很多人遇到过这个异常，解决这个异常很简单只要在AndroidManifest.xml里面注册这个activity就好了。

android.content.ActivityNotFoundException: Unable to find explicit activity class {com.tule.androidhookstartactivity/com.tule.androidhookstartactivity.TestActivity}; have you declared this activity in your AndroidManifest.xml?

除了这样解决之外就没有其他方案了吗？跟着错误栈信息深入的看一下为啥会有这个异常吧

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tule.androidhookstartactivity, PID: 19159
android.content.ActivityNotFoundException: Unable to find explicit activity class {com.tule.androidhookstartactivity/com.tule.androidhookstartactivity.TestActivity}; have you declared this activity in your AndroidManifest.xml?
at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1805)
at android.app.Instrumentation.execStartActivity(Instrumentation.java:1523)
at android.app.Activity.startActivityForResult(Activity.java:4224)
at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:54)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:75)
at android.app.Activity.startActivityForResult(Activity.java:4183)
at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:708)
at android.app.Activity.startActivity(Activity.java:4507)
at android.app.Activity.startActivity(Activity.java:4475)

int result = ActivityManagerNative.getDefault()
                .startActivity(whoThread, who.getBasePackageName(), intent,
                        intent.resolveTypeIfNeeded(who.getContentResolver()),
                        token, target != null ? target.mEmbeddedID : null,
                        requestCode, 0, null, options);
            checkStartActivityResult(result, intent);

背景

android.util.Singleton 单例的帮助类延迟初始化。

package android.util;

/**
 * Singleton helper class for lazily initialization.
 *
 * Modeled after frameworks/base/include/utils/Singleton.h
 *
 * @hide
 */
public abstract class Singleton<T> {
    private T mInstance;

    protected abstract T create();

    public final T get() {
        synchronized (this) {
            if (mInstance == null) {
                mInstance = create();
            }
            return mInstance;
        }
    }
}

调用方式：ActivityManagerNative.getDefault()
调用地点：ActivityManagerNative类
调用作用：是为了获取ActivityManagerProxy

ActivityManagerNative类

    /**
     * Retrieve the system's default/global activity manager.
     */
    static public IActivityManager getDefault() {
        return gDefault.get();
    }
    ……
    private static final Singleton<IActivityManager> gDefault = new Singleton<IActivityManager>() {
        protected IActivityManager create() {
            IBinder b = ServiceManager.getService("activity");
            if (false) {
                Log.v("ActivityManager", "default service binder = " + b);
            }
            IActivityManager am = asInterface(b);
            if (false) {
                Log.v("ActivityManager", "default service = " + am);
            }
            return am;
        }
    };

1. Hook AMS

            // 获取 gDefault 这个字段, 想办法替换它  
            Class<?> amnClazz = Class.forName("android.app.ActivityManagerNative");
            Field defaultField = amnClazz.getDeclaredField("gDefault");
            defaultField.setAccessible(true);
            Object gDefaultObj = defaultField.get(null); //所有静态对象的反射可以通过传null获取。如果是实列必须传实例
            // 4.x+的gDefault是一个 android.util.Singleton对象; 取出这个单例里面的字段  
            Class<?> singletonClazz = Class.forName("android.util.Singleton");
            Field amsField = singletonClazz.getDeclaredField("mInstance");
            amsField.setAccessible(true);
            // ActivityManagerNative 的gDefault对象里面原始的 IActivityManager对象  
            Object amsObj = amsField.get(gDefaultObj);
            // 创建一个这个对象的代理对象, 然后替换这个字段, 让的代理对象帮忙干活  
            amsObj = Proxy.newProxyInstance(MainActivity.class.getClass().getClassLoader(),
                    amsObj.getClass().getInterfaces(),
                    new HookInvocationHandler(amsObj, proxyActivity, originallyActivity));
            amsField.set(gDefaultObj, amsObj);

2. hook ActivityThreadHandlerCallBack

        Class<?> activityThreadClazz = Class.forName("android.app.ActivityThread");
        Field sCurrentActivityThreadField = activityThreadClazz.getDeclaredField("sCurrentActivityThread");
        sCurrentActivityThreadField.setAccessible(true);
        Object sCurrentActivityThreadObj = sCurrentActivityThreadField.get(null);
        Field mHField = activityThreadClazz.getDeclaredField("mH");
        mHField.setAccessible(true);
        Handler mH = (Handler) mHField.get(sCurrentActivityThreadObj);
        Field callBackField = Handler.class.getDeclaredField("mCallback");
        callBackField.setAccessible(true);
        callBackField.set(mH, new ActivityThreadHandlerCallBack())

3. hook ApplicationPackageMangerService

    private static class PackageManagerHandler implements InvocationHandler {
        private Object mActivityManagerObject;

        public PackageManagerHandler(Object mActivityManagerObject) {
            this.mActivityManagerObject = mActivityManagerObject;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (method.getName().equals("getActivityInfo")) {
                ComponentName componentName = new ComponentName(App.getApp().getPackageName(), HostActivity.class.getName());
                args[0] = componentName;
            }
            return method.invoke(mActivityManagerObject, args);
        }
    }