PlatformException(error, Unable to find explicit activity class {com.example.documentmanagement/com.yalantis.ucrop.UCropActivity}; have you declared this activity in your AndroidManifest.xml?, null, android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.documentmanagement/com.yalantis.ucrop.UCropActivity}; have you declared this activity in your AndroidManifest.xml?
AndroidManifest.xml에 Activity를 등록하지 않으면 발생하는 에러
신규 Activity를 <android> ... </android> 사이에 입력해주면 해결된다.
<activity
android:name="com.yalantis.ucrop.UCropActivity"
android:screenOrientation="portrait"
android:theme="@style/Theme.AppCompat.Light.NoActionBar" />