Canvas模拟太阳地球月球的运动过程

先看效果图

代码

package com.test.paintdemo.pathrelate;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.view.View;

import com.test.paintdemo.R;

/**
* Created by ygdx_lk on 17/6/23.
*/

public class PlanetCircle extends View {

private  Paint mPaintCircle, mPaintSun, mPaintOne, mPaintTwo;
private final Bitmap mBitmap;
private float fraction_earth;
private float fraction_moon;
private static final String TAG = "PlanetCircle";
private int mViewWidth, mViewHeight;

public PlanetCircle(Context context) {
super(context);
//轨道画笔
mPaintCircle = new Paint();
mPaintCircle.setStyle(Paint.Style.STROKE);
mPaintCircle.setColor(Color.GRAY);
mPaintCircle.setStrokeWidth(3);
mPaintCircle.setAntiAlias(true);

//太阳
mPaintSun = new Paint();
mPaintSun.setColor(Color.RED);
mPaintSun.setStyle(Paint.Style.FILL);
mPaintSun.setAntiAlias(true);

//地球
mPaintOne = new Paint();
mPaintOne.setAntiAlias(true);
//月亮
mPaintTwo = new Paint();
mPaintTwo.setAntiAlias(true);

//图片
BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 12;       // 缩放图片
mBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.arrow, options);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mViewWidth = w;
mViewHeight = h;
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.WHITE);
//画布平移
canvas.translate(mViewWidth / 2, mViewHeight / 2);

//1.画轨道
Path path = drawPlanetPathWayOval(canvas, - getWidth() / 3, - getWidth() / 4, getWidth() / 3, getWidth() / 4);

//2.画太阳
drawSun(canvas);

//绘制图片
drawBitmap(canvas, path, fraction_earth);

//3.画地球及月球
drawPlanetEarth(canvas, path);

//4.转动
startAnim();
}

/**
* 启动动画
*/
private void startAnim() {
fraction_earth += 0.003;
if(fraction_earth >= 1){
fraction_earth = 0;
}

fraction_moon += 0.006;
if(fraction_moon >= 1){
fraction_moon = 0;
}

invalidate();
}

/**
* 画图片
* @param canvas
*/
private void drawBitmap(Canvas canvas, Path path, float fraction){
PathMeasure measure = new PathMeasure(path, false);
Matrix mMatrixBitMap = new Matrix();
//获取角度和路径
measure.getMatrix(measure.getLength() * fraction, mMatrixBitMap,
PathMeasure.TANGENT_MATRIX_FLAG | PathMeasure.POSITION_MATRIX_FLAG);

// 将图片绘制中心调整到与当前点重合(注意:此处是前乘pre)
mMatrixBitMap.preTranslate(- mBitmap.getWidth() / 2, - mBitmap.getHeight() / 2);

canvas.drawBitmap(mBitmap, mMatrixBitMap, mPaintCircle);

}

/**
* 画月球
* @param canvas
* @param mPath2
* @param fraction
*/
private void drawPlanetMoon(Canvas canvas, Path mPath2, float fraction) {
PathMeasure pathMeasure2 = new PathMeasure();
float[] pos2 = new float[2];
float[] tan2 = new float[2];
Matrix matrix2 = new Matrix();

//测量坐标和角度
pathMeasure2.setPath(mPath2, false);
pathMeasure2.getPosTan(pathMeasure2.getLength() * fraction, pos2, tan2);
//设置shader
matrix2.setRotate(360 * fraction);
RadialGradient mRadialGradient2 = new RadialGradient(pos2[0], pos2[1], 30, new int[]{0x0000FF00, 0xFF00FF00}, null, Shader.TileMode.MIRROR);
mPaintTwo.setShader(mRadialGradient2);
mRadialGradient2.setLocalMatrix(matrix2);

//绘制月球
canvas.drawCircle(pos2[0], pos2[1], 30, mPaintTwo);
}

/**
* 画地球
* @param canvas
*/
private void drawPlanetEarth(Canvas canvas, Path path1) {
PathMeasure pathMeasure1 = new PathMeasure();
float[] pos1 = new float[2];
float[] tan1 = new float[2];
Matrix matrix1 = new Matrix();
//测量坐标和角度
pathMeasure1.setPath(path1, false);
pathMeasure1.getPosTan(pathMeasure1.getLength() * fraction_earth, pos1, tan1);
//旋转shader
matrix1.setRotate(360 * fraction_earth);
RadialGradient mRadialGradient1 = new RadialGradient(pos1[0] + 10, pos1[1] + 10, 50, new int[]{0x000000FF, 0xFF0000FF}, null, Shader.TileMode.MIRROR);
mPaintOne.setShader(mRadialGradient1);
mRadialGradient1.setLocalMatrix(matrix1);
//画地球
canvas.drawCircle(pos1[0], pos1[1], 50, mPaintOne);

//－－－画地球的卫星月球－－－－－－－－－－－－－－
//画月球圆形轨道
Path path = drawPlanetPathWayCircle(canvas, pos1[0], pos1[1], 100);

//画图片
drawBitmap(canvas, path, fraction_moon);

//画月球
drawPlanetMoon(canvas, path, fraction_moon);

}

/**
* 画太阳
*/
private void drawSun(Canvas canvas) {
//创建Shader
RadialGradient mRadialGradientSun = new RadialGradient(20, 20, 100, new int[]{0x00ff0000, 0xffff0000}, null, Shader.TileMode.MIRROR);
//创建Matrix
Matrix matrixSun = new Matrix();
//旋转
matrixSun.setRotate(360 * fraction_earth);
//Shader设置Matrix
mRadialGradientSun.setLocalMatrix(matrixSun);
//画笔设置Shader
mPaintSun.setShader(mRadialGradientSun);
//绘制太阳
canvas.drawCircle(0, 0, 100, mPaintSun);
}

/**
* 绘制圆圈路径
* @param canvas 画笔
* @param x 圆心X坐标
* @param y 圆心Y坐标
* @param radius 圆半径
*/
private Path drawPlanetPathWayCircle(Canvas canvas, float x, float y, int radius){
Path path = new Path();
//画圆
path.addCircle(x, y, radius, Path.Direction.CW);
canvas.drawPath(path, mPaintCircle);
return path;
}

/**
* 绘制椭圆路径
* @param canvas
* @param left
* @param top
* @param right
* @param bottom
* @return
*/
private Path drawPlanetPathWayOval(Canvas canvas, float left, float top, float right, float bottom){
Path path = new Path();
//画椭圆
path.addOval(left, top, right, bottom, Path.Direction.CW);
canvas.drawPath(path, mPaintCircle);
return path;
}

}