事件处理/事件分发机制(一)
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2022-06-22 11:39:41
事件分发原理Android为触摸事件封装了一个类MotionEvent,其实OnTouchEvent的一个参数就是MotionEventMotionEvent中封装了触摸点坐标、点击事件类型等Android中的View可以放在一个ViewGroup中,这个ViewGroup又放在另一ViewGroup中等等,一层层嵌套起来,同一个触摸事件,View和父ViewGroup都想要处理,我们应该传给谁呢,此时就需要事件拦截机制MotionEvent中处理得事件类型为:注意:ACTION_MO....
事件分发原理
Android为触摸事件封装了一个类MotionEvent,其实OnTouchEvent的一个参数就是MotionEventMotionEvent中封装了触摸点坐标、点击事件类型等Android中的View可以放在一个ViewGroup中,这个ViewGroup又放在另一ViewGroup中等等,一层层嵌套起来,同一个触摸事件,View和父ViewGroup都想要处理,我们应该传给谁呢,此时就需要事件拦截机制
MotionEvent中处理得事件类型为:
注意:ACTION_MOVE方法会被调用多次,ACTION_CANCEL:当事件被上层拦截时触发,需要掌握拦截的条件
View的继承关系如下:
事件分发和事件处理流程
事件分发:ViewGroup.java--->dispatchTouchEvent
事件处理:View.java->dispatchTouchEvent
先分析处理流程
Onclick与OnTouch的事件冲突的分析:
button = findViewById(R.id.click1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.i(TAG,"onclick");
}
});
button.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.i(TAG,"onTouch action" + event.getAction());
return false;
}
});
}
返回的结果为:
2020-07-15 11:27:47.174 19712-19712/com.example.clickevent I/ClickTouch: onTouch action0
2020-07-15 11:27:47.265 19712-19712/com.example.clickevent I/ClickTouch: onTouch action1
2020-07-15 11:27:47.285 19712-19712/com.example.clickevent I/ClickTouch: onclick
表明在UP中执行onClick的方法
当reslut为true时,不执行onClick方法
原理分析:
view的事件处理:执行进入View.java->dispatchTouchEvent
view.dispatchTouchEvent
/**
* 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, 0);
}
final int actionMasked = event.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
// Defensive cleanup for new gesture
stopNestedScroll();
}
//核心代码
if (onFilterTouchEventForSecurity(event)) {
if ((mViewFlags & ENABLED_MASK) == ENABLED && handleScrollBarDragging(event)) {
result = true;
}
//noinspection SimplifiableIfStatement
ListenerInfo li = mListenerInfo;
//当控件重写了OnTouchListener,而onTouch的返回值会影响返回值,从运行的结果看到当OnTouch返回为true时,onClick不会被执行,因此返回结果会影响
if (li != null && li.mOnTouchListener != null
&& (mViewFlags & ENABLED_MASK) == ENABLED
&& li.mOnTouchListener.onTouch(this, event)) {
result = true;
}
//result的结果如果为flase的会执行到onTouchEvent
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;
}
如果返回为false会执行到onTouchEvent的流程
public boolean onTouchEvent(MotionEvent event) {
final float x = event.getX();//获得点击事件的X坐标
final float y = event.getY();//获得点击事件的Y坐标
final int viewFlags = mViewFlags;
final int action = event.getAction();//获得Action的状态,UP,DOWN,CANCL等类型
.......
if (clickable || (viewFlags & TOOLTIP) == TOOLTIP) {
switch (action) {
case MotionEvent.ACTION_UP:
mPrivateFlags3 &= ~PFLAG3_FINGER_DOWN;
if ((viewFlags & TOOLTIP) == TOOLTIP) {
handleTooltipUp();
}
........
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();
}
}
}
.........
break;
case MotionEvent.ACTION_DOWN:
.......
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) {
drawableHotspotChanged(x, y);
}
// Be lenient about moving outside of buttons
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;
}
public boolean performClick() {
// We still need to call this method to handle the cases where performClick() was called
// externally, instead of through performClickInternal()
notifyAutofillManagerOnClick();
final boolean result;
final ListenerInfo li = mListenerInfo;
if (li != null && li.mOnClickListener != null) {
playSoundEffect(SoundEffectConstants.CLICK);
li.mOnClickListener.onClick(this);
result = true;
} else {
result = false;
}
sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);
notifyEnterOrExitForAutoFillIfNeeded(true);
return result;
}
总结处理的流程为:
本文地址:https://blog.csdn.net/binghaiwlf/article/details/107358037
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