Android 自定义 HorizontalScrollView 打造再多图片(控件)也不怕 OOM 的横向滑动效果
自从Gallery被谷歌废弃以后,Google推荐使用ViewPager和HorizontalScrollView来实现Gallery的效果。的确HorizontalScrollView可以实现Gallery的效果,但是HorizontalScrollView存在一个很大的问题,如果你仅是用来展示少量的图片,应该是没问题的,但是如果我希望HorizontalScrollView可以想ViewPager一样,既可以绑定数据集(动态改变图片),还能做到,不管多少图片都不会OOM(ViewPager内部一直初始化,回收,至多只保持3个View)。本篇博客首先介绍HorizontalScrollView的简单用法,然后会在此基础上进行扩展,自定义HorizontalScrollView实现我们上面提到的效果,类似一屏可以显示多个View的ViewPager,再多的图片也不怕OOM。
1、HorizontalScrollView的简单用法
HorizontalScrollView其实是FrameLayout的子类,所以内部只能有一个直接的子View。我们用来做Gallery效果,首选当然是LinearLayout,然后方向设置为水平。
1、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"
- >
- <HorizontalScrollView
- android:layout_width="wrap_content"
- android:layout_height="150dp"
- android:layout_gravity="center_vertical"
- android:background="#AA444444"
- android:scrollbars="none" >
- <LinearLayout
- android:id="@+id/id_gallery"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="center_vertical"
- android:orientation="horizontal" >
- </LinearLayout>
- </HorizontalScrollView>
- </LinearLayout>
很简单,就一个HorizontalScrollView内部有个水平方向的LinearLayout
MainActivity:
- package com.example.zhy_horizontalscrollview;
- import android.app.Activity;
- import android.os.Bundle;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.Window;
- import android.widget.ImageView;
- import android.widget.LinearLayout;
- import android.widget.TextView;
- public class MainActivity extends Activity
- {
- private LinearLayout mGallery;
- private int[] mImgIds;
- private LayoutInflater mInflater;
- @Override
- protected void onCreate(Bundle savedInstanceState)
- {
- super.onCreate(savedInstanceState);
- requestWindowFeature(Window.FEATURE_NO_TITLE);
- setContentView(R.layout.activity_main);
- mInflater = LayoutInflater.from(this);
- initData();
- initView();
- }
- private void initData()
- {
- mImgIds = new int[] { 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 };
- }
- private void initView()
- {
- mGallery = (LinearLayout) findViewById(R.id.id_gallery);
- for (int i = 0; i < mImgIds.length; i++)
- {
- View view = mInflater.inflate(R.layout.activity_index_gallery_item,
- mGallery, false);
- ImageView img = (ImageView) view
- .findViewById(R.id.id_index_gallery_item_image);
- img.setImageResource(mImgIds[i]);
- TextView txt = (TextView) view
- .findViewById(R.id.id_index_gallery_item_text);
- txt.setText("some info ");
- mGallery.addView(view);
- }
- }
- }
效果图:
效果还是不错的~如果只需要简单展示几张图片,直接用就可以了。
下面准备进入正题,HorizontalScrollView不管里面多少View都是不会回收的,当达到一定量的时候会发生OOM,下面介绍如何改写HorizontalScollView实现文章开始所说的效果。
2、自定义HorizontalScrollView
思想:
1、首先根据屏幕的大小和Item的大小,计算可以一个屏幕最多可以加载多少个Item,然后加载该数量Item。
2、当用户右滑(从右向左),滑动到一定距离时,加载下一张,删除第一张
3、当用户左滑(从左向右),滑动到一定距离时,加载上一张,删除最后一张
看下最后的效果图:
为了增加一定的趣味,做了一个类似上面的相册效果,支持拖动时自动变化,和点击变化~~是不是很赞~
1、首先看布局文件:
- <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:background="@android:color/white"
- 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_horizontalscrollview.MyHorizontalScrollView
- android:id="@+id/id_horizontalScrollView"
- android:layout_width="wrap_content"
- android:layout_height="150dp"
- android:layout_gravity="bottom"
- android:background="@android:color/white"
- android:scrollbars="none" >
- <LinearLayout
- android:id="@+id/id_gallery"
- android:layout_width="wrap_content"
- android:layout_height="wrap_content"
- android:layout_gravity="center_vertical"
- android:orientation="horizontal" >
- </LinearLayout>
- </com.example.zhy_horizontalscrollview.MyHorizontalScrollView>
- </LinearLayout>
2、为了和国际接轨,我们也搞个Adapter,类似BaseAdapter
- package com.example.zhy_horizontalscrollview;
- import java.util.List;
- import android.content.Context;
- import android.view.LayoutInflater;
- import android.view.View;
- import android.view.ViewGroup;
- import android.widget.BaseAdapter;
- import android.widget.ImageView;
- import android.widget.TextView;
- public class HorizontalScrollViewAdapter
- {
- private Context mContext;
- private LayoutInflater mInflater;
- private List<Integer> mDatas;
- public HorizontalScrollViewAdapter(Context context, List<Integer> mDatas)
- {
- this.mContext = context;
- mInflater = LayoutInflater.from(context);
- this.mDatas = mDatas;
- }
- public int getCount()
- {
- return mDatas.size();
- }
- public Object getItem(int position)
- {
- return mDatas.get(position);
- }
- public long getItemId(int position)
- {
- return position;
- }
- public View getView(int position, View convertView, ViewGroup parent)
- {
- ViewHolder viewHolder = null;
- if (convertView == null)
- {
- viewHolder = new ViewHolder();
- convertView = mInflater.inflate(
- R.layout.activity_index_gallery_item, parent, false);
- viewHolder.mImg = (ImageView) convertView
- .findViewById(R.id.id_index_gallery_item_image);
- viewHolder.mText = (TextView) convertView
- .findViewById(R.id.id_index_gallery_item_text);
- convertView.setTag(viewHolder);
- } else
- {
- viewHolder = (ViewHolder) convertView.getTag();
- }
- viewHolder.mImg.setImageResource(mDatas.get(position));
- viewHolder.mText.setText("some info ");
- return convertView;
- }
- private class ViewHolder
- {
- ImageView mImg;
- TextView mText;
- }
- }
3、下面先看用法:
- package com.example.zhy_horizontalscrollview;
- import java.util.ArrayList;
- import java.util.Arrays;
- import java.util.List;
- import android.app.Activity;
- import android.graphics.Color;
- import android.os.Bundle;
- import android.view.View;
- import android.view.Window;
- import android.widget.ImageView;
- import com.example.zhy_horizontalscrollview.MyHorizontalScrollView.CurrentImageChangeListener;
- import com.example.zhy_horizontalscrollview.MyHorizontalScrollView.OnItemClickListener;
- public class MainActivity extends Activity
- {
- private MyHorizontalScrollView mHorizontalScrollView;
- private HorizontalScrollViewAdapter mAdapter;
- private ImageView mImg;
- private List<Integer> 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));
- @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);
- mHorizontalScrollView = (MyHorizontalScrollView) findViewById(R.id.id_horizontalScrollView);
- mAdapter = new HorizontalScrollViewAdapter(this, mDatas);
- //添加滚动回调
- mHorizontalScrollView
- .setCurrentImageChangeListener(new CurrentImageChangeListener()
- {
- @Override
- public void onCurrentImgChanged(int position,
- View viewIndicator)
- {
- mImg.setImageResource(mDatas.get(position));
- viewIndicator.setBackgroundColor(Color
- .parseColor("#AA024DA4"));
- }
- });
- //添加点击回调
- mHorizontalScrollView.setOnItemClickListener(new OnItemClickListener()
- {
- @Override
- public void onClick(View view, int position)
- {
- mImg.setImageResource(mDatas.get(position));
- view.setBackgroundColor(Color.parseColor("#AA024DA4"));
- }
- });
- //设置适配器
- mHorizontalScrollView.initDatas(mAdapter);
- }
- }
用起来是不是有点像ListView,初始化数据适配器,然后设置数据适配器,然后就是设置各种回调~~
如果仅仅是一堆图片展示,类似商品切换,更见简单,就不需要设置滚动监听和点击监听了~
4、最后看自定义的MyHorizontalScrollView类
- package com.example.zhy_horizontalscrollview;
- import java.util.HashMap;
- import java.util.Map;
- import android.content.Context;
- import android.graphics.Color;
- import android.util.AttributeSet;
- import android.util.DisplayMetrics;
- import android.util.Log;
- import android.view.MotionEvent;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.view.WindowManager;
- import android.widget.HorizontalScrollView;
- import android.widget.LinearLayout;
- public class MyHorizontalScrollView extends HorizontalScrollView implements
- OnClickListener
- {
- /**
- * 图片滚动时的回调接口
- *
- * @author zhy
- *
- */
- public interface CurrentImageChangeListener
- {
- void onCurrentImgChanged(int position, View viewIndicator);
- }
- /**
- * 条目点击时的回调
- *
- * @author zhy
- *
- */
- public interface OnItemClickListener
- {
- void onClick(View view, int pos);
- }
- private CurrentImageChangeListener mListener;
- private OnItemClickListener mOnClickListener;
- private static final String TAG = "MyHorizontalScrollView";
- /**
- * HorizontalListView中的LinearLayout
- */
- private LinearLayout mContainer;
- /**
- * 子元素的宽度
- */
- private int mChildWidth;
- /**
- * 子元素的高度
- */
- private int mChildHeight;
- /**
- * 当前最后一张图片的index
- */
- private int mCurrentIndex;
- /**
- * 当前第一张图片的下标
- */
- private int mFristIndex;
- /**
- * 当前第一个View
- */
- private View mFirstView;
- /**
- * 数据适配器
- */
- private HorizontalScrollViewAdapter mAdapter;
- /**
- * 每屏幕最多显示的个数
- */
- private int mCountOneScreen;
- /**
- * 屏幕的宽度
- */
- private int mScreenWitdh;
- /**
- * 保存View与位置的键值对
- */
- private Map<View, Integer> mViewPos = new HashMap<View, Integer>();
- public MyHorizontalScrollView(Context context, AttributeSet attrs)
- {
- super(context, attrs);
- // 获得屏幕宽度
- WindowManager wm = (WindowManager) context
- .getSystemService(Context.WINDOW_SERVICE);
- DisplayMetrics outMetrics = new DisplayMetrics();
- wm.getDefaultDisplay().getMetrics(outMetrics);
- mScreenWitdh = outMetrics.widthPixels;
- }
- @Override
- protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
- {
- super.onMeasure(widthMeasureSpec, heightMeasureSpec);
- mContainer = (LinearLayout) getChildAt(0);
- }
- /**
- * 加载下一张图片
- */
- protected void loadNextImg()
- {
- // 数组边界值计算
- if (mCurrentIndex == mAdapter.getCount() - 1)
- {
- return;
- }
- //移除第一张图片,且将水平滚动位置置0
- scrollTo(0, 0);
- mViewPos.remove(mContainer.getChildAt(0));
- mContainer.removeViewAt(0);
- //获取下一张图片,并且设置onclick事件,且加入容器中
- View view = mAdapter.getView(++mCurrentIndex, null, mContainer);
- view.setOnClickListener(this);
- mContainer.addView(view);
- mViewPos.put(view, mCurrentIndex);
- //当前第一张图片小标
- mFristIndex++;
- //如果设置了滚动监听则触发
- if (mListener != null)
- {
- notifyCurrentImgChanged();
- }
- }
- /**
- * 加载前一张图片
- */
- protected void loadPreImg()
- {
- //如果当前已经是第一张,则返回
- if (mFristIndex == 0)
- return;
- //获得当前应该显示为第一张图片的下标
- int index = mCurrentIndex - mCountOneScreen;
- if (index >= 0)
- {
- // mContainer = (LinearLayout) getChildAt(0);
- //移除最后一张
- int oldViewPos = mContainer.getChildCount() - 1;
- mViewPos.remove(mContainer.getChildAt(oldViewPos));
- mContainer.removeViewAt(oldViewPos);
- //将此View放入第一个位置
- View view = mAdapter.getView(index, null, mContainer);
- mViewPos.put(view, index);
- mContainer.addView(view, 0);
- view.setOnClickListener(this);
- //水平滚动位置向左移动view的宽度个像素
- scrollTo(mChildWidth, 0);
- //当前位置--,当前第一个显示的下标--
- mCurrentIndex--;
- mFristIndex--;
- //回调
- if (mListener != null)
- {
- notifyCurrentImgChanged();
- }
- }
- }
- /**
- * 滑动时的回调
- */
- public void notifyCurrentImgChanged()
- {
- //先清除所有的背景色,点击时会设置为蓝色
- for (int i = 0; i < mContainer.getChildCount(); i++)
- {
- mContainer.getChildAt(i).setBackgroundColor(Color.WHITE);
- }
- mListener.onCurrentImgChanged(mFristIndex, mContainer.getChildAt(0));
- }
- /**
- * 初始化数据,设置数据适配器
- *
- * @param mAdapter
- */
- public void initDatas(HorizontalScrollViewAdapter mAdapter)
- {
- this.mAdapter = mAdapter;
- mContainer = (LinearLayout) getChildAt(0);
- // 获得适配器中第一个View
- final View view = mAdapter.getView(0, null, mContainer);
- mContainer.addView(view);
- // 强制计算当前View的宽和高
- if (mChildWidth == 0 && mChildHeight == 0)
- {
- int w = View.MeasureSpec.makeMeasureSpec(0,
- View.MeasureSpec.UNSPECIFIED);
- int h = View.MeasureSpec.makeMeasureSpec(0,
- View.MeasureSpec.UNSPECIFIED);
- view.measure(w, h);
- mChildHeight = view.getMeasuredHeight();
- mChildWidth = view.getMeasuredWidth();
- Log.e(TAG, view.getMeasuredWidth() + "," + view.getMeasuredHeight());
- mChildHeight = view.getMeasuredHeight();
- // 计算每次加载多少个View
- mCountOneScreen = mScreenWitdh / mChildWidth+2;
- Log.e(TAG, "mCountOneScreen = " + mCountOneScreen
- + " ,mChildWidth = " + mChildWidth);
- }
- //初始化第一屏幕的元素
- initFirstScreenChildren(mCountOneScreen);
- }
- /**
- * 加载第一屏的View
- *
- * @param mCountOneScreen
- */
- public void initFirstScreenChildren(int mCountOneScreen)
- {
- mContainer = (LinearLayout) getChildAt(0);
- mContainer.removeAllViews();
- mViewPos.clear();
- for (int i = 0; i < mCountOneScreen; i++)
- {
- View view = mAdapter.getView(i, null, mContainer);
- view.setOnClickListener(this);
- mContainer.addView(view);
- mViewPos.put(view, i);
- mCurrentIndex = i;
- }
- if (mListener != null)
- {
- notifyCurrentImgChanged();
- }
- }
- @Override
- public boolean onTouchEvent(MotionEvent ev)
- {
- switch (ev.getAction())
- {
- case MotionEvent.ACTION_MOVE:
- // Log.e(TAG, getScrollX() + "");
- int scrollX = getScrollX();
- // 如果当前scrollX为view的宽度,加载下一张,移除第一张
- if (scrollX >= mChildWidth)
- {
- loadNextImg();
- }
- // 如果当前scrollX = 0, 往前设置一张,移除最后一张
- if (scrollX == 0)
- {
- loadPreImg();
- }
- break;
- }
- return super.onTouchEvent(ev);
- }
- @Override
- public void onClick(View v)
- {
- if (mOnClickListener != null)
- {
- for (int i = 0; i < mContainer.getChildCount(); i++)
- {
- mContainer.getChildAt(i).setBackgroundColor(Color.WHITE);
- }
- mOnClickListener.onClick(v, mViewPos.get(v));
- }
- }
- public void setOnItemClickListener(OnItemClickListener mOnClickListener)
- {
- this.mOnClickListener = mOnClickListener;
- }
- public void setCurrentImageChangeListener(
- CurrentImageChangeListener mListener)
- {
- this.mListener = mListener;
- }
- }
首先,加载第一个Item,根据item的宽计算当前屏幕可以加载多少张图片,然后初始化第一屏的图片,接下来就是从写onTouchEvent,在其中监听用户的ACTION_MOVE,然后根据移动的距离加载前一张或者后一张,同时动态移除不可见的View,回收内存~~~~
代码中有个Map专门存储View和posion的,主要是为了给点击回调提供当前的View的位置,有点类似:Android 自定义 ViewPager 打造千变万化的图片切换效果里面的Map的巧妙用法~~
是不是完全实现了ViewPager和HorizontalScrollView的合体~~~HorizontalScrollView的效果,ViewPager的特性~~~~
最后贴一下旋转屏幕后的效果图:
可以看出,不仅是做相册,还是图片轮播想过都是刚刚的!
如果你的项目中需要用到Gallery类似的效果,果断使用上例尝试吧~~
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