View的触摸反馈
onTouchEvent
重写onTouchEvent(), 原本是长这样的，
@Override
public boolean onTouchEvent(MotionEvent event) {
return super.onTouchEvent(event);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
//这样view就消费了事件
return true;
}
一下这样的话，点击事件才有效果，如上什么都不处理就仅仅返回true，那么在外面添加 onClickListener事件是没有反馈的，这就说明onTouchEvent的优先级高于 OnClickListener.
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getActionMasked() == MotionEvent.ACTION_UP){
performClick();
}
return true;
}
当触摸到黄色块的onTouchEvent 处理了返回true的时候，在它底下的绿色快以及父View的onTouchEvent()都不会收到事件
OnTouchEvent是事件组，只有在 down事件返回true的时候，后续的move、up事件都会传过来。跟上面的直接返回true是一样的。
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getActionMasked() == MotionEvent.ACTION_DOWN){
return true;
}
return super.onTouchEvent(event);
}
event.getAction() 其实包含了两个信息，down事件以
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getActionMasked() == MotionEvent.ACTION_UP){
performClick();
}
//包含两个信息，按下/抬起 ， 第几个手指，处理需要逻辑。所以按下分两种MotionEvent.ACTION_DOWN， MotionEvent.ACTION_POINTER_DOWN。两个信息被压到一个变量里面，类似于MeasureDesc存储
switch (event.getAction()){
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
}
//这里只是包含点击事件
switch (event.getActionMasked()){
case MotionEvent.ACTION_POINTER_DOWN:
case MotionEvent.ACTION_POINTER_UP:
}
//第几个手指
switch (event.getActionIndex()){
}
return true;
}
View的onTouchEvent
点击、长按，右键点击。
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
final boolean clickable = ((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE;
//CONTEXT_CLICKABLE 是历史的长按菜单。
if ((viewFlags & ENABLED_MASK) == DISABLED) {
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != 0){
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
// A disabled view that is clickable still consumes the touch
// events, it just doesn't respond to them.
//事件被consume，但是disabled，自己不能点，底下的父view也不能被点击
return clickable;
}
if (mTouchDelegate != null) {//一般用在增大点击范围。
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
//clickable这个View可点击，比如TextView就没有用。
//(viewFlags & TOOLTIP) == TOOLTIP SDK 28引入的点击，解释性的。
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_DOWN:
//InputDevice.SOURCE_TOUCHSCREEN TOOLTIP 提示文字远一点的距离
if (event.getSource() == InputDevice.SOURCE_TOUCHSCREEN) {
mPrivateFlags3 |= PFLAG3_FINGER_DOWN;
}
mHasPerformedLongPress = false;
if (!clickable) {//给提示性文字用的。
checkForLongClick(0, x, y);
break;
}
//检测鼠标右键点击
if (performButtonActionOnTouchDown(event)) {
break;
}
// Walk up the hierarchy to determine if we're inside a scrolling container.
//是否在滑动空间里。
boolean isInScrollingContainer = isInScrollingContainer();
// For views inside a scrolling container, delay the pressed feedback for
// a short period in case this is a scroll.
if (isInScrollingContainer) {
//在滑动的父控件里面。点下去，有可能是滑动、或者仅仅是点击。记下来，暂时不处理为滑动，当
mPrivateFlags |= PFLAG_PREPRESSED;
if (mPendingCheckForTap == null) {
mPendingCheckForTap = new CheckForTap();
}
mPendingCheckForTap.x = event.getX();
mPendingCheckForTap.y = event.getY();
postDelayed(mPendingCheckForTap,
ViewConfiguration.getTapTimeout());
} else {
// Not inside a scrolling container, so show the feedback right away
setPressed(true, x, y);
checkForLongClick(0, x, y);
}
break;
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP){
//TOOlTIP 延迟消失
handleTooltipUp();
}
if (!clickable) {//这个View仅仅处理 TOOlTI，释放返回
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
}
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != 0;
if ((mPrivateFlags & PFLAG_PRESSED) != 0 || prepressed) {
// take focus if we don't have it already and we should in
// touch mode.
boolean focusTaken = false;
if (isFocusable() && isFocusableInTouchMode() && !isFocused()){
focusTaken = requestFocus();
}
if (prepressed) {
// The button is being released before we actually
// showed it as pressed. Make it show the pressed
// state now (before scheduling the click) to ensure
// the user sees it.
setPressed(true, x, y);
}
if (!mHasPerformedLongPress && !mIgnoreNextUpEvent) {
// This is a tap, so remove the longpress check
removeLongPressCallback();
// Only perform take click actions if we were in the pressed state
if (!focusTaken) {
// Use a Runnable and post this rather than calling
// performClick directly. This lets other visual state
// of the view update before click actions start.
if (mPerformClick == null) {
mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
performClickInternal();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
//预按下，抬起设置延迟，稍微给人感觉到点击了。
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
// If the post failed, unpress right now
mUnsetPressedState.run();
}
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_CANCEL:
if (clickable) {
setPressed(false);
}
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
break;
case MotionEvent.ACTION_MOVE:
if (clickable) {
//波纹效果
drawableHotspotChanged(x, y);
}
// Be lenient about moving outside of buttons
//移出去的宽容距离 mTouchSlop
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
// Remove any future long press/tap checks
removeTapCallback();
removeLongPressCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != 0) {
setPressed(false);
}
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
}
break;
}
return true;
}
return false;
}
/**
* @hide 任何级别的父View是否在滑动空间里。
*/
public boolean isInScrollingContainer() {
ViewParent p = getParent();
while (p != null && p instanceof ViewGroup) {
if (((ViewGroup) p).shouldDelayChildPressedState()) {
return true;
}
p = p.getParent();
}
return false;
}
//需要等待100ms的等待才触发按下。
public boolean shouldDelayChildPressedState() {
return true;
}
ViewGroup的触摸反馈
ListView，ScrollView父view 拦截 onInterceptTouchEvent()
public boolean dispatchTouchEvent(MotionEvent ev){
boolean consume = false;
if(onInterceptTouchEvent(ev)){
consume = onTouchEvent(ev);
}else{
consume = child.dispatchTouchEvent(ev);
}
return consume;
}
在OnInterceptTouchEvent中拦截，并记下拦截时候的坐标等事件。
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
int delta = ev.getY() ????;//纵向距离
if (Math.abs(delta) > SLOP) {
//最后一次触发自己的onInterceptTouchEvent， 第一次去触发自己的
return true;
} else {
//首先返回false，当满足条件后再返回 true。
return false;
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
return super.onTouchEvent(event);
}
触摸反馈的流程
View的dispatchTouchEvent, 外挂的mOnTouchListener 优先级比onTouchEvent(event)更高。
public boolean dispatchTouchEvent(MotionEvent event) {
// If the event should be handled by accessibility focus first.
if (event.isTargetAccessibilityFocus()) {
// We don't have focus or no virtual descendant has it, do not handle the event.
if (!isAccessibilityFocusedViewOrHost()) {
return false;
}
// We have focus and got the event, then use normal event dispatch.
event.setTargetAccessibilityFocus(false);
}
boolean result = false;
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(event, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)){
result = true;
}
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
//
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
if (!result && onTouchEvent(event)) {
result = true;
}
}
if (!result && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(event, 0);
}
// Clean up after nested scrolls if this is the end of a gesture;
// also cancel it if we tried an ACTION_DOWN but we didn't want the rest
// of the gesture.
if (actionMasked == MotionEvent.ACTION_UP ||
actionMasked == MotionEvent.ACTION_CANCEL ||
(actionMasked == MotionEvent.ACTION_DOWN && !result)) {
stopNestedScroll();
}
return result;
}
ViewGroup.dispatchTouchEvent()
-
如果是用户初次按下（Action_down），清空TouchTargets 和 DISALLOW_INTERCEPT标记（requestDisallow）
-
拦截处理
-
如果不拦截并且不是CANCEL事件，并且是DOWN或者POINTER_DOWN, 尝试把pointer(手指)通过 TouchTarget分配给子View；并且如果分配给了新的子View， 调用child.dispatchTouchEvent()把事件传给子View
-
看有没有TouchTarget（有哪些子View要消费事件。）
** 如果没有，调用自己的super.dispatchTouchEvent()
**如果有， 调用child.dispatchTouchEvent()把事件传给对应的子View（如果有的话）
-
如果是POINTER_UP, 从TouchTargets中清除POINTER信息；如果是UP或Cancel，重置状态。
dispatchTransformedTouchEvent：确定要分配给哪个子View
addTouchTarget：分配给哪个子View
