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      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          */
     43         void onShutterButtonFocus(boolean pressed);
     44         void onShutterButtonClick();
     45     }
     46 
     47     private OnShutterButtonListener mListener;
     48     private boolean mOldPressed;
     49 
     50     public ShutterButton(Context context, AttributeSet attrs) {
     51         super(context, attrs);
     52     }
     53 
     54     public void setOnShutterButtonListener(OnShutterButtonListener listener) {
     55         mListener = listener;
     56     }
     57 
     58     @Override
     59     public boolean dispatchTouchEvent(MotionEvent m) {
     60         if (mTouchEnabled) {
     61             return super.dispatchTouchEvent(m);
     62         } else {
     63             return false;
     64         }
     65     }
     66 
     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
     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 
    116     private void callShutterButtonFocus(boolean pressed) {
    117         if (mListener != null) {
    118             mListener.onShutterButtonFocus(pressed);
    119         }
    120     }
    121 
    122     @Override
    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