android学习笔记43——图形图像处理3——Path

Path类

Path类可以预先在View上将N个点连成一条“路径”，然后调用Canavas的drawPath(path,paint)即可沿着路径绘制图形。

android还为路径绘制提供了PathEffect来定义绘制效果，PathEffect包含如下子类——每一个子类代表一种绘制方法：

　　1.ComposePathEffect

　　2.CnonerPathEffect

　　3.DashPathEffect
　　4.DiscretePathEffect

　　5.PathDashPathEffect

　　6.SumPathEffect

实例如下：

100

代码实现==》
package com.example.mypath;
 
import android.os.Bundle;
import android.annotation.SuppressLint;
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.view.Menu;
import android.view.View;
 
public class MainActivity extends Activity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this));
    }
 
    class MyView extends View
    {
        float phase;
        PathEffect[] effects = new PathEffect[7];
        int[] colors;
        private Paint paint;
        Path path;
 
        public MyView(Context context)
        {
            super(context);
 
            paint = new Paint();
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(10);
            // 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，随记生成他们的Y坐标,并将它们连成一条Path
                path.lineTo(i * 30, (float) Math.random() * 100);
            }
            // 初始化7个颜色
            colors = new int[] { Color.BLACK, Color.YELLOW, Color.GRAY, Color.GREEN, Color.BLUE,
                    Color.RED, Color.CYAN };
        }
 
        @SuppressLint("DrawAllocation")
        @Override
        protected void onDraw(Canvas canvas)
        {
            // 将背景色填充为白色
            canvas.drawColor(Color.WHITE);
 
            // 初始化7种路径效果
            effects[0] = null;// 不使用路径效果
            effects[1] = new CornerPathEffect(10);// 使用CornerPathEffect路径效果
            effects[2] = new DiscretePathEffect(3.0f, 5.0f);// 初始化DiscretePathEffect
            effects[3] = new DashPathEffect(new float[] { 20, 10, 5, 10 }, phase);// 初始化DashPathEffect
 
            Path p = new Path();
            p.addRect(0, 0, 8, 8, Path.Direction.CCW);
            effects[4] = new PathDashPathEffect(p, 123, phase, PathDashPathEffect.Style.ROTATE);// 初始化PathDashPathEffect
            effects[5] = new ComposePathEffect(effects[2], effects[4]);// 初始化ComposePathEffect
            effects[6] = new SumPathEffect(effects[4], effects[3]);// 初始化SumPathEffect
 
            // 依次使用7种不同效果路径、7种不同的颜色来绘制路径
            for (int j = 0; j < effects.length; j++)
            {
                paint.setPathEffect(effects[j]);
                paint.setColor(colors[j]);
                canvas.drawPath(path, paint);
                canvas.translate(0, 120);
            }
            // 改变phase值，形成动画效果
            phase++;
            invalidate();
        }
    }
 
    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
 
}