Android画图之Path类的使用

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