see o2/02 log

utilcode/pkg/src/main/java/com/blankj/utilcode/pkg/feature/fragment/ChildFragment.kt

@@ -19,7 +19,7 @@ import kotlinx.android.synthetic.main.fragment_child.*
  * desc  : demo about FragmentUtils
  * ```
  */
-class ChildFragment : BaseLazyFragment(), FragmentUtils.OnBackClickListener {
+class ChildFragment : BaseLazyFragment() {
 
     companion object {
         fun newInstance(): ChildFragment {
@@ -66,9 +66,4 @@ class ChildFragment : BaseLazyFragment(), FragmentUtils.OnBackClickListener {
             R.id.fragmentChildRemoveBtn -> FragmentUtils.remove(this);
         }
     }
-
-    override fun onBackClick(): Boolean {
-        LogUtils.d("child onBackClick")
-        return false
-    }
 }

utilcode/pkg/src/main/java/com/blankj/utilcode/pkg/feature/fragment/ContainerFragment.kt

@@ -8,6 +8,7 @@ import android.transition.*
 import android.view.View
 import com.blankj.lib.base.BaseLazyFragment
 import com.blankj.utilcode.pkg.R
+import com.blankj.utilcode.pkg.R.id.*
 import com.blankj.utilcode.pkg.helper.DialogHelper
 import com.blankj.utilcode.util.ColorUtils
 import com.blankj.utilcode.util.FragmentUtils
@@ -122,7 +123,7 @@ class ContainerFragment : BaseLazyFragment(), FragmentUtils.OnBackClickListener
                     fragmentManager!!,
                     addSharedElement(ChildFragment.newInstance()),
                     id,
-                    false,
+                    true,
                     fragmentRootSharedElementIv
             )
         }

utilcode/pkg/src/main/java/com/blankj/utilcode/pkg/feature/fragment/FragmentActivity.kt

@@ -11,6 +11,7 @@ import com.blankj.lib.base.BaseActivity
 import com.blankj.utilcode.pkg.R
 import com.blankj.utilcode.util.FragmentUtils
 import kotlinx.android.synthetic.main.activity_fragment.*
+import kotlinx.android.synthetic.main.fragment_child.*
 
 /**
  * ```
@@ -29,7 +30,7 @@ class FragmentActivity : BaseActivity() {
         }
     }
 
-    private val mFragments = arrayOfNulls<Fragment>(3)
+    private val mFragments = arrayListOf<Fragment>()
     private var curIndex: Int = 0
 
     private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
@@ -66,9 +67,9 @@ class FragmentActivity : BaseActivity() {
         }
         fragmentNav.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
 
-        mFragments[0] = RootFragment.newInstance()
-        mFragments[1] = RootFragment.newInstance()
-        mFragments[2] = RootFragment.newInstance()
+        mFragments.add(RootFragment.newInstance())
+        mFragments.add(RootFragment.newInstance())
+        mFragments.add(RootFragment.newInstance())
         FragmentUtils.add(
                 supportFragmentManager,
                 mFragments,
@@ -83,14 +84,14 @@ class FragmentActivity : BaseActivity() {
     override fun onWidgetClick(view: View) {}
 
     override fun onBackPressed() {
-        if (!FragmentUtils.dispatchBackPress(supportFragmentManager)) {
+        if (!FragmentUtils.dispatchBackPress(mFragments[curIndex])) {
             super.onBackPressed()
         }
     }
 
     private fun showCurrentFragment(index: Int) {
         curIndex = index
-        FragmentUtils.showHide(index, *mFragments)
+        FragmentUtils.showHide(index, mFragments)
     }
 
     override fun onSaveInstanceState(outState: Bundle, outPersistentState: PersistableBundle) {

utilcode/pkg/src/main/java/com/blankj/utilcode/pkg/feature/fragment/RootFragment.kt

@@ -17,7 +17,7 @@ import kotlinx.android.synthetic.main.fragment_root.*
  * desc  : demo about FragmentUtils
  * ```
  */
-class RootFragment : BaseLazyFragment() {
+class RootFragment : BaseLazyFragment(), FragmentUtils.OnBackClickListener {
 
     companion object {
         fun newInstance(): RootFragment {
@@ -46,4 +46,14 @@ class RootFragment : BaseLazyFragment() {
     override fun doLazyBusiness() {}
 
     override fun onWidgetClick(view: View) {}
+
+    override fun onBackClick(): Boolean {
+        if (FragmentUtils.dispatchBackPress(childFragmentManager)) return true
+        return if (childFragmentManager.backStackEntryCount == 0) {
+            false
+        } else {
+            childFragmentManager.popBackStack()
+            true
+        }
+    }
 }