## GridView 布局：item设置的高度和宽度不起作用、自动适配列数、添加Header和Footer ##

一、item设置的高度和宽度不起作用

转自：http://www.cnblogs.com/0616--ataozhijia/p/6031875.html

[Android Pro] listView和GridView的item设置的高度和宽度不起作用

 

referece to : http://blog.csdn.net/beibeixiao/article/details/9032569

1.     在Android开发中会发现，有时listView和GridView的item顶层布局不起作用，即不能设置高度和宽度

        原因是当用自定义的adapter时，如果使用convertView= mInflater.inflate(R.layout.material_grid_item, null)

方法就不会起作用，这个 方法的第二个参数是父View，传入为空，所以没有加载顶层布局，此时如果使用

convertView= mInflater.inflate(R.layout.material_grid_item, parent,false);传入parent设置的高度和宽度就会起作用了。

二、自动适配列数

转自：http://blog.csdn.net/archer_zoro/article/details/43500389

写了一个展示多张图片的gridview（几乎每个listview里面都有一个gridview）

之前用auto_fit和设置列宽来控制列数，以达到自适应的目的。

this.setNumColumns(GridView.AUTO_FIT);
this.setColumnWidth(getResources().getDimensionPixelSize(R.dimen.item_image_size));
this.setHorizontalSpacing(getResources().getDimensionPixelSize(R.dimen.item_image_spacing));
this.setVerticalSpacing(getResources().getDimensionPixelSize(R.dimen.item_image_spacing));

这样的效果就是图片宽度最小为item_image_size，会在接近这个大小的情况下，自动调整一些大小将gridview占满，间隔不变。3列。

而后来在720p以上的手机上运行时，变成了4列，但是要求是3列，于是我把列数从auto_fit改成了3，依然是上面的显示效果，

但是，在滑动listview的过程中明显比刚才卡顿了，所以有改回了auto_fit，转而把item_image_size增大了。

原理不清楚，留下这个坑待研究

转自：http://blog.csdn.net/maizangxiangwang/article/details/50913900

/**
 * 获取屏幕宽度
*/
public static int getScreenWidth(Context context) {
    WindowManager manager = (WindowManager) context
            .getSystemService(Context.WINDOW_SERVICE);
    Display display = manager.getDefaultDisplay();
    return display.getWidth();
}

public static int dipToPx(Context context, int dip) {
    if(density <= 0.0F) {
        density = context.getResources().getDisplayMetrics().density;
    }

    return (int)((float)dip * density + 0.5F);
}

给gridview子项要屏幕适配，子项item宽度，高度与宽度相同

itemWidth = (getScreenWidth(this)-(3*dipToPx(this, 3)))/2;

在gridview的adapter中的getview中设置子项的参数

public View getView(int position, View convertView, ViewGroup parent) {
    ViewHodler viewHodler;
    String url = blogAlbumList.get(position).getAlbumUrl();
    if (convertView == null) {
        convertView = View.inflate(context, R.layout.celebrity_item, null);
        viewHodler = new ViewHodler();
        viewHodler.iv_image = (ImageView) convertView.findViewById(R.id.iv_image);
        convertView.setTag(viewHodler);
    } else {
        viewHodler = (ViewHodler) convertView.getTag();
    }
    // if (viewHodler.iv_image.getTag()!=url ||viewHodler.iv_image.getTag()==null) {
    ImageTools.getImageLoader().displayImage(blogAlbumList.get(position).getAlbumUrl(), viewHodler.iv_image, mDisplayImageOptions);
    // viewHodler.iv_image.setTag(url);
    // }
    AbsListView.LayoutParams param = new AbsListView.LayoutParams(LeoApplication.itemWidth, LeoApplication.itemWidth);
    convertView.setLayoutParams(param);
    return convertView;
}

其实gridview有个属性.Android:stretchMode=”columnWidth"//缩放与列宽大小同步

GridView的一些特殊属性：

 

1.android:numColumns=”auto_fit”   //GridView的列数设置为自动

2.android:columnWidth=”90dp "       //每列的宽度，也就是Item的宽度

3.android:stretchMode=”columnWidth"//缩放与列宽大小同步

4.android:verticalSpacing=”10dp”          //两行之间的边距

5.android:horizontalSpacing=”10dp”      //两列之间的边距 

6.android:cacheColorHint="#00000000" //去除拖动时默认的黑色背景

7.android:listSelector="#00000000"        //去除选中时的黄色底色

8.android:scrollbars="none"                   //隐藏GridView的滚动条

9.android:fadeScrollbars="true"             //设置为true就可以实现滚动条的自动隐藏和显示

10.android:fastScrollEnabled="true"      //GridView出现快速滚动的按钮(至少滚动4页才会显示)

11.android:fadingEdge="none"                //GridView衰落(褪去)边缘颜色为空，缺省值是vertical。(可以理解为上下边缘的提示色)

12.android:fadingEdgeLength="10dip"   //定义的衰落(褪去)边缘的长度

13.android:stackFromBottom="true"       //设置为true时，你做好的列表就会显示你列表的最下面

14.android:transcriptMode="alwaysScroll" //当你动态添加数据时，列表将自动往下滚动最新的条目可以自动滚动到可视范围内

15.android:drawSelectorOnTop="false"  //点击某条记录不放，颜色会在记录的后面成为背景色,内容的文字可见(缺省为false)

三、添加Header和Footer

转自：http://blog.csdn.net/zhzhyang0313/article/details/39163735

实现这个功能一般有两种思路，一种思路是使用ScrollView+GridView，第二种思路是使用ListView来实现GridView的效果。

第一种思路的具体实现是把HeaderView和GridView都放到ScrollView里面，这里要解决的问题是ScrollView和GridView滑动手势的冲突问题，解决办法是让GridView充满ScrollView，不让GridView滑动而只让ScrollView滑动。具题做法是重载GridView的onMeasure()方法。

public class MyGridView extends GridView {
    public MyGridView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MyGridView(Context context) {
        super(context);
    }

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

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        int expandSpec = MeasureSpec.makeMeasureSpec(
                Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
        super.onMeasure(widthMeasureSpec, expandSpec);
    }
}

这种方法的不足是GridView中的View没有复用，如果内容较多将比较消耗内存。

第二种思路的具体实现是使用ListView的addHeaderView()来添加HeaderView，而ListView的每一行都放一个LinearLayout来保存一行的item，这里要注意的是item的个数和ListView行数的关系。

后来在StackOverFlow上又看到了第三中方法。原来Google已经用GridView实现了，而且很巧妙，下面把代码贴出来

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.photos.views;
import android.content.Context;
import android.database.DataSetObservable;
import android.database.DataSetObserver;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.FrameLayout;
import android.widget.GridView;
import android.widget.ListAdapter;
import android.widget.WrapperListAdapter;
import java.util.ArrayList;
/**
 * A {@link GridView} that supports adding header rows in a
 * very similar way to {@link ListView}.
 * See {@link HeaderGridView#addHeaderView(View, Object, boolean)}
 */
public class HeaderGridView extends GridView {
    private static final String TAG = "HeaderGridView";
    /**
     * A class that represents a fixed view in a list, for example a header at the top
     * or a footer at the bottom.
     */
    private static class FixedViewInfo {
        /** The view to add to the grid */
        public View view;
        public ViewGroup viewContainer;
        /** The data backing the view. This is returned from {@link ListAdapter#getItem(int)}. */
        public Object data;
        /** <code>true</code> if the fixed view should be selectable in the grid */
        public boolean isSelectable;
    }
    private ArrayList<FixedViewInfo> mHeaderViewInfos = new ArrayList<FixedViewInfo>();
    private void initHeaderGridView() {
        super.setClipChildren(false);
    }
    public HeaderGridView(Context context) {
        super(context);
        initHeaderGridView();
    }
    public HeaderGridView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initHeaderGridView();
    }
    public HeaderGridView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initHeaderGridView();
    }
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        ListAdapter adapter = getAdapter();
        if (adapter != null && adapter instanceof HeaderViewGridAdapter) {
            ((HeaderViewGridAdapter) adapter).setNumColumns(getNumColumns());
        }
    }
    @Override
    public void setClipChildren(boolean clipChildren) {
       // Ignore, since the header rows depend on not being clipped
    }
    /**
     * Add a fixed view to appear at the top of the grid. 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: Call this before calling setAdapter. This is so HeaderGridView can wrap
     * the supplied cursor with one that will also account for header views.
     *
     * @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) {
        ListAdapter adapter = getAdapter();
        if (adapter != null && ! (adapter instanceof HeaderViewGridAdapter)) {
            throw new IllegalStateException(
                    "Cannot add header view to grid -- setAdapter has already been called.");
        }
        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);
        // in the case of re-adding a header view, or adding one later on,
        // we need to notify the observer
        if (adapter != null) {
            ((HeaderViewGridAdapter) adapter).notifyDataSetChanged();
        }
    }
    /**
     * Add a fixed view to appear at the top of the grid. 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: Call this before calling setAdapter. This is so HeaderGridView can wrap
     * the supplied cursor with one that will also account for header views.
     *
     * @param v The view to add.
     */
    public void addHeaderView(View v) {
        addHeaderView(v, null, true);
    }
    public int getHeaderViewCount() {
        return mHeaderViewInfos.size();
    }
    /**
     * Removes a previously-added header view.
     *
     * @param v The view to remove
     * @return true if the view was removed, false if the view was not a header
     *         view
     */
    public boolean removeHeaderView(View v) {
        if (mHeaderViewInfos.size() > 0) {
            boolean result = false;
            ListAdapter adapter = getAdapter();
            if (adapter != null && ((HeaderViewGridAdapter) adapter).removeHeader(v)) {
                result = true;
            }
            removeFixedViewInfo(v, mHeaderViewInfos);
            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) {
        if (mHeaderViewInfos.size() > 0) {
            HeaderViewGridAdapter hadapter = new HeaderViewGridAdapter(mHeaderViewInfos, adapter);
            int numColumns = getNumColumns();
            if (numColumns > 1) {
                hadapter.setNumColumns(numColumns);
            }
            super.setAdapter(hadapter);
        } else {
            super.setAdapter(adapter);
        }
    }
    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);
        }
    }
    /**
     * ListAdapter used when a HeaderGridView has header views. This ListAdapter
     * wraps another one and also keeps track of the header views and their
     * associated data objects.
     *<p>This is intended as a base class; you will probably not need to
     * use this class directly in your own code.
     */
    private static class HeaderViewGridAdapter implements WrapperListAdapter, Filterable {
        // This is used to notify the container of updates relating to number of columns
        // or headers changing, which changes the number of placeholders needed
        private final DataSetObservable mDataSetObservable = new DataSetObservable();
        private final ListAdapter mAdapter;
        private int mNumColumns = 1;
        // This ArrayList is assumed to NOT be null.
        ArrayList<FixedViewInfo> mHeaderViewInfos;
        boolean mAreAllFixedViewsSelectable;
        private final boolean mIsFilterable;
        public HeaderViewGridAdapter(ArrayList<FixedViewInfo> headerViewInfos, ListAdapter adapter) {
            mAdapter = adapter;
            mIsFilterable = adapter instanceof Filterable;
            if (headerViewInfos == null) {
                throw new IllegalArgumentException("headerViewInfos cannot be null");
            }
            mHeaderViewInfos = headerViewInfos;
            mAreAllFixedViewsSelectable = areAllListInfosSelectable(mHeaderViewInfos);
        }
        public int getHeadersCount() {
            return mHeaderViewInfos.size();
        }
        @Override
        public boolean isEmpty() {
            return (mAdapter == null || mAdapter.isEmpty()) && getHeadersCount() == 0;
        }
        public void setNumColumns(int numColumns) {
            if (numColumns < 1) {
                throw new IllegalArgumentException("Number of columns must be 1 or more");
            }
            if (mNumColumns != numColumns) {
                mNumColumns = numColumns;
                notifyDataSetChanged();
            }
        }
        private boolean areAllListInfosSelectable(ArrayList<FixedViewInfo> infos) {
            if (infos != null) {
                for (FixedViewInfo info : infos) {
                    if (!info.isSelectable) {
                        return false;
                    }
                }
            }
            return true;
        }
        public boolean removeHeader(View v) {
            for (int i = 0; i < mHeaderViewInfos.size(); i++) {
                FixedViewInfo info = mHeaderViewInfos.get(i);
                if (info.view == v) {
                    mHeaderViewInfos.remove(i);
                    mAreAllFixedViewsSelectable = areAllListInfosSelectable(mHeaderViewInfos);
                    mDataSetObservable.notifyChanged();
                    return true;
                }
            }
            return false;
        }
        @Override
        public int getCount() {
            if (mAdapter != null) {
                return getHeadersCount() * mNumColumns + mAdapter.getCount();
            } else {
                return getHeadersCount() * mNumColumns;
            }
        }
        @Override
        public boolean areAllItemsEnabled() {
            if (mAdapter != null) {
                return mAreAllFixedViewsSelectable && mAdapter.areAllItemsEnabled();
            } else {
                return true;
            }
        }
        @Override
        public boolean isEnabled(int position) {
            // Header (negative positions will throw an ArrayIndexOutOfBoundsException)
            int numHeadersAndPlaceholders = getHeadersCount() * mNumColumns;
            if (position < numHeadersAndPlaceholders) {
                return (position % mNumColumns == 0)
                        && mHeaderViewInfos.get(position / mNumColumns).isSelectable;
            }
            // Adapter
            final int adjPosition = position - numHeadersAndPlaceholders;
            int adapterCount = 0;
            if (mAdapter != null) {
                adapterCount = mAdapter.getCount();
                if (adjPosition < adapterCount) {
                    return mAdapter.isEnabled(adjPosition);
                }
            }
            throw new ArrayIndexOutOfBoundsException(position);
        }
        @Override
        public Object getItem(int position) {
            // Header (negative positions will throw an ArrayIndexOutOfBoundsException)
            int numHeadersAndPlaceholders = getHeadersCount() * mNumColumns;
            if (position < numHeadersAndPlaceholders) {
                if (position % mNumColumns == 0) {
                    return mHeaderViewInfos.get(position / mNumColumns).data;
                }
                return null;
            }
            // Adapter
            final int adjPosition = position - numHeadersAndPlaceholders;
            int adapterCount = 0;
            if (mAdapter != null) {
                adapterCount = mAdapter.getCount();
                if (adjPosition < adapterCount) {
                    return mAdapter.getItem(adjPosition);
                }
            }
            throw new ArrayIndexOutOfBoundsException(position);
        }
        @Override
        public long getItemId(int position) {
            int numHeadersAndPlaceholders = getHeadersCount() * mNumColumns;
            if (mAdapter != null && position >= numHeadersAndPlaceholders) {
                int adjPosition = position - numHeadersAndPlaceholders;
                int adapterCount = mAdapter.getCount();
                if (adjPosition < adapterCount) {
                    return mAdapter.getItemId(adjPosition);
                }
            }
            return -1;
        }
        @Override
        public boolean hasStableIds() {
            if (mAdapter != null) {
                return mAdapter.hasStableIds();
            }
            return false;
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            // Header (negative positions will throw an ArrayIndexOutOfBoundsException)
            int numHeadersAndPlaceholders = getHeadersCount() * mNumColumns ;
            if (position < numHeadersAndPlaceholders) {
                View headerViewContainer = mHeaderViewInfos
                        .get(position / mNumColumns).viewContainer;
                if (position % mNumColumns == 0) {
                    return headerViewContainer;
                } else {
                    if (convertView == null) {
                        convertView = new View(parent.getContext());
                    }
                    // We need to do this because GridView uses the height of the last item
                    // in a row to determine the height for the entire row.
                    convertView.setVisibility(View.INVISIBLE);
                    convertView.setMinimumHeight(headerViewContainer.getHeight());
                    return convertView;
                }
            }
            // Adapter
            final int adjPosition = position - numHeadersAndPlaceholders;
            int adapterCount = 0;
            if (mAdapter != null) {
                adapterCount = mAdapter.getCount();
                if (adjPosition < adapterCount) {
                    return mAdapter.getView(adjPosition, convertView, parent);
                }
            }
            throw new ArrayIndexOutOfBoundsException(position);
        }
        @Override
        public int getItemViewType(int position) {
            int numHeadersAndPlaceholders = getHeadersCount() * mNumColumns;
            if (position < numHeadersAndPlaceholders && (position % mNumColumns != 0)) {
                // Placeholders get the last view type number
                return mAdapter != null ? mAdapter.getViewTypeCount() : 1;
            }
            if (mAdapter != null && position >= numHeadersAndPlaceholders) {
                int adjPosition = position - numHeadersAndPlaceholders;
                int adapterCount = mAdapter.getCount();
                if (adjPosition < adapterCount) {
                    return mAdapter.getItemViewType(adjPosition);
                }
            }
            return AdapterView.ITEM_VIEW_TYPE_HEADER_OR_FOOTER;
        }
        @Override
        public int getViewTypeCount() {
            if (mAdapter != null) {
                return mAdapter.getViewTypeCount() + 1;
            }
            return 2;
        }
        @Override
        public void registerDataSetObserver(DataSetObserver observer) {
            mDataSetObservable.registerObserver(observer);
            if (mAdapter != null) {
                mAdapter.registerDataSetObserver(observer);
            }
        }
        @Override
        public void unregisterDataSetObserver(DataSetObserver observer) {
            mDataSetObservable.unregisterObserver(observer);
            if (mAdapter != null) {
                mAdapter.unregisterDataSetObserver(observer);
            }
        }
        @Override
        public Filter getFilter() {
            if (mIsFilterable) {
                return ((Filterable) mAdapter).getFilter();
            }
            return null;
        }
        @Override
        public ListAdapter getWrappedAdapter() {
            return mAdapter;
        }
        public void notifyDataSetChanged() {
            mDataSetObservable.notifyChanged();
        }
    }
}

代码地址：https://android.googlesource.com/platform/packages/apps/Gallery2/+/idea133/src/com/android/photos/