[Android] 代码重构 (alibaba#1270)

* 1. 解决重复调用onPause导致的空针异常(alibaba#1269)
* 2. ActivityAndFragmentPatch存在的必要性不大，暂时删除

Author: 0xZOne

android/src/main/java/com/idlefish/flutterboost/containers/ActivityAndFragmentPatch.java

@@ -72,7 +72,7 @@ public void onResume() {
         attachToActivity();
         FlutterBoost.instance().getPlugin().onContainerAppeared(this);
         assert (flutterView != null);
-        ActivityAndFragmentPatch.onResumeAttachToFlutterEngine(flutterView, getFlutterEngine());
+        flutterView.attachToFlutterEngine(getFlutterEngine());
         if (DEBUG) Log.e(TAG, "#onResume: " + this);
     }
 
@@ -97,7 +97,7 @@ protected void onPause() {
 
         FlutterBoost.instance().getPlugin().onContainerDisappeared(this);
         assert (flutterView != null);
-        ActivityAndFragmentPatch.onPauseDetachFromFlutterEngine(flutterView, getFlutterEngine());
+        flutterView.detachFromFlutterEngine();
         detachFromActivity();
         platformPlugin.destroy();
         platformPlugin = null;
@@ -143,12 +143,14 @@ public boolean shouldAttachEngineToActivity() {
 
     @Override
     public void onBackPressed() {
-        ActivityAndFragmentPatch.onBackPressed();
+        // Intercept the user's press of the back key.
+        FlutterBoost.instance().getPlugin().popRoute(null, null);
     }
 
     @Override
     public RenderMode getRenderMode() {
-        return ActivityAndFragmentPatch.getRenderMode();
+        // Default to |FlutterTextureView|.
+        return RenderMode.texture;
     }
 
     @Override

android/src/main/java/com/idlefish/flutterboost/containers/FlutterBoostActivity.java

@@ -57,6 +57,7 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle sa
         View view = super.onCreateView(inflater, container, savedInstanceState);
         flutterView = FlutterBoostUtils.findFlutterView(view);
         assert(flutterView != null);
+        // Detach FlutterView from engine before |onResume|.
         flutterView.detachFromFlutterEngine();
         if (DEBUG) Log.e(TAG, "#onCreateView: " + this);
         return view;
@@ -98,7 +99,8 @@ public void onResume() {
 
     @Override
     public RenderMode getRenderMode() {
-        return ActivityAndFragmentPatch.getRenderMode();
+        // Default to |FlutterTextureView|.
+        return RenderMode.texture;
     }
 
     @Override
@@ -135,7 +137,8 @@ public void onDetach() {
 
     @Override
     public void onBackPressed() {
-        ActivityAndFragmentPatch.onBackPressed();
+        // Intercept the user's press of the back key.
+        FlutterBoost.instance().getPlugin().popRoute(null, null);
     }
 
     @Override
@@ -198,20 +201,34 @@ public String getCachedEngineId() {
     }
 
     private void didFragmentShow() {
-        platformPlugin = new PlatformPlugin(getActivity(), getFlutterEngine().getPlatformChannel());
         FlutterBoost.instance().getPlugin().onContainerAppeared(this);
-        // Attache plugins to the activity.
+
+        // Create the platform plugin.
+        if (platformPlugin == null) {
+            platformPlugin = new PlatformPlugin(getActivity(), getFlutterEngine().getPlatformChannel());
+        }
+
+        // Attach plugins to the activity.
         getFlutterEngine().getActivityControlSurface().attachToActivity(getActivity(), getActivity().getLifecycle());
-        ActivityAndFragmentPatch.onResumeAttachToFlutterEngine(flutterView, getFlutterEngine());
+
+        // Attach rendering pipeline.
+        flutterView.attachToFlutterEngine(getFlutterEngine());
     }
 
     private void didFragmentHide() {
         FlutterBoost.instance().getPlugin().onContainerDisappeared(this);
-        ActivityAndFragmentPatch.onPauseDetachFromFlutterEngine(flutterView, getFlutterEngine());
+
         // Plugins are no longer attached to the activity.
         getFlutterEngine().getActivityControlSurface().detachFromActivity();
-        platformPlugin.destroy();
-        platformPlugin = null;
+
+        // Release Flutter's control of UI such as system chrome.
+        if (platformPlugin != null) {
+            platformPlugin.destroy();
+            platformPlugin = null;
+        }
+
+        // Detach rendering pipeline.
+        flutterView.detachFromFlutterEngine();
     }
 
     public static class CachedEngineFragmentBuilder {

android/src/main/java/com/idlefish/flutterboost/containers/FlutterBoostFragment.java

@@ -1,12 +1,14 @@
 package com.idlefish.flutterboost.containers;
 
 import java.util.HashMap;
-import java.util.LinkedHashMap;
 import java.util.LinkedList;
-import java.util.List;
 import java.util.Map;
 
+import io.flutter.Log;
+
 public class FlutterContainerManager {
+    private static final String TAG = "FlutterContainerManager";
+    private static final boolean DEBUG = false;
 
     private FlutterContainerManager() {
     }
@@ -24,7 +26,7 @@ public static FlutterContainerManager instance() {
 
     public void addContainer(String uniqueId, FlutterViewContainer container) {
         allContainers.put(uniqueId, container);
-
+        if (DEBUG) Log.e(TAG, "#addContainer:" + toString());
     }
 
     public void activateContainer(String uniqueId, FlutterViewContainer container) {
@@ -35,12 +37,14 @@ public void activateContainer(String uniqueId, FlutterViewContainer container) {
             activeContainers.remove(container);
         }
         activeContainers.add(container);
+        if (DEBUG) Log.e(TAG, "#activateContainer:" + toString());
     }
 
     public void removeContainer(String uniqueId) {
         if (uniqueId == null) return;
         FlutterViewContainer container = allContainers.remove(uniqueId);
         activeContainers.remove(container);
+        if (DEBUG) Log.e(TAG, "#removeContainer:" + toString());
     }
 
 
@@ -69,4 +73,12 @@ public boolean isTopContainer(String uniqueId) {
     public int getContainerSize() {
         return allContainers.size();
     }
+
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append("activeContainers=" + activeContainers.size() + ", [");
+        activeContainers.forEach((value) -> sb.append(value.getUrl() + ','));
+        sb.append("]");
+        return sb.toString();
+    }
 }

android/src/main/java/com/idlefish/flutterboost/containers/FlutterContainerManager.java

@@ -131,15 +131,15 @@ public void onResume() {
         }
         super.onResume();
         FlutterBoost.instance().getPlugin().onContainerAppeared(this);
-        ActivityAndFragmentPatch.onResumeAttachToFlutterEngine(flutterView(), getFlutterEngine());
+        flutterView().attachToFlutterEngine(getFlutterEngine());
         getFlutterEngine().getLifecycleChannel().appIsResumed();
     }
 
     @Override
     public void onPause() {
         if(hasDestroyed()) return;
         super.onPause();
-        ActivityAndFragmentPatch.onPauseDetachFromFlutterEngine(flutterView(), getFlutterEngine());
+        flutterView().detachFromFlutterEngine();
         getFlutterEngine().getLifecycleChannel().appIsResumed();
     }
 
@@ -169,15 +169,15 @@ public void setVisibility(int visibility) {
 
         if (getVisibility() == View.VISIBLE) {
             FlutterBoost.instance().getPlugin().onContainerAppeared(this);
-            ActivityAndFragmentPatch.onResumeAttachToFlutterEngine(flutterView(), getFlutterEngine());
+            flutterView().attachToFlutterEngine(getFlutterEngine());
         } else if (getVisibility() == View.GONE) {
             FlutterBoost.instance().getPlugin().onContainerDisappeared(this);
-            ActivityAndFragmentPatch.onPauseDetachFromFlutterEngine(flutterView(), getFlutterEngine());
+            flutterView().detachFromFlutterEngine();
         }
     }
 
     public void onBackPressed() {
-        ActivityAndFragmentPatch.onBackPressed();
+        FlutterBoost.instance().getPlugin().popRoute(null, null);
     }
 
     @Override

example/android/app/src/main/java/com/idlefish/flutterboost/containers/FlutterBoostView.java

@@ -11,7 +11,6 @@
 import androidx.fragment.app.FragmentTransaction;
 
 import com.idlefish.flutterboost.FlutterBoost;
-import com.idlefish.flutterboost.containers.ActivityAndFragmentPatch;
 import com.idlefish.flutterboost.containers.FlutterBoostFragment;
 import com.idlefish.flutterboost.example.R;