Android开发滑动悬停效果
Android开发滑动悬停效果，有点难度，但源码中我已经加入相应注释，你只要修改布局即可。很常见的需求
一、思路：
自定义悬停控件LetterStickyNavLayout，它是继承LinearLayout
二、效果图：
看视频更直观点：
Android开发教程实战案例源码分享-滑动悬停效果
三、关键代码：
public class LetterStickyNavLayout extends LinearLayout {
private ScrollListener scrollListener;
private Context mContext;
private View mTop;
private View mNav;
private LinearLayout llContent;
private int mTopViewHeight;
private ViewGroup mInnerScrollView;
private boolean isTopHidden = false;
private OverScroller mScroller;
private VelocityTracker mVelocityTracker;
private int mTouchSlop;
private int mMaximumVelocity, mMinimumVelocity;
private float mLastY;
private boolean mDragging;
private boolean isInControl = false;
private boolean isChange=false;
private int screenWidth;
public LetterStickyNavLayout(Context context, AttributeSet attrs) {
super(context, attrs);
setOrientation(LinearLayout.VERTICAL);
mContext = context;
mScroller = new OverScroller(context);
mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
mMaximumVelocity = ViewConfiguration.get(context)
.getScaledMaximumFlingVelocity();
mMinimumVelocity = ViewConfiguration.get(context)
.getScaledMinimumFlingVelocity();
screenWidth= getScreenWidthPx(mContext);
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
mTop = findViewById(R.id.id_stickynavlayout_topview);
mNav = findViewById(R.id.id_stickynavlayout_indicator);
View llView = findViewById(R.id.id_stickynavlayout_content);
if (!(llView instanceof LinearLayout)) {
throw new RuntimeException(
"id_stickynavlayout_content show used by LinearLayout !");
}
llContent =(LinearLayout)llView;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
ViewGroup.LayoutParams params;
params = llContent.getLayoutParams();
int height;
if(checkDeviceHasNavigationBar(mContext)){
height = getMeasuredHeight() - mNav.getMeasuredHeight() + dip2px(mContext, 34);
}else{
height = getMeasuredHeight() - mNav.getMeasuredHeight();
}
if (height >= screenWidth && !isChange) {
params.height = height;
isChange = true;
}
getChildAt(0).measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
setMeasuredDimension(getMeasuredWidth(), mTop.getMeasuredHeight() + mNav.getMeasuredHeight() + llContent.getMeasuredHeight());
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mTopViewHeight = mTop.getMeasuredHeight() ;
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
int action = ev.getAction();
float y = ev.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastY = y;
break;
case MotionEvent.ACTION_MOVE:
float dy = y - mLastY;
getCurrentScrollView();
if(mInnerScrollView != null && mInnerScrollView.getVisibility()== View.VISIBLE && mInnerScrollView instanceof RecyclerView){
//SwipeRecyclerview mSRRceylerView = (SwipeRecyclerview) mInnerScrollView;
RecyclerView lv = (RecyclerView) mInnerScrollView;
View c = lv.getChildAt(0);
if (!isInControl && c != null && c.getTop() == 0 && isTopHidden
&& dy > 0) {
isInControl = true;
ev.setAction(MotionEvent.ACTION_CANCEL);
MotionEvent ev2 = MotionEvent.obtain(ev);
dispatchTouchEvent(ev);
ev2.setAction(MotionEvent.ACTION_DOWN);
return dispatchTouchEvent(ev2);
}
} else {
if (llContent != null) {
if (!isInControl && androidx.core.view.ViewCompat.canScrollVertically(llContent, -1) && isTopHidden
&& dy > 0) {
isInControl = true;
ev.setAction(MotionEvent.ACTION_CANCEL);
MotionEvent ev2 = MotionEvent.obtain(ev);
dispatchTouchEvent(ev);
ev2.setAction(MotionEvent.ACTION_DOWN);
return dispatchTouchEvent(ev2);
}
}
}
break;
}
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
float y = ev.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
mLastY = y;
break;
case MotionEvent.ACTION_MOVE:
float dy = y - mLastY;
if (Math.abs(dy) > mTouchSlop) {
mDragging = true;
if(mInnerScrollView != null && mInnerScrollView.getVisibility()== View.VISIBLE && mInnerScrollView instanceof RecyclerView){
//SwipeRecyclerview ptrlv = (SwipeRecyclerview) mInnerScrollView;
RecyclerView lv = (RecyclerView) mInnerScrollView;
View c = lv.getChildAt(0);
// 如果topView没有隐藏
// 或sc的PullToRefreshListView在顶部�&& topView隐藏 && 下拉，则拦截
if (!isTopHidden || (c != null && c.getTop() == 0 && isTopHidden && dy > 0 )) {
initVelocityTrackerIfNotExists();
mVelocityTracker.addMovement(ev);
mLastY = y;
return true;
}
} else {
if (llContent != null) {
if (!isTopHidden || (!androidx.core.view.ViewCompat.canScrollVertically(llContent, -1) && isTopHidden && dy > 0)) {
initVelocityTrackerIfNotExists();
mVelocityTracker.addMovement(ev);
mLastY = y;
return true;
}
}
}
}
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
mDragging = false;
recycleVelocityTracker();
break;
}
return super.onInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
initVelocityTrackerIfNotExists();
mVelocityTracker.addMovement(event);
int action = event.getAction();
float y = event.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
if (!mScroller.isFinished())
mScroller.abortAnimation();
mLastY = y;
return true;
case MotionEvent.ACTION_MOVE:
float dy = y - mLastY;
if (!mDragging && Math.abs(dy) > mTouchSlop) {
mDragging = true;
}
if (mDragging) {
scrollBy(0, (int) -dy);
// 如果topView隐藏，且上滑动时，则改变当前事件为ACTION_DOWN
if (getScrollY() == mTopViewHeight && dy < 0) {
event.setAction(MotionEvent.ACTION_DOWN);
dispatchTouchEvent(event);
isInControl = false;
}
}
mLastY = y;
break;
case MotionEvent.ACTION_CANCEL:
mDragging = false;
recycleVelocityTracker();
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
break;
case MotionEvent.ACTION_UP:
mDragging = false;
mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int velocityY = (int) mVelocityTracker.getYVelocity();
if (Math.abs(velocityY) > mMinimumVelocity) {
fling(-velocityY);
}
recycleVelocityTracker();
break;
}
return super.onTouchEvent(event);
}
public void fling(int velocityY) {
mScroller.fling(0, getScrollY(), 0, velocityY, 0, 0, 0, mTopViewHeight);
invalidate();
}
@Override
public void scrollTo(int x, int y) {
if (y < 0) {
y = 0;
}
if (y > mTopViewHeight) {
y = mTopViewHeight;
}
if (y != getScrollY()) {
super.scrollTo(x, y);
}
isTopHidden = getScrollY() == mTopViewHeight;
scrollListener.scrollToTop(isTopHidden);
}
@Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
scrollTo(0, mScroller.getCurrY());
invalidate();
}
}
private void initVelocityTrackerIfNotExists() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
private void getCurrentScrollView() {
if (llContent != null) {
mInnerScrollView = (ViewGroup) (llContent
.findViewById(R.id.id_stickynavlayout_swiperefrecyclerview));
}
}
/**
* 按钮滑动事件
*
* @param listener
*/
public void setOnScrollListener(ScrollListener listener) {
scrollListener = listener;
}
public interface ScrollListener {
public void scrollToTop(boolean flag);
}
//获取是否存在NavigationBar
public static boolean checkDeviceHasNavigationBar(Context context) {
boolean hasNavigationBar = false;
Resources rs = context.getResources();
int id = rs.getIdentifier("config_showNavigationBar", "bool", "android");
if (id > 0) {
hasNavigationBar = rs.getBoolean(id);
}
try {
Class systemPropertiesClass = Class.forName("android.os.SystemProperties");
Method m = systemPropertiesClass.getMethod("get", String.class);
String navBarOverride = (String) m.invoke(systemPropertiesClass, "qemu.hw.mainkeys");
if ("1".equals(navBarOverride)) {
hasNavigationBar = false;
} else if ("0".equals(navBarOverride)) {
hasNavigationBar = true;
}
} catch (Exception e) {
}
return hasNavigationBar;
}
public static int getScreenWidthPx(Context mContext) {
DisplayMetrics dm = mContext.getResources().getDisplayMetrics();
return dm.widthPixels;
}
public static int dip2px(Context context, float dpValue) {
final float scale = context.getResources().getDisplayMetrics().density;
return (int) (dpValue * scale + 0.5f);
}
}
四、项目demo源码结构图
有问题或者需要完整源码私信我