我们熟悉的资源加载代码：
1.Activity.getResources();
2.Context.getResources();
这2种方式获取的都是Resources对象
先看第一种获取Resources对象源码分析：
说明：（AppcompatActivity中getResource()方法与Activity.getResources()是有区别的。AppcompatActivity是new Resources(...)对象）
一：Activity.getResources()源码分析：
Activity.getResources()之间调用的是Activity父类ContextThreadWrapper类中的
@Override
public Resources getResources() {
return getResourcesInternal();
}
private Resources getResourcesInternal() {
if (mResources == null) {
if (mOverrideConfiguration == null) {
mResources = super.getResources();//继续向上 调用mBase.getReources()方法。其中mBase是一个Context对象
} else {
final Context resContext = createConfigurationContext(mOverrideConfiguration);
mResources = resContext.getResources();
}
}
return mResources;
}
从上面知道Activity.getResources() 其实也是调用的Context.getResources()方法
二：继续分析Context.getResources（）方法。
Context是一个抽象类。其中getResources()方法源码：
public abstract Resources getResources()
通过查询资料知道：ContextImpl是Context的实现类。（这里我没有知道源码实现的地方）
ContextImpl源码地址：http://androidxref.com/8.0.0_r4/xref/frameworks/base/core/java/android/app/ContextImpl.java
@Override
public Resources getResources() {
return mResources;
}
ContextImpl的getResources()方法中已实例化了Resources对象
mResources是通过setResources方法赋值：
void setResources(Resources r) {
if (r instanceof CompatResources) {
((CompatResources) r).setContext(this);
}
mResources = r;
}
查找到给mResources赋值的代码：
1 static ContextImpl createAppContext(ActivityThread mainThread, LoadedApk packageInfo) {
2 if (packageInfo == null) throw new IllegalArgumentException("packageInfo");
3 ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, 0,
4 null);
5 context.setResources(packageInfo.getResources());
6 return context;
7 }
8
9 static ContextImpl createActivityContext(ActivityThread mainThread,
10 LoadedApk packageInfo, ActivityInfo activityInfo, IBinder activityToken, int displayId,
11 Configuration overrideConfiguration) {
12 if (packageInfo == null) throw new IllegalArgumentException("packageInfo");
13
14 String[] splitDirs = packageInfo.getSplitResDirs();
15 ClassLoader classLoader = packageInfo.getClassLoader();
16
17 if (packageInfo.getApplicationInfo().requestsIsolatedSplitLoading()) {
18 Trace.traceBegin(Trace.TRACE_TAG_RESOURCES, "SplitDependencies");
19 try {
20 classLoader = packageInfo.getSplitClassLoader(activityInfo.splitName);
21 splitDirs = packageInfo.getSplitPaths(activityInfo.splitName);
22 } catch (NameNotFoundException e) {
23 // Nothing above us can handle a NameNotFoundException, better crash.
24 throw new RuntimeException(e);
25 } finally {
26 Trace.traceEnd(Trace.TRACE_TAG_RESOURCES);
27 }
28 }
29
30 ContextImpl context = new ContextImpl(null, mainThread, packageInfo, activityInfo.splitName,
31 activityToken, null, 0, classLoader);
32
33 // Clamp display ID to DEFAULT_DISPLAY if it is INVALID_DISPLAY.
34 displayId = (displayId != Display.INVALID_DISPLAY) ? displayId : Display.DEFAULT_DISPLAY;
35
36 final CompatibilityInfo compatInfo = (displayId == Display.DEFAULT_DISPLAY)
37 ? packageInfo.getCompatibilityInfo()
38 : CompatibilityInfo.DEFAULT_COMPATIBILITY_INFO;
39
40 final ResourcesManager resourcesManager = ResourcesManager.getInstance();
41
42 // Create the base resources for which all configuration contexts for this Activity
43 // will be rebased upon.
44 context.setResources(resourcesManager.createBaseActivityResources(activityToken,
45 packageInfo.getResDir(),
46 splitDirs,
47 packageInfo.getOverlayDirs(),
48 packageInfo.getApplicationInfo().sharedLibraryFiles,
49 displayId,
50 overrideConfiguration,
51 compatInfo,
52 classLoader));
53 context.mDisplay = resourcesManager.getAdjustedDisplay(displayId,
54 context.getResources());
55 return context;
56 }
mResources赋值代码
分别调用的方法：
一： context.setResources(packageInfo.getResources());
二： context.setResources(resourcesManager.createBaseActivityResources(activityToken,
packageInfo.getResDir(),
splitDirs,
packageInfo.getOverlayDirs(),
packageInfo.getApplicationInfo().sharedLibraryFiles,
displayId,
overrideConfiguration,
compatInfo,
classLoader));
这里只分析第一种：（2种差不多。只是进入ResourcesManager方式不一样）
继续查看LoadedApk类的getResources()方法
public Resources getResources() {
if (mResources == null) {
final String[] splitPaths;
try {
splitPaths = getSplitPaths(null);
} catch (NameNotFoundException e) {
// This should never fail.
throw new AssertionError("null split not found");
}
mResources = ResourcesManager.getInstance().getResources(null, mResDir,
splitPaths, mOverlayDirs, mApplicationInfo.sharedLibraryFiles,
Display.DEFAULT_DISPLAY, null, getCompatibilityInfo(),
getClassLoader());
}
return mResources;
}
继续查看ResourcesManager的getResources()方法
public @Nullable Resources getResources(@Nullable IBinder activityToken,
@Nullable String resDir,
@Nullable String[] splitResDirs,
@Nullable String[] overlayDirs,
@Nullable String[] libDirs,
int displayId,
@Nullable Configuration overrideConfig,
@NonNull CompatibilityInfo compatInfo,
@Nullable ClassLoader classLoader) {
try {
Trace.traceBegin(Trace.TRACE_TAG_RESOURCES, "ResourcesManager#getResources");//C的方法
final ResourcesKey key = new ResourcesKey(//计算哈希值
resDir,
splitResDirs,
overlayDirs,
libDirs,
displayId,
overrideConfig != null ? new Configuration(overrideConfig) : null, // Copy
compatInfo);
classLoader = classLoader != null ? classLoader : ClassLoader.getSystemClassLoader();
return getOrCreateResources(activityToken, key, classLoader);
} finally {
Trace.traceEnd(Trace.TRACE_TAG_RESOURCES);
}
}
继续查看 getOrCreateResources()方法
1 private @Nullable Resources getOrCreateResources(@Nullable IBinder activityToken,
2 @NonNull ResourcesKey key, @NonNull ClassLoader classLoader) {
3 synchronized (this) {
4 if (DEBUG) {
5 Throwable here = new Throwable();
6 here.fillInStackTrace();
7 Slog.w(TAG, "!! Get resources for activity=" + activityToken + " key=" + key, here);
8 }
9
10 if (activityToken != null) {
11 final ActivityResources activityResources =
12 getOrCreateActivityResourcesStructLocked(activityToken);
13
14 // Clean up any dead references so they don‘t pile up.
15 ArrayUtils.unstableRemoveIf(activityResources.activityResources,
16 sEmptyReferencePredicate);
17
18 // Rebase the key‘s override config on top of the Activity‘s base override.
19 if (key.hasOverrideConfiguration()
20 && !activityResources.overrideConfig.equals(Configuration.EMPTY)) {
21 final Configuration temp = new Configuration(activityResources.overrideConfig);
22 temp.updateFrom(key.mOverrideConfiguration);
23 key.mOverrideConfiguration.setTo(temp);
24 }
25
26
27
28 ResourcesImpl resourcesImpl = findResourcesImplForKeyLocked(key);
29 if (resourcesImpl != null) {
30 if (DEBUG) {
31 Slog.d(TAG, "- using existing impl=" + resourcesImpl);
32 }
33 return getOrCreateResourcesForActivityLocked(activityToken, classLoader,
34 resourcesImpl, key.mCompatInfo);
35 }
36
37 // We will create the ResourcesImpl object outside of holding this lock.
38
39 } else {
40 // Clean up any dead references so they don‘t pile up.
41 ArrayUtils.unstableRemoveIf(mResourceReferences, sEmptyReferencePredicate);
42
43 // Not tied to an Activity, find a shared Resources that has the right ResourcesImpl
44 ResourcesImpl resourcesImpl = findResourcesImplForKeyLocked(key);
45 if (resourcesImpl != null) {
46 if (DEBUG) {
47 Slog.d(TAG, "- using existing impl=" + resourcesImpl);
48 }
49 return getOrCreateResourcesLocked(classLoader, resourcesImpl, key.mCompatInfo);
50 }
51
52 // We will create the ResourcesImpl object outside of holding this lock.
53 }
54 }
55
56 // If we‘re here, we didn‘t find a suitable ResourcesImpl to use, so create one now.
57 ResourcesImpl resourcesImpl = createResourcesImpl(key);
58 if (resourcesImpl == null) {
59 return null;
60 }
61
62 synchronized (this) {
63 ResourcesImpl existingResourcesImpl = findResourcesImplForKeyLocked(key);
64 if (existingResourcesImpl != null) {
65 if (DEBUG) {
66 Slog.d(TAG, "- got beat! existing impl=" + existingResourcesImpl
67 + " new impl=" + resourcesImpl);
68 }
69 resourcesImpl.getAssets().close();
70 resourcesImpl = existingResourcesImpl;
71 } else {
72 // Add this ResourcesImpl to the cache.
73 mResourceImpls.put(key, new WeakReference<>(resourcesImpl));
74 }
75
76 final Resources resources;
77 if (activityToken != null) {
78 resources = getOrCreateResourcesForActivityLocked(activityToken, classLoader,
79 resourcesImpl, key.mCompatInfo);
80 } else {
81 resources = getOrCreateResourcesLocked(classLoader, resourcesImpl, key.mCompatInfo);
82 }
83 return resources;
84 }
85 }
getOrCreateResources()方法
其中比较重要方法：
ResourcesImpl resourcesImpl = createResourcesImpl(key);
resources = getOrCreateResourcesLocked(classLoader, resourcesImpl, key.mCompatInfo);
先看：createResourcesImpl(key)方法,它去创建了一个ResourcesImpl对象
private @Nullable ResourcesImpl createResourcesImpl(@NonNull ResourcesKey key) {
final DisplayAdjustments daj = new DisplayAdjustments(key.mOverrideConfiguration);
daj.setCompatibilityInfo(key.mCompatInfo);
final AssetManager assets = createAssetManager(key);
if (assets == null) {
return null;
}
final DisplayMetrics dm = getDisplayMetrics(key.mDisplayId, daj);
final Configuration config = generateConfig(key, dm);
final ResourcesImpl impl = new ResourcesImpl(assets, dm, config, daj);
if (DEBUG) {
Slog.d(TAG, "- creating impl=" + impl + " with key: " + key);
}
return impl;
}
继续向下查看：getOrCreateResourcesLocked(..)方法
private @NonNull Resources getOrCreateResourcesLocked(@NonNull ClassLoader classLoader,
@NonNull ResourcesImpl impl, @NonNull CompatibilityInfo compatInfo) {
// Find an existing Resources that has this ResourcesImpl set.
final int refCount = mResourceReferences.size();
for (int i = 0; i < refCount; i++) {
WeakReference<Resources> weakResourceRef = mResourceReferences.get(i);
Resources resources = weakResourceRef.get();
if (resources != null &&
Objects.equals(resources.getClassLoader(), classLoader) &&
resources.getImpl() == impl) {
if (DEBUG) {
Slog.d(TAG, "- using existing ref=" + resources);
}
return resources;
}
}
// Create a new Resources reference and use the existing ResourcesImpl object.
Resources resources = compatInfo.needsCompatResources() ? new CompatResources(classLoader)
: new Resources(classLoader);
resources.setImpl(impl);
mResourceReferences.add(new WeakReference<>(resources));
if (DEBUG) {
Slog.d(TAG, "- creating new ref=" + resources);
Slog.d(TAG, "- setting ref=" + resources + " with impl=" + impl);
}
return resources;
}
到这里可以之间看到 Resources 对象是之间通过new Resources(ClassLoader)创建的
然后通过resources.setImpl(impl)去设置参数。
我们进一步去查看Resources.getString(int id)方法
@NonNull
public String getString(@StringRes int id) throws NotFoundException {
return getText(id).toString();
}
public CharSequence getText(@StringRes int id, CharSequence def) {
CharSequence res = id != 0 ? mResourcesImpl.getAssets().getResourceText(id) : null;
return res != null ? res : def;
}
这里发现加载资源是通过ResourcesImpl对象去加载的
public AssetManager getAssets() {
return mAssets;
}
进一步查看AssetManager.getResourceText(int id)方法
@Nullable
final CharSequence getResourceText(@StringRes int resId) {
synchronized (this) {
final TypedValue outValue = mValue;
if (getResourceValue(resId, 0, outValue, true)) {
return outValue.coerceToString();
}
return null;
}
}
final boolean getResourceValue(@AnyRes int resId, int densityDpi, @NonNull TypedValue outValue,
boolean resolveRefs) {
synchronized (this) {
final int block = loadResourceValue(resId, (short) densityDpi, outValue, resolveRefs);
if (block < 0) {
return false;
}
// Convert the changing configurations flags populated by native code.
outValue.changingConfigurations = ActivityInfo.activityInfoConfigNativeToJava(
outValue.changingConfigurations);
if (outValue.type == TypedValue.TYPE_STRING) {
outValue.string = mStringBlocks[block].get(outValue.data);
}
return true;
}
}
继续往下 基本就是底层的一些东西了。
总结：Android 资源加载 核心就是AssetManager对象。
（后面写的不是特别详细。。。）
原文地址：https://www.cnblogs.com/kangqi001/p/8381355.html
时间： 2024-10-07 06:13:36