Execution failed for task ':app:processDebugMainManifest'.
> Manifest merger failed : Apps targeting Android 12 and higher are required to specify an explicit value for `android:exported` when the corresponding component has an intent filter defined. See https://developer.android.com/guide/topics/manifest/activity-element#exported for details.

問題描述: Manifest合并失敗：當組件定義了 < intent-filter> 時，針對 Android 12 及更高版本的應用需要為 "android:exported" 指定顯式值(android:exported="true")，

以前加上intent-filter的話，exported就默認是true，Android 12之后開始強制大家宣告exported屬性，

例如：

    <application
        <activity android:name=".actvitiy.MainActivity"
            android:exported="true"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".actvitiy.SchemeActivity"
            android:exported="true"
            >
            <intent-filter>
                ...
            </intent-filter>
        </activity>
    </application>

是的你沒看錯 Main Activity也要加這個，接下來咱們看看官方給出答案，

android:exported

此元素設定Activity是否可以由其他應用程式的組件啟動：

• 如果是"true"，則任何應用都可以訪問該Activity，并且可以通過其確切的類名啟動，
• 如果為"false"，則Activity只能由相同應用程式的組件、具有相同用戶 ID 的應用程式或特權系統組件啟動，這是沒有意圖過濾器時的默認值，

如果你應用中的 Activity 包含 < intent-filter>，請將此元素設定為 "true"，以允許其他應用啟動它，例如，如果Activity是應用程式的Main Activity并包含category："android.intent.category.LAUNCHER"，

如果此元素設定為"false"并且應用程式嘗試啟動該活動，則系統會拋出一個 ActivityNotFoundException.

此屬性不是限制活動暴露于其他應用程式的唯一方法，權限還可用于限制可以呼叫 Activity 的外部物體（請參閱 permission 屬性），

不信邪的我果斷修改代碼進行嘗試

        <activity android:name=".actvitiy.MainActivity"
            android:exported="false"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

果然崩了，但是系統跑出來的不是 ActivityNotFoundException，

日志如下:

2021-10-14 01:38:52.623 1219-1219/com.google.android.apps.nexuslauncher E/BaseDraggingActivity: Unable to launch. tag=AppInfo(id=-1 type=APP container=# com.android.launcher3.logger.LauncherAtom$ContainerInfo@1a1bf6a targetComponent=ComponentInfo{com.scc.demo/com.scc.demo.actvitiy.MainActivity} screen=-1 cell(-1,-1) span(1,1) minSpan(1,1) rank=0 user=UserHandle{0} title=ShuaiCiDemo componentName=ComponentInfo{com.scc.demo/com.scc.demo.actvitiy.MainActivity}) intent=Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.scc.demo/.actvitiy.MainActivity bnds=[1124,1039][1393,1376] }
    java.lang.SecurityException: Permission Denial: starting Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.scc.demo/.actvitiy.MainActivity bnds=[1124,1039][1393,1376] } from ProcessRecord{ae07060 1219:com.google.android.apps.nexuslauncher/u0a128} (pid=1219, uid=10128) not exported from uid 10146
        at android.os.Parcel.createExceptionOrNull(Parcel.java:2425)
        at android.os.Parcel.createException(Parcel.java:2409)
        at android.os.Parcel.readException(Parcel.java:2392)
        at android.os.Parcel.readException(Parcel.java:2334)
        at android.app.IActivityTaskManager$Stub$Proxy.startActivity(IActivityTaskManager.java:2284)
        at android.app.Instrumentation.execStartActivity(Instrumentation.java:1743)
        at android.app.Activity.startActivityForResult(Activity.java:5404)
        at com.android.launcher3.Launcher.startActivityForResult(SourceFile:2)
        at com.android.launcher3.BaseQuickstepLauncher.startActivityForResult(SourceFile:6)
        at android.app.Activity.startActivity(Activity.java:5744)
        at com.android.launcher3.BaseDraggingActivity.startActivitySafely(SourceFile:14)
        at com.android.launcher3.Launcher.startActivitySafely(SourceFile:6)
        at com.android.launcher3.uioverrides.QuickstepLauncher.startActivitySafely(SourceFile:2)
        at com.android.launcher3.touch.ItemClickHandler.startAppShortcutOrInfoActivity(SourceFile:14)
        at com.android.launcher3.touch.ItemClickHandler.onClick(SourceFile:11)
        at com.android.launcher3.touch.ItemClickHandler.b(Unknown Source:0)
        at O0.f.onClick(Unknown Source:0)
        at android.view.View.performClick(View.java:7441)
        at android.view.View.performClickInternal(View.java:7418)
        at android.view.View.access$3700(View.java:835)
        at android.view.View$PerformClick.run(View.java:28676)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7842)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
     Caused by: android.os.RemoteException: Remote stack trace:
        at com.android.server.wm.ActivityTaskSupervisor.checkStartAnyActivityPermission(ActivityTaskSupervisor.java:1047)
        at com.android.server.wm.ActivityStarter.executeRequest(ActivityStarter.java:975)
        at com.android.server.wm.ActivityStarter.execute(ActivityStarter.java:665)
        at com.android.server.wm.ActivityTaskManagerService.startActivityAsUser(ActivityTaskManagerService.java:1201)
        at com.android.server.wm.ActivityTaskManagerService.startActivityAsUser(ActivityTaskManagerService.java:1173)

你看 他也不是 ActivityNotFoundException 呀，

Activity supporting ACTION_VIEW is not exported

當我嘗試將下面帶 ACTION_VIEW 的 Activity 的屬性 android:exported 改為false時，如下圖：

不過也能理解，你這個比較是要接收其他其他頁面和其他app的跳轉，你不允許行程間通信還怎么玩， android:exported 的問題是解決了，但是關于 ActivityNotFoundException 等找到了再補充把，