support-v4のFragmentのrequestPermissionsを使ったとき、onRequestPermissionsResultが呼ばれず少しハマった話

HogeActivity.kt

class HogeActivity : FragmentActivity() {

    override fun onCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {
        super.onCreate(savedInstanceState, persistentState)
        supportFragmentManager.beginTransaction().add(
                android.R.id.content,
                FugaFragment()).commitAllowingStateLoss()
    }

    @RequiresApi(Build.VERSION_CODES.M)
    fun requestContactsPermission() {
        requestPermissions(arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), REQUEST_CONTACTS)
    }
    
    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        if (requestCode == REQUEST_CONTACTS) {
            if (grantResults.size == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 後続処理
            }
        }
    }
    
    companion object {
        private const val REQUEST_CONTACTS = 0
    }
}

FugaFragment.kt

class FugaFragment : Fragment() {

    @TargetApi(Build.VERSION_CODES.M)
    fun requestLocationPermission() {
        requestPermissions(arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), REQUEST_LOCATION)
    }

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {

        if (requestCode == REQUEST_LOCATION) {
            if (grantResults.size == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 後続処理
            }
        }
    }

    companion object {
        private const val REQUEST_LOCATION = 1
    }
}

ActivityとFragmentでそれぞれ別のパーミッションを要求/チェックする処理を実装した。
（例なのですごくシンプルに書いてます。）

これを実行したとき、FragmentのonRequestPermissionsResultが呼ばれずハマった。

Fragmentのコードを見てみる。

android.support.v4.app.Fragment.java

    /**
     * Callback for the result from requesting permissions. This method
     * is invoked for every call on {@link #requestPermissions(String[], int)}.
     * <p>
     * <strong>Note:</strong> It is possible that the permissions request interaction
     * with the user is interrupted. In this case you will receive empty permissions
     * and results arrays which should be treated as a cancellation.
     * </p>
     *
     * @param requestCode The request code passed in {@link #requestPermissions(String[], int)}.
     * @param permissions The requested permissions. Never null.
     * @param grantResults The grant results for the corresponding permissions
     *     which is either {@link android.content.pm.PackageManager#PERMISSION_GRANTED}
     *     or {@link android.content.pm.PackageManager#PERMISSION_DENIED}. Never null.
     *
     * @see #requestPermissions(String[], int)
     */
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
            @NonNull int[] grantResults) {
        /* callback - do nothing */
    }

普通にオーバーライドするだけで大丈夫そう。

FragmentActivityのコードを見てみる

android.support.v4.app.FragmentActivity.java

    /**
     * Callback for the result from requesting permissions. This method
     * is invoked for every call on {@link #requestPermissions(String[], int)}.
     * <p>
     * <strong>Note:</strong> It is possible that the permissions request interaction
     * with the user is interrupted. In this case you will receive empty permissions
     * and results arrays which should be treated as a cancellation.
     * </p>
     *
     * @param requestCode The request code passed in {@link #requestPermissions(String[], int)}.
     * @param permissions The requested permissions. Never null.
     * @param grantResults The grant results for the corresponding permissions
     *     which is either {@link android.content.pm.PackageManager#PERMISSION_GRANTED}
     *     or {@link android.content.pm.PackageManager#PERMISSION_DENIED}. Never null.
     *
     * @see #requestPermissions(String[], int)
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
            @NonNull int[] grantResults) {
        int index = (requestCode >> 16) & 0xffff;
        if (index != 0) {
            index--;

            String who = mPendingFragmentActivityResults.get(index);
            mPendingFragmentActivityResults.remove(index);
            if (who == null) {
                Log.w(TAG, "Activity result delivered for unknown Fragment.");
                return;
            }
            Fragment frag = mFragments.findFragmentByWho(who);
            if (frag == null) {
                Log.w(TAG, "Activity result no fragment exists for who: " + who);
            } else {
                frag.onRequestPermissionsResult(requestCode & 0xffff, permissions, grantResults);
            }
        }
    }

FragmentActivity#onRequestPermissionsResultから、Fragment#onRequestPermissionsResultを呼び出してた。

なので

HogeActivity.java

    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
        if (requestCode == REQUEST_CONTACTS) {
            if (grantResults.size == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // 後続処理
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

Activityで要求した権限じゃないときは、super#onRequestPermissionsResultを呼び出すようにしたらうまく動いた。