Android：谷歌headergridview的示例實現

Question

我搜索了Web，但找不到任何內容，但是該類的源代碼。我還是一個初學者，我完全不明白這個類應該如何實現

https://android.googlesource.com/platform/packages/apps/Gallery2/+/idea133/src/com/android/photos/views/HeaderGridView.java

有人可以給我提供這樣一個類的編碼實現，比如兩個頭，4次用頭，一個頂標題（在網格視圖上方），一個底部頁腳（在網格視圖下方），以及如何實現可過濾的演示？ （在視圖中的文本說）

非常感謝

Answer 1

package com.paging.gridview; 




import android.content.Context; 
import android.util.AttributeSet; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.FrameLayout; 
import android.widget.GridView; 
import android.widget.ListAdapter; 


import java.util.ArrayList; 


public class HeaderGridView extends GridView { 


    private ListAdapter mAdapter; 
    private Context mContext; 


    /** 
    * Should be used by subclasses to listen to changes in the dataset 
    */ 
// AdapterDataSetObserver mDataSetObserver; 

    public HeaderGridView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
     init(context); 
    } 


    public HeaderGridView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     init(context); 
    } 


    public HeaderGridView(Context context) { 
     super(context); 
     init(context); 
    } 

    private void init(Context context){ 
     mContext = context; 
//  super.setOnScrollListener(this); 
    } 
    /** 
    * A class that represents a fixed view in a list, for example a header at the top 
    * or a footer at the bottom. 
    */ 

    private ArrayList<FixedViewInfo> mHeaderViewInfos = new ArrayList<FixedViewInfo>(); 
    private ArrayList<FixedViewInfo> mFooterViewInfos = new ArrayList<FixedViewInfo>(); 

    private void notifiyChanged(){ 
     this.requestLayout(); 
     this.invalidate(); 
    } 




    /** 
    * Add a fixed view to appear at the top of the list. If this method is 
    * called more than once, the views will appear in the order they were 
    * added. Views added using this call can take focus if they want. 
    * <p> 
    * Note: When first introduced, this method could only be called before 
    * setting the adapter with {@link #setAdapter(ListAdapter)}. Starting with 
    * {@link android.os.Build.VERSION_CODES#KITKAT}, this method may be 
    * called at any time. If the ListView's adapter does not extend 
    * {@link FooterViewGridAdapter}, it will be wrapped with a supporting 
    * instance of {@link android.widget.WrapperListAdapter}. 
    * 
    * @param v The view to add. 
    * @param data Data to associate with this view 
    * @param isSelectable whether the item is selectable 
    */ 
    public void addHeaderView(View v, Object data, boolean isSelectable) { 
     final FixedViewInfo info = new FixedViewInfo(); 
     FrameLayout fl = new FullWidthFixedViewLayout(getContext()); 
     fl.addView(v); 
     info.view = v; 
     info.viewContainer = fl; 
     info.data = data; 
     info.isSelectable = isSelectable; 
     mHeaderViewInfos.add(info); 


     // Wrap the adapter if it wasn't already wrapped. 
     if (mAdapter != null) { 
      if (!(mAdapter instanceof FooterViewGridAdapter)) { 
       mAdapter = new FooterViewGridAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter); 
      } 


      // Do not know if this really helps 
      notifiyChanged(); 
     } 
    } 






    /** 
    * Add a fixed view to appear at the top of the list. If addHeaderView is 
    * called more than once, the views will appear in the order they were 
    * added. Views added using this call can take focus if they want. 
    * <p> 
    * Note: When first introduced, this method could only be called before 
    * setting the adapter with {@link #setAdapter(ListAdapter)}. Starting with 
    * {@link android.os.Build.VERSION_CODES#KITKAT}, this method may be 
    * called at any time. If the ListView's adapter does not extend 
    * {@link FooterViewGridAdapter}, it will be wrapped with a supporting 
    * instance of {@link android.widget.WrapperListAdapter}. 
    * 
    * @param v The view to add. 
    */ 
    public void addHeaderView(View v) { 
     addHeaderView(v, null, true); 
    } 


    public int getHeaderViewsCount() { 
     return mHeaderViewInfos.size(); 
    } 


    /** 
    * Add a fixed view to appear at the bottom of the list. If addFooterView is 
    * called more than once, the views will appear in the order they were 
    * added. Views added using this call can take focus if they want. 
    * <p> 
    * Note: When first introduced, this method could only be called before 
    * setting the adapter with {@link #setAdapter(ListAdapter)}. Starting with 
    * {@link android.os.Build.VERSION_CODES#KITKAT}, this method may be 
    * called at any time. If the ListView's adapter does not extend 
    * {@link FooterViewGridAdapter}, it will be wrapped with a supporting 
    * instance of {@link android.widget.WrapperListAdapter}. 
    * 
    * @param v The view to add. 
    * @param data Data to associate with this view 
    * @param isSelectable true if the footer view can be selected 
    */ 
    public void addFooterView(View v, Object data, boolean isSelectable) { 
     final FixedViewInfo info = new FixedViewInfo(); 
     FrameLayout fl = new FullWidthFixedViewLayout(getContext()); 
     fl.addView(v); 
     info.view = v; 
     info.viewContainer = fl; 
     info.data = data; 
     info.isSelectable = isSelectable; 
     mFooterViewInfos.add(info); 


     // Wrap the adapter if it wasn't already wrapped. 
     if (mAdapter != null) { 
      if (!(mAdapter instanceof FooterViewGridAdapter)) { 
       mAdapter = new FooterViewGridAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter); 
      } 


      // Do not know if this really helps 
      notifiyChanged(); 
     } 
    } 


    /** 
    * Add a fixed view to appear at the bottom of the list. If addFooterView is 
    * called more than once, the views will appear in the order they were 
    * added. Views added using this call can take focus if they want. 
    * <p> 
    * Note: When first introduced, this method could only be called before 
    * setting the adapter with {@link #setAdapter(ListAdapter)}. Starting with 
    * {@link android.os.Build.VERSION_CODES#KITKAT}, this method may be 
    * called at any time. If the ListView's adapter does not extend 
    * {@link FooterViewGridAdapter}, it will be wrapped with a supporting 
    * instance of {@link android.widget.WrapperListAdapter}. 
    * 
    * @param v The view to add. 
    */ 
    public void addFooterView(View v) { 
     addFooterView(v, null, true); 
    } 


    public int getFooterViewsCount() { 
     return mFooterViewInfos.size(); 
    } 


    /** 
    * Removes a previously-added footer view. 
    * 
    * @param v The view to remove 
    * @return 
    * true if the view was removed, false if the view was not a footer view 
    */ 
    public boolean removeFooterView(View v) { 
     if (mFooterViewInfos.size() > 0) { 
      boolean result = false; 
      if (mAdapter != null && ((FooterViewGridAdapter) mAdapter).removeFooter(v)) { 
       notifiyChanged(); 
       result = true; 
      } 
      removeFixedViewInfo(v, mFooterViewInfos); 
      return result; 
     } 
     return false; 
    } 


    private void removeFixedViewInfo(View v, ArrayList<FixedViewInfo> where) { 
     int len = where.size(); 
     for (int i = 0; i < len; ++i) { 
      FixedViewInfo info = where.get(i); 
      if (info.view == v) { 
       where.remove(i); 
       break; 
      } 
     } 
    } 




    @Override 
    public void setAdapter(ListAdapter adapter) { 
     this.mAdapter = adapter; 


     if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) { 
      mAdapter = new FooterViewGridAdapter(mHeaderViewInfos, mFooterViewInfos, adapter); 
     } else { 
      mAdapter = adapter; 
     } 


     super.setAdapter(adapter); 
     super.setAdapter(this.mAdapter); 


     requestLayout(); 
    } 


    @Override 
    public ListAdapter getAdapter() { 
     return this.mAdapter; 
    } 


    public class FixedViewInfo { 
     public android.view.View view; 
     public ViewGroup viewContainer; 
     public java.lang.Object data; 
     public boolean isSelectable; 
    } 


    private class FullWidthFixedViewLayout extends FrameLayout { 
     public FullWidthFixedViewLayout(Context context) { 
      super(context); 
     } 


     @Override 
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
      int targetWidth = HeaderGridView.this.getMeasuredWidth() 
       - HeaderGridView.this.getPaddingLeft() 
       - HeaderGridView.this.getPaddingRight(); 
      widthMeasureSpec = MeasureSpec.makeMeasureSpec(targetWidth, 
       MeasureSpec.getMode(widthMeasureSpec)); 
      super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
     } 
    } 
} 

鏈接到項目 https://github.com/nicolasjafelle/PagingGridView/blob/master/PagingGridViewProject/PagingGridView/src/main/java/com/paging/gridview/HeaderGridView.java