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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.graphics.Path;
     20 import android.util.AttributeSet;
     21 
     22 /**
     23  * This base class can be extended to provide motion along a Path to Transitions.
     24  *
     25  * <p>
     26  * Transitions such as {@link android.transition.ChangeBounds} move Views, typically
     27  * in a straight path between the start and end positions. Applications that desire to
     28  * have these motions move in a curve can change how Views interpolate in two dimensions
     29  * by extending PathMotion and implementing {@link #getPath(float, float, float, float)}.
     30  * </p>
     31  * <p>This may be used in XML as an element inside a transition.</p>
     32  * <pre>
     33  * {@code
     34  * <changeBounds>
     35  *     <pathMotion class="my.app.transition.MyPathMotion"/>
     36  * </changeBounds>
     37  * }
     38  * </pre>
     39  */
     40 public abstract class PathMotion {
     41 
     42     public PathMotion() {}
     43 
     44     public PathMotion(Context context, AttributeSet attrs) {}
     45 
     46     /**
     47      * Provide a Path to interpolate between two points <code>(startX, startY)</code> and
     48      * <code>(endX, endY)</code>. This allows controlled curved motion along two dimensions.
     49      *
     50      * @param startX The x coordinate of the starting point.
     51      * @param startY The y coordinate of the starting point.
     52      * @param endX   The x coordinate of the ending point.
     53      * @param endY   The y coordinate of the ending point.
     54      * @return A Path along which the points should be interpolated. The returned Path
     55      * must start at point <code>(startX, startY)</code>, typically using
     56      * {@link android.graphics.Path#moveTo(float, float)} and end at <code>(endX, endY)</code>.
     57      */
     58     public abstract Path getPath(float startX, float startY, float endX, float endY);
     59 }
     60