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
17package com.example.android.curvedmotion;
18
19import android.animation.ObjectAnimator;
20import android.app.Activity;
21import android.os.Bundle;
22import android.view.View;
23import android.view.ViewTreeObserver;
24import android.view.animation.DecelerateInterpolator;
25import android.widget.Button;
26import android.widget.RelativeLayout;
27import 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 */
38public 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 B�zier 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