<Path>类

最新推荐文章于 2023-04-12 17:17:06 发布

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本文介绍如何在Android中利用Path类实现复杂图形绘制，并通过PathEffect应用多种视觉效果，如CornerPathEffect、DiscretePathEffect等，同时展示了如何通过动画效果增强用户体验。

Android 提供的Path 类时一个非常有用的类.它可以预先在View 上将N个点连成一个”路径”,然后调用Canvas 的DrawPath(path , paint)即可沿着路径绘制图形.

package com.test.pathactivity;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ComposePathEffect;
import android.graphics.CornerPathEffect;
import android.graphics.DashPathEffect;
import android.graphics.DiscretePathEffect;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathDashPathEffect;
import android.graphics.PathEffect;
import android.graphics.SumPathEffect;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.View;

public class PathActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_path);
        setContentView(new MyView(this));
    }

    class MyView extends View{

        float phase;
        PathEffect[] mEffects = new PathEffect[7];
        int[] colors;

        private Paint mPaint;
        Path path;


        public MyView(Context context) {
            super(context);
            mPaint = new Paint();

            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setStrokeWidth(5);


            //创建并初始化 Path
            path = new Path();
            path.moveTo(0,0);

            for (int i = 0; i <= 15 ; i++) {
                //生成 15个点,随机生成他们的 y坐标 并将他们连成一个 path
                path.lineTo(i*30, (float) (Math.random()*60));
            }

            //初始化7个颜色
            colors = new int[]{Color.YELLOW,Color.RED,Color.BLUE,Color.GREEN,Color.BLACK,Color.CYAN,Color.MAGENTA};
        }

        @Override
        protected void onDraw(Canvas canvas) {
           // super.onDraw(canvas);

            //将背景色 填充为白色
            canvas.drawColor(Color.WHITE);


            //下面初始化7种路径效果
            //不使用路径效果
            mEffects[0] = null;

            //使用 CornerPathEffect 路径效果
            mEffects[1] = new CornerPathEffect(10);

            //使用 DiscretePathEffect
            mEffects[2] = new DiscretePathEffect(3.3f,5.0f);

            //初始化 DashPathEffect
            mEffects[3] = new DashPathEffect(new float[]{20,10,5,10},phase);

            //初始化 PathDashPathEffect
            Path p = new Path();
            p.addRect(0,0,8,8,Path.Direction.CCW);

            mEffects[4] = new PathDashPathEffect(p,12,phase,PathDashPathEffect.Style.ROTATE);

            mEffects[5] = new ComposePathEffect(mEffects[2],mEffects[4]);
            mEffects[6] = new SumPathEffect(mEffects[4],mEffects[3]);

            //将画布移动到(8,8)出 开始绘制
            canvas.translate(8,8);

            //依次使用7中不同路径效果,7中不同的颜色来绘制路径
            for (int i = 0; i < mEffects.length; i++) {
                mPaint.setPathEffect(mEffects[i]);
                mPaint.setColor(colors[i]);

                canvas.drawPath(path, mPaint);
                canvas.translate(10,60);
            }

            //改变 phase 值 形成动画效果
            phase+=1;
            invalidate();
        }

        public MyView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    }
}