1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License
15  */
16 
17 package com.android.systemui.statusbar.phone;
18 
19 import android.content.Context;
20 import android.util.AttributeSet;
21 import android.view.MotionEvent;
22 import android.view.View;
23 import android.widget.ScrollView;
24 
25 /**
26  * A scroll view which can be observed for scroll change events.
27  */
28 public class ObservableScrollView extends ScrollView {
29 
30     private Listener mListener;
31     private int mLastOverscrollAmount;
32     private boolean mTouchEnabled = true;
33     private boolean mHandlingTouchEvent;
34     private float mLastX;
35     private float mLastY;
36     private boolean mBlockFlinging;
37     private boolean mTouchCancelled;
38 
ObservableScrollView(Context context, AttributeSet attrs)39     public ObservableScrollView(Context context, AttributeSet attrs) {
40         super(context, attrs);
41     }
42 
setListener(Listener listener)43     public void setListener(Listener listener) {
44         mListener = listener;
45     }
46 
setTouchEnabled(boolean touchEnabled)47     public void setTouchEnabled(boolean touchEnabled) {
48         mTouchEnabled = touchEnabled;
49     }
50 
isScrolledToBottom()51     public boolean isScrolledToBottom() {
52         return getScrollY() == getMaxScrollY();
53     }
54 
isHandlingTouchEvent()55     public boolean isHandlingTouchEvent() {
56         return mHandlingTouchEvent;
57     }
58 
getMaxScrollY()59     private int getMaxScrollY() {
60         int scrollRange = 0;
61         if (getChildCount() > 0) {
62             View child = getChildAt(0);
63             scrollRange = Math.max(0,
64                     child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop));
65         }
66         return scrollRange;
67     }
68 
69     @Override
onTouchEvent(MotionEvent ev)70     public boolean onTouchEvent(MotionEvent ev) {
71         mHandlingTouchEvent = true;
72         mLastX = ev.getX();
73         mLastY = ev.getY();
74         boolean result = super.onTouchEvent(ev);
75         mHandlingTouchEvent = false;
76         return result;
77     }
78 
79     @Override
onInterceptTouchEvent(MotionEvent ev)80     public boolean onInterceptTouchEvent(MotionEvent ev) {
81         mHandlingTouchEvent = true;
82         mLastX = ev.getX();
83         mLastY = ev.getY();
84         boolean result = super.onInterceptTouchEvent(ev);
85         mHandlingTouchEvent = false;
86         return result;
87     }
88 
89     @Override
dispatchTouchEvent(MotionEvent ev)90     public boolean dispatchTouchEvent(MotionEvent ev) {
91         if (ev.getAction() == MotionEvent.ACTION_DOWN) {
92             if (!mTouchEnabled) {
93                 mTouchCancelled = true;
94                 return false;
95             }
96             mTouchCancelled = false;
97         } else if (mTouchCancelled) {
98             return false;
99         } else if (!mTouchEnabled) {
100             MotionEvent cancel = MotionEvent.obtain(ev);
101             cancel.setAction(MotionEvent.ACTION_CANCEL);
102             super.dispatchTouchEvent(ev);
103             cancel.recycle();
104             mTouchCancelled = true;
105             return false;
106         }
107         return super.dispatchTouchEvent(ev);
108     }
109 
110     @Override
onScrollChanged(int l, int t, int oldl, int oldt)111     protected void onScrollChanged(int l, int t, int oldl, int oldt) {
112         super.onScrollChanged(l, t, oldl, oldt);
113         if (mListener != null) {
114             mListener.onScrollChanged();
115         }
116     }
117 
118     @Override
overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent)119     protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY,
120             int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY,
121             boolean isTouchEvent) {
122         mLastOverscrollAmount = Math.max(0, scrollY + deltaY - getMaxScrollY());
123         return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY,
124                         maxOverScrollX, maxOverScrollY, isTouchEvent);
125     }
126 
setBlockFlinging(boolean blockFlinging)127     public void setBlockFlinging(boolean blockFlinging) {
128         mBlockFlinging = blockFlinging;
129     }
130 
131     @Override
fling(int velocityY)132     public void fling(int velocityY) {
133         if (!mBlockFlinging) {
134             super.fling(velocityY);
135         }
136     }
137 
138     @Override
onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY)139     protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
140         super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);
141         if (mListener != null && mLastOverscrollAmount > 0) {
142             mListener.onOverscrolled(mLastX, mLastY, mLastOverscrollAmount);
143         }
144     }
145 
146     public interface Listener {
onScrollChanged()147         void onScrollChanged();
onOverscrolled(float lastX, float lastY, int amount)148         void onOverscrolled(float lastX, float lastY, int amount);
149     }
150 }
151