应用源码之ViewPager-实现左右两个屏幕的切换.zip

/* * Copyright 2011 Google Inc. * * 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. */ /** * ATTENTION: Consider using the 'ViewPager' widget, available in the * Android Compatibility Package, r3: * * http://developer.android.com/sdk/compatibility-library.html */ package com.google.android.apps.iosched.ui.widget; import com.google.android.apps.iosched.util.MotionEventUtils; import com.google.android.apps.iosched.util.ReflectionUtils; import android.content.Context; import android.graphics.Canvas; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.os.Parcel; import android.os.Parcelable; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.ViewParent; import android.widget.Scroller; import java.util.ArrayList; /** * A {@link android.view.ViewGroup} that shows one child at a time, allowing the user to swipe * horizontally to page between other child views. Based on <code>Workspace.java</code> in the * <code>Launcher.git</code> AOSP project. * * An improved version of this UI widget named 'ViewPager' is now available in the * <a href="http://developer.android.com/sdk/compatibility-library.html">Android Compatibility * Package, r3</a>. */ public class Workspace extends ViewGroup { private static final String TAG = "Workspace"; private static final int INVALID_SCREEN = -1; /** * The velocity at which a fling gesture will cause us to snap to the next screen */ private static final int SNAP_VELOCITY = 500; /** * The user needs to drag at least this much for it to be considered a fling gesture. This * reduces the chance of a random twitch sending the user to the next screen. */ // TODO: refactor private static final int MIN_LENGTH_FOR_FLING = 100; private int mDefaultScreen; private boolean mFirstLayout = true; private boolean mHasLaidOut = false; private int mCurrentScreen; private int mNextScreen = INVALID_SCREEN; private Scroller mScroller; private VelocityTracker mVelocityTracker; /** * X position of the active pointer when it was first pressed down. */ private float mDownMotionX; /** * Y position of the active pointer when it was first pressed down. */ private float mDownMotionY; /** * This view's X scroll offset when the active pointer was first pressed down. */ private int mDownScrollX; private final static int TOUCH_STATE_REST = 0; private final static int TOUCH_STATE_SCROLLING = 1; private int mTouchState = TOUCH_STATE_REST; private OnLongClickListener mLongClickListener; private boolean mAllowLongPress = true; private int mTouchSlop; private int mPagingTouchSlop; private int mMaximumVelocity; private static final int INVALID_POINTER = -1; private int mActivePointerId = INVALID_POINTER; private Drawable mSeparatorDrawable; private OnScreenChangeListener mOnScreenChangeListener; private OnScrollListener mOnScrollListener; private boolean mLocked; private int mDeferredScreenChange = -1; private boolean mDeferredScreenChangeFast = false; private boolean mDeferredNotify = false; private boolean mIgnoreChildFocusRequests; private boolean mIsVerbose = false; public interface OnScreenChangeListener { void onScreenChanged(View newScreen, int newScreenIndex); void onScreenChanging(View newScreen, int newScreenIndex); } public interface OnScrollListener { void onScroll(float screenFraction); } /** * Used to inflate the com.google.android.ext.workspace.Workspace from XML. * * @param context The application's context. * @param attrs The attributes set containing the com.google.android.ext.workspace.Workspace's * customization values. */ public Workspace(Context context, AttributeSet attrs) { super(context, attrs); mDefaultScreen = 0; mLocked = false; setHapticFeedbackEnabled(false); initWorkspace(); mIsVerbose = Log.isLoggable(TAG, Log.VERBOSE); } /** * Initializes various states for this workspace. */ private void initWorkspace() { mScroller = new Scroller(getContext()); mCurrentScreen = mDefaultScreen; final ViewConfiguration configuration = ViewConfiguration.get(getContext()); mTouchSlop = configuration.getScaledTouchSlop(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); mPagingTouchSlop = ReflectionUtils.callWithDefault(configuration, "getScaledPagingTouchSlop", mTouchSlop * 2); } /** * Returns the index of the currently displayed screen. */ int getCurrentScreen() { return mCurrentScreen; } /** * Returns the number of screens currently contained in this Workspace. */ int getScreenCount() { int childCount = getChildCount(); if (mSeparatorDrawable != null) { return (childCount + 1) / 2; } return childCount; } View getScreenAt(int index) { if (mSeparatorDrawable == null) { return getChildAt(index); } return getChildAt(index * 2); } int getScrollWidth() { int w = getWidth(); if (mSeparatorDrawable != null) { w += mSeparatorDrawable.getIntrinsicWidth(); } return w; } void handleScreenChangeCompletion(int currentScreen) { mCurrentScreen = currentScreen; View screen = getScreenAt(mCurrentScreen); //screen.requestFocus(); try { ReflectionUtils.tryInvoke(screen, "dispatchDisplayHint", new Class[]{int.class}, View.VISIBLE); invalidate(); } catch (NullPointerException e) { Log.e(TAG, "Caught NullPointerException", e); } notifyScreenChangeListener(mCurrentScreen, true); } void notifyScreenChangeListener(int whichScreen, boolean changeComplete) { if (mOnScreenChangeListener != null) { if (changeComplete) mOnScreenChangeListener.onScreenChanged(getScreenAt(whichScreen), whichScreen); else mOnScreenChangeListener.onScreenChanging(getScreenAt(whichScreen), whichScreen); } if (mOnScrollListener != null) { mOnScrollListener.onScroll(getCurrentScreenFraction()); } } /** * Registers the specified listener on each screen contained in this workspace. * * @param listener The listener used to respond to long clicks. */ @Override public void setOnLongClickListener(OnLongClickListener listener) { mLongClickListener = listener; final int count = getScreenCount(); for (int i = 0; i < count; i++) { getScreenAt(i).setOnLongClickListener(listener); } } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { scrollTo(mScroller.getCurrX(), mScroller.getCurrY()); if (mOnScrollListener != null) { mOnScrollListener.onScroll(getCurrentScreenFraction()); } postInval