学步园

/*
 * Copyright 2013 Lars Werkman
 *
 * 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.
 */



import java.util.ArrayList;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ListView;

public class QuickReturnListView extends ListView {

	private int mItemCount;
	private ArrayList<Integer> mItemsHeight;
	private boolean scrollIsComputed = false;
	private int mHeight;

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

	public QuickReturnListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
	}
	
	private void init(){
		mItemsHeight = new ArrayList<Integer>();
	}

	public int getListHeight() {
		return mHeight;
	}
	
	public void setComputed(boolean isComputed){
		scrollIsComputed = isComputed;
	}

	public void computeScrollY() {
		mHeight = 0;
		mItemCount = getAdapter().
				getCount();

		for (int i = 0; i < mItemCount; ++i) {
			if(mItemsHeight.size() <= i || mItemsHeight.get(i) == null){
				View view = getAdapter().getView(i, null, this);
				view.measure(
						MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
						MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
				mItemsHeight.add(i, Integer.valueOf(view.getMeasuredHeight()));
			}
		}
		scrollIsComputed = true;
	}

	public boolean scrollYIsComputed() {
		return scrollIsComputed;
	}

	public int getComputedScrollY() {
		int pos, nScrollY, nItemY;
		View view = null;
		pos = getFirstVisiblePosition();
		view = getChildAt(0);
		nItemY = view.getTop();
		int totalOffset = 0;
		for(int i = 0 ; i< pos ;i++){
			totalOffset += mItemsHeight.get(i);
		}
		nScrollY = totalOffset - nItemY;
		return nScrollY;
	}
}