Android Open Source - nsa-away Shutter Button

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * Copyright (C) 2008 The Android Open Source Project
 * Copyright 2011 Robert Theis/*from  w ww . ja  va2 s.  c om*/
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.sector67.nsaaway.ocr.complex.camera;

import android.content.Context;
import android.util.AttributeSet;
import android.view.SoundEffectConstants;
import android.widget.ImageView;

/**
 * A button designed to be used for the on-screen shutter button.
 * It's currently an {@code ImageView} that can call a delegate when the
 * pressed state changes.
 * 
 * The code for this class was adapted from the ZXing project: http://code.google.com/p/zxing
 */
public class ShutterButton extends ImageView {
  /**
   * A callback to be invoked when a ShutterButton's pressed state changes.
   */
  public interface OnShutterButtonListener {
    /**
     * Called when a ShutterButton has been pressed.
     *
     * @param b The ShutterButton that was pressed.
     */
    void onShutterButtonFocus(ShutterButton b, boolean pressed);

    void onShutterButtonClick(ShutterButton b);
  }

  private OnShutterButtonListener mListener;
  private boolean mOldPressed;

  public ShutterButton(Context context) {
    super (context);
  }

  public ShutterButton(Context context, AttributeSet attrs) {
    super (context, attrs);
  }

  public ShutterButton(Context context, AttributeSet attrs,
      int defStyle) {
    super (context, attrs, defStyle);
  }

  public void setOnShutterButtonListener(OnShutterButtonListener listener) {
    mListener = listener;
  }

  /**
   * Hook into the drawable state changing to get changes to isPressed -- the
   * onPressed listener doesn't always get called when the pressed state
   * changes.
   */
   @Override
   protected void drawableStateChanged() {
     super .drawableStateChanged();
     final boolean pressed = isPressed();
     if (pressed != mOldPressed) {
       if (!pressed) {
         // When pressing the physical camera button the sequence of
         // events is:
         //    focus pressed, optional camera pressed, focus released.
         // We want to emulate this sequence of events with the shutter
         // button. When clicking using a trackball button, the view
         // system changes the the drawable state before posting click
         // notification, so the sequence of events is:
         //    pressed(true), optional click, pressed(false)
         // When clicking using touch events, the view system changes the
         // drawable state after posting click notification, so the
         // sequence of events is:
         //    pressed(true), pressed(false), optional click
         // Since we're emulating the physical camera button, we want to
         // have the same order of events. So we want the optional click
         // callback to be delivered before the pressed(false) callback.
         //
         // To do this, we delay the posting of the pressed(false) event
         // slightly by pushing it on the event queue. This moves it
         // after the optional click notification, so our client always
         // sees events in this sequence:
         //     pressed(true), optional click, pressed(false)
         post(new Runnable() {
           public void run() {
             callShutterButtonFocus(pressed);
           }
         });
       } else {
         callShutterButtonFocus(pressed);
       }
       mOldPressed = pressed;
     }
   }

   private void callShutterButtonFocus(boolean pressed) {
     if (mListener != null) {
       mListener.onShutterButtonFocus(this , pressed);
     }
   }

   @Override
   public boolean performClick() {
     boolean result = super.performClick();
     playSoundEffect(SoundEffectConstants.CLICK);
     if (mListener != null) {
       mListener.onShutterButtonClick(this);
     }
     return result;
   }
}

Java Source Code List

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