上一篇博客我使用自定义HorizontalScrollView写了一个具有HorizontalScrollView效果和ViewPager特性的横向图片轮播,详见:Android 自定义 HorizontalScrollView 打造再多图片(控件)也不怕 OOM 的横向滑动效果。其实制作横向滚动的不得不说另一个控件,就是Google官方最近新增加的RecyclerView,据说是ListView的升级版本,本篇博客,首先介绍RecyclerView的用法,然后经行一定的分析;最后自定义一下RecyclerView实现我们需要的相册效果。
1、RecyclerView的基本用法
首先主Activity的布局文件:
- <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" >
-
- <android.support.v7.widget.RecyclerView
- android:id="@+id/id_recyclerview_horizontal"
- android:layout_width="match_parent"
- android:layout_height="120dp"
- android:layout_centerVertical="true"
- android:background="#FF0000"
- android:scrollbars="none" />
-
- </RelativeLayout>
Item的布局文件:
- <?xml version="1.0" encoding="utf-8"?>
- <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
- android:layout_width="120dp"
- android:layout_height="120dp"
- android:background="@drawable/item_bg02" >
-
- <ImageView
- android:id="@+id/id_index_gallery_item_image"
- android:layout_width="80dp"
- android:layout_height="80dp"
- android:layout_alignParentTop="true"
- android:layout_centerHorizontal="true"
- android:layout_margin="5dp"
- android:scaleType="centerCrop" />
-
- <TextView
- android:id="@+id/id_index_gallery_item_text"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_below="@id/id_index_gallery_item_image"
- android:layout_centerHorizontal="true"
- android:layout_marginBottom="5dp"
- android:layout_marginTop="5dp"
- android:textColor="#ff0000"
- android:text="some info"
- android:textSize="12dp" />
-
- </RelativeLayout>
数据适配器:
- package com.example.zhy_horizontalscrollview03;
-
- import java.util.List;
-
- import android.content.Context;
- import android.support.v7.widget.RecyclerView;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.ViewGroup;
- import android.widget.ImageView;
- import android.widget.TextView;
-
- public class GalleryAdapter extends
- RecyclerView.Adapter<GalleryAdapter.ViewHolder>
- {
-
- private LayoutInflater mInflater;
- private List<Integer> mDatas;
-
- public GalleryAdapter(Context context, List<Integer> datats)
- {
- mInflater = LayoutInflater.from(context);
- mDatas = datats;
- }
-
- public static class ViewHolder extends RecyclerView.ViewHolder
- {
- public ViewHolder(View arg0)
- {
- super(arg0);
- }
-
- ImageView mImg;
- TextView mTxt;
- }
-
- @Override
- public int getItemCount()
- {
- return mDatas.size();
- }
-
-
- @Override
- public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i)
- {
- View view = mInflater.inflate(R.layout.activity_index_gallery_item,
- viewGroup, false);
- ViewHolder viewHolder = new ViewHolder(view);
-
- viewHolder.mImg = (ImageView) view
- .findViewById(R.id.id_index_gallery_item_image);
- return viewHolder;
- }
-
-
- @Override
- public void onBindViewHolder(final ViewHolder viewHolder, final int i)
- {
- viewHolder.mImg.setImageResource(mDatas.get(i));
- }
-
- }
可以看到数据适配器与BaseAdapter比较发生了相当大的变化,主要有3个方法:
getItemCount 这个不用说,获取总的条目数
onCreateViewHolder 创建ViewHolder
onBindViewHolder 将数据绑定至ViewHolder
可见,RecyclerView对ViewHolder也进行了一定的封装,但是如果你仔细观察,你会发出一个疑问,ListView里面有个getView返回View为Item的布局,那么这个Item的样子在哪控制?
其实是这样的,我们创建的ViewHolder必须继承RecyclerView.ViewHolder,这个RecyclerView.ViewHolder的构造时必须传入一个View,这个View相当于我们ListView getView中的convertView (即:我们需要inflate的item布局需要传入)。
还有一点,ListView中convertView是复用的,在RecyclerView中,是把ViewHolder作为缓存的单位了,然后convertView作为ViewHolder的成员变量保持在ViewHolder中,也就是说,假设没有屏幕显示10个条目,则会创建10个ViewHolder缓存起来,每次复用的是ViewHolder,所以他把getView这个方法变为了onCreateViewHolder。有兴趣的自己打印下Log,测试下。
最后在Activity中使用:
- package com.example.zhy_horizontalscrollview03;
-
- import java.util.ArrayList;
- import java.util.Arrays;
- import java.util.List;
-
- import android.app.Activity;
- import android.os.Bundle;
- import android.support.v7.widget.LinearLayoutManager;
- import android.support.v7.widget.RecyclerView;
- import android.view.Window;
-
- public class MainActivity extends Activity
- {
-
- private RecyclerView mRecyclerView;
- private GalleryAdapter mAdapter;
- private List<Integer> mDatas;
-
-
- @Override
- protected void onCreate(Bundle savedInstanceState)
- {
- super.onCreate(savedInstanceState);
- requestWindowFeature(Window.FEATURE_NO_TITLE);
- setContentView(R.layout.activity_main);
-
- initDatas();
-
- mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview_horizontal);
-
- LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
- linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
- mRecyclerView.setLayoutManager(linearLayoutManager);
-
- mAdapter = new GalleryAdapter(this, mDatas);
- mRecyclerView.setAdapter(mAdapter);
-
-
- }
-
-
- private void initDatas()
- {
- mDatas = new ArrayList<Integer>(Arrays.asList(R.drawable.a,
- R.drawable.b, R.drawable.c, R.drawable.d, R.drawable.e,
- R.drawable.f, R.drawable.g, R.drawable.h, R.drawable.l));
- }
-
- }
使用起来也很方便,唯一的区别就是要设置LayoutManager,目前只有一个实现类,就是LinearLayoutManager,可以设置为水平或者垂直。
最后效果图:
效果很不错,这就是RecyclerView的基本用法了,但是你会发现一个坑爹的地方,竟然没有提供setOnItemClickListener这个回调,要不要这么坑爹。。。
2、为RecyclerView添加OnItemClickListener回调
虽然它没有提供,但是添加个OnItemClickListener对我们来说还不是小菜一碟~
我决定在Adapter中添加这个回调接口:
- package com.example.zhy_horizontalscrollview03;
-
- import java.util.List;
-
- import android.content.Context;
- import android.support.v7.widget.RecyclerView;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.view.ViewGroup;
- import android.widget.ImageView;
- import android.widget.TextView;
-
- public class GalleryAdapter extends
- RecyclerView.Adapter<GalleryAdapter.ViewHolder>
- {
-
-
- public interface OnItemClickLitener
- {
- void onItemClick(View view, int position);
- }
-
- private OnItemClickLitener mOnItemClickLitener;
-
- public void setOnItemClickLitener(OnItemClickLitener mOnItemClickLitener)
- {
- this.mOnItemClickLitener = mOnItemClickLitener;
- }
-
- private LayoutInflater mInflater;
- private List<Integer> mDatas;
-
- public GalleryAdapter(Context context, List<Integer> datats)
- {
- mInflater = LayoutInflater.from(context);
- mDatas = datats;
- }
-
- public static class ViewHolder extends RecyclerView.ViewHolder
- {
- public ViewHolder(View arg0)
- {
- super(arg0);
- }
-
- ImageView mImg;
- TextView mTxt;
- }
-
- @Override
- public int getItemCount()
- {
- return mDatas.size();
- }
-
- @Override
- public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i)
- {
- View view = mInflater.inflate(R.layout.activity_index_gallery_item,
- viewGroup, false);
- ViewHolder viewHolder = new ViewHolder(view);
-
- viewHolder.mImg = (ImageView) view
- .findViewById(R.id.id_index_gallery_item_image);
- return viewHolder;
- }
-
- @Override
- public void onBindViewHolder(final ViewHolder viewHolder, final int i)
- {
- viewHolder.mImg.setImageResource(mDatas.get(i));
-
-
- if (mOnItemClickLitener != null)
- {
- viewHolder.itemView.setOnClickListener(new OnClickListener()
- {
- @Override
- public void onClick(View v)
- {
- mOnItemClickLitener.onItemClick(viewHolder.itemView, i);
- }
- });
-
- }
-
- }
-
- }
很简单,创建一个接口,提供一个设置入口,然后在onBindViewHolder中判断即可。
最后在主Activity中设置监听:
- mAdapter = new GalleryAdapter(this, mDatas);
- mAdapter.setOnItemClickLitener(new OnItemClickLitener()
- {
- @Override
- public void onItemClick(View view, int position)
- {
- Toast.makeText(MainActivity.this, position+"", Toast.LENGTH_SHORT)
- .show();
- }
- });
- mRecyclerView.setAdapter(mAdapter);
好了,这样就行了,看效果图:
效果还是不错的,接下来我想改成相册效果,即上面显示一张大图,下面的RecyclerView做为图片切换的指示器。
3、自定义RecyclerView实现滚动时内容联动
首先修改下布局:
布局文件:
- <LinearLayout 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"
- android:orientation="vertical" >
-
- <FrameLayout
- android:layout_width="fill_parent"
- android:layout_height="0dp"
- android:layout_weight="1" >
-
- <ImageView
- android:id="@+id/id_content"
- android:layout_width="fill_parent"
- android:layout_height="fill_parent"
- android:layout_gravity="center"
- android:layout_margin="10dp"
- android:scaleType="centerCrop"
- android:src="@drawable/ic_launcher" />
- </FrameLayout>
-
- <com.example.zhy_horizontalscrollview03.MyRecyclerView
- android:id="@+id/id_recyclerview_horizontal"
- android:layout_width="match_parent"
- android:layout_height="120dp"
- android:layout_gravity="bottom"
- android:background="#FF0000"
- android:scrollbars="none" />
-
- </LinearLayout>
添加一个显示大图的区域,把RecyclerView改为自己定义的。
然后看我们自定义RecyclerView的代码:
- package com.example.zhy_horizontalscrollview03;
-
- import android.content.Context;
- import android.support.v7.widget.RecyclerView;
- import android.util.AttributeSet;
- import android.view.MotionEvent;
- import android.view.View;
-
- public class CopyOfMyRecyclerView extends RecyclerView
- {
-
- public CopyOfMyRecyclerView(Context context, AttributeSet attrs)
- {
- super(context, attrs);
- }
-
- private View mCurrentView;
-
-
- private OnItemScrollChangeListener mItemScrollChangeListener;
-
- public void setOnItemScrollChangeListener(
- OnItemScrollChangeListener mItemScrollChangeListener)
- {
- this.mItemScrollChangeListener = mItemScrollChangeListener;
- }
-
- public interface OnItemScrollChangeListener
- {
- void onChange(View view, int position);
- }
-
- @Override
- protected void onLayout(boolean changed, int l, int t, int r, int b)
- {
- super.onLayout(changed, l, t, r, b);
-
- mCurrentView = getChildAt(0);
-
- if (mItemScrollChangeListener != null)
- {
- mItemScrollChangeListener.onChange(mCurrentView,
- getChildPosition(mCurrentView));
- }
- }
-
- @Override
- public boolean onTouchEvent(MotionEvent e)
- {
-
- if (e.getAction() == MotionEvent.ACTION_MOVE)
- {
- mCurrentView = getChildAt(0);
-
- if (mItemScrollChangeListener != null)
- {
- mItemScrollChangeListener.onChange(mCurrentView,
- getChildPosition(mCurrentView));
-
- }
-
- }
-
- return super.onTouchEvent(e);
- }
-
- }
定义了一个滚动时回调的接口,然后在onTouchEvent中,监听ACTION_MOVE,用户手指滑动时,不断把当前第一个View回调回去~
关于我咋知道getChildAt(0)和getChildPosition()可用,起初我以为有getFirstVisibleItem这个方法,后来发现么有;但是发现了getRecycledViewPool()看名字我觉得是Viewholder那个缓存队列,我想那么直接取这个队列的第一个不就是我要的View么,后来没有成功。我就观察它内部的View,最后发现,第一个显示的始终是它第一个child,至于getChildPosition这个看方法就看出来了。
现在的效果:
和我之前那个例子的效果是一模一样的,不过,我还想做一些改变,我觉得Gallery或者说相册的指示器,下面可能1000来张图片,我不仅喜欢手指在屏幕上滑动时,图片会自动切换。我还希望,如果我给指示器一个加速度,即使手指离开,下面还在滑动,上面也会联动 。而且我还想做些优化,直接在ACTION_MOVE中回调,触发的频率太高了,理论上一张图片只会触发一次~~
4、优化与打造真正的Gallery效果
既然希望手指离开还能联动,那么不仅需要ACTION_MOVE需要监听,还得监听一个加速度,速度到达一定值,然后继续移动~~再理一理,需要这么麻烦么,不是能滚动么,那么应该有OnScrollListener啊,小看一把,果然有,哈哈哈~天助我也,下面看修改后的代码:
- package com.example.zhy_horizontalscrollview03;
-
- import android.content.Context;
- import android.support.v7.widget.RecyclerView;
- import android.support.v7.widget.RecyclerView.OnScrollListener;
- import android.util.AttributeSet;
- import android.view.View;
-
- public class MyRecyclerView extends RecyclerView implements OnScrollListener
- {
-
-
- private View mCurrentView;
-
- private OnItemScrollChangeListener mItemScrollChangeListener;
-
- public void setOnItemScrollChangeListener(
- OnItemScrollChangeListener mItemScrollChangeListener)
- {
- this.mItemScrollChangeListener = mItemScrollChangeListener;
- }
-
- public interface OnItemScrollChangeListener
- {
- void onChange(View view, int position);
- }
-
- public MyRecyclerView(Context context, AttributeSet attrs)
- {
- super(context, attrs);
-
- this.setOnScrollListener(this);
- }
-
- @Override
- protected void onLayout(boolean changed, int l, int t, int r, int b)
- {
- super.onLayout(changed, l, t, r, b);
-
- mCurrentView = getChildAt(0);
-
- if (mItemScrollChangeListener != null)
- {
- mItemScrollChangeListener.onChange(mCurrentView,
- getChildPosition(mCurrentView));
- }
- }
-
-
- @Override
- public void onScrollStateChanged(int arg0)
- {
- }
-
-
- @Override
- public void onScrolled(int arg0, int arg1)
- {
- View newView = getChildAt(0);
-
- if (mItemScrollChangeListener != null)
- {
- if (newView != null && newView != mCurrentView)
- {
- mCurrentView = newView ;
- mItemScrollChangeListener.onChange(mCurrentView,
- getChildPosition(mCurrentView));
-
- }
- }
-
- }
-
- }
我放弃了重写onTouchEvent方法,而是让这个类实现RecyclerView.OnScrollListener接口,然后设置监听,在onScrolled里面进行判断。
至于优化:我使用了一个成员变化存储当前第一个View,只有第一个View发生变化时才回调~~太完美了~
看MainActivity:
- package com.example.zhy_horizontalscrollview03;
-
- import java.util.ArrayList;
- import java.util.Arrays;
- import java.util.List;
-
- import android.app.Activity;
- import android.os.Bundle;
- import android.support.v7.widget.LinearLayoutManager;
- import android.support.v7.widget.RecyclerView;
- import android.view.View;
- import android.view.Window;
- import android.widget.ImageView;
- import android.widget.Toast;
-
- import com.example.zhy_horizontalscrollview03.GalleryAdapter.OnItemClickLitener;
- import com.example.zhy_horizontalscrollview03.MyRecyclerView.OnItemScrollChangeListener;
-
- public class MainActivity extends Activity
- {
-
- private MyRecyclerView mRecyclerView;
- private GalleryAdapter mAdapter;
- private List<Integer> mDatas;
- private ImageView mImg ;
-
-
- @Override
- protected void onCreate(Bundle savedInstanceState)
- {
- super.onCreate(savedInstanceState);
- requestWindowFeature(Window.FEATURE_NO_TITLE);
- setContentView(R.layout.activity_main);
-
- mImg = (ImageView) findViewById(R.id.id_content);
-
- mDatas = new ArrayList<Integer>(Arrays.asList(R.drawable.a,
- R.drawable.b, R.drawable.c, R.drawable.d, R.drawable.e,
- R.drawable.f, R.drawable.g, R.drawable.h, R.drawable.l));
-
- mRecyclerView = (MyRecyclerView) findViewById(R.id.id_recyclerview_horizontal);
- LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
- linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
-
- mRecyclerView.setLayoutManager(linearLayoutManager);
- mAdapter = new GalleryAdapter(this, mDatas);
- mRecyclerView.setAdapter(mAdapter);
-
- mRecyclerView.setOnItemScrollChangeListener(new OnItemScrollChangeListener()
- {
- @Override
- public void onChange(View view, int position)
- {
- mImg.setImageResource(mDatas.get(position));
- };
- });
-
- mAdapter.setOnItemClickLitener(new OnItemClickLitener()
- {
- @Override
- public void onItemClick(View view, int position)
- {
- mImg.setImageResource(mDatas.get(position));
- }
- });
-
- }
-
- }
代码没什么变化~多了个设置回调~
效果图:
可以看到不仅支持手机在上面移动时的变化,如果我给了一个加速度,下面持续滚动,上面也会持续变化~~大赞~每张图片回调一次,效率也相当不错。
好了,看完这边博客,相信大家对于RecyclerView有了一定的认识,甚至对于如何改造一个控件也多了一份了解~~
如果觉得不错,就留个言或者点个赞,表示对我的支持
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