2014.03.07 ——— android GridView 记录和恢复位置

2014.03.07 ——— android GridView 记录和恢复位置

关于listview的记录和恢复数据 参见 http://trylovecatch.iteye.com/blog/2002254

listview 里面 我们主要用了 setSelectionFromTop方法 来实现精确的恢复数据

但是 gridview里面没有这个方法 所以要实现这个方法就很费劲，下面是我的大概实现过程

1、setSelection
这个是可以的 但是就是不够精确

mGridView.setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                
                if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {   
                    mPosition = mGridView.getFirstVisiblePosition();
                } 
                
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            }
        });

mGridView.setSelection(mPosition);

2、用gridview里面提供的api

smoothScrollBy
smoothScrollByOffset
smoothScrollToPositionFromTop

前两个我试了，都没有反应 第三个是可以的，但是如果GridView处于底部 好像就不管用了

mGridView.setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                
                if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {   
                    mPosition = mGridView.getFirstVisiblePosition();
                    View v = mGridView.getChildAt(0);
                    mPositionTop = (v == null) ? 0 : v.getTop();
                    if(mItemHeight <= 0){
                        mItemHeight = v.getHeight();
                    }
                    System.out.println("position: " + mPosition + ", top: " + mPositionTop + ", mItemHeight: " + mItemHeight);
                } 
                
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            }
        });
    }

mGridView.smoothScrollToPositionFromTop(mPosition , mPositionTop);

3、使用scrollTo
这个也是可以实现滚动的，但是每次都会调用 onScrollChanged（int,int ,int,int）方法，视图被视为无效，然后位置是恢复了，但是gridview下面是空白的 只显示position的那一两行

mGridView.setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
 
                if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {   
                    mPosition = mGridView.getFirstVisiblePosition() / 3;
                    View v = mGridView.getChildAt(0);
                    mPositionTop = (v == null) ? 0 : v.getTop();
                    if(mItemHeight <= 0){
                        mItemHeight = v.getHeight();
                    }
                    System.out.println("position: " + mPosition + ", top: " + mPositionTop + ", mItemHeight: " + mItemHeight);
                } 
                
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            }
        });

 mGridView.scrollTo(0, mPosition * mItemHeight + Math.abs(mPositionTop) + mPosition * 10 * 2);

4、嵌套ScrollView
通过3证明了scrollto是可以实现恢复position，所以我想可以再Gridview 外面套一层ScrollView，用它来控制GridView的显示，关于嵌套 参考 http://trylovecatch.iteye.com/blog/2002254

4.1、自定义GridView

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

    public MyGridView(Context context, android.util.AttributeSet attrs) {
        super(context, attrs);
    }

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

4.2、布局文件

<ScrollView
	    android:layout_width="fill_parent"
	    android:layout_height="match_parent"
	    android:fillViewport="true"
	    android:id="@+id/local_scroll_view" 
	    >
	    
	
    <com.test.MyGridView
        android:id="@+id/local_grid_view"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:layout_marginTop="10dp"
        android:cacheColorHint="#ffffff"
        android:clipToPadding="false"
        android:columnWidth="100dip"
        android:divider="@android:color/transparent"
        android:dividerHeight="10dp"
        android:fadingEdge="none"
        android:listSelector="@android:color/transparent"
        android:numColumns="3"
        android:paddingLeft="@dimen/download_layout_horizontal_margin"
        android:paddingRight="@dimen/download_layout_horizontal_margin"
        android:scrollbars="vertical"
        android:scrollbarStyle="outsideOverlay" />
	</ScrollView>

4.3、记录和恢复
 

  @Override
    public void onPause() {
        super.onPause();
        mScrollY = mScroll.getScrollY();
        System.out.println("mScrollY: " + mScrollY);
    }

             

mScroll.postDelayed(new Runnable() {
                                
                                @Override
                                public void run() {
                                    mScroll.scrollTo(0, mScrollY);
                                }
                            }, 200);

大功告成，^_^