自定義上滑菜單SlidingUpMenu

受了張鴻洋大神這篇博文的啓發：http://blog.csdn.net/lmj623565791/article/details/39257409

截圖效果如下(由於截圖是白底的所以看起來怪怪的)：

                                                             

這個效果是舊版的多看閱讀裏面的效果，即上拉的時候會跟隨手指出現一個菜單，當手指離開屏幕的時候，如果手指滑動的距離大於菜單高度的一半就會滑上去，否則滑下去

代碼如下：

package com.jsbtclient.view;

import com.jsbt.R;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.LinearLayout;
import android.widget.ScrollView;

public class SlidingUpMenu extends ScrollView {

	/**
	 * 屏幕高度
	 */
	private int mScreenHeight;

	/**
	 * 菜單高度
	 */
	private int mBottomMenuHeight;

	/**
	 * 菜單高度/2
	 */
	private int halfBottomMenuHeight;

	/**
	 * 菜單高度 = 屏幕高度 - Padding值
	 * 下面就會看到
	 */
	private int mBottomMenuTopPadding;

	/**
	 * menu
	 */
	View mBottomMenu; 

	View mContent;

	private boolean isBottomOpen = false;

	public SlidingUpMenu(Context context) {
		this(context, null);
	}

	public SlidingUpMenu(Context context, AttributeSet attrs) {
		this(context, attrs, 0);
	}

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

		/**
		 * 獲取屏幕高度
		 */
		mScreenHeight = getScreenHeight();

		TypedArray array = context.getTheme().obtainStyledAttributes(attrs,
				R.styleable.SlidingUpMenu, defStyle, 0);

		int num = array.getIndexCount();

		for (int i = 0; i < num; i++) {
			int attr = array.getIndex(i);
			
			/**
			 * 獲取用戶設置的topPadding
			 * 如果topPadding = 100dp， 則bottomMenu的高度 = ScreenHeight - 100dp對應的px值
			 * 
			 */
			switch (attr) {
			case R.styleable.SlidingUpMenu_topPadding:
				mBottomMenuTopPadding = array.getDimensionPixelSize(attr,
						(int) TypedValue.applyDimension(
								TypedValue.COMPLEX_UNIT_DIP, 50f,
								getResources().getDisplayMetrics()));
				break;

			default:
				break;
			}
		}
	}

	public int getScreenHeight() {
		WindowManager wm = (WindowManager) getContext().getSystemService(
				Context.WINDOW_SERVICE);
		DisplayMetrics outMetrics = new DisplayMetrics();
		wm.getDefaultDisplay().getMetrics(outMetrics);
		return outMetrics.heightPixels;
	}

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

		LinearLayout wrapper = (LinearLayout) getChildAt(0);
		mContent = (View) wrapper.getChildAt(0);
		mBottomMenu = (View) wrapper.getChildAt(1);
		mBottomMenuHeight = mScreenHeight - mBottomMenuTopPadding;
		mBottomMenu.getLayoutParams().height = mBottomMenuHeight;//重置底部菜單的高度
		halfBottomMenuHeight = mBottomMenuHeight / 2;
		mContent.getLayoutParams().height = mScreenHeight;//設置內容區的高度始終等於屏幕高度

		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) 
		{
		case MotionEvent.ACTION_UP:
			int scrolly = getScrollY();

			if (scrolly > halfBottomMenuHeight) 
			{
				smoothScrollTo(0, mBottomMenuHeight);
				isBottomOpen = true;

			} else {
				smoothScrollTo(0, 0);
				isBottomOpen = false;
			}
			return true;

		default:
			break;
		}
		return super.onTouchEvent(ev);
	}

	public boolean isBottomOpen() {
		return isBottomOpen;
	}

	public void openBottomMenu() {
		if (!isBottomOpen) {
			smoothScrollTo(0, mBottomMenuHeight);
			isBottomOpen = true;
		}
	}

	public void closeBottomMenu() {
		if (isBottomOpen) {
			smoothScrollTo(0, 0);
			isBottomOpen = false;
		}
	}

	public void toggleBottomMenu() {
		if (isBottomOpen) {
			closeBottomMenu();
		} else {
			openBottomMenu();
		}
	}
}