初学Android,图形图像之使用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 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Pathpath = 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Pathpath.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);//每次把画布的原点下移60像素    }    //改变phase值,形成动画效果    phase += 1;    invalidate();    }    }}

效果如下

path.close 关闭当前的轮廓。如果当前点是不相等的轮廓的第一点，线段自动添加

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