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HorizontalScrollView仿ViewPager设计相册 Android利用HorizontalScrollView仿ViewPager设计简单相册

SunShanai 人气:0
想了解Android利用HorizontalScrollView仿ViewPager设计简单相册的相关内容吗,SunShanai在本文为您仔细讲解HorizontalScrollView仿ViewPager设计相册的相关知识和一些Code实例,欢迎阅读和指正,我们先划重点:Android,HorizontalScrollView,ViewPager,相册,下面大家一起来学习吧。

最近学习了一个视频公开课,讲到了利用HorizontalScrollView仿ViewPager设计的一个简单相册,其实主要用了ViewPager缓存的思想。此篇文章参考:Android自定义HorizontalScrollView打造超强Gallery效果(这篇文章与公开课的讲的大致一样)

 这里简单说一下ViewPager的缓存机制

       1.进入ViewPager时,加载当前页和后一页;

       2.当滑动ViewPager至下一页时,加载后一页,此时第一页是不会销毁的,同时加载当前页的下一页。

其实就是默认加载3页,当前页,前一页和后一页。

而此HorizontalScrollView是默认加载两页的,这个要注意,不然调度代码会让人晕。

话不多说,上代码:

代码结构如下图:

一个View,一个Adapter,一个MainActivity,相信不用解释,大家也相当清楚了,典型的MVC模式~

package com.ssa.horizontalscrollview.myview; 
 
import java.util.HashMap; 
import java.util.Map; 
 
import com.ssa.horizontalscrollview.myUtils.DisplayUtil; 
 
import android.content.Context; 
import android.graphics.Color; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.HorizontalScrollView; 
import android.widget.LinearLayout; 
 
public class GalleryHorizontalScrollView extends HorizontalScrollView implements 
    OnClickListener { 
  private LinearLayout mContainer;// MyHorizontalScrollView中的LinearLayout 
  private int mChildWidth;// 子元素的宽度 
  private int mChildHeight;// 子元素的高度 
 
  private int mAllLastIndex;// 当前的最后一张的index 
  private int mdisplayLastIndex;// 当前显示的最后一张的index 
  private int mAllFirstIndex;// 当前的第一张index 
 
  private GalleryHorizontalScrollViewAdapter mAdapter;// 数据适配器 
  private int mScreenWidth;// 屏幕的宽度 
 
  private int mCountOneScreen; 
 
  private Map<View, Integer> mViewPos = new HashMap<View, Integer>(); 
 
  private OnCurrentImageChangeListener mOnCurrentImageChangeListener; 
 
  private OnClickImageChangeListener mOnClickImageChangeListener; 
 
  public void setmOnCurrentImageChangeListener( 
      OnCurrentImageChangeListener mListener) { 
    this.mOnCurrentImageChangeListener = mListener; 
  } 
 
  public void setmOnClickImageListener(OnClickImageChangeListener mListener) { 
    this.mOnClickImageChangeListener = mListener; 
  } 
 
  /** 
   * 图片滚动时回调接口 
   */ 
  public interface OnCurrentImageChangeListener { 
    void onCurrentImgChanged(int position, View view); 
  } 
 
  /** 
   * 点击图片时回调接口 
   */ 
  public interface OnClickImageChangeListener { 
    void onClickImageChangeListener(int position, View view); 
  } 
 
  public GalleryHorizontalScrollView(Context context, AttributeSet attrs) { 
    super(context, attrs); 
    // 获取屏幕宽度 
    mScreenWidth = getResources().getDisplayMetrics().widthPixels; 
  } 
 
  /** 
   * 初始化数据,设置适配器 
   */ 
  public void initData(GalleryHorizontalScrollViewAdapter mAdapter) { 
    this.mAdapter = mAdapter; 
    mContainer = (LinearLayout) getChildAt(0); 
    final View view = mAdapter.getView(0, null, mContainer); 
    mContainer.addView(view); 
    if (mChildHeight == 0 && mChildWidth == 0) { 
      /*int w = View.MeasureSpec.makeMeasureSpec(0, 
          View.MeasureSpec.UNSPECIFIED); 
      int h = View.MeasureSpec.makeMeasureSpec(0, 
          View.MeasureSpec.UNSPECIFIED);*/ 
      /** 
       * 上面注释掉的是一位老师的写法,但我查了好多资料,用参数0和View.MeasureSpec.UNSPECIFIED是一种不太优美的做法; 
       * 好的做法应该是 
       * 当View为match_parent时,无法测量出View的大小(任玉刚大神讲的,确实是这么一回事,这个具体的原因要结合源码分析,可以看一下任大神的博客) 
       * 当View宽高为具体的数值时,比如100px: 
       * int w =View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY); 
       * int h =View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY); 
       * view.measure(w, h); 
       * 当View宽高为wrap_content时: 
       * int w =View.MeasureSpec.makeMeasureSpec((1<<30)-1, View.MeasureSpec.AT_MOST); 
       * int h =View.MeasureSpec.makeMeasureSpec((1<<30)-1, View.MeasureSpec.AT_MOST); 
       * view.measure(w, h); 
       * 
       * 我的此View高度为固定的150dip,宽度为wrap_content 
       */ 
      int heightPx = DisplayUtil.dip2px(getContext(), 150); 
      int w =View.MeasureSpec.makeMeasureSpec((1<<30)-1, View.MeasureSpec.AT_MOST); 
      int h =View.MeasureSpec.makeMeasureSpec(heightPx, View.MeasureSpec.EXACTLY); 
      view.measure(w, h); 
      mChildHeight = view.getMeasuredHeight(); 
      mChildWidth = view.getMeasuredWidth(); 
      // 计算每次加载多少个item 
      mdisplayLastIndex = mScreenWidth / mChildWidth; 
      mCountOneScreen = mdisplayLastIndex + 1; 
      initFirstScreenChildren(mdisplayLastIndex + 1); 
 
    } 
  } 
 
  /** 
   * 加载第一屏的元素 
   * 
   * @param mDisplayCountOneScreen 
   */ 
  private void initFirstScreenChildren(int mDisplayCountOneScreen) { 
    mContainer = (LinearLayout) getChildAt(0); 
    mContainer.removeAllViews(); 
    mViewPos.clear(); 
    for (int i = 0; i < mDisplayCountOneScreen; i++) { 
      View view = mAdapter.getView(i, null, mContainer); 
      // 待完善的点击事件 
      view.setOnClickListener(this); 
      mContainer.addView(view); 
      mViewPos.put(view, i); 
      mAllLastIndex = i; 
    } 
 
    // 初始化并刷新界面 
    if (null != mOnCurrentImageChangeListener) { 
      notifyCurrentImgChanged(); 
    } 
  } 
 
  private void notifyCurrentImgChanged() { 
    // 先清除所有的背景颜色,点击时设置为蓝色 
    for (int i = 0; i < mContainer.getChildCount(); i++) { 
      mContainer.getChildAt(i).setBackgroundColor(Color.WHITE); 
    } 
    mOnCurrentImageChangeListener.onCurrentImgChanged(mAllFirstIndex, 
        mContainer.getChildAt(0)); 
  } 
 
  @Override 
  public boolean onTouchEvent(MotionEvent ev) { 
    /* 
     * Log.e("X", getX()+""); Log.e("ChildX", 
     * mContainer.getChildAt(0).getX()+""); Log.e("RawX",getLeft() +""); 
     */ 
    switch (ev.getAction()) { 
 
    case MotionEvent.ACTION_MOVE: 
      int scrollX = getScrollX(); 
      Log.e("ScrollX", scrollX + ""); 
      if (scrollX >= mChildWidth) { 
        // 加载下一页,移除第一张 
        loadNextImg(); 
      } 
      if (scrollX == 0) { 
        // 加载上一页,移除最后一张 
        loadPreImg(); 
      } 
      break; 
    } 
 
    return super.onTouchEvent(ev); 
  } 
 
  private void loadNextImg() {// 数组边界值计算 
    if (mAllLastIndex == 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(++mAllLastIndex, null, mContainer); 
    view.setOnClickListener(this); 
    mContainer.addView(view); 
    mViewPos.put(view, mAllLastIndex); 
 
    // 当前第一张图片小标 
    mAllFirstIndex++; 
    // 如果设置了滚动监听则触发 
    if (mOnCurrentImageChangeListener != null) { 
      notifyCurrentImgChanged(); 
    } 
 
  } 
 
  private void loadPreImg() { 
    if (mAllFirstIndex == 0) { 
      return; 
    } 
    int index = mAllLastIndex - mCountOneScreen; 
    if (index >= 0) { 
      // 移除最后一张 
      int oldViewPos = mContainer.getChildCount() - 1; 
      mViewPos.remove(mContainer.getChildAt(oldViewPos)); 
      mContainer.removeViewAt(oldViewPos); 
      // 将加入的View放在第一个位置 
      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的宽度的像素 
      scrollTo(mChildWidth, 0); 
 
      mAllLastIndex--; 
      mAllFirstIndex--; 
 
      if (null != mOnCurrentImageChangeListener) { 
        notifyCurrentImgChanged(); 
      } 
    } 
  } 
 
  @Override 
  public void onClick(View v) { 
    if(null!=mOnClickImageChangeListener){ 
      mOnClickImageChangeListener.onClickImageChangeListener(mViewPos.get(v), v); 
    } 
  } 
} 

下面是Adapter的源码:

package com.ssa.horizontalscrollview.myview; 
 
import java.util.List; 
 
import com.ssa.horizontalscrollview.R; 
 
import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageView; 
import android.widget.TextView; 
 
public class GalleryHorizontalScrollViewAdapter { 
  private LayoutInflater mInflater; 
  private List<Integer> mDatas; 
 
  public GalleryHorizontalScrollViewAdapter(Context context, List<Integer> mDatas) { 
    mInflater = LayoutInflater.from(context); 
    this.mDatas = mDatas; 
  } 
 
  public Object getItem(int position) { 
    return mDatas.get(position); 
  } 
 
  public long getItemId(int position) { 
    return position; 
  } 
 
  public int getCount() { 
    return mDatas.size(); 
  } 
   
  public View getView(int position, View contentView, ViewGroup parent) { 
    ViewHolder myHolder = null; 
    if (null == contentView) { 
      contentView = mInflater.inflate(R.layout.activity_gallery_item, 
          parent, false); 
      myHolder = new ViewHolder(contentView); 
      contentView.setTag(myHolder); 
    }else { 
      myHolder = (ViewHolder)contentView.getTag(); 
    } 
    myHolder.ivImg.setImageResource(mDatas.get(position)); 
    myHolder.tvText.setText("Img_"+position); 
     
     
    return contentView; 
  } 
 
  private static class ViewHolder { 
    ImageView ivImg; 
    TextView tvText; 
 
    public ViewHolder(View view) { 
      ivImg = (ImageView)view.findViewById(R.id.iv_content); 
      tvText =(TextView)view.findViewById(R.id.tv_index); 
    } 
  } 
 
} 

下面是MainActivity的源码:

package com.ssa.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.widget.ImageView; 
 
import com.ssa.horizontalscrollview.myview.GalleryHorizontalScrollView; 
import com.ssa.horizontalscrollview.myview.GalleryHorizontalScrollView.OnClickImageChangeListener; 
import com.ssa.horizontalscrollview.myview.GalleryHorizontalScrollView.OnCurrentImageChangeListener; 
import com.ssa.horizontalscrollview.myview.GalleryHorizontalScrollViewAdapter; 
 
public class MainActivity extends Activity { 
  private GalleryHorizontalScrollView mHorizontalScrollView; 
  private GalleryHorizontalScrollViewAdapter 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)); 
   
   
 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    mImg = (ImageView)findViewById(R.id.iv_content); 
    mHorizontalScrollView = (GalleryHorizontalScrollView)findViewById(R.id.mhsv_gallery_container); 
    mAdapter = new GalleryHorizontalScrollViewAdapter(this, mDatas); 
    mHorizontalScrollView.setmOnCurrentImageChangeListener(new OnCurrentImageChangeListener() { 
       
      @Override 
      public void onCurrentImgChanged(int position, View view) { 
        mImg.setImageResource(mDatas.get(position)); 
        view.setBackgroundColor(Color.parseColor("#6d9eeb")); 
      } 
    }); 
    mHorizontalScrollView.setmOnClickImageListener(new OnClickImageChangeListener() { 
       
      @Override 
      public void onClickImageChangeListener(int position, View view) { 
        mImg.setImageResource(mDatas.get(position)); 
      } 
    }); 
    mHorizontalScrollView.initData(mAdapter); 
  } 
} 

至些,调试运行,读者会发现,整个相册会非常卡,

甚至有的图片还没有显示出来如img_4,看一下logcat,相信大家会发现原因:

信息已经提示的很清楚了,图片太大,

此时大家应该明白了,笔者故意选择了几张很大的图片加载,虽然没大到直接让应用崩掉,但是体验性已经变得非常差了,这是因为课堂上的老师讲课时用的图片都是几十K的小图片,加载当然不会有问题,所以要想使这个相册作为一个实用的相册,还要处理图片过大的问题,不然,依旧会造成OOM。

此时就用到这个工具类了:

package com.ssa.horizontalscrollview.myUtils; 
 
import android.content.res.Resources; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
 
public class BitmapUtil { 
  public static Bitmap decodeSampledBitmapFromResources(Resources res, 
      int resId, int reqWidth, int reqHeight) { 
    final BitmapFactory.Options options = new BitmapFactory.Options(); 
    options.inJustDecodeBounds = true; 
    BitmapFactory.decodeResource(res, resId, options); 
    options.inSampleSize = calculateInsampleSize(options, reqWidth, 
        reqHeight); 
    options.inJustDecodeBounds = false; 
    return BitmapFactory.decodeResource(res, resId, options); 
 
  } 
 
  public static int calculateInsampleSize(BitmapFactory.Options options, 
      int reqWidth, int reqHeight) { 
    final int height = options.outHeight; 
    final int width = options.outWidth; 
    int inSampleSize = 1; 
    if (height > reqHeight || width > reqWidth) { 
      final int halfHeight = height / 2; 
      final int halfWidth = width / 2; 
      while ((halfHeight / inSampleSize) >= reqHeight 
          && (halfWidth / inSampleSize) >= reqWidth) { 
        inSampleSize *= 2; 
      } 
    } 
 
    return inSampleSize; 
  } 
} 

添加了这个工具类,上面几个类的代码也要略微修改一下,具体怎么改,大家可以下载下面我上传的源码:
至于效果如下动图所示(生成的gif图有点卡,大家可以运行看效果):

源码下载:HorizontalScrollView仿ViewPager设计相册

以上就是本文的全部内容,希望对大家学习Android软件编程有所帮助。

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