Home | History | Annotate | Download | only in actions 
      1 /*
      2  * Copyright (C) 2010 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.gallery3d.photoeditor.actions;
     18 
     19 import android.content.Context;
     20 import android.util.AttributeSet;
     21 import android.view.MotionEvent;
     22 
     23 /**
     24  * View that handles touch-events to track flipping directions and angles.
     25  */
     26 class FlipView extends FullscreenToolView {
     27 
     28     /**
     29      * Listens to flip changes.
     30      */
     31     public interface OnFlipChangeListener {
     32 
     33         void onAngleChanged(float horizontalDegrees, float verticalDegrees, boolean fromUser);
     34 
     35         void onStartTrackingTouch();
     36 
     37         void onStopTrackingTouch();
     38     }
     39 
     40     private static final float FIXED_DIRECTION_THRESHOLD = 20;
     41 
     42     private OnFlipChangeListener listener;
     43     private float maxFlipSpan;
     44     private float touchStartX;
     45     private float touchStartY;
     46     private float currentHorizontalDegrees;
     47     private float currentVerticalDegrees;
     48     private float lastHorizontalDegrees;
     49     private float lastVerticalDegrees;
     50     private boolean fixedDirection;
     51     private boolean fixedDirectionHorizontal;
     52 
     53     public FlipView(Context context, AttributeSet attrs) {
     54         super(context, attrs);
     55     }
     56 
     57     public void setOnFlipChangeListener(OnFlipChangeListener listener) {
     58         this.listener = listener;
     59     }
     60 
     61     public void setFlippedAngles(float horizontalDegrees, float verticalDegrees) {
     62         refreshAngle(horizontalDegrees, verticalDegrees, false);
     63     }
     64 
     65     /**
     66      * Sets allowed degrees for every flip before flipping the view.
     67      */
     68     public void setFlipSpan(float degrees) {
     69         // Flip-span limits allowed flipping degrees of every flip for usability purpose; the max.
     70         // flipped angles could be accumulated and larger than allowed flip-span.
     71         maxFlipSpan = degrees;
     72     }
     73 
     74     private float calculateAngle(boolean flipHorizontal, float x, float y) {
     75         // Use partial length along the moving direction to calculate the flip angle.
     76         float maxDistance = (flipHorizontal ? getWidth() : getHeight()) * 0.35f;
     77         float moveDistance = flipHorizontal ? (x - touchStartX) : (touchStartY - y);
     78 
     79         if (Math.abs(moveDistance) > maxDistance) {
     80             moveDistance = (moveDistance > 0) ? maxDistance : -maxDistance;
     81 
     82             if (flipHorizontal) {
     83                 touchStartX = x - moveDistance;
     84             } else {
     85                 touchStartY = moveDistance + y;
     86             }
     87         }
     88         return (moveDistance / maxDistance) * maxFlipSpan;
     89     }
     90 
     91     @Override
     92     public boolean onTouchEvent(MotionEvent ev) {
     93         super.onTouchEvent(ev);
     94 
     95         if (isEnabled()) {
     96             switch (ev.getAction()) {
     97                 case MotionEvent.ACTION_DOWN:
     98                     fixedDirection = false;
     99                     lastHorizontalDegrees = currentHorizontalDegrees;
    100                     lastVerticalDegrees = currentVerticalDegrees;
    101                     touchStartX = ev.getX();
    102                     touchStartY = ev.getY();
    103 
    104                     if (listener != null) {
    105                         listener.onStartTrackingTouch();
    106                     }
    107                     break;
    108 
    109                 case MotionEvent.ACTION_MOVE:
    110                     // Allow only one direction for flipping during movements, and make the
    111                     // direction fixed once it exceeds threshold.
    112                     float x = ev.getX();
    113                     float y = ev.getY();
    114                     boolean flipHorizontal = fixedDirection ? fixedDirectionHorizontal
    115                             : (Math.abs(x - touchStartX) >= Math.abs(y - touchStartY));
    116                     float degrees = calculateAngle(flipHorizontal, x, y);
    117                     if (!fixedDirection && (Math.abs(degrees) > FIXED_DIRECTION_THRESHOLD)) {
    118                         fixedDirection = true;
    119                         fixedDirectionHorizontal = flipHorizontal;
    120                     }
    121 
    122                     if (flipHorizontal) {
    123                         refreshAngle(lastHorizontalDegrees + degrees, lastVerticalDegrees, true);
    124                     } else {
    125                         refreshAngle(lastHorizontalDegrees, lastVerticalDegrees + degrees, true);
    126                     }
    127                    break;
    128 
    129                 case MotionEvent.ACTION_CANCEL:
    130                 case MotionEvent.ACTION_UP:
    131                     if (listener != null) {
    132                         listener.onStopTrackingTouch();
    133                     }
    134                     break;
    135             }
    136         }
    137         return true;
    138     }
    139 
    140     private void refreshAngle(float horizontalDegrees, float verticalDegrees, boolean fromUser) {
    141         currentHorizontalDegrees = horizontalDegrees;
    142         currentVerticalDegrees = verticalDegrees;
    143         if (listener != null) {
    144             listener.onAngleChanged(horizontalDegrees, verticalDegrees, fromUser);
    145         }
    146     }
    147 }
    148