Android之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 com.android.xiong.pathtest;

import android.os.Bundle;
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.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(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7个颜色
			colors = new int[] { Color.RED, Color.BLUE, Color.GREEN,
					Color.YELLOW, Color.BLACK, Color.MAGENTA, Color.CYAN };
		}

		@Override
		protected void onDraw(Canvas canvas) {
			// 将背景填充白色
			canvas.drawColor(Color.WHITE);
			// -----下面开始初始化7中路径效果-------
			// 不实用路径
			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);
			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PathDashPasheEffect
			effects[5] = new ComposePathEffect(effects[2], effects[4]);
			effects[6] = new ComposePathEffect(effects[4], effects[3]);
			// 将画布移动到(8,8)处开始绘制
			canvas.translate(8, 8);
			// 依次使用7中不同的路径效果、7中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();

		}

	}

	@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;
	}

}