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      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      */
     50     public PatternPathMotion() {
     51         mPatternPath.lineTo(1, 0);
     52         mOriginalPatternPath = mPatternPath;
     53     }
     54 
     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      */
     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      */
     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      */
    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
    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