我已经成功实现了一个自定义滚动视图组，可以使用手势在我的不同片段之间滑动。但我想有时禁用刷到下一个片段，同时仍然允许返回到前一个片段。我怎么能根据代码做到这一点？非常感谢你。
我已经创建了一个布尔值来表示这个名称为“allowNext”
import java.util.Vector;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;
public class HorizontalScrollInViewGroup extends ViewGroup {
private boolean allowNext = true;
private Scroller mScroller;
private VelocityTracker mVelocityTracker;
private int mCurScreen;
private int mDefaultScreen = 0;
private static final int TOUCH_STATE_REST = 0;
private static final int TOUCH_STATE_SCROLLING = 1;
private static final int SNAP_VELOCITY = 500;
private int mTouchState = TOUCH_STATE_REST;
private int mTouchSlop;
private float mLastMotionX;
private int sensitivity = 30;
private boolean spring;
private Vector<HorizontalScrollInViewGroupListener> listeners;
//used for the screen changed listener
private OnScreenChangedListener screenChangedCallBack;
public HorizontalScrollInViewGroup(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
mScroller = new Scroller(context);
setCurScreen(mDefaultScreen);
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
listeners = new Vector<HorizontalScrollInViewGroupListener>();
//initiate the screen change listener
screenChangedCallBack = (OnScreenChangedListener)context;
}
// An interface that tells the activity the screen is switched
public interface OnScreenChangedListener {
public void onScreenChanged(int currentScreen);
}
/* (non-Javadoc)
* @see android.view.ViewGroup#onLayout(boolean, int, int, int, int)
*/
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
// TODO Auto-generated method stub
int childLeft = 0;
final int childCount = getChildCount();
for (int i = 0; i < childCount; i++) {
final View childView = getChildAt(i);
if (childView.getVisibility() != View.GONE) {
final int childWidth = childView.getMeasuredWidth();
childView.layout(childLeft, 0, childLeft + childWidth,
childView.getMeasuredHeight());
childLeft += childWidth;
}
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
final int width = MeasureSpec.getSize(widthMeasureSpec);
final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
if (widthMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException(
"HorizontalScrollInViewGroup only canmCurScreen run at EXACTLY mode!");
}
final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (heightMode != MeasureSpec.EXACTLY) {
throw new IllegalStateException(
"HorizontalScrollInViewGroup only can run at EXACTLY mode!");
}
// The children are given the same width and height as the scrollLayout
final int count = getChildCount();
for (int i = 0; i < count; i++) {
getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
}
scrollTo(getCurScreen() * width, 0);
}
@Override
public void computeScroll() {
// TODO Auto-generated method stub
if (mScroller.computeScrollOffset()) {
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
postInvalidate();
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
if (mVelocityTracker == null)
mVelocityTracker = VelocityTracker.obtain();
mVelocityTracker.addMovement(event);
final int action = event.getAction();
final float x = event.getX();
switch (action) {
case MotionEvent.ACTION_DOWN:
if (!mScroller.isFinished())
mScroller.abortAnimation();
mLastMotionX = x;
break;
case MotionEvent.ACTION_MOVE:
int deltaX = (int) (mLastMotionX - x);
if (Math.abs(deltaX) > sensitivity) {
if (spring) {
scrollBy(deltaX, 0);
mLastMotionX = x;
} else {
final int childCount = getChildCount();
boolean max = getCurScreen() < childCount - 1;
boolean min = getCurScreen() > 0;
boolean canMove = deltaX > 0 ? (max ? true : false)
: (min ? true : false);
if (canMove) {
scrollBy(deltaX, 0);
mLastMotionX = x;
}
}
}
break;
case MotionEvent.ACTION_UP:
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000);
int velocityX = (int) velocityTracker.getXVelocity();
if (velocityX > SNAP_VELOCITY && getCurScreen() > 0) {
// Fling enough to move left
snapToScreen(getCurScreen() - 1);
} else if (velocityX < -SNAP_VELOCITY && getCurScreen() < getChildCount() - 1) {
// Fling enough to move right
snapToScreen(getCurScreen() + 1);
} else {
snapToDestination();
}
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
mTouchState = TOUCH_STATE_REST;
break;
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
break;
}
return true;
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
// TODO Auto-generated method stub
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE)
&& (mTouchState != TOUCH_STATE_REST))
return true;
final float x = ev.getX();
switch (action) {
case MotionEvent.ACTION_MOVE:
final int xDiff = (int) Math.abs(mLastMotionX - x);
if (xDiff > mTouchSlop)
mTouchState = TOUCH_STATE_SCROLLING;
break;
case MotionEvent.ACTION_DOWN:
mLastMotionX = x;
mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
: TOUCH_STATE_SCROLLING;
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
mTouchState = TOUCH_STATE_REST;
break;
}
return mTouchState != TOUCH_STATE_REST;
}
public void snapToDestination() {
final int screenWidth = getWidth();
final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
snapToScreen(destScreen);
//call back to let the activity know the current screen
screenChangedCallBack.onScreenChanged(getCurScreen());
}
public void snapToScreen(int whichScreen) {
// get the valid layout page
int lastIndex = getCurScreen();
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
if (getScrollX() != (whichScreen * getWidth())) {
final int delta = whichScreen * getWidth() - getScrollX();
mScroller.startScroll(getScrollX(), 0, delta, 0,
Math.abs(delta) * 2);
setCurScreen(whichScreen);
invalidate(); // Redraw the layout
}
for (HorizontalScrollInViewGroupListener listener : listeners)
listener.turnPage(lastIndex, whichScreen);
//call back to let the activity know the current screen
screenChangedCallBack.onScreenChanged(getCurScreen());
}
public void setToScreen(int whichScreen) {
whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
setCurScreen(whichScreen);
scrollTo(whichScreen * getWidth(), 0);
//call back to let the activity know the current screen
screenChangedCallBack.onScreenChanged(getCurScreen());
}
public int getCurScreen() {
return mCurScreen;
}
public void setCurScreen(int mCurScreen) {
this.mCurScreen = mCurScreen;
}
public boolean isAllowNext() {
return allowNext;
}
public void setAllowNext(boolean allowNext) {
this.allowNext = allowNext;
}
}