Android:如何在扩展 Activity 的类中使用 onDraw 方法? [英] Android: How to use the onDraw method in a class extending Activity?

问题描述

作为一个初学者，我一直在使用简单的布局 xml 和一个名为Counter"的类构建一个简单的计数器应用程序，该类从 Activity 类派生(扩展).

As a beginner, I've been building a simple counter application using a simple layout xml and a class called 'Counter', which derives (extends) from the class Activity.

现在，我想加载一个位图(png 文件)放在柜台旁边.我一直在阅读 onDraw()，但它需要类来扩展视图".我一直在尝试创建此类的对象来使用它，但无济于事.我对这个概念有点困惑，如何轻松地做到这一点.如果有人能解释一下，我将不胜感激.

Now, I want to load a bitmap (png file) to place next to the counter. I've been reading up on onDraw(), but it requires the class to extend 'View'. I've been trying to create an object of this class to use this instead, to no avail. I'm a bit stumped about this concept, how to do it easily. If anyone could explain, I'd appreciate it.

推荐答案

使用onDraw函数的简单示例-它需要类来扩展视图

Simple example using onDraw function-it requires class to extend view

获取当前活动上下文的上下文

Context to get the current activity context

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(new myview(this));


}

class myview extends View
{

    public myview(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }
    @Override
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
        int x=80;
        int y=80;
        int radius=40;
        Paint paint=new Paint();
        // Use Color.parseColor to define HTML colors
        paint.setColor(Color.parseColor("#CD5C5C"));
        canvas.drawCircle(x, y, radius, paint);
    }

}

}

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