初学Android 图形图像之使用Path类 二十六

Path类可以预先在View上将N个点连成一条"路径",然后调用Canvas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

ComposePathEffect

CornerPathEffect

DashPathEffect

DiscretePathEffect

PathDashPathEffect

SumPathEffect

下面的示例将会逐一使用上面的绘制效果

package WangLi.Graphics.PathTest;

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.view.View;

public class PathTest extends Activity {
    /** Called when the activity is first created. */
    @Override
    public 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(4);
			//创建,并初始化Path
			path = new Path();
			path.moveTo(0, 0);
			for(int i = 1; i<= 15; i++)
			{
				//生成15个点,随机生成它们的坐标,并将它们连成一条Path
				path.lineTo(i*20, (float)Math.random()*60);
			}
			//初始化七个颜色
			colors = new int[] {
					Color.BLACK,Color.BLUE,Color.CYAN,
					Color.GREEN,Color.MAGENTA,Color.RED,Color.YELLOW
			};
		}
    	protected void onDraw(Canvas canvas)
    	{
    		//将背景填充成白色
    		canvas.drawColor(Color.WHITE);
    		//-------下面开始初始化7中路径的效果
    		//使用路径效果
    		effects[0] = null;
    		//使用CornerPathEffect路径效果
    		effects[1] = new CornerPathEffect(10);
    		//初始化DiscretePathEffect
    		effects[2] = new DiscretePathEffect(3.0f,5.0f);
    		//初始化DashPathEffect
    		effects[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);
    		effects[4] = new PathDashPathEffect(p,12,phase,PathDashPathEffect.Style.ROTATE);
    		//初始化PathDashPathEffect
    		effects[5] = new ComposePathEffect(effects[2],effects[4]);
    		effects[6] = new SumPathEffect(effects[4],effects[3]);
    		//将画布移到8,8处开始绘制
    		canvas.translate(8, 8);
    		//依次使用7中不同路径效果,7种不同的颜色来绘制路径
    		for(int i = 0; i < effects.length; i++)
    		{
    			paint.setPathEffect(effects[i]);
    			paint.setColor(colors[i]);
    			canvas.drawPath(path, paint);
    			canvas.translate(0, 60);
    		}
    		//改变phase值,形成动画效果
    		phase += 1;
    		invalidate();
    	}
    }
}

效果如下

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