android点击查看大图，ViewPager实现左右滑动切换、缩放图片

package com.lcp.imagebrowsing; /* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import android.content.Context; import android.database.DataSetObserver; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.os.Parcel; import android.os.Parcelable; import android.os.SystemClock; import android.support.v4.os.ParcelableCompat; import android.support.v4.os.ParcelableCompatCreatorCallbacks; import android.support.v4.view.KeyEventCompat; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.PagerAdapter; import android.support.v4.view.VelocityTrackerCompat; import android.support.v4.view.ViewCompat; import android.support.v4.view.ViewConfigurationCompat; import android.support.v4.widget.EdgeEffectCompat; import android.util.AttributeSet; import android.util.Log; import android.view.FocusFinder; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.SoundEffectConstants; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.ViewParent; import android.view.accessibility.AccessibilityEvent; import android.view.animation.Interpolator; import android.widget.Scroller; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; /** * Layout manager that allows the user to flip left and right * through pages of data. You supply an implementation of a * {@link PagerAdapter} to generate the pages that the view shows. * * <p>Note this class is currently under early design and * development. The API will likely change in later updates of * the compatibility library, requiring changes to the source code * of apps when they are compiled against the newer version.</p> */ public class LazyViewPager extends ViewGroup { private static final String TAG = "LazyViewPager"; private static final boolean DEBUG = false; private static final boolean USE_CACHE = false; private static final int DEFAULT_OFFSCREEN_PAGES = 0; private static final int MAX_SETTLE_DURATION = 600; static class ItemInfo { Object object; int position; boolean scrolling; } private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>(){ @Override public int compare(ItemInfo lhs, ItemInfo rhs) { return lhs.position - rhs.position; }}; private static final Interpolator sInterpolator = new Interpolator() { public float getInterpolation(float t) { // _o(t) = t * t * ((tension + 1) * t + tension) // o(t) = _o(t - 1) + 1 t -= 1.0f; return t * t * t + 1.0f; } }; private final ArrayList<ItemInfo> mItems = new ArrayList<ItemInfo>(); private PagerAdapter mAdapter; private int mCurItem; // Index of currently displayed page. private int mRestoredCurItem = -1; private Parcelable mRestoredAdapterState = null; private ClassLoader mRestoredClassLoader = null; private Scroller mScroller; private PagerObserver mObserver; private int mPageMargin; private Drawable mMarginDrawable; private int mChildWidthMeasureSpec; private int mChildHeightMeasureSpec; private boolean mInLayout; private boolean mScrollingCacheEnabled; private boolean mPopulatePending; private boolean mScrolling; private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES; private boolean mIsBeingDragged; private boolean mIsUnableToDrag; private int mTouchSlop; private float mInitialMotionX; /** * Position of the last motion event. */ private float mLastMotionX; private float mLastMotionY; /** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */ private int mActivePointerId = INVALID_POINTER; /** * Sentinel value for no current active pointer. * Used by {@link #mActivePointerId}. */ private static final int INVALID_POINTER = -1; /** * Determines speed during touch scrolling */ private VelocityTracker mVelocityTracker; private int mMinimumVelocity; private int mMaximumVelocity; private float mBaseLineFlingVelocity; private float mFlingVelocityInfluence; private boolean mFakeDragging; private long mFakeDragBeginTime; private EdgeEffectCompat mLeftEdge; private EdgeEffectCompat mRightEdge; private boolean mFirstLayout = true; private OnPageChangeListener mOnPageChangeListener; /** * Indicates that the pager is in an idle, settled state. The current page * is fully in view and no animation is in progress. */ public static final int SCROLL_STATE_IDLE = 0; /** * Indicates that the pager is currently being dragged by the user. */ public static final int SCROLL_STATE_DRAGGING = 1; /** * Indicates that the pager is in the process of settling to a final position. */ public static final int SCROLL_STATE_SETTLING = 2; private int mScrollState = SCROLL_STATE_IDLE; /** * Callback interface for responding to changing state of the selected page. */ public interface OnPageChangeListener { /** * This method will be invoked when the current page is scrolled, either as part * of a programmatically initiated smooth scroll or a user initiated touch scroll. * * @param position Position index of the first page currently being displayed. * Page position+1 will be visible if positionOffset is nonzero. * @param positionOffset Value from [0, 1) indicating the offset from the page at position. * @param positionOffsetPixels Value in pixels indicating the offset from position. */ public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels); /** * This method will be invoked when a new page becomes selected. Animation is not * necessarily complete. * * @param position Position index of the new selected page. */ public void onPageSelected(int position); /** * Called when the scroll state changes. Useful for discovering when the user * begins dragging, when the pager is automatically settling to the current page, * or when it is fully stopped/idle. * * @param state The new scroll state. * @see android.support.v4.view.ViewPager#SCROLL_STATE_IDLE * @see android.support.v4.view.ViewPager#SCROLL_STATE_DRAGGING * @see android.support.v4.view.ViewPager#SCROLL_STATE_SETTLING */ public void onPageScrollStateChanged(int state); } /** * Simple implementation of the {@link android.support.v4.view.LazyViewPager.OnPageChangeListener} interface with stub * implementations of each method. Extend this if you do not intend to override * every method of {@link android.support.v4.view.LazyViewPager.OnPageChangeListener}.