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      1 /*
      2  * Copyright (C) 2013 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.example.android.curvedmotion;
     18 
     19 import android.animation.ObjectAnimator;
     20 import android.app.Activity;
     21 import android.os.Bundle;
     22 import android.view.View;
     23 import android.view.ViewTreeObserver;
     24 import android.view.animation.DecelerateInterpolator;
     25 import android.widget.Button;
     26 import android.widget.RelativeLayout;
     27 import android.widget.RelativeLayout.LayoutParams;
     28 
     29 /**
     30  * This app shows how to move a view in a curved path between two endpoints.
     31  * The real work is done by PathEvaluator, which interpolates along a path
     32  * using Bezier control and anchor points in the path.
     33  *
     34  * Watch the associated video for this demo on the DevBytes channel of developer.android.com
     35  * or on the DevBytes playlist in the androiddevelopers channel on YouTube at
     36  * https://www.youtube.com/playlist?list=PLWz5rJ2EKKc_XOgcRukSoKKjewFJZrKV0.
     37  */
     38 public class CurvedMotion extends Activity {
     39 
     40     private static final DecelerateInterpolator sDecelerateInterpolator =
     41             new DecelerateInterpolator();
     42     boolean mTopLeft = true;
     43     Button mButton;
     44 
     45     @Override
     46     protected void onCreate(Bundle savedInstanceState) {
     47         super.onCreate(savedInstanceState);
     48         setContentView(R.layout.activity_curved_motion);
     49 
     50         mButton = (Button) findViewById(R.id.button);
     51         mButton.setOnClickListener(new View.OnClickListener() {
     52 
     53             @Override
     54             public void onClick(View v) {
     55                 // Capture current location of button
     56                 final int oldLeft = mButton.getLeft();
     57                 final int oldTop = mButton.getTop();
     58 
     59                 // Change layout parameters of button to move it
     60                 moveButton();
     61 
     62                 // Add OnPreDrawListener to catch button after layout but before drawing
     63                 mButton.getViewTreeObserver().addOnPreDrawListener(
     64                         new ViewTreeObserver.OnPreDrawListener() {
     65                             public boolean onPreDraw() {
     66                                 mButton.getViewTreeObserver().removeOnPreDrawListener(this);
     67 
     68                                 // Capture new location
     69                                 int left = mButton.getLeft();
     70                                 int top = mButton.getTop();
     71                                 int deltaX = left - oldLeft;
     72                                 int deltaY = top - oldTop;
     73 
     74                                 // Set up path to new location using a Bzier spline curve
     75                                 AnimatorPath path = new AnimatorPath();
     76                                 path.moveTo(-deltaX, -deltaY);
     77                                 path.curveTo(-(deltaX/2), -deltaY, 0, -deltaY/2, 0, 0);
     78 
     79                                 // Set up the animation
     80                                 final ObjectAnimator anim = ObjectAnimator.ofObject(
     81                                         CurvedMotion.this, "buttonLoc",
     82                                         new PathEvaluator(), path.getPoints().toArray());
     83                                 anim.setInterpolator(sDecelerateInterpolator);
     84                                 anim.start();
     85                                 return true;
     86                             }
     87                         });
     88             }
     89         });
     90     }
     91 
     92     /**
     93      * Toggles button location on click between top-left and bottom-right
     94      */
     95     private void moveButton() {
     96         LayoutParams params = (LayoutParams) mButton.getLayoutParams();
     97         if (mTopLeft) {
     98             params.removeRule(RelativeLayout.ALIGN_PARENT_LEFT);
     99             params.removeRule(RelativeLayout.ALIGN_PARENT_TOP);
    100             params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
    101             params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
    102         } else {
    103             params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
    104             params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
    105             params.removeRule(RelativeLayout.ALIGN_PARENT_RIGHT);
    106             params.removeRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
    107         }
    108         mButton.setLayoutParams(params);
    109         mTopLeft = !mTopLeft;
    110     }
    111 
    112     /**
    113      * We need this setter to translate between the information the animator
    114      * produces (a new "PathPoint" describing the current animated location)
    115      * and the information that the button requires (an xy location). The
    116      * setter will be called by the ObjectAnimator given the 'buttonLoc'
    117      * property string.
    118      */
    119     public void setButtonLoc(PathPoint newLoc) {
    120         mButton.setTranslationX(newLoc.mX);
    121         mButton.setTranslationY(newLoc.mY);
    122     }
    123 
    124 }
    125