從Android源碼分析Intent查詢婚配的完成。本站提示廣大學習愛好者：（從Android源碼分析Intent查詢婚配的完成）文章只能為提供參考，不一定能成為您想要的結果。以下是從Android源碼分析Intent查詢婚配的完成正文
媒介
這篇文章重要是引見一下Android Intent，而且從Android源碼的角度對Intent查詢婚配進程停止剖析。
Intent引見
Intent的中文是“意圖”的意思，而意圖是一個異常籠統的概念，那末在Android的編碼設計中，若何實例化意圖呢？是以Android體系明白指定一個Intent可由兩方面屬性來權衡。
重要屬性：包含Action和Data。個中Action用於表現該Intent所表達的舉措意圖，Data用於表現該Action所操作的數據。
主要屬性：包含Category、Type、Component和Extras。個中Category表現種別，Type表現數據的MIME類型，Component可用於指定特定的Intent的呼應者（例如指定intent為某個包下的某個class類），Extras用於承載其他的信息。
Android體系中重要有兩品種型的Intent，顯示Intent（Explicit Intent）和隱式Intent（Implicit Intent）。
Explicit Intent：這類Intent明白指清楚明了要找哪一個Component。在代碼中可以經由過程setClassName或許setComponent來鎖定目的對象。
Implicit Intent：這類Intent不明白指明要啟動哪一個Component，而是設置Action、Data、Category讓體系來挑選出適合的Component。
接上去，寫兩個代碼示例，來引見一下Explicit Intent和Implict Inent。起首是Explicit Intent：
private void startExplicitIntentWithComponent() {
Intent intent = new Intent();
ComponentName component = new ComponentName("com.example.photocrop", "com.example.photocrop.MainActivity");
intent.setComponent(component);
startActivity(intent);
}
private void startExplicitIntentWithClassName() {
Intent intent = new Intent();
intent.setClassName("com.example.photocrop", "com.example.photocrop.MainActivity");
startActivity(intent);
}
然則，從源碼外面去看，發明setClassName也是借助了ComponentName完成了Explicit Intent。源碼以下：
public Intent setClassName(String packageName, String className) {
mComponent = new ComponentName(packageName, className);
return this;
}
然後，在給出一個Implict Intent的代碼示例。我這裡用一個Activity標注一些Intent Filter為例，然後在寫一個Intent用於啟動它。
<activity
android:name=".SendIntentType">
<intent-filter >
<action android:name="justtest"/>
<category android:name="justcategory"/>
</intent-filter>
</activity>
在以後運用的AndroidManifest.xml中，給SendIntentType類增長了intent-filter，action的名字為“justtest”，category的名字為“justcategory”。啟動該Activity的代碼以下：
private void startImplictIntent() {
Intent intent = new Intent();
intent.setAction("justaction");
intent.addCategory("justcategory");
startActivity(intent);
}
體系在婚配Implict Intent的進程中，將以Intent Filter列出的3項內容為參考尺度，詳細步調以下：
Activityi信息的治理
從下面的剖析可以看出，體系的婚配Intent的進程中，起首須要治理以後體系中一切Activity信息。Activity的信息是PackageManagerService在掃描APK的時刻停止搜集和治理的。相干源碼以下：
// 處置該package的activity信息
N = pkg.activities.size();
r = null;
for (i = 0; i < N; i++) {
PackageParser.Activity a = pkg.activities.get(i);
a.info.processName = fixProcessName(pkg.applicationInfo.processName, a.info.processName,
pkg.applicationInfo.uid);
mActivities.addActivity(a, "activity");
}
下面代碼中，有兩個比擬主要的數據構造，以下圖所示。
聯合代碼和上圖的數據構造，可知：
mAcitivitys為ActivityIntentResolver類型，是PKMS的成員變量，用於保留體系中一切與Activity相干的信息。此數據構造外部也有一個mActivities變量，它以ComponentName為key，保留PackageParser.Activity對象。
從APK中解析獲得的一切和Acitivity相干的信息（包含XML中聲明的IntentFilter標簽）都由PackageParser.Activity來保留。
後面代碼中挪用addActivity函數完成了公有信息的私有化。addActivity函數的代碼以下：
public final void addActivity(PackageParser.Activity a, String type) {
final boolean systemApp = isSystemApp(a.info.applicationInfo);
mActivities.put(a.getComponentName(), a);
final int NI = a.intents.size();
for (int j = 0; j < NI; j++) {
PackageParser.ActivityIntentInfo intent = a.intents.get(j);
if (!systemApp && intent.getPriority() > 0 && "activity".equals(type)) {
// 非體系APK的priority必需為0
intent.setPriority(0);
}
addFilter(intent);
}
}
接上去看一下addFilter函數。函數源碼以下：
public void addFilter(F f) {
// mFilters保留一切IntentFilter信息
mFilters.add(f);
int numS = register_intent_filter(f, f.schemesIterator(),
mSchemeToFilter, " Scheme: ");
int numT = register_mime_types(f, " Type: ");
if (numS == 0 && numT == 0) {
register_intent_filter(f, f.actionsIterator(),
mActionToFilter, " Action: ");
}
if (numT != 0) {
register_intent_filter(f, f.actionsIterator(),
mTypedActionToFilter, " TypedAction: ");
}
}
這裡又湧現了幾種數據構造，它們的相似都是ArrayMap<String, F[ ]>，個中F為模板參數。
懂得了年夜概的數據構造以後，我們來看一下register_intent_filter的函數完成：
private final int register_intent_filter(F filter, Iterator<String> i,
ArrayMap<String, F[]> dest, String prefix) {
if (i == null) {
return 0;
}
int num = 0;
while (i.hasNext()) {
String name = i.next();
num++;
addFilter(dest, name, filter);
}
return num;
}
然後又是一個addFilter函數，顯著是一個函數重載，我們來看一下這個addFilter的完成：
private final void addFilter(ArrayMap<String, F[]> map, String name, F filter) {
F[] array = map.get(name);
if (array == null) {
array = newArray(2);
map.put(name, array);
array[0] = filter;
} else {
final int N = array.length;
int i = N;
while (i > 0 && array[i-1] == null) {
i--;
}
if (i < N) {
array[i] = filter;
} else {
F[] newa = newArray((N*3)/2);
System.arraycopy(array, 0, newa, 0, N);
newa[N] = filter;
map.put(name, newa);
}
}
}
其實代碼照樣很簡略的，假如F數組存在，則斷定容量，不敷則擴容，夠的話就找到地位拔出。假如F數組不存在，則創立一個容量為2的數組，將0號元素賦值為該filter。
Intent婚配查詢剖析
客戶端經由過程ApplicationPackageManager輸入的queryIntentActivities函數向PackageManagerService提議一次查詢要求，代碼以下：
@Override
public List<ResolveInfo> queryIntentActivities(Intent intent,
int flags) {
return queryIntentActivitiesAsUser(intent, flags, mContext.getUserId());
}
/** @hide Same as above but for a specific user */
@Override
public List<ResolveInfo> queryIntentActivitiesAsUser(Intent intent,
int flags, int userId) {
try {
return mPM.queryIntentActivities(
intent,
intent.resolveTypeIfNeeded(mContext.getContentResolver()),
flags,
userId);
} catch (RemoteException e) {
throw new RuntimeException("Package manager has died", e);
}
}
可以看到，queryIntentActivities的真正完成是在PackageManagerService.java中，函數代碼以下：
public List<ResolveInfo> queryIntentActivities(Intent intent, String resolvedType, int flags, int userId) {
if (!sUserManager.exists(userId))
return Collections.emptyList();
enforceCrossUserPermission(Binder.getCallingUid(), userId, false, "query intent activities");
ComponentName comp = intent.getComponent();
if (comp == null) {
if (intent.getSelector() != null) {
intent = intent.getSelector();
comp = intent.getComponent();
}
}
if (comp != null) {
// Explicit的Intent，直接依據component獲得對應的ActivityInfo
final List<ResolveInfo> list = new ArrayList<ResolveInfo>(1);
final ActivityInfo ai = getActivityInfo(comp, flags, userId);
if (ai != null) {
final ResolveInfo ri = new ResolveInfo();
ri.activityInfo = ai;
list.add(ri);
}
return list;
}
// reader
synchronized (mPackages) {
final String pkgName = intent.getPackage();
if (pkgName == null) {
// Implicit Intent
return mActivities.queryIntent(intent, resolvedType, flags, userId);
}
final PackageParser.Package pkg = mPackages.get(pkgName);
if (pkg != null) {
// 指定了包名的Intent
return mActivities.queryIntentForPackage(intent, resolvedType, flags, pkg.activities, userId);
}
return new ArrayList<ResolveInfo>();
}
}
可以看到，Explicit Intent的完成較為簡略，我們重點來看一下Implict Intent完成。Implicit Intent挪用了queryIntent辦法，我們來看一下queryIntent的完成代碼：
public List<ResolveInfo> queryIntent(Intent intent, String resolvedType, int flags, int userId) {
if (!sUserManager.exists(userId))
return null;
mFlags = flags;
return super.queryIntent(intent, resolvedType, (flags & PackageManager.MATCH_DEFAULT_ONLY) != 0, userId);
}
持續跟蹤到IntentResolver.java的queryIntent辦法，源碼以下：
public List<R> queryIntent(Intent intent, String resolvedType, boolean defaultOnly,
int userId) {
String scheme = intent.getScheme();
ArrayList<R> finalList = new ArrayList<R>();
// 最多有4輪婚配操作
F[] firstTypeCut = null;
F[] secondTypeCut = null;
F[] thirdTypeCut = null;
F[] schemeCut = null;
// If the intent includes a MIME type, then we want to collect all of
// the filters that match that MIME type.
if (resolvedType != null) {
int slashpos = resolvedType.indexOf('/');
if (slashpos > 0) {
final String baseType = resolvedType.substring(0, slashpos);
if (!baseType.equals("*")) {
if (resolvedType.length() != slashpos+2
|| resolvedType.charAt(slashpos+1) != '*') {
// Not a wild card, so we can just look for all filters that
// completely match or wildcards whose base type matches.
firstTypeCut = mTypeToFilter.get(resolvedType);
secondTypeCut = mWildTypeToFilter.get(baseType);
} else {
// We can match anything with our base type.
firstTypeCut = mBaseTypeToFilter.get(baseType);
secondTypeCut = mWildTypeToFilter.get(baseType);
}
// Any */* types always apply, but we only need to do this
// if the intent type was not already */*.
thirdTypeCut = mWildTypeToFilter.get("*");
} else if (intent.getAction() != null) {
// The intent specified any type ({@literal *}/*). This
// can be a whole heck of a lot of things, so as a first
// cut let's use the action instead.
firstTypeCut = mTypedActionToFilter.get(intent.getAction());
}
}
}
// If the intent includes a data URI, then we want to collect all of
// the filters that match its scheme (we will further refine matches
// on the authority and path by directly matching each resulting filter).
if (scheme != null) {
schemeCut = mSchemeToFilter.get(scheme);
}
// If the intent does not specify any data -- either a MIME type or
// a URI -- then we will only be looking for matches against empty
// data.
if (resolvedType == null && scheme == null && intent.getAction() != null) {
firstTypeCut = mActionToFilter.get(intent.getAction());
}
FastImmutableArraySet<String> categories = getFastIntentCategories(intent);
if (firstTypeCut != null) {
buildResolveList(intent, categories, debug, defaultOnly,
resolvedType, scheme, firstTypeCut, finalList, userId);
}
if (secondTypeCut != null) {
buildResolveList(intent, categories, debug, defaultOnly,
resolvedType, scheme, secondTypeCut, finalList, userId);
}
if (thirdTypeCut != null) {
buildResolveList(intent, categories, debug, defaultOnly,
resolvedType, scheme, thirdTypeCut, finalList, userId);
}
if (schemeCut != null) {
buildResolveList(intent, categories, debug, defaultOnly,
resolvedType, scheme, schemeCut, finalList, userId);
}
sortResults(finalList);
return finalList;
}
詳細的查詢婚配進程是由buildResolveList函數完成了。查詢的婚配完成我就不貼代碼了，年夜家本身去查詢看就行了。
