[英]How can I draw a polyline on a canvas in android?
I've been trying to draw a polyline on a canvas.我一直在尝试在画布上绘制多段线。 There are no errors in my codes, but the connected sequence of line segments are not showing.Please find code snippet below;
我的代码没有错误,但是没有显示连接的线段序列。请在下面找到代码片段;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.view.View;
public class MyView extends View {
private Paint redPaint;
public MyView(Context context) {
super(context, null);
redPaint=new Paint(Paint.ANTI_ALIAS_FLAG);
redPaint.setStyle(Paint.Style.STROKE);
redPaint.setColor(0xffff0000);
redPaint.setStrokeWidth(5);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawRect(10,30,200,200,redPaint);
canvas.drawCircle(300,300,250,redPaint);
Path mylines=new Path();
mylines.moveTo(0,0);
mylines.lineTo(1,1);
mylines.lineTo(2,2);
mylines.lineTo(3,3);
mylines.lineTo(4,4);
Paint GreenPaint=new Paint();
GreenPaint.setARGB(255,0,255,0);
canvas.drawPath(mylines,GreenPaint);
}
}
Your code is largely correct.您的代码在很大程度上是正确的。 You do not completely initialized
GreenPaint
like you do redPaint
and that is a problem.你不完全初始化
GreenPaint
像你这样redPaint
,这是一个问题。 The second issue, although it may not be a problem, is that your polyline shape is so small that you may miss it even with a fully initialized GreenPaint
.第二个问题,虽然它可能不是问题,但您的折线形状太小以至于即使使用完全初始化的
GreenPaint
也可能会错过它。
Here is an updated version of your custom view with an additional constructor and an initialized greenPaint
.这是自定义视图的更新版本,带有一个额外的构造函数和一个初始化的
greenPaint
。 I also changed the shape of the polyline and made it larger to be easily seen - it is just a speck in your code.我还更改了多段线的形状并使其变大以便于查看 - 它只是您代码中的一个斑点。 In addition I moved object allocation out of
onDraw()
.此外,我将对象分配移出了
onDraw()
。
public class MyView extends View {
Path mylines = new Path();
private Paint redPaint;
private Paint greenPaint;
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public MyView(Context context) {
super(context, null);
init();
}
private void init() {
redPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
redPaint.setStyle(Paint.Style.STROKE);
redPaint.setColor(0xffff0000);
redPaint.setStrokeWidth(5);
greenPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
greenPaint.setStyle(Paint.Style.STROKE);
greenPaint.setARGB(255, 0, 255, 0);
greenPaint.setStrokeWidth(5);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawRect(10, 30, 200, 200, redPaint);
canvas.drawCircle(300, 300, 250, redPaint);
mylines.moveTo(0, 0);
mylines.lineTo(200, 50);
mylines.lineTo(300, 150);
mylines.lineTo(400, 250);
mylines.lineTo(500, 300);
canvas.drawPath(mylines, greenPaint);
}
}
Here is the display.这是显示器。 (I added a gray background for visibility of the view but it is not needed.)
(我为视图的可见性添加了灰色背景,但不需要。)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.