联系人数据库设计之PhotoPriorityResolver

package com.android.providers.contacts;

import com.android.internal.util.XmlUtils;
import com.google.android.collect.Maps;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;

import android.accounts.AccountManager;
import android.accounts.AuthenticatorDescription;
import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.ServiceInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.res.XmlResourceParser;
import android.util.Log;

import java.io.IOException;
import java.util.HashMap;

/**
* Maintains a cache of photo priority per account type.  During contact aggregation
* photo with a higher priority is chosen for the the entire contact, barring an
* explicit override by the user, which is captured as the is_superprimary flag
* on the photo itself.
* 为每一个accountType保持一个photo priority缓冲。在整个联系期间，选择优先级较高的photo。
* 用户显式重写，用于photo的is_superprimary标志
*/
public class PhotoPriorityResolver  {
private static final String TAG = "PhotoPriorityResolver";

public static final int DEFAULT_PRIORITY = 7;

/**
* Meta-data key for the contacts configuration associated with a sync service.
* 联系人配置的Metadata关键字和syncService相关
*/
private static final String METADATA_CONTACTS = "android.provider.CONTACTS_STRUCTURE";

/**
* The XML tag capturing the picture priority. The syntax is:
* <code><Picture android:priority="6"/></code>
*/
private static final String PICTURE_TAG = "Picture";

/**
* Name of the attribute of the Picture tag capturing the priority itself.
*/
private static final String PRIORITY_ATTR = "priority";

private Context mContext;
private HashMap<String, Integer> mPhotoPriorities = Maps.newHashMap();

public PhotoPriorityResolver(Context context) {
mContext = context;
}

/**
* Returns the photo priority for the specified account type.  Maintains cache
* of photo priorities.
* 为指定account_typt返回photo priority
*/
public synchronized int getPhotoPriority(String accountType) {
if (accountType == null) {
return DEFAULT_PRIORITY;
}

Integer priority = mPhotoPriorities.get(accountType);
if (priority == null) {
priority = resolvePhotoPriority(accountType);
mPhotoPriorities.put(accountType, priority);
}
return priority;
}

/**
* Finds photo priority for the specified account type.
* 为指定account_type返回photo priority
*/
private int resolvePhotoPriority(String accountType) {
final AccountManager am = AccountManager.get(mContext);

for (AuthenticatorDescription auth : am.getAuthenticatorTypes()) {
if (accountType.equals(auth.type)) {
return resolvePhotoPriorityFromMetaData(auth.packageName);
}
}

return DEFAULT_PRIORITY;
}

/**
* Finds the meta-data XML containing the contacts configuration and
* reads the picture priority from that file.
* 返回指定packageName的含有meta-Data 联系人配置的XML文件，读取其中picture priority属性
*/
/* package */ int resolvePhotoPriorityFromMetaData(String packageName) {
final PackageManager pm = mContext.getPackageManager();
try {
PackageInfo pi = pm.getPackageInfo(packageName, PackageManager.GET_SERVICES
| PackageManager.GET_META_DATA);
if (pi != null && pi.services != null) {
for (ServiceInfo si : pi.services) {
final XmlResourceParser parser = si.loadXmlMetaData(pm, METADATA_CONTACTS);
if (parser != null) {
return loadPhotoPriorityFromXml(mContext, parser);
}
}
}
} catch (NameNotFoundException e) {
Log.w(TAG, "Problem loading photo priorities: " + e.toString());
}
return DEFAULT_PRIORITY;
}
/**
* 读取xml文件内容，解析picture priority属性
* @param context
* @param parser
* @return
*/
private int loadPhotoPriorityFromXml(Context context, XmlPullParser parser) {
int priority = DEFAULT_PRIORITY;
try {
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG
&& type != XmlPullParser.END_DOCUMENT) {
// Drain comments and whitespace
}

if (type != XmlPullParser.START_TAG) {
throw new IllegalStateException("No start tag found");
}

final int depth = parser.getDepth();
while (((type = parser.next()) != XmlPullParser.END_TAG || parser.getDepth() > depth)
&& type != XmlPullParser.END_DOCUMENT) {
String name = parser.getName();
if (type == XmlPullParser.START_TAG && PICTURE_TAG.equals(name)) {
int attributeCount = parser.getAttributeCount();
for (int i = 0; i < attributeCount; i++) {
String attr = parser.getAttributeName(i);
if (PRIORITY_ATTR.equals(attr)) {
priority = XmlUtils.convertValueToInt(parser.getAttributeValue(i),
DEFAULT_PRIORITY);
} else {
throw new IllegalStateException("Unsupported attribute " + attr);
}
}
}
}
} catch (XmlPullParserException e) {
throw new IllegalStateException("Problem reading XML", e);
} catch (IOException e) {
throw new IllegalStateException("Problem reading XML", e);
}

return priority;
}
}