帆布在Java的Andr​​oid不拉丝 [英] canvas not drawing in java android

问题描述

我觉得code是正确的，但我无法找到什么错。任何人都可以帮助请搞清楚什么是不正确的？

多数民众赞成在活动文档：

 包com.example.crazyeights;进口android.os.Bundle;
进口android.app.Activity;
进口android.view.Menu;公共类CrazyEightsActivity延伸活动{    @覆盖
    保护无效的onCreate（捆绑savedInstanceState）{
        super.onCreate（savedInstanceState）;
        MyView的观点=新的MyView的（本）;
        的setContentView（视图）;
    }    @覆盖
    公共布尔onCreateOptionsMenu（菜单菜单）{
        //充气菜单;如果是present这增加了项目操作栏。
        。getMenuInflater（）膨胀（R.menu.crazy_eights，菜单）;
        返回true;
    }}
 

这就是我想要的屏幕显示：

 包com.example.crazyeights;
进口android.content.Context;
进口android.view.View;
进口android.graphics.Canvas;
进口android.graphics.Color;
进口android.graphics.Paint;公共类MyView的扩展视图{    私人涂料redPaint;
    私人诠释circleX;
    私人诠释circleY;
    私人浮动半径;    公共MyView的（上下文的背景下）{
        超级（上下文）;
        redPaint =新的油漆（）;
        redPaint.setAntiAlias​​（真）;
        redPaint.setColor（Color.RED）;
        circleX = 100;
        circleY = 100;
        半径= 30;
    }
    保护无效的OnDraw（帆布油画）{
             canvas.drawCircle（circleX，circleY，半径redPaint）;
    }
}
 

解决方案

您指定的大写的OnDraw（）方法将不会被调用的方式。实际上，你需要重写的onDraw（）方法，使用自定义视图时，例如：

  @覆盖
保护无效的onDraw（帆布油画）{
    canvas.drawCircle（circleX，circleY，半径redPaint）;
}
 

我测试了它，并绘制一个红色圆圈。请参阅自定义绘图 rel=\"nofollow\">这里，特别是替换文档的onDraw（）部分。

I think the code is right, but I'm unable to find what's going wrong. Can anyone help please in figuring out what's incorrect ?

Thats the activity document:

package com.example.crazyeights;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class CrazyEightsActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        MyView view = new MyView(this);
        setContentView(view);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.crazy_eights, menu);
        return true;
    }

}

thats what i want to display in the screen:

package com.example.crazyeights;
import android.content.Context; 
import android.view.View;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;

public class MyView extends View{

    private Paint redPaint;
    private int circleX;
    private int circleY;
    private float radius;

    public MyView(Context context) {
        super(context);
        redPaint = new Paint();
        redPaint.setAntiAlias(true);
        redPaint.setColor(Color.RED);
        circleX = 100;
        circleY = 100;
        radius = 30;
    }
    protected void OnDraw(Canvas canvas){
             canvas.drawCircle(circleX, circleY, radius, redPaint);
    }
}

解决方案

The uppercase OnDraw() method you specified will not be called that way. You actually need to override the onDraw() method when using a custom view, e.g:

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawCircle(circleX, circleY, radius, redPaint);
}

I tested it and that draws a red circle. See documentation on Custom Drawing here, specifically the Override onDraw() section.

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