在android觸屏事件中，我們經常會碰到
onclick()
,
onTouch()
,
onTouchEven()
等方法，那誰會先執行，執行順序又是怎麼樣呢？
View的觸屏事件處理
為弄清除上面那些，首先從源碼入手，看看其整個觸屏事件分發的過程．
先從
dispatchTouchEvent()
分析:
/**
* Pass the touch screen motion event down to the target view, or this
* view if it is the target.
*
* @param event The motion event to be dispatched.
* @return True if the event was handled by the view, false otherwise.
*/
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, );
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
if (onFilterTouchEventForSecurity(event)) {
//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, );
}
// 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;
}
分析這段源碼，便知道有些細節地方，如果目标View不能擷取焦點，那麼就不會處理觸屏事件，而是直接傳回false ，否則判斷目标View是否滿足注冊了
onTouchListener()
監聽以及可點選的條件，滿足則會調用
onTouch()
，如果
onTouch()
傳回true,那麼就不會再執行
onTouchEvent()
了，如果前面
onTouch()
傳回了false,那麼就會由
onTouchEvent()
的傳回值來确定最終的結果值了,是以遵從
onTouch()==true? true:onTouchEvent()
規則．在這段源碼中，可以看出其執行順序的優先級是
dispatchOnTouchEvent()
>>>>
onTouch()
>>>>
onTouchEvent()
．
再來看看
onTouchEvent()
在View.java源碼中有的實作:
/**
* Implement this method to handle touch screen motion events.
* <p>
* If this method is used to detect click actions, it is recommended that
* the actions be performed by implementing and calling
* {@link #performClick()}. This will ensure consistent system behavior,
* including:
* <ul>
* <li>obeying click sound preferences
* <li>dispatching OnClickListener calls
* <li>handling {@link AccessibilityNodeInfo#ACTION_CLICK ACTION_CLICK} when
* accessibility features are enabled
* </ul>
*
* @param event The motion event.
* @return True if the event was handled, false otherwise.
*/
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();
final float y = event.getY();
final int viewFlags = mViewFlags;
final int action = event.getAction();
if ((viewFlags & ENABLED_MASK) == DISABLED) {
if (action == MotionEvent.ACTION_UP && (mPrivateFlags & PFLAG_PRESSED) != ) {
setPressed(false);
}
// A disabled view that is clickable still consumes the touch
// events, it just doesn't respond to them.
return (((viewFlags & CLICKABLE) == CLICKABLE
|| (viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE)
|| (viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE);
}
if (mTouchDelegate != null) {
if (mTouchDelegate.onTouchEvent(event)) {
return true;
}
}
if (((viewFlags & CLICKABLE) == CLICKABLE ||
(viewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) ||
(viewFlags & CONTEXT_CLICKABLE) == CONTEXT_CLICKABLE) {
switch (action) {
case MotionEvent.ACTION_UP:
boolean prepressed = (mPrivateFlags & PFLAG_PREPRESSED) != ;
if ((mPrivateFlags & PFLAG_PRESSED) != || 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);
}
//如果onLongClick()傳回true,就不會執行onClick()
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)) {
performClick();
}
}
}
if (mUnsetPressedState == null) {
mUnsetPressedState = new UnsetPressedState();
}
if (prepressed) {
postDelayed(mUnsetPressedState,
ViewConfiguration.getPressedStateDuration());
} else if (!post(mUnsetPressedState)) {
// If the post failed, unpress right now
mUnsetPressedState.run();
}
removeTapCallback();
}
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_DOWN:
mHasPerformedLongPress = false;
if (performButtonActionOnTouchDown(event)) {
break;
}
// Walk up the hierarchy to determine if we're inside a scrolling container.
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) {
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();
}
break;
case MotionEvent.ACTION_CANCEL:
setPressed(false);
removeTapCallback();
removeLongPressCallback();
mInContextButtonPress = false;
mHasPerformedLongPress = false;
mIgnoreNextUpEvent = false;
break;
case MotionEvent.ACTION_MOVE:
drawableHotspotChanged(x, y);
// Be lenient about moving outside of buttons
if (!pointInView(x, y, mTouchSlop)) {
// Outside button
removeTapCallback();
if ((mPrivateFlags & PFLAG_PRESSED) != ) {
// Remove any future long press/tap checks
removeLongPressCallback();
setPressed(false);
}
}
break;
}
return true;
}
return false;
}
private void checkForLongClick(int delayOffset) {
if ((mViewFlags & LONG_CLICKABLE) == LONG_CLICKABLE) {
mHasPerformedLongPress = false;
if (mPendingCheckForLongPress == null) {
mPendingCheckForLongPress = new CheckForLongPress();
}
mPendingCheckForLongPress.rememberWindowAttachCount();
postDelayed(mPendingCheckForLongPress,
ViewConfiguration.getLongPressTimeout() - delayOffset);
}
}
private final class CheckForTap implements Runnable {
public float x;
public float y;
@Override
public void run() {
mPrivateFlags &= ~PFLAG_PREPRESSED;
setPressed(true, x, y);
checkForLongClick(ViewConfiguration.getTapTimeout());
}
}
private final class CheckForLongPress implements Runnable {
private int mOriginalWindowAttachCount;
@Override
public void run() {
if (isPressed() && (mParent != null)
&& mOriginalWindowAttachCount == mWindowAttachCount) {
//傳回true的話,就不執行onclick()
if (performLongClick()) {
mHasPerformedLongPress = true;
}
}
}
public void rememberWindowAttachCount() {
mOriginalWindowAttachCount = mWindowAttachCount;
}
}
private final class PerformClick implements Runnable {
@Override
public void run() {
performClick();
}
}
這段代碼稍微多一點，但也有好多細節要注意的，如果有目标View有傳入過
TouchDelegate
對象，那麼一切來到這裡的觸屏事件都會交給其
TouchDelegate.onTouchEvent()
處理并傳回true,在
ACTION_DOWN
階段中，如果頂層容器不是滾動類的容器，那麼直接通知目标View轉變按壓視圖狀态，并且開始通過
postDelayed()
來設定
CheckForLongPress()
對象，一旦長按時間超過了
ViewConfiguration.getLongPressTimeout()
，
CheckForLongPress()
對象就會執行對應長按回調方法，如果頂層容器是滾動類的容器，那麼會通過
postDelayed()
傳入
CheckForTap()
對象,直到
ViewConfiguration.getTapTimeout()
時候才讓View轉變按壓視圖狀态，而不是立刻改變，同時
CheckForTap()
對象也建立對應
CheckForLongPress()
對象．同時還帶有prepressed時期标記，在
ACTION_UP
階段中,如果目标View沒有長按(既不會執行
CheckForLongPress()
對象裡的方法)，同時不能擷取到焦點并傳回false，那麼便會執行
PerformClick()
對應方法，進而調用
OnClickListener.onclick()
,還有最後一點的細節就是，如果目标View滿足
CLICKABLE
,
LONG_CLICKABLE
,
CONTEXT_CLICKABLE
其中一個條件，那麼
onTouchEvent()
就會傳回true.在經過一些列的分析，可以看出其執行的順序優先級：
`onTouchEvent()
>>>>
TouchDelegate.onTouchEvent()
>>>>
onLongClick()
>>>>
onClick()
.
ViewGroup的觸屏分發實作
上面的那段是基于View.java源碼分析,那麼來分析一下其ViewGroup.java源碼,看看其又是如何分發觸屏事件的.
/**
* Transforms a motion event into the coordinate space of a particular child view,
* filters out irrelevant pointer ids, and overrides its action if necessary.
* If child is null, assumes the MotionEvent will be sent to this ViewGroup instead.
*/
//用來派發給子View觸屏事件
private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
View child, int desiredPointerIdBits) {
final boolean handled;
// Canceling motions is a special case. We don't need to perform any transformations
// or filtering. The important part is the action, not the contents.
final int oldAction = event.getAction();
if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
event.setAction(MotionEvent.ACTION_CANCEL);
//如果child為空,則會回調父類的dispatchTouchEvent()
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
handled = child.dispatchTouchEvent(event);
}
event.setAction(oldAction);
return handled;
}
// Calculate the number of pointers to deliver.
final int oldPointerIdBits = event.getPointerIdBits();
final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;
// If for some reason we ended up in an inconsistent state where it looks like we
// might produce a motion event with no pointers in it, then drop the event.
if (newPointerIdBits == ) {
return false;
}
// If the number of pointers is the same and we don't need to perform any fancy
// irreversible transformations, then we can reuse the motion event for this
// dispatch as long as we are careful to revert any changes we make.
// Otherwise we need to make a copy.
final MotionEvent transformedEvent;
if (newPointerIdBits == oldPointerIdBits) {
if (child == null || child.hasIdentityMatrix()) {
if (child == null) {
handled = super.dispatchTouchEvent(event);
} else {
//如果觸屏事件設定偏移量以和支援機關矩陣變換的子view一緻
//如子View做一些平移等動畫操作時的點選
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
event.offsetLocation(offsetX, offsetY);
handled = child.dispatchTouchEvent(event);
event.offsetLocation(-offsetX, -offsetY);
}
return handled;
}
transformedEvent = MotionEvent.obtain(event);
} else {
transformedEvent = event.split(newPointerIdBits);
}
// Perform any necessary transformations and dispatch.
if (child == null) {
handled = super.dispatchTouchEvent(transformedEvent);
} else {
final float offsetX = mScrollX - child.mLeft;
final float offsetY = mScrollY - child.mTop;
transformedEvent.offsetLocation(offsetX, offsetY);
if (! child.hasIdentityMatrix()) {
//恢複原來觸屏事件發生坐标,即相當于撤銷了offsetLocation()作用
transformedEvent.transform(child.getInverseMatrix());
}
handled = child.dispatchTouchEvent(transformedEvent);
}
// Done.
transformedEvent.recycle();
return handled;
}
在觸屏事件分發給子View的邏輯中可以知道一個細節,如果child為空,那麼會回調父類的
dispatchTouchEvent()
方法,否則就調用子View的
dispatchTouchEvent()
,執行順序的優先級:目前ViewGroup的
dispatchTouchEvent()
>>>>>childView!=null?
dispatchTouchEvent()
:
super.dispatchTouchEvent()
.
/* Describes a touched view and the ids of the pointers that it has captured.
*
* This code assumes that pointer ids are always in the range 0..31 such that
* it can use a bitfield to track which pointer ids are present.
* As it happens, the lower layers of the input dispatch pipeline also use the
* same trick so the assumption should be safe here...
*/
private static final class TouchTarget {
private static final int MAX_RECYCLED = ;
private static final Object sRecycleLock = new Object[];
private static TouchTarget sRecycleBin;
private static int sRecycledCount;
public static final int ALL_POINTER_IDS = -; // all ones
// The touched child view.
public View child;
// The combined bit mask of pointer ids for all pointers captured by the target.
public int pointerIdBits;//通過位标記來記錄節點在連結清單的位置
// The next target in the target list.
public TouchTarget next;
private TouchTarget() {
}
public static TouchTarget obtain(View child, int pointerIdBits) {
final TouchTarget target;
synchronized (sRecycleLock) {
if (sRecycleBin == null) {
target = new TouchTarget();
} else {
target = sRecycleBin;
sRecycleBin = target.next;
sRecycledCount--;
target.next = null;
}
}
target.child = child;
target.pointerIdBits = pointerIdBits;
return target;
}
public void recycle() {
synchronized (sRecycleLock) {
if (sRecycledCount < MAX_RECYCLED) {
next = sRecycleBin;
sRecycleBin = this;
sRecycledCount += ;
} else {
next = null;
}
child = null;
}
}
}
通過連結清單方式來維護觸屏事件的,但在這裡有個很巧妙的地方,也通過sRecycleBin指針來複用對象,很多地方都用類似的技巧來複用對象,如listView建立item對象,具體過程如圖所示(假設初始化時,不串聯對象):
在
dispatchTouchEvent()
方法中,由于這段代碼還比較長,很多細節,是以我把代碼分成兩個階段去分析.
//第一階段 攔截事件時,觸屏事件的分發處理
//即某段時刻intercepted會傳回true.
/**
* {@inheritDoc}
*/
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onTouchEvent(ev, );
}
// If the event targets the accessibility focused view and this is it, start
// normal event dispatch. Maybe a descendant is what will handle the click.
if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
ev.setTargetAccessibilityFocus(false);
}
boolean handled = false;
if (onFilterTouchEventForSecurity(ev)) {
final int action = ev.getAction();
final int actionMasked = action & MotionEvent.ACTION_MASK;
// Handle an initial down.
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Throw away all previous state when starting a new touch gesture.
// The framework may have dropped the up or cancel event for the previous gesture
// 在ACTION_DOWN會丢棄以前的觸屏事件和清除觸屏狀态
cancelAndClearTouchTargets(ev);
resetTouchState();
}
// Check for interception.
final boolean intercepted;
//在ACTION_DOWN時候會執行或有目标子View的時候
//如果沒有找到處理觸屏事件的View那麼其他的
//後續觸屏事件會被目前的容器攔截,不再分發給子View
if (actionMasked == MotionEvent.ACTION_DOWN
|| mFirstTouchTarget != null) {
final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != ;
if (!disallowIntercept) {
intercepted = onInterceptTouchEvent(ev);
ev.setAction(action); // restore action in case it was changed
} else {
intercepted = false;
}
} else {
// There are no touch targets and this action is not an initial down
// so this view group continues to intercept touches.
intercepted = true;
}
// If intercepted, start normal event dispatch. Also if there is already
// a view that is handling the gesture, do normal event dispatch.
if (intercepted || mFirstTouchTarget != null) {
ev.setTargetAccessibilityFocus(false);
}
// Check for cancelation.
final boolean canceled = resetCancelNextUpFlag(this)
|| actionMasked == MotionEvent.ACTION_CANCEL;
// Update list of touch targets for pointer down, if needed.
final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != ;
TouchTarget newTouchTarget = null;
boolean alreadyDispatchedToNewTouchTarget = false;
if (!canceled && !intercepted){
//省略另一階段的代碼.............................
}
// Dispatch to touch targets.
//攔截事件且沒有子View處理觸屏事件的時候,即回調父類的dispatchTransformedTouchEvent()
if (mFirstTouchTarget == null) {
// No touch targets so treat this as an ordinary view.
handled = dispatchTransformedTouchEvent(ev, canceled, null,
TouchTarget.ALL_POINTER_IDS);
} else {
// Dispatch to touch targets, excluding the new touch target if we already
// dispatched to it. Cancel touch targets if necessary.
//會把在攔截事件前所捕獲到的觸屏事件交給子View去處理,攔截事件後的觸屏事件交給自己去
處理
TouchTarget predecessor = null;//前個觸屏事件節點
TouchTarget target = mFirstTouchTarget;//目前觸屏事件節點
while (target != null) {
final TouchTarget next = target.next;
if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
handled = true;
} else {
//派發攔截事件前的觸屏事件給子View,如果攔截(intercepted==true)
//則觸屏事件交給父類dispatchOnTouchEvent()
final boolean cancelChild = resetCancelNextUpFlag(target.child)
|| intercepted;
if (dispatchTransformedTouchEvent(ev, cancelChild,
target.child, target.pointerIdBits)) {
handled = true;
}
if (cancelChild) {
if (predecessor == null) {
mFirstTouchTarget = next;
} else {
predecessor.next = next;
}
target.recycle();
target = next;
continue;
}
}
predecessor = target;
target = next;
}
}
// Update list of touch targets for pointer up or cancel, if needed.
if (canceled
|| actionMasked == MotionEvent.ACTION_UP
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
//清除觸屏事件狀态
resetTouchState();
} else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {
final int actionIndex = ev.getActionIndex();
final int idBitsToRemove = << ev.getPointerId(actionIndex);
removePointersFromTouchTargets(idBitsToRemove);
}
}
if (!handled && mInputEventConsistencyVerifier != null) {
mInputEventConsistencyVerifier.onUnhandledEvent(ev, );
}
return handled;
}
在分析上面第一階段時,注意到一些細節處理,如果ViewGroup沒有嵌套子View的話,那麼就會回調父類的
dispatchTouchEvent()
,但如果ViewGroup有嵌套子View,但沒有一開始攔截的話,那就會将攔截前的觸屏事件交給子View
dispatchTouchEvent()
去處理,攔截後的觸屏事件交給父類的
dispatchTouchEvent()
去處理.還有一點就是如果某個子View在
dispatchTouchEvent()
和
onTouch()
和
onTouchEvent()
都不處理觸屏事件
ACTION_DOWN
或
ACTON_MOVE
等階段,即都傳回false,那子View就再也接受不到觸屏事件的後續階段了(如ACTION_UP).
//第二階段不攔截觸屏事件
/**
* {@inheritDoc}
*/
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
//省略代碼............................................
if (!canceled && !intercepted) {
// If the event is targeting accessiiblity focus we give it to the
// view that has accessibility focus and if it does not handle it
// we clear the flag and dispatch the event to all children as usual.
// We are looking up the accessibility focused host to avoid keeping
// state since these events are very rare.
View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
? findChildWithAccessibilityFocus() : null;
if (actionMasked == MotionEvent.ACTION_DOWN
|| (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
|| actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
final int actionIndex = ev.getActionIndex(); // always 0 for down
final int idBitsToAssign = split ? << ev.getPointerId(actionIndex)
: TouchTarget.ALL_POINTER_IDS;
// Clean up earlier touch targets for this pointer id in case they
// have become out of sync.
removePointersFromTouchTargets(idBitsToAssign);
final int childrenCount = mChildrenCount;
if (newTouchTarget == null && childrenCount != ) {
final float x = ev.getX(actionIndex);
final float y = ev.getY(actionIndex);
// Find a child that can receive the event.
// Scan children from front to back.
final ArrayList<View> preorderedList = buildOrderedChildList();
final boolean customOrder = preorderedList == null
&& isChildrenDrawingOrderEnabled();
final View[] children = mChildren;
for (int i = childrenCount - ; i >= ; i--) {
final int childIndex = customOrder
? getChildDrawingOrder(childrenCount, i) : i;
final View child = (preorderedList == null)
? children[childIndex] : preorderedList.get(childIndex);
// If there is a view that has accessibility focus we want it
// to get the event first and if not handled we will perform a
// normal dispatch. We may do a double iteration but this is
// safer given the timeframe.
if (childWithAccessibilityFocus != null) {
if (childWithAccessibilityFocus != child) {
continue;
}
childWithAccessibilityFocus = null;
i = childrenCount - ;
}
if (!canViewReceivePointerEvents(child)
|| !isTransformedTouchPointInView(x, y, child, null)) {
ev.setTargetAccessibilityFocus(false);
continue;
}
newTouchTarget = getTouchTarget(child);
if (newTouchTarget != null) {
// Child is already receiving touch within its bounds.
// Give it the new pointer in addition to the ones it is handling.
newTouchTarget.pointerIdBits |= idBitsToAssign;
break;
}
resetCancelNextUpFlag(child);
if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
// Child wants to receive touch within its bounds.
mLastTouchDownTime = ev.getDownTime();
if (preorderedList != null) {
// childIndex points into presorted list, find original index
for (int j = ; j < childrenCount; j++) {
if (children[childIndex] == mChildren[j]) {
mLastTouchDownIndex = j;
break;
}
}
} else {
mLastTouchDownIndex = childIndex;
}
mLastTouchDownX = ev.getX();
mLastTouchDownY = ev.getY();
newTouchTarget = addTouchTarget(child, idBitsToAssign);
alreadyDispatchedToNewTouchTarget = true;
break;
}
// The accessibility focus didn't handle the event, so clear
// the flag and do a normal dispatch to all children.
ev.setTargetAccessibilityFocus(false);
}
if (preorderedList != null) preorderedList.clear();
}
if (newTouchTarget == null && mFirstTouchTarget != null) {
// Did not find a child to receive the event.
// Assign the pointer to the least recently added target.
newTouchTarget = mFirstTouchTarget;
while (newTouchTarget.next != null) {
newTouchTarget = newTouchTarget.next;
}
newTouchTarget.pointerIdBits |= idBitsToAssign;
}
}
}
//省略代碼.........................................................
return handled;
}
這段代碼主要處理
ACTION_DOWN
階段,隻在
ACTION_DOWN
階段僅一次或0次調用
onInterceptTouchEvent()
來決定要不要攔截觸屏事件,如果不攔截,那就找消費觸屏事件的子View,即子View處理觸屏事件的最終結果傳回true,然後做一些記錄操,最後用連結清單串聯觸屏對象.在結合第一段階段的代碼,可以看出其觸屏事件執行順序的優先級:
目前容器的dispatchTouchEvent()
>>>>>
onInterceptTouchEvent()
>>>>>
childView!=null?dispatchTouchEvent():super.dispatchTouchEvent()
.
觸屏事件處理DEMO
上面圍繞一大堆源碼分析後,可能很容易被搞混,為印象更加深刻,基于上面理論實踐一個demo來驗證,并畫出對應的處理流程圖.
public class MyButton extends Button implements View.OnClickListener,View.OnTouchListener,View.OnLongClickListener{
private static final String TAG = MyButton.class.getName();
public MyButton(Context context, AttributeSet attrs) {
super(context, attrs);
setOnClickListener(this);
setOnTouchListener(this);
setOnLongClickListener(this);
Button button=new Button(context){
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.i(TAG,"OtherButton>>>>>>>>>>>onTouchEvent()");
return true;
}
};
DisplayMetrics displayMetrics=context.getResources().getDisplayMetrics();
setTouchDelegate(new TouchDelegate(new Rect(,,displayMetrics.widthPixels,displayMetrics.heightPixels),button));
}
@Override
public boolean onLongClick(View view) {
Log.i(TAG,"MyButton>>>>>>>>>>>onLongClick");
return false;
}
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
Log.i(TAG,"MyButton>>>>>>>>>>>onTouch");
return false;
}
@Override
public void onClick(View view) {
Log.i(TAG,"MyButton>>>>>>>>>>>onClick");
}
@Override
public boolean onTouchEvent(MotionEvent event) {
Log.i(TAG,"MyButton>>>>>>>>>>>onTouchEvent");
return super.onTouchEvent(event);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
Log.i(TAG,"event_action>>>>>>>>>>>"+event.getAction());
Log.i(TAG,"MyButton>>>>>>>>>>>DispatchTouchEvent");
return super.dispatchTouchEvent(event);
}
}
将代理的button的
onTouch()
傳回false.其短按和長按事件處理流程如圖:
短按:
長按:
對于View處理觸屏事件的其他的情況,我就不再一一測試了,總的來說,View處理觸屏事件流程就如圖所示:
//子布局
public class MyButton extends Button implements View.OnClickListener, View.OnTouchListener, View.OnLongClickListener {
private static final String TAG = MyButton.class.getName();
public MyButton(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>DispatchTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>DispatchTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>DispatchTouchEvent");
break;
}
return false;
}
}
//父布局,該布局會嵌套MyButton
public class MyRelativeLayout extends RelativeLayout {
private static final String TAG = MyRelativeLayout.class.getName();
public MyRelativeLayout(Context context, AttributeSet attrs) {
super(context, attrs);
//setClickable(true);
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>dispatchTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>dispatchTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>dispatchTouchEvent");
break;
}
return super.dispatchTouchEvent(event);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>onInterceptTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>onInterceptTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>onInterceptTouchEvent");
break;
}
return false;
}
@Override
public String toString() {
return "MyRelativeLayout";
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>onTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>onTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>onTouchEvent");
break;
}
return true;
}
}
日志可以看出子View沒有消費觸屏事件的話,會回傳給父容器去處理觸屏事件的,并且隻在ACTION_DOWN階段調用
onInterceptTouchEvent()
,再把
MyRelativeLayout.onInterceptTouchEvent()
改為true.
再把
MyRelativeLayout.onTouchEvent()
傳回false,那麼又會怎麼樣呢?
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
switch (ev.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>dispatchTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>dispatchTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>dispatchTouchEvent");
break;
}
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
Log.i(TAG, "ACTION_DOWN>>>>>>>>>>>onTouchEvent");
break;
case MotionEvent.ACTION_MOVE:
Log.i(TAG, "ACTION_MOVE>>>>>>>>>>>onTouchEvent");
break;
case MotionEvent.ACTION_UP:
Log.i(TAG, "ACTION_UP>>>>>>>>>>>onTouchEvent");
break;
}
return true;
}
}
子View再也沒有收到觸屏事件了吧,如果最頂層容器
onTouchEvent()
傳回false不消費觸屏事件的話,那麼回回傳給Actvitiy的
onTouchEvent()
去處理,即使Activitiy的
onTouchEvent()
傳回false,也會能接受到觸屏事件的後續階段.到這裡,我畫個總的流程圖來概況一下: