通常情况下,粘性标题的工作方式是将可滚动数据划分为各自具有标题的部分,并随着向下滚动,后续部分的标题取代了
我需要在各自的部分中有额外的粘性标题。例如,如果
这里是实现一维粘性标题的
https://github.com/emilsjolander/StickyScrollViewItems
我想要做的是适应我的需求,但我尝试浏览这个实现方式以了解它如何实现将视图粘贴在
ScrollView
顶部的标题。我需要在各自的部分中有额外的粘性标题。例如,如果
header1
固定在顶部,则它的第一个部分的标题——header1a
——会固定在其下方,但是当我们到达第1b
节时,1b
的标题将替换1a
的标题,但保留header1
固定在原地;最后,当我们到达第2
节时,header2
将替换前一节的当前固定标题——header1
和header1b
。这里是实现一维粘性标题的
ScrollView
实现:https://github.com/emilsjolander/StickyScrollViewItems
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AlphaAnimation;
import java.util.ArrayList;
/**
*
* @author Emil Sj�lander - sjolander.emil@gmail.com
*
*/
public class StickyScrollView extends ScrollView {
/**
* Tag for views that should stick and have constant drawing. e.g. TextViews, ImageViews etc
*/
public static final String STICKY_TAG = "sticky";
/**
* Flag for views that should stick and have non-constant drawing. e.g. Buttons, ProgressBars etc
*/
public static final String FLAG_NONCONSTANT = "-nonconstant";
/**
* Flag for views that have aren't fully opaque
*/
public static final String FLAG_HASTRANSPARANCY = "-hastransparancy";
/**
* Default height of the shadow peeking out below the stuck view.
*/
private static final int DEFAULT_SHADOW_HEIGHT = 10; // dp;
private ArrayList<View> mStickyViews;
private View mCurrentlyStickingView;
private float mStickyViewTopOffset;
private int mStickyViewLeftOffset;
private boolean mRedirectTouchesToStickyView;
private boolean mClippingToPadding;
private boolean mClipToPaddingHasBeenSet;
private int mShadowHeight;
private Drawable mShadowDrawable;
private final Runnable mInvalidateRunnable = new Runnable() {
@Override
public void run() {
if(mCurrentlyStickingView !=null){
int l = getLeftForViewRelativeOnlyChild(mCurrentlyStickingView);
int t = getBottomForViewRelativeOnlyChild(mCurrentlyStickingView);
int r = getRightForViewRelativeOnlyChild(mCurrentlyStickingView);
int b = (int) (getScrollY() + (mCurrentlyStickingView.getHeight() + mStickyViewTopOffset));
invalidate(l,t,r,b);
}
postDelayed(this, 16);
}
};
public StickyScrollView(Context context) {
this(context, null);
}
public StickyScrollView(Context context, AttributeSet attrs) {
this(context, attrs, android.R.attr.scrollViewStyle);
}
public StickyScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
setup();
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.StickyScrollView, defStyle, 0);
final float density = context.getResources().getDisplayMetrics().density;
int defaultShadowHeightInPix = (int) (DEFAULT_SHADOW_HEIGHT * density + 0.5f);
mShadowHeight = a.getDimensionPixelSize(
R.styleable.StickyScrollView_stuckShadowHeight,
defaultShadowHeightInPix);
int shadowDrawableRes = a.getResourceId(
R.styleable.StickyScrollView_stuckShadowDrawable, -1);
if (shadowDrawableRes != -1) {
mShadowDrawable = context.getResources().getDrawable(
shadowDrawableRes);
}
a.recycle();
}
/**
* Sets the height of the shadow drawable in pixels.
*
* @param height
*/
public void setShadowHeight(int height) {
mShadowHeight = height;
}
public void setup(){
mStickyViews = new ArrayList<View>();
}
private int getLeftForViewRelativeOnlyChild(View v){
int left = v.getLeft();
while(v.getParent() != getChildAt(0)){
v = (View) v.getParent();
left += v.getLeft();
}
return left;
}
private int getTopForViewRelativeOnlyChild(View v){
int top = v.getTop();
while(v.getParent() != getChildAt(0)){
v = (View) v.getParent();
top += v.getTop();
}
return top;
}
private int getRightForViewRelativeOnlyChild(View v){
int right = v.getRight();
while(v.getParent() != getChildAt(0)){
v = (View) v.getParent();
right += v.getRight();
}
return right;
}
private int getBottomForViewRelativeOnlyChild(View v){
int bottom = v.getBottom();
while(v.getParent() != getChildAt(0)){
v = (View) v.getParent();
bottom += v.getBottom();
}
return bottom;
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if(!mClipToPaddingHasBeenSet){
mClippingToPadding = true;
}
notifyHierarchyChanged();
}
@Override
public void setClipToPadding(boolean clipToPadding) {
super.setClipToPadding(clipToPadding);
mClippingToPadding = clipToPadding;
mClipToPaddingHasBeenSet = true;
}
@Override
public void addView(View child) {
super.addView(child);
findStickyViews(child);
}
@Override
public void addView(View child, int index) {
super.addView(child, index);
findStickyViews(child);
}
@Override
public void addView(View child, int index, android.view.ViewGroup.LayoutParams params) {
super.addView(child, index, params);
findStickyViews(child);
}
@Override
public void addView(View child, int width, int height) {
super.addView(child, width, height);
findStickyViews(child);
}
@Override
public void addView(View child, android.view.ViewGroup.LayoutParams params) {
super.addView(child, params);
findStickyViews(child);
}
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
if(mCurrentlyStickingView != null){
canvas.save();
canvas.translate(getPaddingLeft() + mStickyViewLeftOffset, getScrollY() + mStickyViewTopOffset + (mClippingToPadding ? getPaddingTop() : 0));
canvas.clipRect(0, (mClippingToPadding ? -mStickyViewTopOffset : 0), getWidth() - mStickyViewLeftOffset,mCurrentlyStickingView.getHeight() + mShadowHeight + 1);
if (mShadowDrawable != null) {
int left = 0;
int right = mCurrentlyStickingView.getWidth();
int top = mCurrentlyStickingView.getHeight();
int bottom = mCurrentlyStickingView.getHeight() + mShadowHeight;
mShadowDrawable.setBounds(left, top, right, bottom);
mShadowDrawable.draw(canvas);
}
canvas.clipRect(0, (mClippingToPadding ? -mStickyViewTopOffset : 0), getWidth(), mCurrentlyStickingView.getHeight());
if(getStringTagForView(mCurrentlyStickingView).contains(FLAG_HASTRANSPARANCY)){
showView(mCurrentlyStickingView);
mCurrentlyStickingView.draw(canvas);
hideView(mCurrentlyStickingView);
}else{
mCurrentlyStickingView.draw(canvas);
}
canvas.restore();
}
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if(ev.getAction()==MotionEvent.ACTION_DOWN){
mRedirectTouchesToStickyView = true;
}
if(mRedirectTouchesToStickyView){
mRedirectTouchesToStickyView = mCurrentlyStickingView != null;
if(mRedirectTouchesToStickyView){
mRedirectTouchesToStickyView =
ev.getY()<=(mCurrentlyStickingView.getHeight()+ mStickyViewTopOffset) &&
ev.getX() >= getLeftForViewRelativeOnlyChild(mCurrentlyStickingView) &&
ev.getX() <= getRightForViewRelativeOnlyChild(mCurrentlyStickingView);
}
}else if(mCurrentlyStickingView == null){
mRedirectTouchesToStickyView = false;
}
if(mRedirectTouchesToStickyView){
ev.offsetLocation(0, -1*((getScrollY() + mStickyViewTopOffset) - getTopForViewRelativeOnlyChild(mCurrentlyStickingView)));
}
return super.dispatchTouchEvent(ev);
}
private boolean hasNotDoneActionDown = true;
@Override
public boolean onTouchEvent(MotionEvent ev) {
if(mRedirectTouchesToStickyView){
ev.offsetLocation(0, ((getScrollY() + mStickyViewTopOffset) - getTopForViewRelativeOnlyChild(mCurrentlyStickingView)));
}
if(ev.getAction()==MotionEvent.ACTION_DOWN){
hasNotDoneActionDown = false;
}
if(hasNotDoneActionDown){
MotionEvent down = MotionEvent.obtain(ev);
down.setAction(MotionEvent.ACTION_DOWN);
super.onTouchEvent(down);
hasNotDoneActionDown = false;
}
if(ev.getAction()==MotionEvent.ACTION_UP || ev.getAction()==MotionEvent.ACTION_CANCEL){
hasNotDoneActionDown = true;
}
return super.onTouchEvent(ev);
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
doTheStickyThing();
}
private void doTheStickyThing() {
View viewThatShouldStick = null;
View approachingStickyView = null;
for(View v : mStickyViews){
int viewTop = getTopForViewRelativeOnlyChild(v) - getScrollY() + (mClippingToPadding ? 0 : getPaddingTop());
if(viewTop<=0){
if(viewThatShouldStick==null || viewTop>(getTopForViewRelativeOnlyChild(viewThatShouldStick) - getScrollY() + (mClippingToPadding ? 0 : getPaddingTop()))){
viewThatShouldStick = v;
}
}else{
if(approachingStickyView == null || viewTop<(getTopForViewRelativeOnlyChild(approachingStickyView) - getScrollY() + (mClippingToPadding ? 0 : getPaddingTop()))){
approachingStickyView = v;
}
}
}
if(viewThatShouldStick!=null){
mStickyViewTopOffset = approachingStickyView == null ? 0 : Math.min(0, getTopForViewRelativeOnlyChild(approachingStickyView) - getScrollY() + (mClippingToPadding ? 0 : getPaddingTop()) - viewThatShouldStick.getHeight());
if(viewThatShouldStick != mCurrentlyStickingView){
if(mCurrentlyStickingView !=null){
stopStickingCurrentlyStickingView();
}
// only compute the left offset when we start sticking.
mStickyViewLeftOffset = getLeftForViewRelativeOnlyChild(viewThatShouldStick);
startStickingView(viewThatShouldStick);
}
}else if(mCurrentlyStickingView !=null){
stopStickingCurrentlyStickingView();
}
}
private void startStickingView(View viewThatShouldStick) {
mCurrentlyStickingView = viewThatShouldStick;
if(getStringTagForView(mCurrentlyStickingView).contains(FLAG_HASTRANSPARANCY)){
hideView(mCurrentlyStickingView);
}
if(((String) mCurrentlyStickingView.getTag()).contains(FLAG_NONCONSTANT)){
post(mInvalidateRunnable);
}
}
private void stopStickingCurrentlyStickingView() {
if(getStringTagForView(mCurrentlyStickingView).contains(FLAG_HASTRANSPARANCY)){
showView(mCurrentlyStickingView);
}
mCurrentlyStickingView = null;
removeCallbacks(mInvalidateRunnable);
}
/**
* Notify that the sticky attribute has been added or removed from one or more views in the View hierarchy
*/
public void notifyStickyAttributeChanged(){
notifyHierarchyChanged();
}
private void notifyHierarchyChanged(){
if(mCurrentlyStickingView !=null){
stopStickingCurrentlyStickingView();
}
mStickyViews.clear();
findStickyViews(getChildAt(0));
doTheStickyThing();
invalidate();
}
private void findStickyViews(View v) {
if(v instanceof ViewGroup){
ViewGroup vg = (ViewGroup)v;
for(int i = 0 ; i<vg.getChildCount() ; i++){
String tag = getStringTagForView(vg.getChildAt(i));
if(tag!=null && tag.contains(STICKY_TAG)){
mStickyViews.add(vg.getChildAt(i));
}else if(vg.getChildAt(i) instanceof ViewGroup){
findStickyViews(vg.getChildAt(i));
}
}
}else{
String tag = (String) v.getTag();
if(tag!=null && tag.contains(STICKY_TAG)){
mStickyViews.add(v);
}
}
}
private String getStringTagForView(View v){
Object tagObject = v.getTag();
return String.valueOf(tagObject);
}
private void hideView(View v) {
if(Build.VERSION.SDK_INT>=11){
v.setAlpha(0);
}else{
AlphaAnimation anim = new AlphaAnimation(1, 0);
anim.setDuration(0);
anim.setFillAfter(true);
v.startAnimation(anim);
}
}
private void showView(View v) {
if(Build.VERSION.SDK_INT>=11){
v.setAlpha(1);
}else{
AlphaAnimation anim = new AlphaAnimation(0, 1);
anim.setDuration(0);
anim.setFillAfter(true);
v.startAnimation(anim);
}
}
}
我想要做的是适应我的需求,但我尝试浏览这个实现方式以了解它如何实现将视图粘贴在
ScrollView
的顶部,但我无法弄清楚它是如何实现的。有人知道这是如何工作的吗?
编辑:
这是我想要应用此概念的布局:
*请记住,Headers
(Header 1和2)是自定义的ViewGroups
,包含Sub-Headers
(Header 1a,1b,2a),后者也是自定义的ViewGroups
,包含自定义视图,即Items
。