Add helper class FoldStateListener

Reduces the need for each code that needs to know about fold/unfold from
duplicating the exact same code.

Bug: 184795211
Test: They pass!
Change-Id: Ic05a2067c2ec64db7dab0227a7204283c1144a5f

core/java/android/hardware/devicestate/DeviceStateManager.java

@@ -24,7 +24,10 @@ import android.annotation.SystemService;
 import android.annotation.TestApi;
 import android.content.Context;
 
+import com.android.internal.util.ArrayUtils;
+
 import java.util.concurrent.Executor;
+import java.util.function.Consumer;
 
 /**
  * Manages the state of the system for devices with user-configurable hardware like a foldable
@@ -170,4 +173,34 @@ public final class DeviceStateManager {
          */
         void onStateChanged(int state);
     }
+
+    /**
+     * Listens to changes in device state and reports the state as folded if the device state
+     * matches the value in the {@link com.android.internal.R.integer.config_foldedDeviceState}
+     * resource.
+     * @hide
+     */
+    public static class FoldStateListener implements DeviceStateCallback {
+        private final int[] mFoldedDeviceStates;
+        private final Consumer<Boolean> mDelegate;
+
+        @Nullable
+        private Boolean lastResult;
+
+        public FoldStateListener(Context context, Consumer<Boolean> listener) {
+            mFoldedDeviceStates = context.getResources().getIntArray(
+                    com.android.internal.R.array.config_foldedDeviceStates);
+            mDelegate = listener;
+        }
+
+        @Override
+        public final void onStateChanged(int state) {
+            final boolean folded = ArrayUtils.contains(mFoldedDeviceStates, state);
+
+            if (lastResult == null || !lastResult.equals(folded)) {
+                lastResult = folded;
+                mDelegate.accept(folded);
+            }
+        }
+    }
 }

services/core/java/com/android/server/policy/DisplayFoldController.java

@@ -21,6 +21,7 @@ import android.content.Context;
 import android.graphics.Rect;
 import android.hardware.ICameraService;
 import android.hardware.devicestate.DeviceStateManager;
+import android.hardware.devicestate.DeviceStateManager.FoldStateListener;
 import android.hardware.display.DisplayManagerInternal;
 import android.os.Handler;
 import android.os.HandlerExecutor;
@@ -75,7 +76,7 @@ class DisplayFoldController {
 
         DeviceStateManager deviceStateManager = context.getSystemService(DeviceStateManager.class);
         deviceStateManager.registerCallback(new HandlerExecutor(handler),
-                new DeviceStateListener(context));
+                new FoldStateListener(context, folded -> setDeviceFolded(folded)));
     }
 
     void finishedGoingToSleep() {
@@ -202,30 +203,4 @@ class DisplayFoldController {
         return new DisplayFoldController(context, windowManagerService, displayService,
                 cameraServiceProxy, displayId, foldedArea, DisplayThread.getHandler());
     }
-
-    /**
-     * Listens to changes in device state and reports the state as folded if the device state
-     * matches the value in the {@link com.android.internal.R.integer.config_foldedDeviceState}
-     * resource.
-     */
-    private class DeviceStateListener implements DeviceStateManager.DeviceStateCallback {
-        private final int[] mFoldedDeviceStates;
-
-        DeviceStateListener(Context context) {
-            mFoldedDeviceStates = context.getResources().getIntArray(
-                    com.android.internal.R.array.config_foldedDeviceStates);
-        }
-
-        @Override
-        public void onStateChanged(int deviceState) {
-            boolean folded = false;
-            for (int i = 0; i < mFoldedDeviceStates.length; i++) {
-                if (deviceState == mFoldedDeviceStates[i]) {
-                    folded = true;
-                    break;
-                }
-            }
-            setDeviceFolded(folded);
-        }
-    }
 }