android 自定义gallerey并实现预览功能

来源：互联网发布：21级战舰升级数据编辑：程序博客网时间：2024/05/22 06:51

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。

首先差一张图片

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

public class MyHorizontalScrollView extends HorizontalScrollView implements        OnClickListener {    private CurrentImageChangeListener mListener;    private OnItemClickListener mOnClickListener;    private LinearLayout mContainer;    private int mChildWidth;    private int mChildHeight;    private int mCurrentIndex;    private int mFristIndex;    private HorizontalScrollViewAdapter mAdapter;    private int mCountOneScreen;    private int mScreenWitdh;    private Map<View, Integer> mViewPos = new HashMap<View, Integer>();    public MyHorizontalScrollView(Context context, AttributeSet attrs) {        super(context, attrs);        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);    }    protected void loadNextImg() {        if (mCurrentIndex == mAdapter.getCount() - 1) {            return;        }        scrollTo(0, 0);        mViewPos.remove(mContainer.getChildAt(0));        mContainer.removeViewAt(0);        View view = mAdapter.getView(++mCurrentIndex, null, mContainer);        view.setOnClickListener(this);        mContainer.addView(view);        mViewPos.put(view, mCurrentIndex);        mFristIndex++;        if (mListener != null) {            notifyCurrentImgChanged();        }    }    protected void loadPreImg() {        if (mFristIndex == 0)            return;        int index = mCurrentIndex - mCountOneScreen;        if (index >= 0) {            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--;            if (mListener != null) {                notifyCurrentImgChanged();            }        }    }    //更改当前背景色    public void notifyCurrentImgChanged() {        for (int i = 0; i < mContainer.getChildCount(); i++) {            mContainer.getChildAt(i).setBackgroundColor(Color.WHITE);        }        mListener.onCurrentImgChanged(mFristIndex, mContainer.getChildAt(0));    }    public void setDatas(HorizontalScrollViewAdapter mAdapter) {        this.mAdapter = mAdapter;        mContainer = (LinearLayout) getChildAt(0);        final View view = mAdapter.getView(0, null, mContainer);        mContainer.addView(view);        if (mChildWidth == 0 && mChildHeight == 0) {            int w = MeasureSpec.makeMeasureSpec(0,                    MeasureSpec.UNSPECIFIED);            int h = MeasureSpec.makeMeasureSpec(0,                    MeasureSpec.UNSPECIFIED);            view.measure(w, h);            mChildHeight = view.getMeasuredHeight();            mChildWidth = view.getMeasuredWidth();            mChildHeight = view.getMeasuredHeight();            mCountOneScreen = (mScreenWitdh / mChildWidth == 0) ? mScreenWitdh / mChildWidth + 1 : mScreenWitdh / mChildWidth + 2;        }        initFirstScreenChildren(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:                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;    }    public interface CurrentImageChangeListener {        void onCurrentImgChanged(int position, View viewIndicator);    }    public interface OnItemClickListener {        void onClick(View view, int pos);    }}

接下来我们写一个Adapter用来填充界面，然后在我们首页组装下数据，设置下适配器就好了，是不是很简单。

public class HorizontalScrollViewAdapter extends BaseAdapter{    private Context mContext;    private LayoutInflater mInflater;    private List<GalleryModel> mDatas;    public HorizontalScrollViewAdapter(Context context, List<GalleryModel> 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) {            convertView = mInflater.inflate(                    R.layout.activity_gallery_item, parent, false);            viewHolder = new ViewHolder(convertView);        } else {            viewHolder = (ViewHolder) convertView.getTag();        }        initItem(viewHolder,position);        return convertView;    }    private void initItem(ViewHolder viewHolder, int position) {        viewHolder.itemImage.setImageResource(mDatas.get(position).image);        viewHolder.itemText.setText(mDatas.get(position).name);    }     class ViewHolder {        @Bind(R.id.item_image)        ImageView itemImage;        @Bind(R.id.item_text)        TextView itemText;        public ViewHolder(View parent) {            ButterKnife.bind(this, parent);            parent.setTag(this);        }    }}

有兴趣的可以下载代码：

https://github.com/xiangzhihong/gallery

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