Android Path Time ScrollBar（Path 时间轴）
版本号：1.0 日期：2014.4.22 版权：© 2014 kince 转载注明出处 这是仿Path2.0UI的一个demo的截图，我最早是在农民伯伯的这篇博客中看到的 【Andorid X 项目笔记】开源项目使用（6） ，他说这个程序是反编译Path的。可是这次我特地看了一下代码，发现事实上不是这种。原帖地址应该是这个： http://www.eoeandroid.com/forum.php?mod=viewthread&tid=187725 ，作者使用的是github上的一个开源项目： Android-ScrollBarPanel ，它实现的效果例如以下： 已经非常接近Path的效果了。还有墨迹天气的实景也是使用了这种效果： 并且，墨迹天气用的也是这个开源项目。效果什么基本都没改。所以以下重点说一下这个开源项目的实现。 在看它的代码之前先来分析一下这个效果该怎样实现，它就是在滚动栏（scrollbar）的旁边动态显示一个View。这个View里面显示的内容会随着滚动栏的位置变化而变化。一般像带滑动效果的容器控制都会有滚动栏，比方ScrollView、ListView、GeidView等。那这个滚动栏究竟是什么呢？它是一个View的属性，该属性是继承view的， 目的设置滚动栏显示。有以下设置none（隐藏）。horizontal（水平），vertical （垂直）。并非全部的view设置就有效果。 LinearLayout 设置也没有效果。 要想在超过一屏时拖动效果，在最外层加上ScrollView。并且能够自己定义滚动栏的样式和位置。但Path用的并非自己定义的滚动栏，它是在滚动栏旁边加的View。如图： 若是在滚动栏的旁边加入显示View，首先须要获取滚动栏的位置，当在滑动的时候在显示滚动栏的同一时候也让加入的View显示出来，也就是说它和滚动栏的显示是同步的。 那究竟怎样实现呢。带着这些疑问看一下源代码： package com.dafruits.android.library.widgets; import android.content.Context; import android.content.res.TypedArray; import android.graphics.Canvas; import android.os.Handler; import android.util.AttributeSet; import android.view.LayoutInflater; import android.view.View; import android.view.ViewConfiguration; import android.view.animation.Animation; import android.view.animation.Animation.AnimationListener; import android.view.animation.AnimationUtils; import android.widget.AbsListView; import android.widget.AbsListView.OnScrollListener; import android.widget.ListView; import com.dafruits.android.library.R; public class ExtendedListView extends ListView implements OnScrollListener { public static interface OnPositionChangedListener { public void onPositionChanged(ExtendedListView listView, int position, View scrollBarPanel); } private OnScrollListener mOnScrollListener = null; private View mScrollBarPanel = null; private int mScrollBarPanelPosition = 0; private OnPositionChangedListener mPositionChangedListener; private int mLastPosition = -1; private Animation mInAnimation = null; private Animation mOutAnimation = null; private final Handler mHandler = new Handler(); private final Runnable mScrollBarPanelFadeRunnable = new Runnable() { @Override public void run() { if (mOutAnimation != null) { mScrollBarPanel.startAnimation(mOutAnimation); } } }; /* * keep track of Measure Spec */ private int mWidthMeasureSpec; private int mHeightMeasureSpec; public ExtendedListView(Context context) { this(context, null); } public ExtendedListView(Context context, AttributeSet attrs) { this(context, attrs, android.R.attr.listViewStyle); } public ExtendedListView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); super.setOnScrollListener(this); final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ExtendedListView); final int scrollBarPanelLayoutId = a.getResourceId(R.styleable.ExtendedListView_scrollBarPanel, -1); final int scrollBarPanelInAnimation = a.getResourceId(R.styleable.ExtendedListView_scrollBarPanelInAnimation, R.anim.in_animation); final int scrollBarPanelOutAnimation = a.getResourceId(R.styleable.ExtendedListView_scrollBarPanelOutAnimation, R.anim.out_animation); a.recycle(); if (scrollBarPanelLayoutId != -1) { setScrollBarPanel(scrollBarPanelLayoutId); } final int scrollBarPanelFadeDuration = ViewConfiguration.getScrollBarFadeDuration(); if (scrollBarPanelInAnimation > 0) { mInAnimation = AnimationUtils.loadAnimation(getContext(), scrollBarPanelInAnimation); } if (scrollBarPanelOutAnimation > 0) { mOutAnimation = AnimationUtils.loadAnimation(getContext(), scrollBarPanelOutAnimation); mOutAnimation.setDuration(scrollBarPanelFadeDuration); mOutAnimation.setAnimationListener(new AnimationListener() { @Override public void onAnimationStart(Animation animation) { } @Override public void onAnimationRepeat(Animation animation) { } @Override public void onAnimationEnd(Animation animation) { if (mScrollBarPanel != null) { mScrollBarPanel.setVisibility(View.GONE); } } }); } } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { if (mOnScrollListener != null) { mOnScrollListener.onScrollStateChanged(view, scrollState); } } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { if (null != mPositionChangedListener && null != mScrollBarPanel) { // Don't do anything if there is no itemviews if (totalItemCount > 0) { /* * from android source code (ScrollBarDrawable.java) */ final int thickness = getVerticalScrollbarWidth(); int height = Math.round((float) getMeasuredHeight() * computeVerticalScrollExtent() / computeVerticalScrollRange()); int thumbOffset = Math.round((float) (getMeasuredHeight() - height) * computeVerticalScrollOffset() / (computeVerticalScrollRange() - computeVerticalScrollExtent())); final int minLength = thickness * 2; if (height < minLength) { height = minLength; } thumbOffset += height / 2; /* * find out which itemviews the center of thumb is on */ final int count = getChildCount(); for (int i = 0; i < count; ++i) { final View childView = getChildAt(i); if (childView != null) { if (thumbOffset > childView.getTop() && thumbOffset < childView.getBottom()) { /* * we have our candidate */ if (mLastPosition != firstVisibleItem + i) { mLastPosition = firstVisibleItem + i; /* * inform the position of the panel has changed */ mPositionChangedListener.onPositionChanged(this, mLastPosition, mScrollBarPanel); /* * measure panel right now since it has just changed * * INFO: quick hack to handle TextView has ScrollBarPanel (to wrap text in * case TextView's content has changed) */ measureChild(mScrollBarPanel, mWidthMeasureSpec, mHeightMeasureSpec); } break; } } } /* * update panel position */ mScrollBarPanelPosition = thumbOffset - mScrollBarPanel.getMeasuredHeight() / 2; final int x = getMeasuredWidth() - mScrollBarPanel.getMeasuredWidth() - getVerticalScrollbarWidth(); mScrollBarPanel.layout(x, mScrollBarPanelPosition, x + mScrollBarPanel.getMeasuredWidth(), mScrollBarPanelPosition + mScrollBarPanel.getMeasuredHeight()); } } if (mOnScrollListener != null) { mOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount); } } public void setOnPositionChangedListener(OnPositionChangedListener onPositionChangedListener) { mPositionChangedListener = onPositionChangedListener; } @Override public void setOnScrollListener(OnScrollListener onScrollListener) { mOnScrollListener = onScrollListener; } public void setScrollBarPanel(View scrollBarPanel) { mScrollBarPanel = scrollBarPanel; mScrollBarPanel.setVisibility(View.GONE); requestLayout(); } public void setScrollBarPanel(int resId) { setScrollBarPanel(LayoutInflater.from(getContext()).inflate(resId, this, false)); } public View getScrollBarPanel() { return mScrollBarPanel; } @Override protected boolean awakenScrollBars(int startDelay, boolean invalidate) { final boolean isAnimationPlayed = super.awakenScrollBars(startDelay, invalidate); if (isAnimationPlayed == true && mScrollBarPanel != null) { if (mScrollBarPanel.getVisibility() == View.GONE) { mScrollBarPanel.setVisibility(View.VISIBLE); if (mInAnimation != null) { mScrollBarPanel.startAnimation(mInAnimation); } } mHandler.removeCallbacks(mScrollBarPanelFadeRunnable); mHandler.postAtTime(mScrollBarPanelFadeRunnable, AnimationUtils.currentAnimationTimeMillis() + startDelay); } return isAnimationPlayed; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (mScrollBarPanel != null && getAdapter() != null) { mWidthMeasureSpec = widthMeasureSpec; mHeightMeasureSpec = heightMeasureSpec; measureChild(mScrollBarPanel, widthMeasureSpec, heightMeasureSpec); } } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); if (mScrollBarPanel != null) { final int x = getMeasuredWidth() - mScrollBarPanel.getMeasuredWidth() - getVerticalScrollbarWidth(); mScrollBarPanel.layout(x, mScrollBarPanelPosition, x + mScrollBarPanel.getMeasuredWidth(), mScrollBarPanelPosition + mScrollBarPanel.getMeasuredHeight()); } } @Override protected void dispatchDraw(Canvas canvas) { super.dispatchDraw(canvas); if (mScrollBarPanel != null && mScrollBarPanel.getVisibility() == View.VISIBLE) { drawChild(canvas, mScrollBarPanel, getDrawingTime()); } } @Override public void onDetachedFromWindow() { super.onDetachedFromWindow(); mHandler.removeCallbacks(mScrollBarPanelFadeRunnable); } } 通过阅读源代码发现，这是一个自己定义的ListView，并且继承了OnScrollListener接口。这个接口是在AbsListView.java里面定义的。主要是负责滑动事件的处理，它的代码例如以下： /** * Interface definition for a callback to be invoked when the list or grid * has been scrolled. */ public interface OnScrollListener { /** * The view is not scrolling. Note navigating the list using the trackball counts as * being in the idle state since these transitions are not animated. */ public static int SCROLL_STATE_IDLE = 0; /** * The user is scrolling using touch, and their finger is still on the screen */ public static int SCROLL_STATE_TOUCH_SCROLL = 1; /** * The user had previously been scrolling using touch and had performed a fling. The * animation is now coasting to a stop */ public static int SCROLL_STATE_FLING = 2; /** * Callback method to be invoked while the list view or grid view is being scrolled. If the * view is being scrolled, this method will be called before the next frame of the scroll is * rendered. In particular, it will be called before any calls to * {@link Adapter#getView(int, View, ViewGroup)}. * * @param view The view whose scroll state is being reported * * @param scrollState The current scroll state. One of {@link #SCROLL_STATE_IDLE}, * {@link #SCROLL_STATE_TOUCH_SCROLL} or {@link #SCROLL_STATE_IDLE}. */ public void onScrollStateChanged(AbsListView view, int scrollState); /** * Callback method to be invoked when the list or grid has been scrolled. This will be * called after the scroll has completed * @param view The view whose scroll state is being reported * @param firstVisibleItem the index of the first visible cell (ignore if * visibleItemCount == 0) * @param visibleItemCount the number of visible cells * @param totalItemCount the number of items in the list adaptor */ public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount); } OnScrollListener定义了三个常量。分别表示当屏幕停止滚动时为0；当屏幕滚动且用户使用的触碰或手指还在屏幕上时为1；由于用户的操作。屏幕产生惯性滑动时为2。详细解释例如以下： new OnScrollListener() { boolean isLastRow = false; @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { //滚动时一直回调，直到停止滚动时才停止回调。单击时回调一次。 //firstVisibleItem：当前能看见的第一个列表项ID（从0開始） //visibleItemCount：当前能看见的列表项个数（小半个也算） //totalItemCount：列表项共数 //推断是否滚到最后一行 if (firstVisibleItem + visibleItemCount == totalItemCount && totalItemCount > 0) { isLastRow = true; } } @Override public void onScrollStateChanged(AbsListView view, int scrollState) { //正在滚动时回调，回调2-3次，手指没抛则回调2次。 scrollState = 2的这次不回调 //回调顺序例如以下 //第1次：scrollState = SCROLL_STATE_TOUCH_SCROLL(1) 正在滚动 //第2次：scrollState = SCROLL_STATE_FLING(2) 手指做了抛的动作（手指离开屏幕前，用力滑了一下） //第3次：scrollState = SCROLL_STATE_IDLE(0) 停止滚动 //当屏幕停止滚动时为0；当屏幕滚动且用户使用的触碰或手指还在屏幕上时为1。 //由于用户的操作，屏幕产生惯性滑动时为2 //当滚到最后一行且停止滚动时，运行载入 if (isLastRow && scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) { //载入元素 ...... isLastRow = false; } } } 了解完OnScrollListener这个接口再回头看一下代码，首先定义了一个回调： public static interface OnPositionChangedListener { public void onPositionChanged(ExtendedListView listView, int position, View scrollBarPanel); } 这个用来在Activity中设置监听事件的，Activity的代码例如以下： package com.dafruits.android.samples; import android.app.Activity; import android.graphics.Color; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; import com.dafruits.android.library.widgets.ExtendedListView; import com.dafruits.android.library.widgets.ExtendedListView.OnPositionChangedListener; public class DemoScrollBarPanelActivity extends Activity implements OnPositionChangedListener { private ExtendedListView mListView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mListView = (ExtendedListView) findViewById(android.R.id.list); mListView.setAdapter(new DummyAdapter()); mListView.setCacheColorHint(Color.TRANSPARENT); mListView.setOnPositionChangedListener(this); } private class DummyAdapter extends BaseAdapter { private int mNumDummies = 100; @Override public int getCount() { return mNumDummies; } @Override public Object getItem(int position) { return position; } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = LayoutInflater.from(DemoScrollBarPanelActivity.this).inflate(R.layout.list_item, parent, false); } TextView textView = (TextView) convertView; textView.setText("" + position); return convertView; } } @Override public void onPositionChanged(ExtendedListView listView, int firstVisiblePosition, View scrollBarPanel) { ((TextView) scrollBarPanel).setText("Position " + firstVisiblePosition); } } 接着看一下第三个构造方法，由于这个自己定义的ListView定义了自己的属性。所以须要从attrs文件里来取出这些属性。自己定义的属性包含三个部分，一是在ListView滑动时弹出的View，二是这个View弹出时的动画，三是这个View消失时的动画。然后開始设置这个弹出的View： if (scrollBarPanelLayoutId != -1) { setScrollBarPanel(scrollBarPanelLayoutId); } 看一下设置的方法。 public void setScrollBarPanel(View scrollBarPanel) { mScrollBarPanel = scrollBarPanel; mScrollBarPanel.setVisibility(View.GONE); requestLayout(); } public void setScrollBarPanel(int resId) { setScrollBarPanel(LayoutInflater.from(getContext()).inflate(resId, this, false)); } 先是调用以下这种方法。从xml文件里载入弹出View的布局，在这个地方须要说一下假设自己定义的View不须要手动绘制的话，那么就能够使用LayoutInflater去在xml中载入一个已经配置好的视图，本例中就是使用这个方式。这样mScrollBarPanel就储存了弹出的View。然后设置为不可见。使用requestLayout()刷新一下视图。再接着就是载入两个弹出的动画。特别的。在mOutAnimation动画中设置了监听器，在动画结束的时候设置弹出的View不可见。 回到第三个构造方法中，在第二行设置了super.setOnScrollListener(this)，这种方法是效果实现的关键。为什么这么说。先看一下它的源代码。 它是在AbsListView中定义的。 /** * Set the listener that will receive notifications every time the list scrolls. * * @param l the scroll listener */ public void setOnScrollListener(OnScrollListener l) { mOnScrollListener = l; invokeOnItemScrollListener(); }设置这种方法后，会传递一个 OnScrollListener对象给 mOnScrollListener，然后调用 invokeOnItemScrollListener()方法，它的代码例如以下： /** * Notify our scroll listener (if there is one) of a change in scroll state */ void invokeOnItemScrollListener() { if (mFastScroller != null) { mFastScroller.onScroll(this, mFirstPosition, getChildCount(), mItemCount); } if (mOnScrollListener != null) { mOnScrollListener.onScroll(this, mFirstPosition, getChildCount(), mItemCount); } onScrollChanged(0, 0, 0, 0); // dummy values, View's implementation does not use these. } 假设mOnScrollListener不为空的话，就调用mOnScrollListener的onScroll方法。而onScroll方法正是OnScrollListener接口定义的抽象方法，由于我们在ListView中继承了OnScrollListener接口，重载了onScroll方法，所以将会调用我们自己实现的onScroll方法。就是这样一个流程。 然后看一下onScroll方法的实现， @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { Log.i("onScroll", "onScroll"); if (null != mPositionChangedListener && null != mScrollBarPanel) { // Don't do anything if there is no itemviews if (totalItemCount > 0) { /* * from android source code (ScrollBarDrawable.java) */ final int thickness = getVerticalScrollbarWidth(); int height = Math.round((float) getMeasuredHeight() * computeVerticalScrollExtent() / computeVerticalScrollRange()); int thumbOffset = Math .round((float) (getMeasuredHeight() - height) * computeVerticalScrollOffset() / (computeVerticalScrollRange() - computeVerticalScrollExtent())); final int minLength = thickness * 2; if (height < minLength) { height = minLength; } thumbOffset += height / 2; /* * find out which itemviews the center of thumb is on */ final int count = getChildCount(); for (int i = 0; i < count; ++i) { final View childView = getChildAt(i); if (childView != null) { if (thumbOffset > childView.getTop() && thumbOffset < childView.getBottom()) { /* * we have our candidate */ if (mLastPosition != firstVisibleItem + i) { mLastPosition = firstVisibleItem + i; /* * inform the position of the panel has changed */ mPositionChangedListener.onPositionChanged( this, mLastPosition, mScrollBarPanel); /* * measure panel right now since it has just * changed * * INFO: quick hack to handle TextView has * ScrollBarPanel (to wrap text in case * TextView's content has changed) */ measureChild(mScrollBarPanel, mWidthMeasureSpec, mHeightMeasureSpec); } break; } } } /* * update panel position */ mScrollBarPanelPosition = thumbOffset - mScrollBarPanel.getMeasuredHeight() / 2; final int x = getMeasuredWidth() - mScrollBarPanel.getMeasuredWidth() - getVerticalScrollbarWidth(); mScrollBarPanel.layout( x, mScrollBarPanelPosition, x + mScrollBarPanel.getMeasuredWidth(), mScrollBarPanelPosition + mScrollBarPanel.getMeasuredHeight()); } } if (mOnScrollListener != null) { mOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount); } } 上面已经说到。这个onScroll是随着滑动而一直调用的，而我们的需求就是在滑动的时候弹出一个View来。所以这种方法正是处理问题的关键位置。能够在这里绘制弹出View的视图。从上面的代码也能够看出，就是在这里进行弹出View大小的计算以及位置的设定等。 最后就是之前说的自己定义ViewGroup的问题了。重载onMeasure()、onLayout()、ondispatchDraw()方法了，这个在本例中也是有所体现的，只是都比較简单，相信都看得懂。 可是这几个方法都是在View初始化的时候调用的，并且仅仅是调用一次。这样并不适合动态的绘制视图。所以这也是为什么本样例继承了OnScrollListener，然后在其onScroll方法中去绘制视图。由于onScroll方法在滑动的时候会调用，所以在滑动的时候就会绘制视图了。 因此也能够看出本例採用的是动态画图的方式，不是显示隐藏的方式。 本文转自mfrbuaa博客园博客，原文链接：http://www.cnblogs.com/mfrbuaa/p/5396685.html，如需转载请自行联系原作者
