android 广告图片 banner 滚动效果

/* * Copyright (C) 2011 Patrik Åkerfeldt * * 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. */ package org.taptwo.android.widget; import java.util.ArrayList; import java.util.LinkedList; import com.viewflowtest.cjy.R; import android.content.Context; import android.content.res.Configuration; import android.content.res.TypedArray; import android.database.DataSetObserver; import android.os.Handler; import android.os.Message; 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.view.ViewTreeObserver.OnGlobalLayoutListener; import android.widget.AbsListView; import android.widget.Adapter; import android.widget.AdapterView; import android.widget.Scroller; /** * A horizontally scrollable {@link ViewGroup} with items populated from an * {@link Adapter}. The ViewFlow uses a buffer to store loaded {@link View}s in. * The default size of the buffer is 3 elements on both sides of the currently * visible {@link View}, making up a total buffer size of 3 * 2 + 1 = 7. The * buffer size can be changed using the {@code sidebuffer} xml attribute. * */ public class ViewFlow extends AdapterView<Adapter> { private static final int SNAP_VELOCITY = 1000; private static final int INVALID_SCREEN = -1; private final static int TOUCH_STATE_REST = 0; private final static int TOUCH_STATE_SCROLLING = 1; private LinkedList<View> mLoadedViews; private int mCurrentBufferIndex; private int mCurrentAdapterIndex; private int mSideBuffer = 2; private Scroller mScroller; private VelocityTracker mVelocityTracker; private int mTouchState = TOUCH_STATE_REST; private float mLastMotionX; private int mTouchSlop; private int mMaximumVelocity; private int mCurrentScreen; private int mNextScreen = INVALID_SCREEN; private boolean mFirstLayout = true; private ViewSwitchListener mViewSwitchListener; private Adapter mAdapter; private int mLastScrollDirection; private AdapterDataSetObserver mDataSetObserver; private FlowIndicator mIndicator; private int mLastOrientation = -1; private long timeSpan = 3000; private Handler handler; private OnGlobalLayoutListener orientationChangeListener = new OnGlobalLayoutListener() { @Override public void onGlobalLayout() { getViewTreeObserver().removeGlobalOnLayoutListener( orientationChangeListener); setSelection(mCurrentAdapterIndex); } }; /** * Receives call backs when a new {@link View} has been scrolled to. */ public static interface ViewSwitchListener { /** * This method is called when a new View has been scrolled to. * * @param view * the {@link View} currently in focus. * @param position * The position in the adapter of the {@link View} currently in focus. */ void onSwitched(View view, int position); } public ViewFlow(Context context) { super(context); mSideBuffer = 3; init(); } public ViewFlow(Context context, int sideBuffer) { super(context); mSideBuffer = sideBuffer; init(); } public ViewFlow(Context context, AttributeSet attrs) { super(context, attrs); TypedArray styledAttrs = context.obtainStyledAttributes(attrs, R.styleable.ViewFlow); mSideBuffer = styledAttrs.getInt(R.styleable.ViewFlow_sidebuffer, 3); init(); } private void init() { mLoadedViews = new LinkedList<View>(); mScroller = new Scroller(getContext()); final ViewConfiguration configuration = ViewConfiguration .get(getContext()); mTouchSlop = configuration.getScaledTouchSlop(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); } public void startAutoFlowTimer(){ handler = new Handler(){ @Override public void handleMessage(Message msg) { snapToScreen((mCurrentScreen+1)%getChildCount()); Message message = handler.obtainMessage(0); sendMessageDelayed(message, timeSpan); } }; Message message = handler.obtainMessage(0); handler.sendMessageDelayed(message, timeSpan); } public void stopAutoFlowTimer(){ if(handler!=null) handler.removeMessages(0); handler = null; } public void onConfigurationChanged(Configuration newConfig) { if (newConfig.orientation != mLastOrientation) { mLastOrientation = newConfig.orientation; getViewTreeObserver().addOnGlobalLayoutListener(orientationChangeListener); } } public int getViewsCount() { return mSideBuffer; } @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 && !isInEditMode()) { throw new IllegalStateException( "ViewFlow can only be used in EXACTLY mode."); } final int heightMode = MeasureSpec.getMode(heightMeasureSpec); if (heightMode != MeasureSpec.EXACTLY && !isInEditMode()) { throw new IllegalStateException( "ViewFlow can only be used in EXACTLY mode."); } // The children are given the same width and height as the workspace final int count = getChildCount(); for (int i = 0; i < count; i++) { getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec); } if (mFirstLayout) { mScroller.startScroll(0, 0, mCurrentScreen * width, 0, 0); mFirstLayout = false; } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { int childLeft = 0; final int count = getChildCount(); for (int i = 0; i < count; i++) { final View child = getChildAt(i); if (child.getVisibility() != View.GONE) { final int childWidth = child.getMeasuredWidth(); child.layout(childLeft, 0, childLeft + childWidth, child.getMeasuredHeight()); childLeft += childWidth; } } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (getChildCount() == 0) return false; if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(ev); final int action = ev.getAction(); final float x = ev.getX(); switch (action) { case MotionEvent.ACTION_DOWN: /* * If being flinged and user touches, stop the fling. isFinished * will be false if being flinged. */ if (!mScroller.isFinished()) { mScroller.abortAnimation(); } // Remember where the motion event started mLastMotionX = x; mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING; if(handler!=null) handler.removeMessages(0); break; case MotionEvent.ACTION_MOVE: final int xDiff = (int) Math.abs(x - mLastMotionX); boolean xMoved = xDiff > mTouchSlop; if (xMoved) { // Scroll if the user moved far enough along the X axis mTouchState = TOUCH_STATE_SCROLLING; } if (mTouchState == TOUCH_STATE_SCROLLING) { // Scroll to follow the motion event final int deltaX = (int) (mLastMotionX - x); mLastMotionX = x; final int scrollX = getScrollX(); if (deltaX < 0) { if (scrollX > 0) { scrollBy(Math.max(-scrollX, deltaX), 0); } } else if (deltaX > 0) { final int availableToScroll = getChildAt( getChildCount() - 1).getRight() - scrollX - getWidth(); if (availableToScroll > 0) { scrollBy(Math.min(availableToScroll, deltaX), 0); } } return true; } break;