view;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.LayoutManager;
import android.support.v7.widget.RecyclerView.State;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.View;
public class DividerGridItemDecoration extends RecyclerView.ItemDecoration
{
private static final int[] ATTRS = new int[] { android.R.attr.listDivider };
private Drawable mDivider;
public DividerGridItemDecoration(Context context)
{
final TypedArray a = context.obtainStyledAttributes(ATTRS);
mDivider = a.getDrawable(0);
a.recycle();
}
@Override
public void onDraw(Canvas c, RecyclerView parent, State state)
{
drawHorizontal(c, parent);
drawVertical(c, parent);
}
private int getSpanCount(RecyclerView parent)
{
// 列数
int spanCount = -1;
LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager)
{
spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
} else if (layoutManager instanceof StaggeredGridLayoutManager)
{
spanCount = ((StaggeredGridLayoutManager) layoutManager)
.getSpanCount();
}
return spanCount;
}
public void drawHorizontal(Canvas c, RecyclerView parent)
{
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++)
{
final View child = parent.getChildAt(i);
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
.getLayoutParams();
final int left = child.getLeft() - params.leftMargin;
final int right = child.getRight() + params.rightMargin
+ mDivider.getIntrinsicWidth();
final int top = child.getBottom() + params.bottomMargin;
final int bottom = top + mDivider.getIntrinsicHeight();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
public void drawVertical(Canvas c, RecyclerView parent)
{
final int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++)
{
final View child = parent.getChildAt(i);
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
.getLayoutParams();
final int top = child.getTop() - params.topMargin;
final int bottom = child.getBottom() + params.bottomMargin;
final int left = child.getRight() + params.rightMargin;
final int right = left + mDivider.getIntrinsicWidth();
mDivider.setBounds(left, top, right, bottom);
mDivider.draw(c);
}
}
private boolean isLastColum(RecyclerView parent, int pos, int spanCount,
int childCount)
{
LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager)
{
if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
{
return true;
}
} else if (layoutManager instanceof StaggeredGridLayoutManager)
{
int orientation = ((StaggeredGridLayoutManager) layoutManager)
.getOrientation();
if (orientation == StaggeredGridLayoutManager.VERTICAL)
{
if ((pos + 1) % spanCount == 0)// 如果是最后一列，则不需要绘制右边
{
return true;
}
} else
{
childCount = childCount - childCount % spanCount;
if (pos >= childCount)// 如果是最后一列，则不需要绘制右边
return true;
}
}
return false;
}
private boolean isLastRaw(RecyclerView parent, int pos, int spanCount,
int childCount)
{
LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager)
{
childCount = childCount - childCount % spanCount;
if (pos >= childCount)// 如果是最后一行，则不需要绘制底部
return true;
} else if (layoutManager instanceof StaggeredGridLayoutManager)
{
int orientation = ((StaggeredGridLayoutManager) layoutManager)
.getOrientation();
// StaggeredGridLayoutManager 且纵向滚动
if (orientation == StaggeredGridLayoutManager.VERTICAL)
{
childCount = childCount - childCount % spanCount;
// 如果是最后一行，则不需要绘制底部
if (pos >= childCount)
return true;
} else
// StaggeredGridLayoutManager 且横向滚动
{
// 如果是最后一行，则不需要绘制底部
if ((pos + 1) % spanCount == 0)
{
return true;
}
}
}
return false;
}
@Override
public void getItemOffsets(Rect outRect, int itemPosition,
RecyclerView parent)
{
int spanCount = getSpanCount(parent);
int childCount = parent.getAdapter().getItemCount();
if (isLastRaw(parent, itemPosition, spanCount, childCount))// 如果是最后一行，则不需要绘制底部
{
outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
} else if (isLastColum(parent, itemPosition, spanCount, childCount))// 如果是最后一列，则不需要绘制右边
{
outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
} else
{
outRect.set(0, 0, mDivider.getIntrinsicWidth(),
mDivider.getIntrinsicHeight());
}
}
}在这里要给上面写的shape中size节点添加一个width属性，不然无法显示，android:width="4dp"。
3.item的动画效果。
ItemAnimator也是一个抽象类，好在系统为我们提供了一种默认的实现类，期待系统多添加些默认的实现。
// 设置item动画，这个系统的动画效果。
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
public void addData(int position) {
mDatas.add(position, "Insert One");
notifyItemInserted(position);
}
public void removeData(int position) {
mDatas.remove(position);
notifyItemRemoved(position);
}
在Activity中添加两个menu
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
getMenuInflater().inflate(R.menu.main, menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId())
{
case R.id.id_action_add:
mAdapter.addData(1);
break;
case R.id.id_action_delete:
mAdapter.removeData(1);
break;
}
return true;
}
系统动画效果还可以，要想更多了动画效果，自己可以搜索。
到此这个控件的基本使用已经完全可以搞定了。
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