1 /* 2 * Copyright (C) 2017 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.support.animation; 18 19 import android.content.Context; 20 import android.graphics.Canvas; 21 import android.graphics.Paint; 22 import android.util.AttributeSet; 23 import android.view.View; 24 25 /** 26 * The view that draws the spring as it reacts (i.e. expands/compresses) to the user touch. 27 */ 28 public class SpringView extends View { 29 final Paint mPaint = new Paint(); 30 private float mLastHeight = 175; 31 SpringView(Context context, AttributeSet attrs)32 public SpringView(Context context, AttributeSet attrs) { 33 super(context, attrs); 34 setWillNotDraw(false); 35 mPaint.setColor(context.getResources().getColor(R.color.springColor)); 36 mPaint.setStrokeWidth(10); 37 } 38 39 /** 40 * Sets the other end of the spring. 41 * 42 * @param height height of the mass, which is used to derive how to draw the spring 43 */ setMassHeight(float height)44 public void setMassHeight(float height) { 45 mLastHeight = height; 46 invalidate(); 47 } 48 49 @Override onDraw(Canvas canvas)50 public void onDraw(Canvas canvas) { 51 // Draws the spring 52 // 30px long, 15 sections 53 int num = 20; 54 float sectionLen = 150; // px 55 final float x = canvas.getWidth() / 2; 56 float y = 0; 57 float sectionHeight = mLastHeight / num; 58 float sectionWidth = (float) Math.sqrt(sectionLen * sectionLen 59 - sectionHeight * sectionHeight); 60 canvas.drawLine(x, 0, x + sectionWidth / 2, sectionHeight / 2, mPaint); 61 float lastX = x + sectionWidth / 2; 62 float lastY = sectionHeight / 2; 63 for (int i = 1; i < num; i++) { 64 canvas.drawLine(lastX, lastY, 2 * x - lastX, lastY + sectionHeight, mPaint); 65 lastX = 2 * x - lastX; 66 lastY = lastY + sectionHeight; 67 } 68 canvas.drawLine(lastX, lastY, x, mLastHeight, mPaint); 69 } 70 } 71