StartActivityForResult启动模式在不同场景下的不同结果

这里写图片描述

在4.4 singleTask加taskaffinity也能新建任务栈

4.4，Main3设置singleInstance，则建立新的任务栈

一，使用startActivityForResult
在4.4:
1.启动一个正常的LaunchMode是standard的activity ，可以接收到resultOK
2.启动一个有NEW_TASK的flag的activity（如设置singleTask（即使没设置affnity,和启动activity在同一个栈中也是不能成功），或者singleInstance的，都不能正常接收的result.返回result_Cancel,在启动另一个Activity的时候会立即返回一个Result_Cancel,且空intent）
PS：这时候的newTask标签（singleTask设置taskAffnity或singleInstance模式）能正常打开新的task栈
在5.0以上手机：
1.只要是通过startActivityForResult启动的activity，不管启动的activity的flag属性及launchMode,一律作为sub_activity,放在启动者当前的任务栈中，接受到的result是成功的
2.启动者的模式即使是singleInstance，被启动的activity仍然会放到同一个栈中。
二，使用startActivity即使用startActivityForResult（requestCode = -1,认为是普通的startActivity）
1.在4.4：
表现均一样。
2.在5.0+：

startActivityForResult的源码注释

说明了问题，requestCode >=0 表示是需要返回结果的，要启动的Activity会作为sub_activity添加到你的栈中，否则认为是普通的startActivity

/**
     * Launch an activity for which you would like a result when it finished.
     * When this activity exits, your
     * onActivityResult() method will be called with the given requestCode.
     * Using a negative requestCode is the same as calling
     * {@link #startActivity} (the activity is not launched as a sub-activity).
     *
     * 
Note that this method should only be used with Intent protocols
     * that are defined to return a result.  In other protocols (such as
     * {@link Intent#ACTION_MAIN} or {@link Intent#ACTION_VIEW}), you may
     * not get the result when you expect.  For example, if the activity you
     * are launching uses {@link Intent#FLAG_ACTIVITY_NEW_TASK}, it will not
     * run in your task and thus you will immediately receive a cancel result.
     *
     * 
As a special case, if you call startActivityForResult() with a requestCode
     * >= 0 during the initial onCreate(Bundle savedInstanceState)/onResume() of your
     * activity, then your window will not be displayed until a result is
     * returned back from the started activity.  This is to avoid visible
     * flickering when redirecting to another activity.
     *