为什么ActivityCompat.requestPermissions()只接受0-255之间的整数请求码？

Question

最近更新了一个app，targetSdkVersion为23，实现了各种权限请求。我最初尝试使用 ActivityCompat.requestPermissions() 导致从 FragmentActivity 的内部抛出 IllegalArgumentException：

int REQUEST_CODE_A = 9001;
ActivityCompat.requestPermissions(new String[ {Manifest.permission.WRITE_CONTACTS}, REQUEST_CODE_A); // crashes

java.lang.IllegalArgumentException: Can only use lower 8 bits for requestCode

但是，如果请求代码在 0-255 之间，则一切正常，权限请求按预期工作。

int REQUEST_CODE_B = 101;
ActivityCompat.requestPermissions(new String[ {Manifest.permission.WRITE_CONTACTS}, REQUEST_CODE_B); // works correctly

那么问题来了，有什么理由像这样限制API中整数的可能取值呢？可以使用字节来提供相同的信息，但是（显然）已经有意识地决定使用整数来代替。这仅仅是允许未来可扩展性的情况吗？

Answer 1

在似乎抛出此异常的地方引用 the source code to FragmentActivity：

    // We use 8 bits of the request code to encode the fragment id when
    // requesting permissions from a fragment. Hence, requestPermissions()
    // should validate the code against that but we cannot override it as
    // we can not then call super and also the ActivityCompat would call
    // back to this override. To handle this we use dependency inversion
    // where we are the validator of request codes when requesting
    // permissions in ActivityCompat.

startActivityForResult()请求码有16位限制，至少在FragmentActivity.

为什么ActivityCompat.requestPermissions()只接受0-255之间的整数请求码？

Why does ActivityCompat.requestPermissions() only accept an integer request code between 0-255?

java

android

android-support-library

android-permissions