debug-viewpager点击事件响应延迟

bug描述

viewpager 无限循环，复用显示的view时出现点击view 响应延迟直到下一次预加载对应view才执行。

bug原因

viewpager 内部的view在移出屏幕后调用了view的onDetachedFromWindow方法 。
因为我们无限循环的viewpager复用view的原因导致在viewpager 调用view的onDetachedFromWindow方法之前
view又再次显示被添加到界面，被用户看见并且可以点击，在这之后viewpager因为之前view离开界面调用onDetachedFromWindow方法导致点击事件没有被立即执行
直到下一次调用 dispatchAttachedToWindow方法后才执行，导致点击事件延迟响应。

堆栈跟踪信息

E: ac26520  onDetachedFromWindow
    java.lang.Exception: remove pos:2 1073741828 time:1542073406206 adapter:4c87493
        at com.kanshu.ksgb.fastread.common.view.TestImage.onDetachedFromWindow(TestImage.kt:35)
        at android.view.View.dispatchDetachedFromWindow(View.java:17456)
        at android.view.ViewGroup.finishAnimatingView(ViewGroup.java:6723)
        at android.view.View.draw(View.java:19051)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4216)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4026)
        at android.view.View.draw(View.java:19148)
        at android.support.v4.view.ViewPager.draw(ViewPager.java:2420)
        at android.view.View.updateDisplayListIfDirty(View.java:18095)
        at android.view.View.draw(View.java:18873)
        at android.view.ViewGroup.drawChild(ViewGroup.java:4216)
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4002)
        at android.view.View.updateDisplayListIfDirty(View.java:18086)
        at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4200)
        at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4180)
        at android.view.View.updateDisplayListIfDirty(View.java:18054)
E: ac26520 onTouchEvent 1542073407022
E: ac26520  onAttachedToWindow
    java.lang.Exception: add pos:2 1073741831 time:1542073415028 adapter:4c87493
        at com.kanshu.ksgb.fastread.common.view.TestImage.onAttachedToWindow(TestImage.kt:41)
        at android.view.View.dispatchAttachedToWindow(View.java:17400)
        at android.view.ViewGroup.addViewInner(ViewGroup.java:4957)
        at android.view.ViewGroup.addView(ViewGroup.java:4748)
        at android.support.v4.view.ViewPager.addView(ViewPager.java:1479)
        at android.view.ViewGroup.addView(ViewGroup.java:4688)
        at android.view.ViewGroup.addView(ViewGroup.java:4661)
        at com.kanshu.ksgb.fastread.common.view.BannerLayout$LoopPagerAdapter.instantiateItem(BannerLayout.java:544)
        at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1004)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1218)
        at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:663)
        at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:625)
        at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:617)
        at com.kanshu.ksgb.fastread.common.view.BannerLayout$1.handleMessage(BannerLayout.java:116)
        at android.os.Handler.dispatchMessage(Handler.java:101)
        at android.os.Looper.loop(Looper.java:171)
        at android.app.ActivityThread.main(ActivityThread.java:6699)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:246)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:783)

关键代码

view ontouch点击事件触发

if (mPerformClick == null) {
    mPerformClick = new PerformClick();
}
if (!post(mPerformClick)) {
    performClick();
}

public boolean post(Runnable action) {
    final AttachInfo attachInfo = mAttachInfo;
    if (attachInfo != null) {
        return attachInfo.mHandler.post(action);
    }

    // Postpone the runnable until we know on which thread it needs to run.
    // Assume that the runnable will be successfully placed after attach.
    getRunQueue().post(action);
    return true;
}

dispatchAttachedToWindow 执行之前的动作

// Transfer all pending runnables.
if (mRunQueue != null) {
    mRunQueue.executeActions(info.mHandler);
    mRunQueue = null;
}