1 /*
2  * Copyright (C) 2008 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.camera;
18 
19 import android.content.Context;
20 import android.util.AttributeSet;
21 import android.view.View;
22 import android.widget.ImageView;
23 
24 /**
25  * A button designed to be used for the on-screen shutter button.
26  * It's currently an {@code ImageView} that can call a delegate when the
27  * pressed state changes.
28  */
29 public class ShutterButton extends ImageView {
30     /**
31      * A callback to be invoked when a ShutterButton's pressed state changes.
32      */
33     public interface OnShutterButtonListener {
34         /**
35          * Called when a ShutterButton has been pressed.
36          *
37          * @param pressed The ShutterButton that was pressed.
38          */
onShutterButtonFocus(boolean pressed)39         void onShutterButtonFocus(boolean pressed);
onShutterButtonClick()40         void onShutterButtonClick();
41     }
42 
43     private OnShutterButtonListener mListener;
44     private boolean mOldPressed;
45 
ShutterButton(Context context, AttributeSet attrs)46     public ShutterButton(Context context, AttributeSet attrs) {
47         super(context, attrs);
48     }
49 
setOnShutterButtonListener(OnShutterButtonListener listener)50     public void setOnShutterButtonListener(OnShutterButtonListener listener) {
51         mListener = listener;
52     }
53 
54     /**
55      * Hook into the drawable state changing to get changes to isPressed -- the
56      * onPressed listener doesn't always get called when the pressed state
57      * changes.
58      */
59     @Override
drawableStateChanged()60     protected void drawableStateChanged() {
61         super.drawableStateChanged();
62         final boolean pressed = isPressed();
63         if (pressed != mOldPressed) {
64             if (!pressed) {
65                 // When pressing the physical camera button the sequence of
66                 // events is:
67                 //    focus pressed, optional camera pressed, focus released.
68                 // We want to emulate this sequence of events with the shutter
69                 // button. When clicking using a trackball button, the view
70                 // system changes the the drawable state before posting click
71                 // notification, so the sequence of events is:
72                 //    pressed(true), optional click, pressed(false)
73                 // When clicking using touch events, the view system changes the
74                 // drawable state after posting click notification, so the
75                 // sequence of events is:
76                 //    pressed(true), pressed(false), optional click
77                 // Since we're emulating the physical camera button, we want to
78                 // have the same order of events. So we want the optional click
79                 // callback to be delivered before the pressed(false) callback.
80                 //
81                 // To do this, we delay the posting of the pressed(false) event
82                 // slightly by pushing it on the event queue. This moves it
83                 // after the optional click notification, so our client always
84                 // sees events in this sequence:
85                 //     pressed(true), optional click, pressed(false)
86                 post(new Runnable() {
87                     public void run() {
88                         callShutterButtonFocus(pressed);
89                     }
90                 });
91             } else {
92                 callShutterButtonFocus(pressed);
93             }
94             mOldPressed = pressed;
95         }
96     }
97 
callShutterButtonFocus(boolean pressed)98     private void callShutterButtonFocus(boolean pressed) {
99         if (mListener != null) {
100             mListener.onShutterButtonFocus(pressed);
101         }
102     }
103 
104     @Override
performClick()105     public boolean performClick() {
106         boolean result = super.performClick();
107         if (mListener != null) {
108             mListener.onShutterButtonClick();
109         }
110         return result;
111     }
112 }
113