Solving tips for Android sliding conflicts

The principle of sliding conflict

AndroidThe event distribution mechanism is based onViewGroupof. When the user touches on the screen, the event is first passed to the topmostViewGroup。ViewGroupWill decide whether to intercept events based on your sliding direction and sliding ability. ifViewGroupIf an event is intercepted, the event will not be passed to the child.View. ifViewGroupThere is no intercepting event, then the event will be passed to the child.View。

If the childViewIt also needs to respond to sliding events, thenViewNeed to be rewriteonTouchEvent()Method to handle events. sonViewCan be passedrequestDisallowInterceptTouchEvent()Method to tell the parentViewGroupDo not intercept events.

Sliding conflict refers to two or moreViewSliding events are received at the same time, resulting in the failure to slide normally. There are many reasons for sliding conflicts, such as:

• twoViewThe sliding direction is the same, e.g.RecyclerViewandScrollViewSlide at the same time.
• twoViewThe sliding directions are different, but the sliding ranges overlap, for exampleHorizontalScrollViewandWebViewSlide at the same time.

Solution

AndroidThere are two main solutions to sliding conflicts: external interception method and internal interception method.

• External interception method: by the parentViewIntercept the event and pass the event to the child as neededView。
• Internal interception method: YuziViewIntercept the event and pass the event to the parent as neededView。

External interception method

The external interception method isAndroidThe default sliding conflict resolution method. In this way, the parentViewThe event will be intercepted first, and then the event will be passed to the child as needed.View。

fatherViewCan be rewriteonInterceptTouchEvent()Method to implement external interception method. existonInterceptTouchEvent()In the method, we can judge whether the event needs to be intercepted based on the type and location of the event. If an event is required, returntrue, otherwise returnfalse。

class CustomParentView(context: Context, attrs: AttributeSet) : ViewGroup(context, attrs) {

    private var downX: Float = 0F
    private var downY: Float = 0F

    override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
        when () {
            MotionEvent.ACTION_DOWN -> {
                downX = 
                downY = 
            }
            MotionEvent.ACTION_MOVE -> {
                val deltaX =  - downX
                val deltaY =  - downY

                //Judge whether to intercept the event based on the sliding direction                if ((deltaX) > (deltaY)) {
                    return true
                }
            }
        }
        return (ev)
    }

    override fun onTouchEvent(event: MotionEvent): Boolean {
        // Handle sliding logic        return true
    }

    // Other related codes}

advantage:Simple and easy to use, suitable for most sliding conflict issues.

shortcoming:May cause the parentViewGroupUnable to respond to events such as parentViewGroupThe sonViewSliding, while the parentViewGroupThe sliding event was also intercepted.

Internal interception method

Internal interception method refers to YuziViewIntercept the event and pass the event to the parent as neededView。

sonViewCan be rewritedispatchTouchEvent()Method to implement internal interception method. existdispatchTouchEvent()In the method, we can judge whether the event needs to be intercepted based on the type and location of the event. If an event is required, callrequestDisallowInterceptTouchEvent()Method to tell the parentViewDo not intercept events.

class MyView : View {

    // Implement internal interception by rewriting the dispatchTouchEvent method    override fun dispatchTouchEvent(ev: MotionEvent): Boolean {
        when () {
            MotionEvent.ACTION_DOWN -> {
                // When pressed, the parent View is prohibited from intercepting events                (true)
            }
            MotionEvent.ACTION_MOVE -> {
                //Judge whether to intercept events based on business logic                if (shouldInterceptTouchEvent(ev)) {
                    return true
                }
            }
            MotionEvent.ACTION_UP -> {
                // When finger is raised, allow parent View to intercept events                (false)
            }
        }
        return (ev)
    }

}

advantage:Will not cause the parentViewGroupUnable to respond to events, applicable to parentViewGroupHeziViewAll need to slide.

shortcoming:Need to rewrite the subViewofdispatchTouchEvent()Methods, may cause code complexity.

Notes and optimization tips

• When judging whether an event needs to be intercepted, factors such as the direction of the event, sliding distance, etc. need to be considered.
• If the parentViewGroupHeziViewIf all need to slide, you can use the event distribution mechanism to resolve sliding conflicts.
• Avoid too much nesting and minimize the nesting hierarchy of the layout to reduce the probability of sliding conflicts.

Summarize

AndroidThere are two main ways to resolve sliding conflicts: external interception method and internal interception method. I hope this article can help readers resolve sliding conflict problems and improveAndroidDevelopment level.

This is the end of this article about the solution to Android sliding conflict. For more related content on Android sliding conflict, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!