Java Android：为请求代码值选择什么？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/33331073/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Android: what to choose for requestcode values?
提问by Jon
Methods like ActivityCompat.requestPermissionsrequire that I pass them a requestcode that I can later test in a callback (in this case onRequestPermissionsResult). Is there some best practice sort of value I'm supposed to pass in the requestcode? I've noticed that if I just enter a random intI sometimes get an error like this:
像这样的方法ActivityCompat.requestPermissions需要我向他们传递一个请求代码，我可以稍后在回调中测试（在这种情况下onRequestPermissionsResult）。我应该在请求代码中传递一些最佳实践值吗？我注意到，如果我只是输入一个随机数，int我有时会收到这样的错误：
java.lang.IllegalArgumentException: Can only use lower 8 bits for requestCode
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: FATAL EXCEPTION: main
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: Process: my package, PID: 8315
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{mypackage.myactivity}: java.lang.IllegalArgumentException: Can only use lower 8 bits for requestCode
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.-wrap11(ActivityThread.java)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:102)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.os.Looper.loop(Looper.java:148)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5417)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: Caused by: java.lang.IllegalArgumentException: Can only use lower 8 bits for requestCode
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.support.v4.app.FragmentActivity.validateRequestPermissionsRequestCode(FragmentActivity.java:799)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.support.v4.app.ActivityCompatApi23.requestPermissions(ActivityCompat23.java:29)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.support.v4.app.ActivityCompat.requestPermissions(ActivityCompat.java:316)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at mypackage.myactivity.checkReadPhoneState(PermissionsGatewayActivity.java:48)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at mypackage.myactivity.onCreate(PermissionsGatewayActivity.java:36)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.Activity.performCreate(Activity.java:6237)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.-wrap11(ActivityThread.java)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:102)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.os.Looper.loop(Looper.java:148)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5417)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)?
10-25 16:47:43.652 8315-8315/? E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)?
采纳答案by Henry
Documenting the findings for future reference:
记录调查结果以备将来参考：
The following are code from android.support.v4.app.FragmentActivity
以下代码来自 android.support.v4.app.FragmentActivity
/**
* Modifies the standard behavior to allow results to be delivered to fragments.
* This imposes a restriction that requestCode be <= 0xffff.
*/
@Override
public void startActivityForResult(Intent intent, int requestCode) {
if (requestCode != -1 && (requestCode&0xffff0000) != 0) {
throw new IllegalArgumentException("Can only use lower 16 bits for requestCode");
}
super.startActivityForResult(intent, requestCode);
}
@Override
public final void validateRequestPermissionsRequestCode(int requestCode) {
// We use 16 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.
if (!mRequestedPermissionsFromFragment
&& requestCode != -1 && (requestCode & 0xffff0000) != 0) {
throw new IllegalArgumentException("Can only use lower 16 bits for requestCode");
}
}
RANGEstartActivityForResult()in FragmentActivityrequires the requestCode to be of 16 bits, meaning the range is from 0 to 65535.
RANGEstartActivityForResult()inFragmentActivity要求 requestCode 为 16 位，这意味着范围是从0 到 65535。
Also, validateRequestPermissionsRequestCodein FragmentActivityrequires requestCode to be of 16 bits, meaning the range is from 0 to 65535.
此外，validateRequestPermissionsRequestCodeinFragmentActivity要求 requestCode 为 16 位，这意味着范围是从0 到 65535。
