无限滑动切换View

 import android.content.Context;
 
 
import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.view.View;
 import android.widget.Scroller;
 
 
public class SView extends View {
 protected Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);
 private Scroller mScroller;
 private int index;//坐标
 private int criticalWidth;//
 private int width, height;
 private int lastPointX, lastPointY;
 private int lastMoveX, lastMoveY;
 private boolean isEvent;
 
 
public SView(Context context) {
 this(context, null);
 }
 
 
public SView(Context context, AttributeSet attrs) {
 this(context, attrs, 0);
 }
 
 
public SView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 mScroller = new Scroller(context);
 mPaint.setTextAlign(Paint.Align.CENTER);
 }
 
 
@Override
 public void computeScroll() {
 if (mScroller.computeScrollOffset()) {
 scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
 invalidate();
 } else {
 requestLayout();
 }
 }
 
 
@Override
 
 
public boolean onTouchEvent(MotionEvent event) {
 switch (event.getAction()) {
 case MotionEvent.ACTION_DOWN:
 mScroller.forceFinished(true);
 isEvent = false;
 lastPointX = (int) event.getX();
 lastPointY = (int) event.getY();
 break;
 case MotionEvent.ACTION_MOVE:
 if (Math.abs(lastPointX - event.getX()) > 100) {
 isEvent = true;
 }
 if (isEvent) {
 int totalMoveX = (int) (lastPointX - event.getX()) + lastMoveX;
 smoothScrollTo(totalMoveX);
 }
 break;
 case MotionEvent.ACTION_UP:
 if (isEvent) {
 if (Math.abs(lastPointX - event.getX()) > 25) {
 if (lastPointX > event.getX() &&
 Math.abs(lastPointX - event.getX()) >= criticalWidth) {
 index++;
 } else if (lastPointX < event.getX() &&
 Math.abs(lastPointX - event.getX()) >= criticalWidth) {
 index--;
 }
 smoothScrollTo(width * index);
 lastMoveX = width * index;
 }
 }
 break;
 }
 return true;
 }
 
 
@Override
 protected void onSizeChanged(int w, int h, int oldW, int oldH) {
 width = w;
 height = h;
 criticalWidth = (int) (1F / 5F * width);
 }
 
 
@Override
 protected void onDraw(Canvas canvas) {
 //根据坐标画左右和中间的视图
 draw(canvas, width * (index - 1));
 draw(canvas, width * index);
 draw(canvas, width * (index + 1));
 }
 
 
private void draw(Canvas canvas, int x) {
 canvas.save();
 canvas.translate(x, 0);
 canvas.drawCircle(width / 2, height / 2, 20, mPaint);
 canvas.restore();
 }
 
 
private void smoothScrollTo(int fx) {
 int dx = fx - mScroller.getFinalX();
 int dy = -mScroller.getFinalY();
 smoothScrollBy(dx, dy);
 }
 
 
private void smoothScrollBy(int dx, int dy) {
 mScroller.startScroll(mScroller.getFinalX(), mScroller.getFinalY(), dx, dy, 500);
 invalidate();
 }
 }