1、RecyclerView的基本用法
首先主Activity的佈局文件:
- <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的佈局文件:
- <?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>
數據適配器:
- 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();
- }
- /**
- * 創建ViewHolder
- */
- @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;
- }
- /**
- * 設置值
- */
- @Override
- public void onBindViewHolder(final ViewHolder viewHolder, final int i)
- {
- viewHolder.mImg.setImageResource(mDatas.get(i));
- }
- }
可以看到數據適配器與BaseAdapter比較發生了相當大的變化,主要有3個方法:
getItemCount 這個不用說,獲取總的條目數
onCreateViewHolder 創建ViewHolder
onBindViewHolder 將數據綁定至ViewHolder
可見,RecyclerView對ViewHolder也進行了一定的封裝,但是如果你仔細觀察,你會發出一個疑問,ListView裏面有個getView返回View爲Item的佈局,那麼這個Item的樣子在哪控制?
其實是這樣的,我們創建的ViewHolder必須繼承RecyclerView.ViewHolder,這個RecyclerView.ViewHolder的構造時必須傳入一個View,這個View相當於我們ListView getView中的convertView (即:我們需要inflate的item佈局需要傳入)。
還有一點,ListView中convertView是複用的,在RecyclerView中,是把ViewHolder作爲緩存的單位了,然後convertView作爲ViewHolder的成員變量保持在ViewHolder中,也就是說,假設沒有屏幕顯示10個條目,則會創建10個ViewHolder緩存起來,每次複用的是ViewHolder,所以他把getView這個方法變爲了onCreateViewHolder。有興趣的自己打印下Log,測試下。
最後在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();
- //得到控件
- mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview_horizontal);
- //設置佈局管理器
- LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
- linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
- mRecyclerView.setLayoutManager(linearLayoutManager);
- //設置適配器
- 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));
- }
- }
使用起來也很方便,唯一的區別就是要設置LayoutManager,目前只有一個實現類,就是LinearLayoutManager,可以設置爲水平或者垂直。
最後效果圖:
效果很不錯,這就是RecyclerView的基本用法了,但是你會發現一個坑爹的地方,竟然沒有提供setOnItemClickListener這個回調,要不要這麼坑爹。。。
2、爲RecyclerView添加OnItemClickListener回調
雖然它沒有提供,但是添加個OnItemClickListener對我們來說還不是小菜一碟~
我決定在Adapter中添加這個回調接口:
- 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>
- {
- /**
- * ItemClick的回調接口
- * @author zhy
- *
- */
- 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));
- //如果設置了回調,則設置點擊事件
- if (mOnItemClickLitener != null)
- {
- viewHolder.itemView.setOnClickListener(new OnClickListener()
- {
- @Override
- public void onClick(View v)
- {
- mOnItemClickLitener.onItemClick(viewHolder.itemView, i);
- }
- });
- }
- }
- }
很簡單,創建一個接口,提供一個設置入口,然後在onBindViewHolder中判斷即可。
最後在主Activity中設置監聽:
- 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,這樣就行了,看效果圖:
效果還是不錯的,接下來我想改成相冊效果,即上面顯示一張大圖,下面的RecyclerView做爲圖片切換的指示器。
3、自定義RecyclerView實現滾動時內容聯動
首先修改下佈局:
佈局文件:
- <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>
添加一個顯示大圖的區域,把RecyclerView改爲自己定義的。
然後看我們自定義RecyclerView的代碼:
- 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;
- /**
- * 滾動時回調的接口
- */
- 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);
- // Log.e("TAG", getChildPosition(getChildAt(0)) + "");
- if (mItemScrollChangeListener != null)
- {
- mItemScrollChangeListener.onChange(mCurrentView,
- getChildPosition(mCurrentView));
- }
- }
- return super.onTouchEvent(e);
- }
- }
定義了一個滾動時回調的接口,然後在onTouchEvent中,監聽ACTION_MOVE,用戶手指滑動時,不斷把當前第一個View回調回去~
關於我咋知道getChildAt(0)和getChildPosition()可用,起初我以爲有getFirstVisibleItem這個方法,後來發現麼有;但是發現了getRecycledViewPool()看名字我覺得是Viewholder那個緩存隊列,我想那麼直接取這個隊列的第一個不就是我要的View麼,後來沒有成功。我就觀察它內部的View,最後發現,第一個顯示的始終是它第一個child,至於getChildPosition這個看方法就看出來了。
現在的效果:
和我之前那個例子的效果是一模一樣的,不過,我還想做一些改變,我覺得Gallery或者說相冊的指示器,下面可能1000來張圖片,我不僅喜歡手指在屏幕上滑動時,圖片會自動切換。我還希望,如果我給指示器一個加速度,即使手指離開,下面還在滑動,上面也會聯動 。而且我還想做些優化,直接在ACTION_MOVE中回調,觸發的頻率太高了,理論上一張圖片只會觸發一次~~
4、優化與打造真正的Gallery效果
既然希望手指離開還能聯動,那麼不僅需要ACTION_MOVE需要監聽,還得監聽一個加速度,速度到達一定值,然後繼續移動~~再理一理,需要這麼麻煩麼,不是能滾動麼,那麼應該有OnScrollListener啊,小看一把,果然有,哈哈哈~天助我也,下面看修改後的代碼:
- 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
- {
- /**
- * 記錄當前第一個View
- */
- 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);
- // TODO Auto-generated constructor stub
- 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)
- {
- }
- /**
- *
- * 滾動時,判斷當前第一個View是否發生變化,發生纔回調
- */
- @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));
- }
- }
- }
- }
我放棄了重寫onTouchEvent方法,而是讓這個類實現RecyclerView.OnScrollListener接口,然後設置監聽,在onScrolled裏面進行判斷。
至於優化:我使用了一個成員變化存儲當前第一個View,只有第一個View發生變化時纔回調~~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)
- {
- // Toast.makeText(getApplicationContext(), position + "", Toast.LENGTH_SHORT)
- // .show();
- mImg.setImageResource(mDatas.get(position));
- }
- });
- }
- }
代碼沒什麼變化~多了個設置回調~
效果圖:
可以看到不僅支持手機在上面移動時的變化,如果我給了一個加速度,下面持續滾動,上面也會持續變化~~大讚~每張圖片回調一次,效率也相當不錯。
好了,看完這邊博客,相信大家對於RecyclerView有了一定的認識,甚至對於如何改造一個控件也多了一份瞭解~~
如果覺得不錯,就留個言或者點個贊,表示對我的支持