android上下滑動View的實現

先放上這個自定義的View的代碼，

package com.example.viewpagervertical;

import android.content.Context;

import android.util.AttributeSet;

import android.util.Log;

import android.view.MotionEvent;

import android.view.VelocityTracker;

import android.view.View;

import android.view.ViewGroup;

import android.view.animation.Interpolator;

import android.widget.Scroller;

import android.widget.Toast;

/**

 * 實現這個上下滑動的效果，主要利用了屏幕座標系和滾動條

 * @author Administrator

 *

 */

public class VerticalPager extends ViewGroup{

private Scroller mScroller;  //滾動條

private Context mContext;

private final static int RATE = 5; //速率標準

private final static int DISTANCE = 300;//須要滾動的距離

private VelocityTracker mVelocityTracker;//經過此類能夠計算速度

public VerticalPager(Context context, AttributeSet attrs) {

super(context, attrs);

this.mContext=context;

mScroller=new Scroller(context);

}

@Override

protected void onLayout(boolean changed, int l, int t, int r, int b) {

int totalHeight=0;

int count=getChildCount();

for(int i=0;i<count;i++){

View childView=getChildAt(i);

childView.layout(l, totalHeight, r, totalHeight+b);

totalHeight+=b;

}

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

int width=MeasureSpec.getSize(widthMeasureSpec);

int height=MeasureSpec.getSize(heightMeasureSpec);

int count=getChildCount();

for(int i=0;i<count;i++){

getChildAt(i).measure(width, height);

}

setMeasuredDimension(width, height);

}

private int mLastMotionY;

@Override

public boolean onTouchEvent(MotionEvent event) {

if(mVelocityTracker==null){

mVelocityTracker=VelocityTracker.obtain();

}

mVelocityTracker.addMovement(event);

int action=event.getAction();

float y=event.getY();

switch(action){

case MotionEvent.ACTION_DOWN:

if(!mScroller.isFinished()){

mScroller.abortAnimation();

}

mLastMotionY=(int) y;

Log.d("montion", ""+getScrollY());

break;

case MotionEvent.ACTION_MOVE:

int deltaY=(int) (mLastMotionY-y);

scrollBy(0,deltaY);

invalidate();

mLastMotionY=(int) y;

break;

case MotionEvent.ACTION_UP:

// if(mVelocityTracker!=null){

// mVelocityTracker.recycle();

// mVelocityTracker=null;

// }

mVelocityTracker.computeCurrentVelocity(1, 1000); //單位爲1說明，一秒一個像素，最大值爲1000

float vy = mVelocityTracker.getYVelocity();  //vy表明Y軸方向的速率

Log.i("test","velocityTraker : "+mVelocityTracker.getYVelocity());     

if(getScrollY()<0){

mScroller.startScroll(0, -DISTANCE, 0, DISTANCE);

}else if(getScrollY()>(getHeight()*(getChildCount()-1))){

View lastView=getChildAt(getChildCount()-1);

mScroller.startScroll(0,lastView.getTop()+DISTANCE, 0, -DISTANCE);

}else{

int position=getScrollY()/getHeight();

View positionView = null;

if(vy<-RATE){  //下滑

positionView=getChildAt(position+1);

mScroller.startScroll(0, positionView.getTop()-DISTANCE, 0, +DISTANCE);

}else if(vy>RATE){//上滑

positionView=getChildAt(position);

mScroller.startScroll(0, positionView.getTop()-DISTANCE, 0, +DISTANCE);

}else {

int mod=getScrollY()%getHeight();

if(mod>getHeight()/2){

positionView=getChildAt(position+1);

mScroller.startScroll(0, positionView.getTop()-DISTANCE, 0, +DISTANCE);

}else{

positionView=getChildAt(position);

mScroller.startScroll(0, positionView.getTop()+DISTANCE, 0, -DISTANCE);

}

}

}

invalidate();

break;

}

return true; //返回true表示事件由本View消費掉

}

@Override

public void computeScroll() {

super.computeScroll();

if(mScroller.computeScrollOffset()){

scrollTo(0, mScroller.getCurrY());

}

}

}

而後是佈局文件activity_main.xml:

<?xml version="1.0" encoding="UTF-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <com.example.viewpagervertical.VerticalPager

        android:id="@+id/vertyPager1"

        android:layout_width="fill_parent"

        android:layout_height="fill_parent" >

        <TextView

            android:background="@drawable/iv_guide1"

            android:id="@+id/textView1"

            android:layout_width="match_parent"

            android:layout_height="100dp"

            android:text="TextView1111" />

        <TextView

             android:background="@drawable/iv_guide2"

            android:id="@+id/textView2"

            android:layout_width="fill_parent"

            android:layout_height="100dp"

            android:text="TextView2222" />

         <TextView

             android:background="@drawable/iv_guide3"

            android:id="@+id/textView3"

            android:layout_width="fill_parent"

            android:layout_height="100dp"

            android:text="TextView2222" />

          <TextView

             android:background="@drawable/iv_guide4"

            android:id="@+id/textView4"

            android:layout_width="fill_parent"

            android:layout_height="100dp"

            android:text="TextView2222" />

    </com.example.viewpagervertical.VerticalPager>

</LinearLayout>

MainActivity.java不用動，由eclipse建立的就行。