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
17package com.android.camera;
18
19import android.content.Context;
20import android.util.AttributeSet;
21import android.view.View;
22import 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 */
29public 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         */
39        void onShutterButtonFocus(boolean pressed);
40        void onShutterButtonClick();
41    }
42
43    private OnShutterButtonListener mListener;
44    private boolean mOldPressed;
45
46    public ShutterButton(Context context, AttributeSet attrs) {
47        super(context, attrs);
48    }
49
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
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
98    private void callShutterButtonFocus(boolean pressed) {
99        if (mListener != null) {
100            mListener.onShutterButtonFocus(pressed);
101        }
102    }
103
104    @Override
105    public boolean performClick() {
106        boolean result = super.performClick();
107        if (mListener != null) {
108            mListener.onShutterButtonClick();
109        }
110        return result;
111    }
112}
113