在Android中复杂的图形的绘制绝大多数是通过path来实现，比如绘制一条曲线，然后让一个物体随着这个曲线运动，比如搜索按钮，比如一个简单时钟的实现：
那么什么是path呢！
定义：path 就是路径，就是图形的路径的集合，它里边包含了路径里边的坐标点，等等的属性。我们可以获取到任意点的坐标，正切值。
那么要获取Path上边所有点的坐标还需要用到一个类,PathMeasure;
PathMesure:
PathMeasure是一个用来测量Path的类，主要有以下方法:
构造方法
公共方法
可以看到，这个就等于是一个Path的一个工具类，方法很简单，那么就开始我们所要做的按钮跟时钟的开发吧
（1）搜索按钮，首先上图：
要实现这个功能首先要把他分解开来做；
创建搜索按钮的path路径，然后创建外圈旋转的path，
public void initPath(){
mPath_search = new Path();
mPath_circle = new Path();
mMeasure = new PathMeasure();
// 注意,不要到360度,否则内部会自动优化,测量不能取到需要的数值
RectF oval1 = new RectF(-50, -50, 50, 50); // 放大镜圆环
mPath_search.addArc(oval1, 45, 359.9f);
RectF oval2 = new RectF(-100, -100, 100, 100); // 外部圆环
mPath_circle.addArc(oval2, 45, -359.9f);
float[] pos = new float[2];
mMeasure.setPath(mPath_circle, false); // 放大镜把手的位置
mMeasure.getPosTan(0, pos, null);
mPath_search.lineTo(pos[0], pos[1]); // 放大镜把手
Log.i("TAG", "pos=" + pos[0] + ":" + pos[1]);
}
我们要的效果就是点击搜索按钮的时候开始从按钮变为旋转，然后搜索结束以后变为搜索按钮。
所以我们可以确定有四种状态：
public enum Seach_State{
START,END,NONE,SEARCHING
}
然后根据状态来进行动态绘制path，动态绘制path就要使用到PathMeasure测量当前path的坐标，然后进行绘制。
private void drawPath(Canvas c) {
c.translate(mWidth / 2, mHeight / 2);
switch (mState){
case NONE:
c.drawPath(mPath_search,mPaint);
break;
case START:
mMeasure.setPath(mPath_search,true);
Path path = new Path();
mMeasure.getSegment(mMeasure.getLength() * curretnAnimationValue,mMeasure.getLength(),path, true);
c.drawPath(path,mPaint);
break;
case SEARCHING:
mMeasure.setPath(mPath_circle,true);
Path path_search = new Path();
mMeasure.getSegment(mMeasure.getLength()*curretnAnimationValue -30,mMeasure.getLength()*curretnAnimationValue,path_search,true);
c.drawPath(path_search,mPaint);
break;
case END:
mMeasure.setPath(mPath_search,true);
Path path_view = new Path();
mMeasure.getSegment(0,mMeasure.getLength()*curretnAnimationValue,path_view,true);
c.drawPath(path_view,mPaint);
break;
}
}
然后就是需要通过使用属性动画来返回当前该绘制的百分百，通过这个值来进行计算要绘制的path。
下边是整个代码：
package com.duoku.platform.demo.canvaslibrary.attract.view;
import android.animation.Animator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
public class SearchView extends View {
private Paint mPaint;
private Context mContext;
private Path mPath_circle;
private Path mPath_search;
private PathMeasure mMeasure;
private ValueAnimator mValueAnimator_search;
private long defaultduration=3000;
private float curretnAnimationValue;
private Seach_State mState = Seach_State.SEARCHING;
public SearchView(Context context) {
super(context);
init(context);
}
public SearchView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
public SearchView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context);
}
public void init(Context context){
this.mContext = context;
initPaint();
initPath();
initAnimation();
}
public void initPaint(){
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setStrokeCap(Paint.Cap.ROUND);//设置笔头效果
mPaint.setAntiAlias(true);
mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(3);
mPaint.setStyle(Paint.Style.STROKE);
}
public void initPath(){
mPath_search = new Path();
mPath_circle = new Path();
mMeasure = new PathMeasure();
// 注意,不要到360度,否则内部会自动优化,测量不能取到需要的数值
RectF oval1 = new RectF(-50, -50, 50, 50); // 放大镜圆环
mPath_search.addArc(oval1, 45, 359.9f);
RectF oval2 = new RectF(-100, -100, 100, 100); // 外部圆环
mPath_circle.addArc(oval2, 45, -359.9f);
float[] pos = new float[2];
mMeasure.setPath(mPath_circle, false); // 放大镜把手的位置
mMeasure.getPosTan(0, pos, null);
mPath_search.lineTo(pos[0], pos[1]); // 放大镜把手
Log.i("TAG", "pos=" + pos[0] + ":" + pos[1]);
}
public void initAnimation(){
mValueAnimator_search = ValueAnimator.ofFloat(0f,1.0f).setDuration(defaultduration);
mValueAnimator_search.addUpdateListener(updateListener);
mValueAnimator_search.addListener(animationListener);
}
private ValueAnimator.AnimatorUpdateListener updateListener = new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
curretnAnimationValue = (float) animation.getAnimatedValue();
invalidate();
}
};
private Animator.AnimatorListener animationListener = new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
if(mState ==Seach_State.START){
setState(Seach_State.SEARCHING);
}
}
@Override
public void onAnimationCancel(Animator animation) {
}
@Override
public void onAnimationRepeat(Animator animation) {
}
};
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawPath(canvas);
}
private int mWidth,mHeight;
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mWidth = w;
mHeight = h;
}
private void drawPath(Canvas c) {
c.translate(mWidth / 2, mHeight / 2);
switch (mState){
case NONE:
c.drawPath(mPath_search,mPaint);
break;
case START:
mMeasure.setPath(mPath_search,true);
Path path = new Path();
mMeasure.getSegment(mMeasure.getLength() * curretnAnimationValue,mMeasure.getLength(),path, true);
c.drawPath(path,mPaint);
break;
case SEARCHING:
mMeasure.setPath(mPath_circle,true);
Path path_search = new Path();
mMeasure.getSegment(mMeasure.getLength()*curretnAnimationValue -30,mMeasure.getLength()*curretnAnimationValue,path_search,true);
c.drawPath(path_search,mPaint);
break;
case END:
mMeasure.setPath(mPath_search,true);
Path path_view = new Path();
mMeasure.getSegment(0,mMeasure.getLength()*curretnAnimationValue,path_view,true);
c.drawPath(path_view,mPaint);
break;
}
}
public void setState(Seach_State state){
this.mState = state;
startSearch();
}
public void startSearch(){
switch (mState){
case START:
mValueAnimator_search.setRepeatCount(0);
break;
case SEARCHING:
mValueAnimator_search.setRepeatCount(ValueAnimator.INFINITE);
mValueAnimator_search.setRepeatMode(ValueAnimator.REVERSE);
break;
case END:
mValueAnimator_search.setRepeatCount(0);
break;
}
mValueAnimator_search.start();
}
public enum Seach_State{
START,END,NONE,SEARCHING
}
}
（学习的点：path可以组合，可以把不同的path放置到一个path里边，然后进行统一的绘制）
（2）时钟效果：
说一下时钟的思路啊，网上很多时钟都是通过Canvas绘制基本图形实现的，没有通过path来实现的，使用path实现是为了以后更加灵活的控制时钟的绘制效果，比如我们要让最外边的圆圈逆时针旋转，还比如在上边添加些小星星啥的，用path的话会更加灵活。
时钟的实现分部分：
1、创建外圈path路径
2、创建刻度path路径，要区分整点，绘制时间点
3、绘制指针，（这个使用的是canvas绘制的线段，也可以使用Path，可以自己测试）
需要计算当前时针，分针，秒针的角度，然后进行绘制
整体代码：
package com.duoku.platform.demo.canvaslibrary.attract.view;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;
import java.util.Calendar;
public class TimeView extends View {
private Paint mPaint,mPaint_time;
private Paint mPaint_h,mPaint_m,mPaint_s;
private Path mPath_Circle;
private Path mPath_Circle_h;
private Path mPath_Circle_m;
private Path mPath_h,mPath_m,mPath_s;
private Path mPath_duration;
private PathMeasure mMeasure;
private PathMeasure mMeasure_h;
private PathMeasure mMeasure_m;
private Handler mHandler = new Handler();
private Runnable clockRunnable;
private boolean isRunning;
public TimeView(Context context) {
super(context);
init();
}
public TimeView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public TimeView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
int t = 3;
public void init(){
//初始化画笔
mPaint = new Paint();
mPaint.setDither(true);
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(2);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setColor(Color.RED);
mPaint_time = new Paint();
mPaint_time.setDither(true);
mPaint_time.setAntiAlias(true);
mPaint_time.setStyle(Paint.Style.STROKE);
mPaint_time.setStrokeWidth(2);
mPaint_time.setTextSize(15);
mPaint_time.setStrokeCap(Paint.Cap.ROUND);
mPaint_time.setStrokeJoin(Paint.Join.ROUND);
mPaint_time.setColor(Color.RED);
mPaint_h = new Paint();
mPaint_h.setDither(true);
mPaint_h.setAntiAlias(true);
mPaint_h.setStyle(Paint.Style.STROKE);
mPaint_h.setStrokeWidth(6);
mPaint_h.setTextSize(15);
mPaint_h.setStrokeCap(Paint.Cap.ROUND);
mPaint_h.setStrokeJoin(Paint.Join.ROUND);
mPaint_h.setColor(Color.RED);
mPaint_m = new Paint();
mPaint_m.setDither(true);
mPaint_m.setAntiAlias(true);
mPaint_m.setStyle(Paint.Style.STROKE);
mPaint_m.setStrokeWidth(4);
mPaint_m.setTextSize(15);
mPaint_m.setStrokeCap(Paint.Cap.ROUND);
mPaint_m.setStrokeJoin(Paint.Join.ROUND);
mPaint_m.setColor(Color.RED);
mPaint_s = new Paint();
mPaint_s.setDither(true);
mPaint_s.setAntiAlias(true);
mPaint_s.setStyle(Paint.Style.STROKE);
mPaint_s.setStrokeWidth(2);
mPaint_s.setTextSize(15);
mPaint_s.setStrokeCap(Paint.Cap.ROUND);
mPaint_s.setStrokeJoin(Paint.Join.ROUND);
mPaint_s.setColor(Color.RED);
//初始化刻度
mPath_Circle = new Path();
mPath_Circle.addCircle(0,0,250, Path.Direction.CCW);
mPath_Circle_h = new Path();
mPath_Circle_h.addCircle(0,0,220, Path.Direction.CCW);
mPath_Circle_m = new Path();
mPath_Circle_m.addCircle(0,0,235, Path.Direction.CCW);
//初始化PathMeasure测量path坐标，
mMeasure = new PathMeasure();
mMeasure.setPath(mPath_Circle,true);
mMeasure_h = new PathMeasure();
mMeasure_h.setPath(mPath_Circle_h,true);
mMeasure_m = new PathMeasure();
mMeasure_m.setPath(mPath_Circle_m,true);
//获取刻度path
mPath_duration = new Path();
for (int i = 60; i>0 ;i --){
Path path = new Path();
float pos [] = new float[2];
float tan [] = new float[2];
float pos2 [] = new float[2];
float tan2 [] = new float[2];
float pos3 [] = new float[2];
float tan3 [] = new float[2];
mMeasure.getPosTan(mMeasure.getLength()*i/60,pos,tan);
mMeasure_h.getPosTan(mMeasure_h.getLength()*i/60,pos2,tan2);
mMeasure_m.getPosTan(mMeasure_m.getLength()*i/60,pos3,tan3);
float x = pos[0];
float y = pos[1];
float x2 = pos2[0];
float y2 = pos2[1];
float x3 = pos3[0];
float y3 = pos3[1];
path.moveTo(x , y);
if(i% 5 ==0){
path.lineTo(x2,y2);
if(t>12){
t = t-12;
}
String time = t++ +"";
Path path_time = new Path();
mMeasure_h.getPosTan(mMeasure_h.getLength()*(i-1)/60,pos2,tan2);
mPaint.getTextPath(time,0,time.length(),(x2- (x2/15)),y2-(y2/15),path_time);
path.close();
path.addPath(path_time);
}else{
path.lineTo(x3,y3);
}
mPath_duration.addPath(path);
clockRunnable = new Runnable() {//里面做的事情就是每隔一秒，刷新一次界面
@Override
public void run() {
//线程中刷新界面
postInvalidate();
mHandler.postDelayed(this, 1000);
}
};
}
mPath_h = new Path();
mPath_h.rLineTo(50,30);
mPath_m = new Path();
mPath_m.rLineTo(80,80);
mPath_s = new Path();
mPath_s.rLineTo(130,50);
}
private int mWidth,mHeight;
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mWidth = w;
mHeight = h;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if(!isRunning){
isRunning = true;
mHandler.postDelayed(clockRunnable,1000);
}else{
canvas.translate(mWidth/2,mHeight/2);
canvas.drawPath(mPath_Circle,mPaint);
canvas.save();
canvas.drawPath(mPath_duration,mPaint_time);
canvas.drawPoint(0,0,mPaint_time);
drawClockPoint(canvas);
}
}
private Calendar cal;
private int hour;
private int min;
private int second;
private float hourAngle,minAngle,secAngle;
private void drawClockPoint(Canvas canvas) {
cal = Calendar.getInstance();
hour = cal.get(Calendar.HOUR);//Calendar.HOUR获取的是12小时制，Calendar.HOUR_OF_DAY获取的是24小时制
min = cal.get(Calendar.MINUTE);
second = cal.get(Calendar.SECOND);
//计算时分秒指针各自需要偏移的角度
hourAngle = (float)hour / 12 * 360 + (float)min / 60 * (360 / 12);//360/12是指每个数字之间的角度
minAngle = (float)min / 60 * 360;
secAngle = (float)second / 60 * 360;
//下面将时、分、秒指针按照各自的偏移角度进行旋转，每次旋转前要先保存canvas的原始状态
canvas.save();
canvas.rotate(hourAngle,0, 0);
canvas.drawLine(0, 0, mWidth/6, getHeight() / 6 - 65, mPaint_h);//时针长度设置为65
canvas.restore();
canvas.save();
canvas.rotate(minAngle,0, 0);
canvas.drawLine(0, 0, mWidth/6, getHeight() / 6 - 90 , mPaint_m);//分针长度设置为90
canvas.restore();
canvas.save();
canvas.rotate(secAngle,0, 0);
canvas.drawLine(0, 0, mWidth/6, getHeight() / 6 - 110 , mPaint_s);//秒针长度设置为110
canvas.restore();
}
}
这其实还不算特别复杂的动画，也许你有啥好的想法，可以自己通过Path + 属性动画来实现更好看的效果；
比如星空的效果，比如动态绘制文字 + 路径实现类似ppt中播放的一些特效，比如电子书的自动翻页。
（3）下边再介绍一个知识，就是svg：
svg是什么东西呢？
他的学名叫做可缩放矢量图形，是基于可扩展标记语言（标准通用标记语言的子集），用于描述二维矢量图形的一种图形格式。
这种格式的图形式可以加载到Android的Path里边。
既然可以加载到Path里边，那么是不是就可以实现更复杂的效果呢，下边看图：（明天再写了）
