CustomView

自定义View基类，如果你的自定义View继承这个类则能自动获取到View大小与一个默认到Paint，可以帮助你节省部分代码，示例如下:

通常的自定义View

public class MyView extends View {

    private int mWidth;
    private int mHeight;
    private Paint mPaint;

    public MyView(Context context) {
        this(context, null);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 初始化画笔
        mPaint.setColor(Color.GRAY);
    }
    

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mWidth = w;
        mHeight = h;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // 获取View宽高与画笔并根据此绘制内容

        canvas.translate(mWidth / 2, mHeight / 2);
        canvas.drawCircle(0,0,100,mPaint);
    }
}

继承CustomView

public class MyView extends CustomView {

    public MyView(Context context) {
        this(context, null);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // 初始化画笔
        mDefaultTextPaint.setColor(Color.GRAY);
    }
    
    
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // 获取View宽高与画笔并根据此绘制内容

        canvas.translate(mViewWidth / 2, mViewHeight / 2);
        canvas.drawCircle(0,0,100,mDeafultPaint);
    }
}