Android开发

Anroid ListView分组和悬浮Header实现方法

本文主要是介绍Anroid ListView分组和悬浮Header实现方法,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!

之前在使用iOS时,看到过一种分组的View,每一组都有一个Header,在上下滑动的时候,会有一个悬浮的Header,这种体验觉得很不错,请看下图:

上图中标红的1,2,3,4四张图中,当向上滑动时,仔细观察灰色条的Header变化,当第二组向上滑动时,会把第一组的悬浮Header挤上去。

这种效果在Android是没有的,iOS的SDK就自带这种效果。这篇文章就介绍如何在Android实现这种效果。

1、悬浮Header的实现

其实Android自带的联系人的App中就有这样的效果,我也是把他的类直接拿过来的,实现了PinnedHeaderListView这么一个类,扩展于ListView,核心原理就是在ListView的最顶部绘制一个调用者设置的Header View,在滑动的时候,根据一些状态来决定是否向上或向下移动Header View(其实就是调用其layout方法,理论上在绘制那里作一些平移也是可以的)。下面说一下具体的实现:

1.1、PinnedHeaderAdapter接口

这个接口需要ListView的Adapter来实现,它定义了两个方法,一个是让Adapter告诉ListView当前指定的position的数据的状态,比如指定position的数据可能是组的header;另一个方法就是设置Header View,比如设置Header View的文本,图片等,这个方法是由调用者去实现的。

/** 
 * Adapter interface. The list adapter must implement this interface. 
 */ 
public interface PinnedHeaderAdapter { 
 
  /** 
   * Pinned header state: don't show the header. 
   */ 
  public static final int PINNED_HEADER_GONE = 0; 
 
  /** 
   * Pinned header state: show the header at the top of the list. 
   */ 
  public static final int PINNED_HEADER_VISIBLE = 1; 
 
  /** 
   * Pinned header state: show the header. If the header extends beyond 
   * the bottom of the first shown element, push it up and clip. 
   */ 
  public static final int PINNED_HEADER_PUSHED_UP = 2; 
 
  /** 
   * Computes the desired state of the pinned header for the given 
   * position of the first visible list item. Allowed return values are 
   * {@link #PINNED_HEADER_GONE}, {@link #PINNED_HEADER_VISIBLE} or 
   * {@link #PINNED_HEADER_PUSHED_UP}. 
   */ 
  int getPinnedHeaderState(int position); 
 
  /** 
   * Configures the pinned header view to match the first visible list item. 
   * 
   * @param header pinned header view. 
   * @param position position of the first visible list item. 
   * @param alpha fading of the header view, between 0 and 255. 
   */ 
  void configurePinnedHeader(View header, int position, int alpha); 
} 

1.2、如何绘制Header View

这是在dispatchDraw方法中绘制的:

@Override 
protected void dispatchDraw(Canvas canvas) { 
  super.dispatchDraw(canvas); 
  if (mHeaderViewVisible) { 
    drawChild(canvas, mHeaderView, getDrawingTime()); 
  } 
} 

1.3、配置Header View

核心就是根据不同的状态值来控制Header View的状态,比如PINNED_HEADER_GONE(隐藏)的情况,可能需要设置一个flag标记,不绘制Header View,那么就达到隐藏的效果。当PINNED_HEADER_PUSHED_UP状态时,可能需要根据不同的位移来计算Header View的移动位移。下面是具体的实现:

public void configureHeaderView(int position) { 
  if (mHeaderView == null || null == mAdapter) { 
    return; 
  } 
   
  int state = mAdapter.getPinnedHeaderState(position); 
  switch (state) { 
    case PinnedHeaderAdapter.PINNED_HEADER_GONE: { 
      mHeaderViewVisible = false; 
      break; 
    } 
 
    case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE: { 
      mAdapter.configurePinnedHeader(mHeaderView, position, MAX_ALPHA); 
      if (mHeaderView.getTop() != 0) { 
        mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight); 
      } 
      mHeaderViewVisible = true; 
      break; 
    } 
 
    case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP: { 
      View firstView = getChildAt(0); 
      int bottom = firstView.getBottom(); 
       int itemHeight = firstView.getHeight(); 
      int headerHeight = mHeaderView.getHeight(); 
      int y; 
      int alpha; 
      if (bottom < headerHeight) { 
        y = (bottom - headerHeight); 
        alpha = MAX_ALPHA * (headerHeight + y) / headerHeight; 
      } else { 
        y = 0; 
        alpha = MAX_ALPHA; 
      } 
      mAdapter.configurePinnedHeader(mHeaderView, position, alpha); 
      if (mHeaderView.getTop() != y) { 
        mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight + y); 
      } 
      mHeaderViewVisible = true; 
      break; 
    } 
  } 
} 

1.4、onLayout和onMeasure

在这两个方法中,控制Header View的位置及大小

@Override 
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
  super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
  if (mHeaderView != null) { 
    measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec); 
    mHeaderViewWidth = mHeaderView.getMeasuredWidth(); 
    mHeaderViewHeight = mHeaderView.getMeasuredHeight(); 
  } 
} 
 
@Override 
protected void onLayout(boolean changed, int left, int top, int right, int bottom) { 
  super.onLayout(changed, left, top, right, bottom); 
  if (mHeaderView != null) { 
    mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight); 
    configureHeaderView(getFirstVisiblePosition()); 
  } 
} 

好了,到这里,悬浮Header View就完了,各位可能看不到完整的代码,只要明白这几个核心的方法,自己写出来,也差不多了。

2、ListView Section实现

有两种方法实现ListView Section效果:

方法一:

每一个ItemView中包含Header,通过数据来控制其显示或隐藏,实现原理如下图:

优点:

1,实现简单,在Adapter.getView的实现中,只需要根据数据来判断是否是header,不是的话,隐藏Item view中的header部分,否则显示。

2,Adapter.getItem(int n)始终返回的数据是在数据列表中对应的第n个数据,这样容易理解。

3,控制header的点击事件更加容易

缺点:
1、使用更多的内存,第一个Item view中都包含一个header view,这样会费更多的内存,多数时候都可能header都是隐藏的。

方法二:

使用不同类型的View:重写getItemViewType(int)和getViewTypeCount()方法。

优点:

1,允许多个不同类型的item

2,理解更加简单

缺点:

1,实现比较复杂

2,得到指定位置的数据变得复杂一些

到这里,我的实现方式是选择第二种方案,尽管它的实现方式要复杂一些,但优点比较明显。

3、Adapter的实现

这里主要就是说一下getPinnedHeaderState和configurePinnedHeader这两个方法的实现

private class ListViewAdapter extends BaseAdapter implements PinnedHeaderAdapter { 
   
  private ArrayList<Contact> mDatas; 
  private static final int TYPE_CATEGORY_ITEM = 0;  
  private static final int TYPE_ITEM = 1;  
   
  public ListViewAdapter(ArrayList<Contact> datas) { 
    mDatas = datas; 
  } 
   
  @Override 
  public boolean areAllItemsEnabled() { 
    return false; 
  } 
   
  @Override 
  public boolean isEnabled(int position) { 
    // 异常情况处理  
    if (null == mDatas || position < 0|| position > getCount()) { 
      return true; 
    }  
     
    Contact item = mDatas.get(position); 
    if (item.isSection) { 
      return false; 
    } 
     
    return true; 
  } 
   
  @Override 
  public int getCount() { 
    return mDatas.size(); 
  } 
   
  @Override 
  public int getItemViewType(int position) { 
    // 异常情况处理  
    if (null == mDatas || position < 0|| position > getCount()) { 
      return TYPE_ITEM; 
    }  
     
    Contact item = mDatas.get(position); 
    if (item.isSection) { 
      return TYPE_CATEGORY_ITEM; 
    } 
     
    return TYPE_ITEM; 
  } 
 
  @Override 
  public int getViewTypeCount() { 
    return 2; 
  } 
 
  @Override 
  public Object getItem(int position) { 
    return (position >= 0 && position < mDatas.size()) ? mDatas.get(position) : 0; 
  } 
 
  @Override 
  public long getItemId(int position) { 
    return 0; 
  } 
 
  @Override 
  public View getView(int position, View convertView, ViewGroup parent) { 
    int itemViewType = getItemViewType(position); 
    Contact data = (Contact) getItem(position); 
    TextView itemView; 
     
    switch (itemViewType) { 
    case TYPE_ITEM: 
      if (null == convertView) { 
        itemView = new TextView(SectionListView.this); 
        itemView.setLayoutParams(new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 
            mItemHeight)); 
        itemView.setTextSize(16); 
        itemView.setPadding(10, 0, 0, 0); 
        itemView.setGravity(Gravity.CENTER_VERTICAL); 
        //itemView.setBackgroundColor(Color.argb(255, 20, 20, 20)); 
        convertView = itemView; 
      } 
       
      itemView = (TextView) convertView; 
      itemView.setText(data.toString()); 
      break; 
       
    case TYPE_CATEGORY_ITEM: 
      if (null == convertView) { 
        convertView = getHeaderView(); 
      } 
      itemView = (TextView) convertView; 
      itemView.setText(data.toString()); 
      break; 
    } 
     
    return convertView; 
  } 
 
  @Override 
  public int getPinnedHeaderState(int position) { 
    if (position < 0) { 
      return PINNED_HEADER_GONE; 
    } 
     
    Contact item = (Contact) getItem(position); 
    Contact itemNext = (Contact) getItem(position + 1); 
    boolean isSection = item.isSection; 
    boolean isNextSection = (null != itemNext) ? itemNext.isSection : false; 
    if (!isSection && isNextSection) { 
      return PINNED_HEADER_PUSHED_UP; 
    } 
     
    return PINNED_HEADER_VISIBLE; 
  } 
 
  @Override 
  public void configurePinnedHeader(View header, int position, int alpha) { 
    Contact item = (Contact) getItem(position); 
    if (null != item) { 
      if (header instanceof TextView) { 
        ((TextView) header).setText(item.sectionStr); 
      } 
    } 
  } 
} 

在getPinnedHeaderState方法中,如果第一个item不是section,第二个item是section的话,就返回状态PINNED_HEADER_PUSHED_UP,否则返回PINNED_HEADER_VISIBLE。
在configurePinnedHeader方法中,就是将item的section字符串设置到header view上面去。

【重要说明】

Adapter中的数据里面已经包含了section(header)的数据,数据结构中有一个方法来标识它是否是section。那么,在点击事件就要注意了,通过position可能返回的是section数据结构。

数据结构Contact的定义如下:

public class Contact { 
  int id; 
  String name; 
  String pinyin; 
  String sortLetter = "#"; 
  String sectionStr; 
  String phoneNumber; 
  boolean isSection; 
  static CharacterParser sParser = CharacterParser.getInstance(); 
   
  Contact() { 
     
  } 
   
  Contact(int id, String name) { 
    this.id = id; 
    this.name = name; 
    this.pinyin = sParser.getSpelling(name); 
    if (!TextUtils.isEmpty(pinyin)) { 
      String sortString = this.pinyin.substring(0, 1).toUpperCase(); 
      if (sortString.matches("[A-Z]")) { 
        this.sortLetter = sortString.toUpperCase(); 
      } else { 
        this.sortLetter = "#"; 
      } 
    } 
  } 
   
  @Override 
  public String toString() { 
    if (isSection) { 
      return name; 
    } else { 
      //return name + " (" + sortLetter + ", " + pinyin + ")"; 
      return name + " (" + phoneNumber + ")"; 
    } 
  } 
}  

完整的代码

package com.lee.sdk.test.section; 
 
import java.util.ArrayList; 
 
import android.graphics.Color; 
import android.os.Bundle; 
import android.view.Gravity; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AbsListView; 
import android.widget.AdapterView; 
import android.widget.AdapterView.OnItemClickListener; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 
import android.widget.Toast; 
 
import com.lee.sdk.test.GABaseActivity; 
import com.lee.sdk.test.R; 
import com.lee.sdk.widget.PinnedHeaderListView; 
import com.lee.sdk.widget.PinnedHeaderListView.PinnedHeaderAdapter; 
 
public class SectionListView extends GABaseActivity { 
 
  private int mItemHeight = 55; 
  private int mSecHeight = 25; 
   
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
     
    float density = getResources().getDisplayMetrics().density; 
    mItemHeight = (int) (density * mItemHeight); 
    mSecHeight = (int) (density * mSecHeight); 
     
    PinnedHeaderListView mListView = new PinnedHeaderListView(this); 
    mListView.setAdapter(new ListViewAdapter(ContactLoader.getInstance().getContacts(this))); 
    mListView.setPinnedHeaderView(getHeaderView()); 
    mListView.setBackgroundColor(Color.argb(255, 20, 20, 20)); 
    mListView.setOnItemClickListener(new OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
        ListViewAdapter adapter = ((ListViewAdapter) parent.getAdapter()); 
        Contact data = (Contact) adapter.getItem(position); 
        Toast.makeText(SectionListView.this, data.toString(), Toast.LENGTH_SHORT).show(); 
      } 
    }); 
 
    setContentView(mListView); 
  } 
   
  private View getHeaderView() { 
    TextView itemView = new TextView(SectionListView.this); 
    itemView.setLayoutParams(new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 
        mSecHeight)); 
    itemView.setGravity(Gravity.CENTER_VERTICAL); 
    itemView.setBackgroundColor(Color.WHITE); 
    itemView.setTextSize(20); 
    itemView.setTextColor(Color.GRAY); 
    itemView.setBackgroundResource(R.drawable.section_listview_header_bg); 
    itemView.setPadding(10, 0, 0, itemView.getPaddingBottom()); 
     
    return itemView; 
  } 
 
  private class ListViewAdapter extends BaseAdapter implements PinnedHeaderAdapter { 
     
    private ArrayList<Contact> mDatas; 
    private static final int TYPE_CATEGORY_ITEM = 0;  
    private static final int TYPE_ITEM = 1;  
     
    public ListViewAdapter(ArrayList<Contact> datas) { 
      mDatas = datas; 
    } 
     
    @Override 
    public boolean areAllItemsEnabled() { 
      return false; 
    } 
     
    @Override 
    public boolean isEnabled(int position) { 
      // 异常情况处理  
      if (null == mDatas || position < 0|| position > getCount()) { 
        return true; 
      }  
       
      Contact item = mDatas.get(position); 
      if (item.isSection) { 
        return false; 
      } 
       
      return true; 
    } 
     
    @Override 
    public int getCount() { 
      return mDatas.size(); 
    } 
     
    @Override 
    public int getItemViewType(int position) { 
      // 异常情况处理  
      if (null == mDatas || position < 0|| position > getCount()) { 
        return TYPE_ITEM; 
      }  
       
      Contact item = mDatas.get(position); 
      if (item.isSection) { 
        return TYPE_CATEGORY_ITEM; 
      } 
       
      return TYPE_ITEM; 
    } 
 
    @Override 
    public int getViewTypeCount() { 
      return 2; 
    } 
 
    @Override 
    public Object getItem(int position) { 
      return (position >= 0 && position < mDatas.size()) ? mDatas.get(position) : 0; 
    } 
 
    @Override 
    public long getItemId(int position) { 
      return 0; 
    } 
 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
      int itemViewType = getItemViewType(position); 
      Contact data = (Contact) getItem(position); 
      TextView itemView; 
       
      switch (itemViewType) { 
      case TYPE_ITEM: 
        if (null == convertView) { 
          itemView = new TextView(SectionListView.this); 
          itemView.setLayoutParams(new AbsListView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 
              mItemHeight)); 
          itemView.setTextSize(16); 
          itemView.setPadding(10, 0, 0, 0); 
          itemView.setGravity(Gravity.CENTER_VERTICAL); 
          //itemView.setBackgroundColor(Color.argb(255, 20, 20, 20)); 
          convertView = itemView; 
        } 
         
        itemView = (TextView) convertView; 
        itemView.setText(data.toString()); 
        break; 
         
      case TYPE_CATEGORY_ITEM: 
        if (null == convertView) { 
          convertView = getHeaderView(); 
        } 
        itemView = (TextView) convertView; 
        itemView.setText(data.toString()); 
        break; 
      } 
       
      return convertView; 
    } 
 
    @Override 
    public int getPinnedHeaderState(int position) { 
      if (position < 0) { 
        return PINNED_HEADER_GONE; 
      } 
       
      Contact item = (Contact) getItem(position); 
      Contact itemNext = (Contact) getItem(position + 1); 
      boolean isSection = item.isSection; 
      boolean isNextSection = (null != itemNext) ? itemNext.isSection : false; 
      if (!isSection && isNextSection) { 
        return PINNED_HEADER_PUSHED_UP; 
      } 
       
      return PINNED_HEADER_VISIBLE; 
    } 
 
    @Override 
    public void configurePinnedHeader(View header, int position, int alpha) { 
      Contact item = (Contact) getItem(position); 
      if (null != item) { 
        if (header instanceof TextView) { 
          ((TextView) header).setText(item.sectionStr); 
        } 
      } 
    } 
  } 
} 

最后来一张截图:
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