SimpleNavigatorProvider.java revision 6acf1d8307805fb382e8cc4883ddae89f1c21eb0 
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
17package androidx.navigation;
18
19import android.support.annotation.NonNull;
20import android.support.annotation.Nullable;
21import android.support.annotation.RestrictTo;
22
23import java.util.HashMap;
24
25/**
26 * Simple implementation of a {@link NavigatorProvider} that stores instances of
27 * {@link Navigator navigators} by name, using the {@link Navigator.Name} when given a class name.
28 *
29 * @hide
30 */
31@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
32public class SimpleNavigatorProvider implements NavigatorProvider {
33    private static final HashMap<Class, String> sAnnotationNames = new HashMap<>();
34
35    private final HashMap<String, Navigator<? extends NavDestination>> mNavigators =
36            new HashMap<>();
37
38    @NonNull
39    private String getNameForNavigator(@NonNull Class<? extends Navigator> navigatorClass) {
40        String name = sAnnotationNames.get(navigatorClass);
41        if (name == null) {
42            Navigator.Name annotation = navigatorClass.getAnnotation(Navigator.Name.class);
43            name = annotation != null ? annotation.value() : null;
44            if (!validateName(name)) {
45                throw new IllegalArgumentException("No @Navigator.Name annotation found for "
46                        + navigatorClass.getSimpleName());
47            }
48            sAnnotationNames.put(navigatorClass, name);
49        }
50        return name;
51    }
52
53    @NonNull
54    @Override
55    public <D extends NavDestination, T extends Navigator<? extends D>> T getNavigator(
56            @NonNull Class<T> navigatorClass) {
57        String name = getNameForNavigator(navigatorClass);
58        return getNavigator(name);
59    }
60
61    @NonNull
62    @Override
63    public <D extends NavDestination, T extends Navigator<? extends D>> T getNavigator(
64            @NonNull String name) {
65        if (!validateName(name)) {
66            throw new IllegalArgumentException("navigator name cannot be an empty string");
67        }
68
69        Navigator<? extends NavDestination> navigator = mNavigators.get(name);
70        if (navigator == null) {
71            throw new IllegalStateException("Could not find Navigator with name \"" + name
72                    + "\". You must call NavController.addNavigator() for each navigation type.");
73        }
74        //noinspection unchecked
75        return (T) navigator;
76    }
77
78    @Nullable
79    @Override
80    public Navigator<? extends NavDestination> addNavigator(
81            @NonNull Navigator<? extends NavDestination> navigator) {
82        String name = getNameForNavigator(navigator.getClass());
83
84        return addNavigator(name, navigator);
85    }
86
87    @Nullable
88    @Override
89    public Navigator<? extends NavDestination> addNavigator(@NonNull String name,
90            @NonNull Navigator<? extends NavDestination> navigator) {
91        if (!validateName(name)) {
92            throw new IllegalArgumentException("navigator name cannot be an empty string");
93        }
94        return mNavigators.put(name, navigator);
95    }
96
97    private boolean validateName(String name) {
98        return name != null && !name.isEmpty();
99    }
100}
101