我列出了按月和年分开的事件列表（2010年6月，2010年7月等）。我启用了快速滚动，因为列表很长。我还实现了SectionIndexer，这样当人们快速向下滚动事件列表时，人们就可以看到他们当前正在查看的月份和年份。
我对实现没有任何问题，只是如何显示信息。使用SectionIndexer进行快速滚动似乎只能支持带有单个字母的标签。如果列表是字母表，这将是完美的，但我希望它显示更多的文本。
如果你看下面的截图，你会看到我遇到的问题。
我想知道的是：是否可以更改屏幕中心文本的显示方式。我可以以某种方式改变它以使其看起来正确（背景覆盖所有文本）。
提前致谢。如果您需要任何澄清，或只是问一下代码。
答案 0 :(得分：24)
编辑：此解决方案的完整示例代码可用here。
我遇到了同样的问题 - 我需要在叠加矩形中显示全文而不是单个字符。我设法使用以下代码作为示例解决了它：http://code.google.com/p/apps-for-android/source/browse/trunk/RingsExtended/src/com/example/android/rings_extended/FastScrollView.java
作者说这是从联系人应用中复制的，该应用显然使用了自己的实现，而不仅仅是在fastScrollEnabled="true"上设置ListView。我稍微修改了一下，以便您可以自定义覆盖矩形宽度，覆盖矩形高度，覆盖文本大小和滚动拇指宽度。
对于记录，最终结果如下所示：http://nolanwlawson.files.wordpress.com/2011/03/pokedroid_1.png
您需要做的就是将这些值添加到res / values / attrs.xml：
<declare-styleable name="CustomFastScrollView">
<attr name="overlayWidth" format="dimension"/>
<attr name="overlayHeight" format="dimension"/>
<attr name="overlayTextSize" format="dimension"/>
<attr name="overlayScrollThumbWidth" format="dimension"/>
</declare-styleable>
然后使用此CustomFastScrollView而不是链接中的那个：
public class CustomFastScrollView extends FrameLayout
implements OnScrollListener, OnHierarchyChangeListener {
private Drawable mCurrentThumb;
private Drawable mOverlayDrawable;
private int mThumbH;
private int mThumbW;
private int mThumbY;
private RectF mOverlayPos;
// custom values I defined
private int mOverlayWidth;
private int mOverlayHeight;
private float mOverlayTextSize;
private int mOverlayScrollThumbWidth;
private boolean mDragging;
private ListView mList;
private boolean mScrollCompleted;
private boolean mThumbVisible;
private int mVisibleItem;
private Paint mPaint;
private int mListOffset;
private Object [] mSections;
private String mSectionText;
private boolean mDrawOverlay;
private ScrollFade mScrollFade;
private Handler mHandler = new Handler();
private BaseAdapter mListAdapter;
private boolean mChangedBounds;
public static interface SectionIndexer {
Object[] getSections();
int getPositionForSection(int section);
int getSectionForPosition(int position);
}
public CustomFastScrollView(Context context) {
super(context);
init(context, null);
}
public CustomFastScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
public CustomFastScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context, attrs);
}
private void useThumbDrawable(Drawable drawable) {
mCurrentThumb = drawable;
mThumbW = mOverlayScrollThumbWidth;//mCurrentThumb.getIntrinsicWidth();
mThumbH = mCurrentThumb.getIntrinsicHeight();
mChangedBounds = true;
}
private void init(Context context, AttributeSet attrs) {
// set all attributes from xml
if (attrs != null) {
TypedArray typedArray = context.obtainStyledAttributes(attrs,
R.styleable.CustomFastScrollView);
mOverlayHeight = typedArray.getDimensionPixelSize(
R.styleable.CustomFastScrollView_overlayHeight, 0);
mOverlayWidth = typedArray.getDimensionPixelSize(
R.styleable.CustomFastScrollView_overlayWidth, 0);
mOverlayTextSize = typedArray.getDimensionPixelSize(
R.styleable.CustomFastScrollView_overlayTextSize, 0);
mOverlayScrollThumbWidth = typedArray.getDimensionPixelSize(
R.styleable.CustomFastScrollView_overlayScrollThumbWidth, 0);
}
// Get both the scrollbar states drawables
final Resources res = context.getResources();
Drawable thumbDrawable = res.getDrawable(R.drawable.scrollbar_handle_accelerated_anim2);
useThumbDrawable(thumbDrawable);
mOverlayDrawable = res.getDrawable(android.R.drawable.alert_dark_frame);
mScrollCompleted = true;
setWillNotDraw(false);
// Need to know when the ListView is added
setOnHierarchyChangeListener(this);
mOverlayPos = new RectF();
mScrollFade = new ScrollFade();
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setTextAlign(Paint.Align.CENTER);
mPaint.setTextSize(mOverlayTextSize);
mPaint.setColor(0xFFFFFFFF);
mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
}
private void removeThumb() {
mThumbVisible = false;
// Draw one last time to remove thumb
invalidate();
}
@Override
public void draw(Canvas canvas) {
super.draw(canvas);
if (!mThumbVisible) {
// No need to draw the rest
return;
}
final int y = mThumbY;
final int viewWidth = getWidth();
final CustomFastScrollView.ScrollFade scrollFade = mScrollFade;
int alpha = -1;
if (scrollFade.mStarted) {
alpha = scrollFade.getAlpha();
if (alpha < ScrollFade.ALPHA_MAX / 2) {
mCurrentThumb.setAlpha(alpha * 2);
}
int left = viewWidth - (mThumbW * alpha) / ScrollFade.ALPHA_MAX;
mCurrentThumb.setBounds(left, 0, viewWidth, mThumbH);
mChangedBounds = true;
}
canvas.translate(0, y);
mCurrentThumb.draw(canvas);
canvas.translate(0, -y);
// If user is dragging the scroll bar, draw the alphabet overlay
if (mDragging && mDrawOverlay) {
mOverlayDrawable.draw(canvas);
final Paint paint = mPaint;
float descent = paint.descent();
final RectF rectF = mOverlayPos;
canvas.drawText(mSectionText, (int) (rectF.left + rectF.right) / 2,
(int) (rectF.bottom + rectF.top) / 2 + descent, paint);
} else if (alpha == 0) {
scrollFade.mStarted = false;
removeThumb();
} else {
invalidate(viewWidth - mThumbW, y, viewWidth, y + mThumbH);
}
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (mCurrentThumb != null) {
mCurrentThumb.setBounds(w - mThumbW, 0, w, mThumbH);
}
final RectF pos = mOverlayPos;
pos.left = (w - mOverlayWidth) / 2;
pos.right = pos.left + mOverlayWidth;
pos.top = h / 10; // 10% from top
pos.bottom = pos.top + mOverlayHeight;
mOverlayDrawable.setBounds((int) pos.left, (int) pos.top,
(int) pos.right, (int) pos.bottom);
}
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
int totalItemCount) {
if (totalItemCount - visibleItemCount > 0 && !mDragging) {
mThumbY = ((getHeight() - mThumbH) * firstVisibleItem) / (totalItemCount - visibleItemCount);
if (mChangedBounds) {
final int viewWidth = getWidth();
mCurrentThumb.setBounds(viewWidth - mThumbW, 0, viewWidth, mThumbH);
mChangedBounds = false;
}
}
mScrollCompleted = true;
if (firstVisibleItem == mVisibleItem) {
return;
}
mVisibleItem = firstVisibleItem;
if (!mThumbVisible || mScrollFade.mStarted) {
mThumbVisible = true;
mCurrentThumb.setAlpha(ScrollFade.ALPHA_MAX);
}
mHandler.removeCallbacks(mScrollFade);
mScrollFade.mStarted = false;
if (!mDragging) {
mHandler.postDelayed(mScrollFade, 1500);
}
}
private void getSections() {
Adapter adapter = mList.getAdapter();
if (adapter instanceof HeaderViewListAdapter) {
mListOffset = ((HeaderViewListAdapter)adapter).getHeadersCount();
adapter = ((HeaderViewListAdapter)adapter).getWrappedAdapter();
}
if (adapter instanceof SectionIndexer) {
mListAdapter = (BaseAdapter) adapter;
mSections = ((SectionIndexer) mListAdapter).getSections();
}
}
public void onChildViewAdded(View parent, View child) {
if (child instanceof ListView) {
mList = (ListView)child;
mList.setOnScrollListener(this);
getSections();
}
}
public void onChildViewRemoved(View parent, View child) {
if (child == mList) {
mList = null;
mListAdapter = null;
mSections = null;
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if (mThumbVisible && ev.getAction() == MotionEvent.ACTION_DOWN) {
if (ev.getX() > getWidth() - mThumbW && ev.getY() >= mThumbY &&
ev.getY() <= mThumbY + mThumbH) {
mDragging = true;
return true;
}
}
return false;
}
private void scrollTo(float position) {
int count = mList.getCount();
mScrollCompleted = false;
final Object[] sections = mSections;
int sectionIndex;
if (sections != null && sections.length > 1) {
final int nSections = sections.length;
int section = (int) (position * nSections);
if (section >= nSections) {
section = nSections - 1;
}
sectionIndex = section;
final SectionIndexer baseAdapter = (SectionIndexer) mListAdapter;
int index = baseAdapter.getPositionForSection(section);
// Given the expected section and index, the following code will
// try to account for missing sections (no names starting with..)
// It will compute the scroll space of surrounding empty sections
// and interpolate the currently visible letter's range across the
// available space, so that there is always some list movement while
// the user moves the thumb.
int nextIndex = count;
int prevIndex = index;
int prevSection = section;
int nextSection = section + 1;
// Assume the next section is unique
if (section < nSections - 1) {
nextIndex = baseAdapter.getPositionForSection(section + 1);
}
// Find the previous index if we're slicing the previous section
if (nextIndex == index) {
// Non-existent letter
while (section > 0) {
section--;
prevIndex = baseAdapter.getPositionForSection(section);
if (prevIndex != index) {
prevSection = section;
sectionIndex = section;
break;
}
}
}
// Find the next index, in case the assumed next index is not
// unique. For instance, if there is no P, then request for P's
// position actually returns Q's. So we need to look ahead to make
// sure that there is really a Q at Q's position. If not, move
// further down...
int nextNextSection = nextSection + 1;
while (nextNextSection < nSections &&
baseAdapter.getPositionForSection(nextNextSection) == nextIndex) {
nextNextSection++;
nextSection++;
}
// Compute the beginning and ending scroll range percentage of the
// currently visible letter. This could be equal to or greater than
// (1 / nSections).
float fPrev = (float) prevSection / nSections;
float fNext = (float) nextSection / nSections;
index = prevIndex + (int) ((nextIndex - prevIndex) * (position - fPrev)
/ (fNext - fPrev));
// Don't overflow
if (index > count - 1) index = count - 1;
mList.setSelectionFromTop(index + mListOffset, 0);
} else {
int index = (int) (position * count);
mList.setSelectionFromTop(index + mListOffset, 0);
sectionIndex = -1;
}
if (sectionIndex >= 0) {
String text = mSectionText = sections[sectionIndex].toString();
mDrawOverlay = (text.length() != 1 || text.charAt(0) != ' ') &&
sectionIndex < sections.length;
} else {
mDrawOverlay = false;
}
}
private void cancelFling() {
// Cancel the list fling
MotionEvent cancelFling = MotionEvent.obtain(0, 0, MotionEvent.ACTION_CANCEL, 0, 0, 0);
mList.onTouchEvent(cancelFling);
cancelFling.recycle();
}
@Override
public boolean onTouchEvent(MotionEvent me) {
if (me.getAction() == MotionEvent.ACTION_DOWN) {
if (me.getX() > getWidth() - mThumbW
&& me.getY() >= mThumbY
&& me.getY() <= mThumbY + mThumbH) {
mDragging = true;
if (mListAdapter == null && mList != null) {
getSections();
}
cancelFling();
return true;
}
} else if (me.getAction() == MotionEvent.ACTION_UP) {
if (mDragging) {
mDragging = false;
final Handler handler = mHandler;
handler.removeCallbacks(mScrollFade);
handler.postDelayed(mScrollFade, 1000);
return true;
}
} else if (me.getAction() == MotionEvent.ACTION_MOVE) {
if (mDragging) {
final int viewHeight = getHeight();
mThumbY = (int) me.getY() - mThumbH + 10;
if (mThumbY < 0) {
mThumbY = 0;
} else if (mThumbY + mThumbH > viewHeight) {
mThumbY = viewHeight - mThumbH;
}
// If the previous scrollTo is still pending
if (mScrollCompleted) {
scrollTo((float) mThumbY / (viewHeight - mThumbH));
}
return true;
}
}
return super.onTouchEvent(me);
}
public class ScrollFade implements Runnable {
long mStartTime;
long mFadeDuration;
boolean mStarted;
static final int ALPHA_MAX = 200;
static final long FADE_DURATION = 200;
void startFade() {
mFadeDuration = FADE_DURATION;
mStartTime = SystemClock.uptimeMillis();
mStarted = true;
}
int getAlpha() {
if (!mStarted) {
return ALPHA_MAX;
}
int alpha;
long now = SystemClock.uptimeMillis();
if (now > mStartTime + mFadeDuration) {
alpha = 0;
} else {
alpha = (int) (ALPHA_MAX - ((now - mStartTime) * ALPHA_MAX) / mFadeDuration);
}
return alpha;
}
public void run() {
if (!mStarted) {
startFade();
invalidate();
}
if (getAlpha() > 0) {
final int y = mThumbY;
final int viewWidth = getWidth();
invalidate(viewWidth - mThumbW, y, viewWidth, y + mThumbH);
} else {
mStarted = false;
removeThumb();
}
}
}
}
您还可以使用ALPHA_MAX调整滚动缩略图的半透明度。
然后在你的布局xml文件中输入这样的内容：
<com.myapp.CustomFastScrollView android:layout_width="wrap_content"
android:layout_height="fill_parent"
myapp:overlayWidth="175dp" myapp:overlayHeight="110dp" myapp:overlayTextSize="36dp"
myapp:overlayScrollThumbWidth="60dp" android:id="@+id/fast_scroll_view">
<ListView android:id="@android:id/list" android:layout_width="wrap_content"
android:layout_height="fill_parent"/>
<TextView android:id="@android:id/empty"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="" />
</com.myapp.CustomFastScrollView>
不要忘记在布局xml文件中声明属性：
... xmlns:myapp= "http://schemas.android.com/apk/res/com.myapp" ...
您还需要从该Android源代码中获取R.drawable.scrollbar_handle_accelerated_anim2个drawable。上面的链接只包含mdpi。
答案 1 :(得分：2)
FastScroller小部件负责绘制叠加层。你应该看看它的来源：
https://android.googlesource.com/platform/frameworks/base/+/gingerbread-release/core/java/android/widget/FastScroller.java
搜索评论：
// If user is dragging the scroll bar, draw the alphabet overlay