Version gate and take fps directly

Author: GaryQian

shell/platform/android/io/flutter/embedding/engine/loader/FlutterLoader.java

@@ -10,6 +10,7 @@
 import android.content.pm.PackageManager;
 import android.content.res.AssetManager;
 import android.hardware.display.DisplayManager;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Looper;
@@ -159,9 +160,17 @@ public void startInitialization(@NonNull Context applicationContext, @NonNull Se
     initStartTimestampMillis = SystemClock.uptimeMillis();
     flutterApplicationInfo = ApplicationInfoLoader.load(appContext);
 
-    final DisplayManager dm = appContext.getSystemService(DisplayManager.class);
-    final Display primaryDisplay = dm.getDisplay(Display.DEFAULT_DISPLAY);
-    VsyncWaiter.getInstance(primaryDisplay).init();
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+      final DisplayManager dm = appContext.getSystemService(DisplayManager.class);
+      final Display primaryDisplay = dm.getDisplay(Display.DEFAULT_DISPLAY);
+      VsyncWaiter.getInstance(primaryDisplay.getRefreshRate()).init();
+    } else {
+      VsyncWaiter.getInstance(
+              ((WindowManager) appContext.getSystemService(Context.WINDOW_SERVICE))
+                  .getDefaultDisplay()
+                  .getRefreshRate())
+          .init();
+    }
 
     // Use a background thread for initialization tasks that require disk access.
     Callable<InitResult> initTask =

shell/platform/android/io/flutter/view/VsyncWaiter.java

@@ -5,7 +5,6 @@
 package io.flutter.view;
 
 import android.view.Choreographer;
-import android.view.Display;
 import androidx.annotation.NonNull;
 import io.flutter.embedding.engine.FlutterJNI;
 
@@ -14,14 +13,14 @@ public class VsyncWaiter {
   private static VsyncWaiter instance;
 
   @NonNull
-  public static VsyncWaiter getInstance(@NonNull Display display) {
+  public static VsyncWaiter getInstance(@NonNull float fps) {
     if (instance == null) {
-      instance = new VsyncWaiter(display);
+      instance = new VsyncWaiter(fps);
     }
     return instance;
   }
 
-  @NonNull private final Display display;
+  @NonNull private final float fps;
 
   private final FlutterJNI.AsyncWaitForVsyncDelegate asyncWaitForVsyncDelegate =
       new FlutterJNI.AsyncWaitForVsyncDelegate() {
@@ -32,7 +31,6 @@ public void asyncWaitForVsync(long cookie) {
                   new Choreographer.FrameCallback() {
                     @Override
                     public void doFrame(long frameTimeNanos) {
-                      float fps = display.getRefreshRate();
                       long refreshPeriodNanos = (long) (1000000000.0 / fps);
                       FlutterJNI.nativeOnVsync(
                           frameTimeNanos, frameTimeNanos + refreshPeriodNanos, cookie);
@@ -41,15 +39,14 @@ public void doFrame(long frameTimeNanos) {
         }
       };
 
-  private VsyncWaiter(@NonNull Display display) {
-    this.display = display;
+  private VsyncWaiter(@NonNull float fps) {
+    this.fps = fps;
   }
 
   public void init() {
     FlutterJNI.setAsyncWaitForVsyncDelegate(asyncWaitForVsyncDelegate);
 
     // TODO(mattcarroll): look into moving FPS reporting to a plugin
-    float fps = display.getRefreshRate();
     FlutterJNI.setRefreshRateFPS(fps);
   }
 }