1. 作用：

记录一个Activity的历史任务(封装了包含启动Activity过程中的信息)

2. 路径：

frameworks/base/services/core/java/com/android/server/wm/ActivityRecord.java

3. 主要属性

/**
 * An entry in the history task, representing an activity.
 */
final class ActivityRecord extends WindowToken implements WindowManagerService.AppFreezeListener {
    private static final String TAG = TAG_WITH_CLASS_NAME ? "ActivityRecord" : TAG_ATM;// ActivityTaskManager
    
    final ActivityTaskManagerService mAtmService;
    @NonNull
    final ActivityInfo info; // activity info provided by developer in AndroidManifest
    // Which user is this running for?
    final int mUserId;
    // The package implementing intent's component
    // TODO: rename to mPackageName
    final String packageName;
    // the intent component, or target of an alias.
    final ComponentName mActivityComponent; 
    
    final int launchedFromPid; // always the pid who started the activity. //是谁启动这个Activity的
    final int launchedFromUid; // always the uid who started the activity.  //是谁启动这个Activity的
    final String launchedFromPackage; // always the package who started the activity.

    final Intent intent;    // the original intent that generated us // 创建这个Activity的原始Intent
    final String shortComponentName; // the short component name of the intent
    final String resolvedType; // as per original caller; // 前一个原始的调用者
    final String processName; // process where this component wants to run  
    
    ActivityRecord resultTo; // who started this entry, so will get our reply //当前Activity?
    final String resultWho; // additional identifier for use by resultTo.   
    
    ...

3. toString 打印的信息

    public String toString() {
        if (stringName != null) {
            return stringName + " t" + (task == null ? INVALID_TASK_ID : task.mTaskId) +
                    (finishing ? " f}" : "") + (mIsExiting ? " isExiting" : "") + "}";
        }
        StringBuilder sb = new StringBuilder(128);
        sb.append("ActivityRecord{");
        sb.append(Integer.toHexString(System.identityHashCode(this)));
        sb.append(" u");
        sb.append(mUserId);
        sb.append(' ');
        sb.append(intent.getComponent().flattenToShortString());
        sb.append("}");
        stringName = sb.toString();
        return stringName;
    }

例如： sourceRecord=ActivityRecord{e39ee2f u0 android/com.android.internal.app.ChooserActivity} t12}

4.其它常用方法

静态方法 isInAnyTask，根据IBinder 获取 ActivityRecord对象

    @Nullable
    static ActivityRecord isInAnyTask(IBinder token) {
        final ActivityRecord r = ActivityRecord.forTokenLocked(token);
        return (r != null && r.isAttached()) ? r : null;
    }

再调用forTokenLocked

    static @Nullable ActivityRecord forTokenLocked(IBinder token) {
        final ActivityRecord r = forToken(token);
        return r == null || r.getRootTask() == null ? null : r;
    }   

再再调用 forToken， 有可能不存在的

    /** Gets the corresponding record by the token. Note that it may not exist in the hierarchy. */
    @Nullable
    static ActivityRecord forToken(IBinder token) {
        if (token == null) return null;
        final Token activityToken;
        try {
            activityToken = (Token) token;
        } catch (ClassCastException e) {
            Slog.w(TAG, "Bad activity token: " + token, e);
            return null;
        }
        return activityToken.mActivityRef.get();
    }   

此外，判断是否为 ResolverActivity 或者 它的子类的方法（isAssignableFrom）

    static boolean isResolverActivity(String className) {
        return ResolverActivity.class.getName().equals(className);
    }

    boolean isResolverOrChildActivity() {
        if (!"android".equals(packageName)) {
            return false;
        }
        try {
            return ResolverActivity.class.isAssignableFrom(
                    Object.class.getClassLoader().loadClass(mActivityComponent.getClassName()));
        } catch (ClassNotFoundException e) {
            return false;
        }
    }