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Android: что выбрать для значений кода запроса?

Такие методы, как ActivityCompat.requestPermissions, требуют, чтобы я передал им код запроса, который позже можно проверить в обратном вызове (в данном случае onRequestPermissionsResult). Есть ли какая-то лучшая практика, которую я должен передать в коде запроса? Я заметил, что если я просто введу случайный int, я иногда получаю такую ​​ошибку:

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) 
4b9b3361

Ответ 1

Документирование результатов для дальнейшего использования:

Ниже приведен код из 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");
    }
}


RANGE
startActivityForResult() в FragmentActivity требует, чтобы requestCode имел 16 бит, то есть диапазон от от 0 до 65535.

Кроме того, validateRequestPermissionsRequestCode в FragmentActivity требует, чтобы requestCode имел 16 бит, то есть диапазон от от 0 до 65535.