1 /*
2  * Copyright (C) 2014 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 package android.transition;
17 
18 import android.content.Context;
19 import android.content.res.TypedArray;
20 import android.graphics.Matrix;
21 import android.graphics.Path;
22 import android.graphics.PathMeasure;
23 import android.util.AttributeSet;
24 import android.util.PathParser;
25 
26 import com.android.internal.R;
27 
28 /**
29  * A PathMotion that takes a Path pattern and applies it to the separation between two points.
30  * The starting point of the Path will be moved to the origin and the end point will be scaled
31  * and rotated so that it matches with the target end point.
32  * <p>This may be used in XML as an element inside a transition.</p>
33  * <pre>{@code
34  * <changeBounds>
35  *     <patternPathMotion android:patternPathData="M0 0 L0 100 L100 100"/>
36  * </changeBounds>}
37  * </pre>
38  */
39 public class PatternPathMotion extends PathMotion {
40 
41     private Path mOriginalPatternPath;
42 
43     private final Path mPatternPath = new Path();
44 
45     private final Matrix mTempMatrix = new Matrix();
46 
47     /**
48      * Constructs a PatternPathMotion with a straight-line pattern.
49      */
PatternPathMotion()50     public PatternPathMotion() {
51         mPatternPath.lineTo(1, 0);
52         mOriginalPatternPath = mPatternPath;
53     }
54 
PatternPathMotion(Context context, AttributeSet attrs)55     public PatternPathMotion(Context context, AttributeSet attrs) {
56         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.PatternPathMotion);
57         try {
58             String pathData = a.getString(R.styleable.PatternPathMotion_patternPathData);
59             if (pathData == null) {
60                 throw new RuntimeException("pathData must be supplied for patternPathMotion");
61             }
62             Path pattern = PathParser.createPathFromPathData(pathData);
63             setPatternPath(pattern);
64         } finally {
65             a.recycle();
66         }
67 
68     }
69 
70     /**
71      * Creates a PatternPathMotion with the Path defining a pattern of motion between two
72      * coordinates. The pattern will be translated, rotated, and scaled to fit between the start
73      * and end points. The pattern must not be empty and must have the end point differ from the
74      * start point.
75      *
76      * @param patternPath A Path to be used as a pattern for two-dimensional motion.
77      */
PatternPathMotion(Path patternPath)78     public PatternPathMotion(Path patternPath) {
79         setPatternPath(patternPath);
80     }
81 
82     /**
83      * Returns the Path defining a pattern of motion between two coordinates.
84      * The pattern will be translated, rotated, and scaled to fit between the start and end points.
85      * The pattern must not be empty and must have the end point differ from the start point.
86      *
87      * @return the Path defining a pattern of motion between two coordinates.
88      * @attr ref android.R.styleable#PatternPathMotion_patternPathData
89      */
getPatternPath()90     public Path getPatternPath() {
91         return mOriginalPatternPath;
92     }
93 
94     /**
95      * Sets the Path defining a pattern of motion between two coordinates.
96      * The pattern will be translated, rotated, and scaled to fit between the start and end points.
97      * The pattern must not be empty and must have the end point differ from the start point.
98      *
99      * @param patternPath A Path to be used as a pattern for two-dimensional motion.
100      * @attr ref android.R.styleable#PatternPathMotion_patternPathData
101      */
setPatternPath(Path patternPath)102     public void setPatternPath(Path patternPath) {
103         PathMeasure pathMeasure = new PathMeasure(patternPath, false);
104         float length = pathMeasure.getLength();
105         float[] pos = new float[2];
106         pathMeasure.getPosTan(length, pos, null);
107         float endX = pos[0];
108         float endY = pos[1];
109         pathMeasure.getPosTan(0, pos, null);
110         float startX = pos[0];
111         float startY = pos[1];
112 
113         if (startX == endX && startY == endY) {
114             throw new IllegalArgumentException("pattern must not end at the starting point");
115         }
116 
117         mTempMatrix.setTranslate(-startX, -startY);
118         float dx = endX - startX;
119         float dy = endY - startY;
120         float distance = (float) Math.hypot(dx, dy);
121         float scale = 1 / distance;
122         mTempMatrix.postScale(scale, scale);
123         double angle = Math.atan2(dy, dx);
124         mTempMatrix.postRotate((float) Math.toDegrees(-angle));
125         patternPath.transform(mTempMatrix, mPatternPath);
126         mOriginalPatternPath = patternPath;
127     }
128 
129     @Override
getPath(float startX, float startY, float endX, float endY)130     public Path getPath(float startX, float startY, float endX, float endY) {
131         double dx = endX - startX;
132         double dy = endY - startY;
133         float length = (float) Math.hypot(dx, dy);
134         double angle = Math.atan2(dy, dx);
135 
136         mTempMatrix.setScale(length, length);
137         mTempMatrix.postRotate((float) Math.toDegrees(angle));
138         mTempMatrix.postTranslate(startX, startY);
139         Path path = new Path();
140         mPatternPath.transform(mTempMatrix, path);
141         return path;
142     }
143 
144 }
145