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/*
* 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.android.setupwizardlib.items;
import android.content.res.Resources;
import android.content.res.XmlResourceParser;
import android.util.AttributeSet;
import android.util.Log;
import android.util.Xml;
import android.view.InflateException;
import androidx.annotation.NonNull;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import java.io.IOException;
/**
* A simple XML inflater, which takes care of moving the parser to the correct position. Subclasses
* need to implement {@link #onCreateItem(String, AttributeSet)} to create an object representation
* and {@link #onAddChildItem(Object, Object)} to attach a child tag to the parent 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 SimpleInflater<T> {
private static final String TAG = "SimpleInflater";
private static final boolean DEBUG = false;
protected final Resources mResources;
/**
* Create a new inflater instance associated with a particular Resources bundle.
*
* @param resources The Resources class used to resolve given resource IDs.
*/
protected SimpleInflater(@NonNull Resources resources) {
mResources = resources;
}
public Resources getResources() {
return mResources;
}
/**
* Inflate a new hierarchy from the specified XML resource. Throws InflaterException if there is
* an error.
*
* @param resId ID for an XML resource to load (e.g. <code>R.xml.my_xml</code>)
* @return The root of the inflated hierarchy.
*/
public T inflate(int resId) {
XmlResourceParser parser = getResources().getXml(resId);
try {
return inflate(parser);
} finally {
parser.close();
}
}
/**
* Inflate a new hierarchy from the specified XML node. Throws InflaterException if there is an
* error.
* <p>
* <em><strong>Important</strong></em> For performance
* reasons, inflation relies heavily on pre-processing of XML files
* that is done at build time. Therefore, it is not currently possible to
* use inflater with an XmlPullParser over a plain XML file at runtime.
*
* @param parser XML dom node containing the description of the hierarchy.
* @return The root of the inflated hierarchy.
*/
public T inflate(XmlPullParser parser) {
final AttributeSet attrs = Xml.asAttributeSet(parser);
T createdItem;
try {
// Look for the root node.
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG
&& type != XmlPullParser.END_DOCUMENT) {
// continue
}
if (type != XmlPullParser.START_TAG) {
throw new InflateException(parser.getPositionDescription()
+ ": No start tag found!");
}
createdItem = createItemFromTag(parser.getName(), attrs);
rInflate(parser, createdItem, attrs);
} catch (XmlPullParserException e) {
throw new InflateException(e.getMessage(), e);
} catch (IOException e) {
throw new InflateException(parser.getPositionDescription() + ": " + e.getMessage(), e);
}
return createdItem;
}
/**
* This routine is responsible for creating the correct subclass of item
* given the xml element name.
*
* @param tagName The XML tag name for the item to be created.
* @param attrs An AttributeSet of attributes to apply to the item.
* @return The item created.
*/
protected abstract T onCreateItem(String tagName, AttributeSet attrs);
private T createItemFromTag(String name, AttributeSet attrs) {
try {
T item = onCreateItem(name, attrs);
if (DEBUG) Log.v(TAG, item + " created for <" + name + ">");
return item;
} catch (InflateException e) {
throw e;
} catch (Exception e) {
throw new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
}
}
/**
* Recursive method used to descend down the xml hierarchy and instantiate
* items, instantiate their children, and then call onFinishInflate().
*/
private void rInflate(XmlPullParser parser, T parent, final AttributeSet attrs)
throws XmlPullParserException, IOException {
final int depth = parser.getDepth();
int type;
while (((type = parser.next()) != XmlPullParser.END_TAG
|| parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) {
if (type != XmlPullParser.START_TAG) {
continue;
}
if (onInterceptCreateItem(parser, parent, attrs)) {
continue;
}
String name = parser.getName();
T item = createItemFromTag(name, attrs);
onAddChildItem(parent, item);
rInflate(parser, item, attrs);
}
}
/**
* Whether item creation should be intercepted to perform custom handling on the parser rather
* than creating an object from it. This is used in rare cases where a tag doesn't correspond
* to creation of an object.
*
* The parser will be pointing to the start of a tag, you must stop parsing and return when you
* reach the end of this element. That is, this method is responsible for parsing the element
* at the given position together with all of its child tags.
*
* Note that parsing of the root tag cannot be intercepted.
*
* @param parser XML dom node containing the description of the hierarchy.
* @param parent The item that should be the parent of whatever you create.
* @param attrs An AttributeSet of attributes to apply to the item.
* @return True to continue parsing without calling {@link #onCreateItem(String, AttributeSet)},
* or false if this inflater should proceed to create an item.
*/
protected boolean onInterceptCreateItem(XmlPullParser parser, T parent, AttributeSet attrs)
throws XmlPullParserException {
return false;
}
protected abstract void onAddChildItem(T parent, T child);
}
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