fix: 首次提交

SettingsLib/ActionBarShadow/src/com/android/settingslib/widget/ActionBarShadowController.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settingslib.widget;
+
+import static androidx.lifecycle.Lifecycle.Event.ON_START;
+import static androidx.lifecycle.Lifecycle.Event.ON_STOP;
+
+import android.app.ActionBar;
+import android.app.Activity;
+import android.view.View;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
+
+/**
+ * UI controller that adds a shadow appear/disappear animation to action bar scroll.
+ */
+public class ActionBarShadowController implements LifecycleObserver {
+
+    @VisibleForTesting
+    static final float ELEVATION_HIGH = 8;
+    @VisibleForTesting
+    static final float ELEVATION_LOW = 0;
+
+    @VisibleForTesting
+    ScrollChangeWatcher mScrollChangeWatcher;
+    private View mScrollView;
+    private boolean mIsScrollWatcherAttached;
+
+    /**
+     * Wire up the animation to to an {@link Activity}. Shadow will be applied to activity's
+     * action bar.
+     */
+    public static ActionBarShadowController attachToView(
+            Activity activity, Lifecycle lifecycle, View scrollView) {
+        return new ActionBarShadowController(activity, lifecycle, scrollView);
+    }
+
+    /**
+     * Wire up the animation to to a {@link View}. Shadow will be applied to the view.
+     */
+    public static ActionBarShadowController attachToView(
+            View anchorView, Lifecycle lifecycle, View scrollView) {
+        return new ActionBarShadowController(anchorView, lifecycle, scrollView);
+    }
+
+    private ActionBarShadowController(Activity activity, Lifecycle lifecycle, View scrollView) {
+        mScrollChangeWatcher = new ActionBarShadowController.ScrollChangeWatcher(activity);
+        mScrollView = scrollView;
+        attachScrollWatcher();
+        lifecycle.addObserver(this);
+    }
+
+    private ActionBarShadowController(View anchorView, Lifecycle lifecycle, View scrollView) {
+        mScrollChangeWatcher = new ActionBarShadowController.ScrollChangeWatcher(anchorView);
+        mScrollView = scrollView;
+        attachScrollWatcher();
+        lifecycle.addObserver(this);
+    }
+
+    @OnLifecycleEvent(ON_START)
+    private void attachScrollWatcher() {
+        if (!mIsScrollWatcherAttached) {
+            mIsScrollWatcherAttached = true;
+            mScrollView.setOnScrollChangeListener(mScrollChangeWatcher);
+            mScrollChangeWatcher.updateDropShadow(mScrollView);
+        }
+    }
+
+    @OnLifecycleEvent(ON_STOP)
+    private void detachScrollWatcher() {
+        mScrollView.setOnScrollChangeListener(null);
+        mIsScrollWatcherAttached = false;
+    }
+
+    /**
+     * Update the drop shadow as the scrollable entity is scrolled.
+     */
+    final class ScrollChangeWatcher implements View.OnScrollChangeListener {
+
+        private final Activity mActivity;
+        private final View mAnchorView;
+
+        ScrollChangeWatcher(Activity activity) {
+            mActivity = activity;
+            mAnchorView = null;
+        }
+
+        ScrollChangeWatcher(View anchorView) {
+            mAnchorView = anchorView;
+            mActivity = null;
+        }
+
+        @Override
+        public void onScrollChange(View view, int scrollX, int scrollY, int oldScrollX,
+                int oldScrollY) {
+            updateDropShadow(view);
+        }
+
+        public void updateDropShadow(View view) {
+            final boolean shouldShowShadow = view.canScrollVertically(-1);
+            if (mAnchorView != null) {
+                mAnchorView.setElevation(shouldShowShadow ? ELEVATION_HIGH : ELEVATION_LOW);
+            } else if (mActivity != null) { // activity can become null when running monkey
+                final ActionBar actionBar = mActivity.getActionBar();
+                if (actionBar != null) {
+                    actionBar.setElevation(shouldShowShadow ? ELEVATION_HIGH : ELEVATION_LOW);
+                }
+            }
+        }
+    }
+}