问题描述
采用Application.startActivity()偶现无法启动Activity的现象。
原因分析
首先查询Context.java中startActivity()方法的描述，部分内容如下：
/**
* Launch a new activity. You will not receive any information about when
* the activity exits.
*
* <p>Note that if this method is being called from outside of an
* {@link android.app.Activity} Context, then the Intent must include
* the {@link Intent#FLAG_ACTIVITY_NEW_TASK} launch flag. This is because,
* without being started from an existing Activity, there is no existing
* task in which to place the new activity and thus it needs to be placed
* in its own separate task.
*
* <p>This method throws {@link ActivityNotFoundException}
* if there was no Activity found to run the given Intent.
*
从以上描述可以看出，如果调用startActivity()方法的Context不是Activity的话，Intent必须要包含FLAGIntent.FLAG_ACTIVITY_NEW_TASK，原因是因为没有Activity启动Activity时可能不存在Activity栈，所以需要添加Intent属性来创建一个Activity栈。
解决办法
为启动的Intent设置intent.flags即可解决此问题。
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
