android中的左右滑动
iphone中有很多应用都能够左右滑动，非常cool，关键是实现起来非常简单。android比起来就差远了，网上有不少帖子。 我在这边重新分享下自己的经验吧，将实现细节详细解释下。
FlingGallery这个类摘自网上，有少许修改。
package com.nuomi.ui;
import java.util.HashSet;
import java.util.Set;
import android.content.Context;
import android.view.GestureDetector;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
import android.view.animation.Transformation;
import android.widget.Adapter;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
public class FlingGallery extends FrameLayout
{
private Set<OnGalleryChangeListener> listeners;
private final int swipe_min_distance = 120;
private final int swipe_max_off_path = 250;
private final int swipe_threshold_veloicty = 400;
private int mViewPaddingWidth = 0;
private int mAnimationDuration = 250;
private float mSnapBorderRatio = 0.5f;
private boolean mIsGalleryCircular = true;
private int mGalleryWidth = 0;
private boolean mIsTouched = false;
private boolean mIsDragging = false;
private float mCurrentOffset = 0.0f;
private long mScrollTimestamp = 0;
private int mFlingDirection = 0;
private int mCurrentPosition = 0;
private int mCurrentViewNumber = 0;
private Context mContext;
private Adapter mAdapter;
private FlingGalleryView[] mViews;
private FlingGalleryAnimation mAnimation;
private GestureDetector mGestureDetector;
private Interpolator mDecelerateInterpolater;
public FlingGallery(Context context)
{
super(context);
listeners = new HashSet<OnGalleryChangeListener>();
mContext = context;
mAdapter = null;
mViews = new FlingGalleryView[3];
mViews[0] = new FlingGalleryView(0, this);
mViews[1] = new FlingGalleryView(1, this);
mViews[2] = new FlingGalleryView(2, this);
mAnimation = new FlingGalleryAnimation();
mGestureDetector = new GestureDetector(new FlingGestureDetector());
mDecelerateInterpolater = AnimationUtils.loadInterpolator(mContext, android.R.anim.decelerate_interpolator);
}
public void addGalleryChangeListener(OnGalleryChangeListener listener){
listeners.add(listener);
}
public void setPaddingWidth(int viewPaddingWidth)
{
mViewPaddingWidth = viewPaddingWidth;
}
public void setAnimationDuration(int animationDuration)
{
mAnimationDuration = animationDuration;
}
public void setSnapBorderRatio(float snapBorderRatio)
{
mSnapBorderRatio = snapBorderRatio;
}
public void setIsGalleryCircular(boolean isGalleryCircular)
{
if (mIsGalleryCircular != isGalleryCircular)
{
mIsGalleryCircular = isGalleryCircular;
if (mCurrentPosition == getFirstPosition())
{
// We need to reload the view immediately to the left to change it to circular view or blank
mViews[getPrevViewNumber(mCurrentViewNumber)].recycleView(getPrevPosition(mCurrentPosition));
}
if (mCurrentPosition == getLastPosition())
{
// We need to reload the view immediately to the right to change it to circular view or blank
mViews[getNextViewNumber(mCurrentViewNumber)].recycleView(getNextPosition(mCurrentPosition));
}
}
}
public int getGalleryCount()
{
return (mAdapter == null) ? 0 : mAdapter.getCount();
}
public int getFirstPosition()
{
return 0;
}
public int getLastPosition()
{
return (getGalleryCount() == 0) ? 0 : getGalleryCount() - 1;
}
private int getPrevPosition(int relativePosition)
{
int prevPosition = relativePosition - 1;
if (prevPosition < getFirstPosition())
{
prevPosition = getFirstPosition() - 1;
if (mIsGalleryCircular == true)
{
prevPosition = getLastPosition();
}
}
NotifyGalleryChange();
return prevPosition;
}
private int getNextPosition(int relativePosition)
{
int nextPosition = relativePosition + 1;
if (nextPosition > getLastPosition())
{
nextPosition = getLastPosition() + 1;
if (mIsGalleryCircular == true)
{
nextPosition = getFirstPosition();
}
}
NotifyGalleryChange();
return nextPosition;
}
//
private void NotifyGalleryChange() {
for (OnGalleryChangeListener listener :listeners) {
listener.onGalleryChange(mCurrentPosition);
}
}
private int getPrevViewNumber(int relativeViewNumber)
{
return (relativeViewNumber == 0) ? 2 : relativeViewNumber - 1;
}
private int getNextViewNumber(int relativeViewNumber)
{
return (relativeViewNumber == 2) ? 0 : relativeViewNumber + 1;
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom)
{
super.onLayout(changed, left, top, right, bottom);
// Calculate our view width
mGalleryWidth = right - left;
if (changed)
{
// Position views at correct starting offsets
mViews[0].setOffset(0, 0, mCurrentViewNumber);
mViews[1].setOffset(0, 0, mCurrentViewNumber);
mViews[2].setOffset(0, 0, mCurrentViewNumber);
}
}
public void setAdapter(Adapter adapter)
{
mAdapter = adapter;
mCurrentPosition = 0;
mCurrentViewNumber = 0;
// Load the initial views from adapter
mViews[0].recycleView(mCurrentPosition);
mViews[1].recycleView(getNextPosition(mCurrentPosition));
mViews[2].recycleView(getPrevPosition(mCurrentPosition));
// Position views at correct starting offsets
mViews[0].setOffset(0, 0, mCurrentViewNumber);
mViews[1].setOffset(0, 0, mCurrentViewNumber);
mViews[2].setOffset(0, 0, mCurrentViewNumber);
}
private int getViewOffset(int viewNumber, int relativeViewNumber)
{
// Determine width including configured padding width
int offsetWidth = mGalleryWidth + mViewPaddingWidth;
// Position the previous view one measured width to left
if (viewNumber == getPrevViewNumber(relativeViewNumber))
{
return offsetWidth;
}
// Position the next view one measured width to the right
if (viewNumber == getNextViewNumber(relativeViewNumber))
{
return offsetWidth * -1;
}
return 0;
}
void movePrevious()
{
// Slide to previous view
mFlingDirection = 1;
processGesture();
}
void moveNext()
{
// Slide to next view
mFlingDirection = -1;
processGesture();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
switch (keyCode)
{
case KeyEvent.KEYCODE_DPAD_LEFT:
movePrevious();
return true;
case KeyEvent.KEYCODE_DPAD_RIGHT:
moveNext();
return true;
case KeyEvent.KEYCODE_DPAD_CENTER:
case KeyEvent.KEYCODE_ENTER:
}
return super.onKeyDown(keyCode, event);
}
public boolean onGalleryTouchEvent(MotionEvent event)
{
boolean consumed = mGestureDetector.onTouchEvent(event);
if (event.getAction() == MotionEvent.ACTION_UP)
{
if (mIsTouched || mIsDragging)
{
processScrollSnap();
processGesture();
}
}
return consumed;
}
void processGesture()
{
int newViewNumber = mCurrentViewNumber;
int reloadViewNumber = 0;
int reloadPosition = 0;
mIsTouched = false;
mIsDragging = false;
if (mFlingDirection > 0)
{
if (mCurrentPosition > getFirstPosition() || mIsGalleryCircular == true)
{
// Determine previous view and outgoing view to recycle
newViewNumber = getPrevViewNumber(mCurrentViewNumber);
mCurrentPosition = getPrevPosition(mCurrentPosition);
reloadViewNumber = getNextViewNumber(mCurrentViewNumber);
reloadPosition = getPrevPosition(mCurrentPosition);
}
}
if (mFlingDirection < 0)
{
if (mCurrentPosition < getLastPosition() || mIsGalleryCircular == true)
{
// Determine the next view and outgoing view to recycle
newViewNumber = getNextViewNumber(mCurrentViewNumber);
mCurrentPosition = getNextPosition(mCurrentPosition);
reloadViewNumber = getPrevViewNumber(mCurrentViewNumber);
reloadPosition = getNextPosition(mCurrentPosition);
}
}
if (newViewNumber != mCurrentViewNumber)
{
mCurrentViewNumber = newViewNumber;
// Reload outgoing view from adapter in new position
mViews[reloadViewNumber].recycleView(reloadPosition);
}
// Ensure input focus on the current view
mViews[mCurrentViewNumber].requestFocus();
// Run the slide animations for view transitions
mAnimation.prepareAnimation(mCurrentViewNumber);
this.startAnimation(mAnimation);
// Reset fling state
mFlingDirection = 0;
}
void processScrollSnap()
{
// Snap to next view if scrolled passed snap position
float rollEdgeWidth = mGalleryWidth * mSnapBorderRatio;
int rollOffset = mGalleryWidth - (int) rollEdgeWidth;
int currentOffset = mViews[mCurrentViewNumber].getCurrentOffset();
if (currentOffset <= rollOffset * -1)
{
// Snap to previous view
mFlingDirection = 1;
}
if (currentOffset >= rollOffset)
{
// Snap to next view
mFlingDirection = -1;
}
}
private class FlingGalleryView
{
private int mViewNumber;
private FrameLayout mParentLayout;
private FrameLayout mInvalidLayout = null;
private LinearLayout mInternalLayout = null;
private View mExternalView = null;
public FlingGalleryView(int viewNumber, FrameLayout parentLayout)
{
mViewNumber = viewNumber;
mParentLayout = parentLayout;
// Invalid layout is used when outside gallery
mInvalidLayout = new FrameLayout(mContext);
mInvalidLayout.setLayoutParams(new LinearLayout.LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
// Internal layout is permanent for duration
mInternalLayout = new LinearLayout(mContext);
mInternalLayout.setLayoutParams(new LinearLayout.LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
mParentLayout.addView(mInternalLayout);
}
public void recycleView(int newPosition)
{
if (mExternalView != null)
{
mInternalLayout.removeView(mExternalView);
}
if (mAdapter != null)
{
if (newPosition >= getFirstPosition() && newPosition <= getLastPosition())
{
mExternalView = mAdapter.getView(newPosition, mExternalView, mInternalLayout);
}
else
{
mExternalView = mInvalidLayout;
}
}
if (mExternalView != null)
{
mInternalLayout.addView(mExternalView, new LinearLayout.LayoutParams(
LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
}
}
public void setOffset(int xOffset, int yOffset, int relativeViewNumber)
{
// Scroll the target view relative to its own position relative to currently displayed view
mInternalLayout.scrollTo(getViewOffset(mViewNumber, relativeViewNumber) + xOffset, yOffset);
}
public int getCurrentOffset()
{
// Return the current scroll position
return mInternalLayout.getScrollX();
}
public void requestFocus()
{
mInternalLayout.requestFocus();
}
}
private class FlingGalleryAnimation extends Animation
{
private boolean mIsAnimationInProgres;
private int mRelativeViewNumber;
private int mInitialOffset;
private int mTargetOffset;
private int mTargetDistance;
public FlingGalleryAnimation()
{
mIsAnimationInProgres = false;
mRelativeViewNumber = 0;
mInitialOffset = 0;
mTargetOffset = 0;
mTargetDistance = 0;
}
public void prepareAnimation(int relativeViewNumber)
{
// If we are animating relative to a new view
if (mRelativeViewNumber != relativeViewNumber)
{
if (mIsAnimationInProgres == true)
{
// We only have three views so if requested again to animate in same direction we must snap
int newDirection = (relativeViewNumber == getPrevViewNumber(mRelativeViewNumber)) ? 1 : -1;
int animDirection = (mTargetDistance < 0) ? 1 : -1;
// If animation in same direction
if (animDirection == newDirection)
{
// Ran out of time to animate so snap to the target offset
mViews[0].setOffset(mTargetOffset, 0, mRelativeViewNumber);
mViews[1].setOffset(mTargetOffset, 0, mRelativeViewNumber);
mViews[2].setOffset(mTargetOffset, 0, mRelativeViewNumber);
}
}
// Set relative view number for animation
mRelativeViewNumber = relativeViewNumber;
}
// Note: In this implementation the targetOffset will always be zero
// as we are centering the view; but we include the calculations of
// targetOffset and targetDistance for use in future implementations
mInitialOffset = mViews[mRelativeViewNumber].getCurrentOffset();
mTargetOffset = getViewOffset(mRelativeViewNumber, mRelativeViewNumber);
mTargetDistance = mTargetOffset - mInitialOffset;
// Configure base animation properties
this.setDuration(mAnimationDuration);
this.setInterpolator(mDecelerateInterpolater);
// Start/continued animation
mIsAnimationInProgres = true;
}
@Override
protected void applyTransformation(float interpolatedTime, Transformation transformation)
{
// Ensure interpolatedTime does not over-shoot then calculate new offset
interpolatedTime = (interpolatedTime > 1.0f) ? 1.0f : interpolatedTime;
int offset = mInitialOffset + (int) (mTargetDistance * interpolatedTime);
for (int viewNumber = 0; viewNumber < 3; viewNumber++)
{
// Only need to animate the visible views as the other view will always be off-screen
if ((mTargetDistance > 0 && viewNumber != getNextViewNumber(mRelativeViewNumber)) ||
(mTargetDistance < 0 && viewNumber != getPrevViewNumber(mRelativeViewNumber)))
{
mViews[viewNumber].setOffset(offset, 0, mRelativeViewNumber);
}
}
}
@Override
public boolean getTransformation(long currentTime, Transformation outTransformation)
{
if (super.getTransformation(currentTime, outTransformation) == false)
{
// Perform final adjustment to offsets to cleanup animation
mViews[0].setOffset(mTargetOffset, 0, mRelativeViewNumber);
mViews[1].setOffset(mTargetOffset, 0, mRelativeViewNumber);
mViews[2].setOffset(mTargetOffset, 0, mRelativeViewNumber);
// Reached the animation target
mIsAnimationInProgres = false;
return false;
}
// Cancel if the screen touched
if (mIsTouched || mIsDragging)
{
// Note that at this point we still consider ourselves to be animating
// because we have not yet reached the target offset; its just that the
// user has temporarily interrupted the animation with a touch gesture
return false;
}
return true;
}
}
private class FlingGestureDetector extends GestureDetector.SimpleOnGestureListener
{
@Override
public boolean onDown(MotionEvent e)
{
// Stop animation
mIsTouched = true;
// Reset fling state
mFlingDirection = 0;
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
{
if (e2.getAction() == MotionEvent.ACTION_MOVE)
{
if (mIsDragging == false)
{
// Stop animation
mIsTouched = true;
// Reconfigure scroll
mIsDragging = true;
mFlingDirection = 0;
mScrollTimestamp = System.currentTimeMillis();
mCurrentOffset = mViews[mCurrentViewNumber].getCurrentOffset();
}
float maxVelocity = mGalleryWidth / (mAnimationDuration / 1000.0f);
long timestampDelta = System.currentTimeMillis() - mScrollTimestamp;
float maxScrollDelta = maxVelocity * (timestampDelta / 1000.0f);
float currentScrollDelta = e1.getX() - e2.getX();
if (currentScrollDelta < maxScrollDelta * -1) currentScrollDelta = maxScrollDelta * -1;
if (currentScrollDelta > maxScrollDelta) currentScrollDelta = maxScrollDelta;
int scrollOffset = Math.round(mCurrentOffset + currentScrollDelta);
// We can't scroll more than the width of our own frame layout
if (scrollOffset >= mGalleryWidth) scrollOffset = mGalleryWidth;
if (scrollOffset <= mGalleryWidth * -1) scrollOffset = mGalleryWidth * -1;
mViews[0].setOffset(scrollOffset, 0, mCurrentViewNumber);
mViews[1].setOffset(scrollOffset, 0, mCurrentViewNumber);
mViews[2].setOffset(scrollOffset, 0, mCurrentViewNumber);
}
return false;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
{
if (Math.abs(e1.getY() - e2.getY()) <= swipe_max_off_path)
{
if (e2.getX() - e1.getX() > swipe_min_distance && Math.abs(velocityX) > swipe_threshold_veloicty)
{
movePrevious();
}
if(e1.getX() - e2.getX() > swipe_min_distance && Math.abs(velocityX) > swipe_threshold_veloicty)
{
moveNext();
}
}
return false;
}
@Override
public void onLongPress(MotionEvent e)
{
// Finalise scrolling
mFlingDirection = 0;
processGesture();
}
@Override
public void onShowPress(MotionEvent e)
{
}
@Override
public boolean onSingleTapUp(MotionEvent e)
{
// Reset fling state
mFlingDirection = 0;
return false;
}
}
public GestureDetector getMGestureDetector() {
return mGestureDetector;
}
}
由于我需要在滑动页面时，改动title中的文字，这里采用了观察者模式，加了个OnGalleryChangeListener，有同样需求的同学可以参考下。
public interface OnGalleryChangeListener {
public void onGalleryChange(int currentItem);
}
在Activity中，
FlingGallery gallery = new FlingGallery(this);
gallery.setAdapter(new ArrayAdapter<String>(getApplicationContext(),
android.R.layout.simple_list_item_1, new String[xxxx]) {
public View getView(int position, View convertView, ViewGroup parent) {
// 返回滑动的deal
return dealViews[position];
}
});
gallery.addGalleryChangeListener(new OnGalleryChangeListener() {
@Override
public void onGalleryChange(int currentItem) {
// 干些想干的事件
}
});
将gallery加到Activity中的最终需要显示的类中。
Adapter中的getView方法中，将需要用来滑动的view添加进来。在GalleryChangeListener中，可以干一些自己想要的滑动后的事情。我在这里改动了标题的文字，进行了我的view中图片的lazyloading。
这里提一下另一个问题。我的这个类，最终嵌入到了tab中，需要在你的tabActivity中dispatchKeyEvent一下，将按键事件分发下去。
最开始，我的滑动的view写得比较通用，所以包含了ScrollView来满足比较长的屏幕,导致手势监听会出一些问题，会出现抖动。当时的解决方案是针对不同屏幕尽量保证一屏能够显示，在res目录下，增加layout-800x480之类的目录，针对每个不同屏幕设计单独的layout，放弃上下滑动，效果也不错。