Android重写ViewPager修改滑动灵敏度

使用ViewPager作为一个页面进行切换，里面可以存放很多View，但有时在操作View时不小心滑动一下就有可能跳到下一页，这并不是我们想要的，这里就需要重写ViewPager修改它的滑动条件

效果图



程序目录结构



BTViewPager.java

package com.example.viewpagerdemo;

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.widget.Scroller;

/**
 * 解决ViewPager滑动过于灵敏，只有滑动距离大于100才滑到另一页
 * 
 * @author Administrator
 * 
 */
public class BTViewPager extends ViewPager {

	private static final String TAG = "dzt_pager";
	private static final int MOVE_LIMITATION = 100;// 触发移动的像素距离
	private float mLastMotionX; // 手指触碰屏幕的最后一次x坐标
	private int mCurScreen;

	private Scroller mScroller; // 滑动控件

	public BTViewPager(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
		init(context);
	}

	public BTViewPager(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		init(context);
	}

	private void init(Context context) {
		mScroller = new Scroller(context);
		mCurScreen = 0;// 默认设置显示第一个VIEW
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// TODO Auto-generated method stub

		final int action = event.getAction();
		final float x = event.getX();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			Log.d(TAG, "[BTViewPager->]onTouchEvent ACTION_DOWN");
			mLastMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			Log.d(TAG, "[BTViewPager->]onTouchEvent ACTION_MOVE");
			break;
		case MotionEvent.ACTION_UP:
			Log.d(TAG, "Item = " + getCurrentItem() + " count = "
					+ getChildCount());

			if (Math.abs(x - mLastMotionX) < MOVE_LIMITATION) {
				// snapToDestination(); // 跳到指定页
				snapToScreen(getCurrentItem());
				return true;
			}
			break;
		default:
			break;
		}
		Log.d(TAG, "[BTViewPager->]onTouchEvent--end");
		return super.onTouchEvent(event);
	}

	@Override
	public void computeScroll() {
		// TODO Auto-generated method stub
		Log.d(TAG, "[BTViewPager->]computeScroll");
		super.computeScroll();

		if (mScroller.computeScrollOffset()) {
			Log.d(TAG,
					"[BTViewPager->]computeScroll x = " + mScroller.getCurrX());
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			invalidate();
		}

	}

	/**
	 * 根据滑动的距离判断移动到第几个视图
	 */
	public void snapToDestination() {
		final int screenWidth = getWidth();
		final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
		Log.d(TAG, "[BTViewPager->]snapToDestination screenWidth = "
				+ screenWidth + " destScreen = " + destScreen);
		snapToScreen(destScreen);
	}

	/**
	 * 滚动到制定的视图
	 * 
	 * @param whichScreen
	 *            视图下标
	 */
	public void snapToScreen(int whichScreen) {
		// whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() -
		// 1));
		if (getScrollX() != (whichScreen * getWidth())) {

			final int delta = whichScreen * getWidth() - getScrollX();
			Log.d(TAG, "[BTViewPager->]snapToScreen-whichScreen = "
					+ whichScreen + " delta = " + delta + " scrollX = "
					+ getScrollX());
			mScroller.startScroll(getScrollX(), 0, delta, 0,
					Math.abs(delta) * 2);
			mCurScreen = whichScreen;
			invalidate();
		}
	}

	/**
	 * 用于拦截手势事件的，每个手势事件都会先调用这个方法。Layout里的onInterceptTouchEvent默认返回值是false,
	 * 这样touch事件会传递到childview控件 ，如果返回false子控件可以响应，否则了控件不响应，这里主要是拦截子控件的响应，
	 * 对ViewGroup不管返回值是什么都会执行onTouchEvent
	 */
	@Override
	public boolean onInterceptTouchEvent(MotionEvent arg0) {
		// TODO Auto-generated method stub
		Log.d(TAG, "[BTViewPager->]onInterceptTouchEvent");
		final int action = arg0.getAction();
		final float x = arg0.getX();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			Log.d(TAG, "onInterceptTouchEvent---ACTION_DOWN ");
			mLastMotionX = x;
			break;
		case MotionEvent.ACTION_MOVE:
			Log.d(TAG, "onInterceptTouchEvent---ACTION_MOVE ");
			break;
		case MotionEvent.ACTION_UP:
			Log.d(TAG, "onInterceptTouchEvent---ACTION_UP ");
			break;
		default:
			break;
		}
		return super.onInterceptTouchEvent(arg0);
	}
}

只要是在onTouchEvent的UP中处理滑动的条件

if (Math.abs(x - mLastMotionX) < MOVE_LIMITATION) {
				// snapToDestination(); // 跳到指定页
				snapToScreen(getCurrentItem());
				return true;
			}

只有滑动的距离大于100才进行上下页处理，否则就停在当前页，当前页使用getCurrentItem()获取，有一点要注意在ViewPager中getChildCount()获取的值是错误的，不清楚是什么原因，在ViewGroup中是有效的，这个可能要查看ViewPager源码才能弄清楚是什么原因，有知道的朋友可以告知我！

完整Demo：http://download.csdn.net/detail/deng0zhaotai/7384637