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.MotionEvent;
22 import android.view.View;
23 import android.widget.ImageView;
24 
25 /**
26  * A button designed to be used for the on-screen shutter button.
27  * It's currently an {@code ImageView} that can call a delegate when the
28  * pressed state changes.
29  */
30 public class ShutterButton extends ImageView {
31 
32     private boolean mTouchEnabled = true;
33 
34     /**
35      * A callback to be invoked when a ShutterButton's pressed state changes.
36      */
37     public interface OnShutterButtonListener {
38         /**
39          * Called when a ShutterButton has been pressed.
40          *
41          * @param pressed The ShutterButton that was pressed.
42          */
onShutterButtonFocus(boolean pressed)43         void onShutterButtonFocus(boolean pressed);
onShutterButtonClick()44         void onShutterButtonClick();
45     }
46 
47     private OnShutterButtonListener mListener;
48     private boolean mOldPressed;
49 
ShutterButton(Context context, AttributeSet attrs)50     public ShutterButton(Context context, AttributeSet attrs) {
51         super(context, attrs);
52     }
53 
setOnShutterButtonListener(OnShutterButtonListener listener)54     public void setOnShutterButtonListener(OnShutterButtonListener listener) {
55         mListener = listener;
56     }
57 
58     @Override
dispatchTouchEvent(MotionEvent m)59     public boolean dispatchTouchEvent(MotionEvent m) {
60         if (mTouchEnabled) {
61             return super.dispatchTouchEvent(m);
62         } else {
63             return false;
64         }
65     }
66 
enableTouch(boolean enable)67     public void enableTouch(boolean enable) {
68         mTouchEnabled = enable;
69     }
70 
71     /**
72      * Hook into the drawable state changing to get changes to isPressed -- the
73      * onPressed listener doesn't always get called when the pressed state
74      * changes.
75      */
76     @Override
drawableStateChanged()77     protected void drawableStateChanged() {
78         super.drawableStateChanged();
79         final boolean pressed = isPressed();
80         if (pressed != mOldPressed) {
81             if (!pressed) {
82                 // When pressing the physical camera button the sequence of
83                 // events is:
84                 //    focus pressed, optional camera pressed, focus released.
85                 // We want to emulate this sequence of events with the shutter
86                 // button. When clicking using a trackball button, the view
87                 // system changes the drawable state before posting click
88                 // notification, so the sequence of events is:
89                 //    pressed(true), optional click, pressed(false)
90                 // When clicking using touch events, the view system changes the
91                 // drawable state after posting click notification, so the
92                 // sequence of events is:
93                 //    pressed(true), pressed(false), optional click
94                 // Since we're emulating the physical camera button, we want to
95                 // have the same order of events. So we want the optional click
96                 // callback to be delivered before the pressed(false) callback.
97                 //
98                 // To do this, we delay the posting of the pressed(false) event
99                 // slightly by pushing it on the event queue. This moves it
100                 // after the optional click notification, so our client always
101                 // sees events in this sequence:
102                 //     pressed(true), optional click, pressed(false)
103                 post(new Runnable() {
104                     @Override
105                     public void run() {
106                         callShutterButtonFocus(pressed);
107                     }
108                 });
109             } else {
110                 callShutterButtonFocus(pressed);
111             }
112             mOldPressed = pressed;
113         }
114     }
115 
callShutterButtonFocus(boolean pressed)116     private void callShutterButtonFocus(boolean pressed) {
117         if (mListener != null) {
118             mListener.onShutterButtonFocus(pressed);
119         }
120     }
121 
122     @Override
performClick()123     public boolean performClick() {
124         boolean result = super.performClick();
125         if (mListener != null && getVisibility() == View.VISIBLE) {
126             mListener.onShutterButtonClick();
127         }
128         return result;
129     }
130 }
131