1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package androidx.navigation; 18 19 import android.content.Context; 20 import android.os.Bundle; 21 import android.support.annotation.NonNull; 22 import android.support.annotation.Nullable; 23 24 /** 25 * A Navigator built specifically for {@link NavGraph} elements. Handles navigating to the 26 * correct destination when the NavGraph is the target of navigation actions. 27 */ 28 @Navigator.Name("navigation") 29 public class NavGraphNavigator extends Navigator<NavGraph> { 30 private Context mContext; 31 32 /** 33 * Construct a Navigator capable of routing incoming navigation requests to the proper 34 * destination within a {@link NavGraph}. 35 * @param context 36 */ 37 public NavGraphNavigator(@NonNull Context context) { 38 mContext = context; 39 } 40 41 /** 42 * Creates a new {@link NavGraph} associated with this navigator. 43 * @return 44 */ 45 @NonNull 46 @Override 47 public NavGraph createDestination() { 48 return new NavGraph(this); 49 } 50 51 @Override 52 public void navigate(@NonNull NavGraph destination, @Nullable Bundle args, 53 @Nullable NavOptions navOptions) { 54 int startId = destination.getStartDestination(); 55 if (startId == 0) { 56 throw new IllegalStateException("no start destination defined via" 57 + " app:startDestination for " 58 + (destination.getId() != 0 59 ? NavDestination.getDisplayName(mContext, destination.getId()) 60 : "the root navigation")); 61 } 62 NavDestination startDestination = destination.findNode(startId, false); 63 if (startDestination == null) { 64 final String dest = NavDestination.getDisplayName(mContext, startId); 65 throw new IllegalArgumentException("navigation destination " + dest 66 + " is not a direct child of this NavGraph"); 67 } 68 dispatchOnNavigatorNavigated(destination.getId(), BACK_STACK_DESTINATION_ADDED); 69 startDestination.navigate(args, navOptions); 70 } 71 72 @Override 73 public boolean popBackStack() { 74 return false; 75 } 76 } 77
