背景

安卓显示的dialog是依附于activity的,如果在dialog显示前,activity已经消失了,那dialog显示时就会导致crash.

报错日志如下:

AndroidRuntime: FATAL EXCEPTION: main
Process: com.cxyzy.safedialog, PID: 32155
android.view.WindowManager$BadTokenException: Unable to add window -- token android.os.BinderProxy@b194e0a for displayid = 0 is not valid; is your activity running?
at android.view.ViewRootImpl.setView(ViewRootImpl.java:936)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:398)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:131)
at android.app.Dialog.show(Dialog.java:531)

初步解决方案

遇到这样的问题,大家自然也知道怎么办,那就是在显示dialog前对activity进行判断

if (!(activity.isFinishing || (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1 && activity.isDestroyed)) {
dialog.show()
}

于是代码里到处都充斥着这样的代码.

宝宝表示,很难过.

优化解决方案

归一化处理,让所有dialog集成基础dialog类,在基础dialog类里显示之前做一次判断.

/**
* 安全显示dialog
* 对所属activity应销毁的情况进行保护,避免显示时crash
*/
open class SafeBaseDialog : Dialog {
private var mActivity: Activity

constructor(activity: Activity) : super(activity) {
mActivity = activity
}

constructor(activity: Activity, themeResId: Int) : super(activity, themeResId) {
mActivity = activity
}

override fun show() {
if (!isFinishingOrDestroyed(mActivity)) {
super.show()
}
}

private fun isFinishingOrDestroyed(activity: Activity): Boolean {
return activity.isFinishing
|| (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1 && activity.isDestroyed)
}
}

思考题

为什么google官方不直接在Dialog的show方法里做这个判断呢?

是我打开dialog的姿势不太好?