| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.google.android.setupdesign.items; |
| |
| import android.content.Context; |
| import android.util.AttributeSet; |
| import android.view.InflateException; |
| import androidx.annotation.NonNull; |
| import androidx.annotation.Nullable; |
| import java.lang.reflect.Constructor; |
| import java.util.HashMap; |
| |
| /** |
| * An XML inflater that creates items by reading the tag as a class name, and constructs said class |
| * by invoking the 2-argument constructor {@code Constructor(Context, AttributeSet)} via reflection. |
| * |
| * <p>Optionally a "default package" can be specified so that for unqualified tag names (i.e. names |
| * that do not contain "."), the default package will be prefixed onto the tag. |
| * |
| * @param <T> The class where all instances (including child elements) belong to. If parent and |
| * child elements belong to different class hierarchies, it's OK to set this to {@link Object}. |
| */ |
| public abstract class ReflectionInflater<T> extends SimpleInflater<T> { |
| |
| /* static section */ |
| |
| private static final Class<?>[] CONSTRUCTOR_SIGNATURE = |
| new Class<?>[] {Context.class, AttributeSet.class}; |
| |
| private static final HashMap<String, Constructor<?>> constructorMap = new HashMap<>(); |
| |
| /* non-static section */ |
| |
| // Array used to contain the constructor arguments (Context, AttributeSet), to avoid allocating |
| // a new array for creation of every item. |
| private final Object[] tempConstructorArgs = new Object[2]; |
| |
| @Nullable private String defaultPackage; |
| |
| @NonNull private final Context context; |
| |
| /** |
| * Create a new inflater instance associated with a particular Context. |
| * |
| * @param context The context used to resolve resource IDs. This context is also passed to the |
| * constructor of the items created as the first argument. |
| */ |
| protected ReflectionInflater(@NonNull Context context) { |
| super(context.getResources()); |
| this.context = context; |
| } |
| |
| @NonNull |
| public Context getContext() { |
| return context; |
| } |
| |
| /** |
| * Instantiate the class by name. This attempts to instantiate class of the given {@code name} |
| * found in this inflater's ClassLoader. |
| * |
| * @param tagName The full name of the class to be instantiated. |
| * @param attrs The XML attributes supplied for this instance. |
| * @return The newly instantiated item. |
| */ |
| @NonNull |
| public final T createItem(String tagName, String prefix, AttributeSet attrs) { |
| String qualifiedName = tagName; |
| if (prefix != null && qualifiedName.indexOf('.') == -1) { |
| qualifiedName = prefix.concat(qualifiedName); |
| } |
| @SuppressWarnings("unchecked") // qualifiedName should correspond to a subclass of T |
| Constructor<? extends T> constructor = |
| (Constructor<? extends T>) constructorMap.get(qualifiedName); |
| |
| try { |
| if (constructor == null) { |
| // Class not found in the cache, see if it's real, and try to add it |
| @SuppressWarnings("unchecked") // qualifiedName should correspond to a subclass of T |
| Class<? extends T> clazz = |
| (Class<? extends T>) context.getClassLoader().loadClass(qualifiedName); |
| constructor = clazz.getConstructor(CONSTRUCTOR_SIGNATURE); |
| constructor.setAccessible(true); |
| constructorMap.put(tagName, constructor); |
| } |
| |
| tempConstructorArgs[0] = context; |
| tempConstructorArgs[1] = attrs; |
| final T item = constructor.newInstance(tempConstructorArgs); |
| tempConstructorArgs[0] = null; |
| tempConstructorArgs[1] = null; |
| return item; |
| } catch (Exception e) { |
| throw new InflateException( |
| attrs.getPositionDescription() + ": Error inflating class " + qualifiedName, e); |
| } |
| } |
| |
| @Override |
| protected T onCreateItem(String tagName, AttributeSet attrs) { |
| return createItem(tagName, defaultPackage, attrs); |
| } |
| |
| /** |
| * Sets the default package that will be searched for classes to construct for tag names that have |
| * no explicit package. |
| * |
| * @param defaultPackage The default package. This will be prepended to the tag name, so it should |
| * end with a period. |
| */ |
| public void setDefaultPackage(@Nullable String defaultPackage) { |
| this.defaultPackage = defaultPackage; |
| } |
| |
| /** |
| * Returns the default package, or null if it is not set. |
| * |
| * @see #setDefaultPackage(String) |
| * @return The default package. |
| */ |
| @Nullable |
| public String getDefaultPackage() { |
| return defaultPackage; |
| } |
| } |