自定义View简单示例

//创建一个类继承View
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {

	private Paint paint;
	private int cx;
	private int cy;

	public MyView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// 初始化画笔
		initView();

	}

	private void initView() {
		// 得到画笔
		paint = new Paint();
		// 设置画笔属性
		paint.setAlpha(255);// 透明度

		paint.setStyle(Style.STROKE);// //设置画笔为空心
		paint.setStrokeWidth(2);// 画笔线宽
		paint.setColor(Color.RED);// 画笔颜色
		paint.setAntiAlias(true);// /抗锯齿

	}

	@Override
	// 测量
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		// TODO Auto-generated method stub
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		// 从新设置当前view的大小
		setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
	}

	@Override
	// 布局
	protected void onLayout(boolean changed, int left, int top, int right,
			int bottom) {
		if (changed) {
			cx = getWidth() / 2;

			cy = getHeight() / 2;
		}
	}

	@Override
	// 绘制
	protected void onDraw(Canvas canvas) {
		for (int i = 0; i < getWidth(); i = i + 20) {
			// 画直线.
			// 直线的x起始点,y起始点y终点,y终点//横线
			canvas.drawLine(0, i, getWidth(), i, paint);
			// 竖线
			canvas.drawLine(i, 0, i, getHeight(), paint);

		}
		for (int i = 0; i < getWidth(); i = i + 20) {
			// 画点
			paint.setColor(Color.GREEN);
			paint.setStrokeWidth(10);
			canvas.drawPoint(i, i, paint);

		}

		// 画圆
		// X坐标
		// y坐标
		// 半径
		// 画笔
		paint.setColor(Color.BLUE);
		paint.setStrokeWidth(20);
		canvas.drawCircle(cx, cy, 60, paint);
	}

}
//布局文件中控件是类的全路径
<pre name="code" class="java">    <com.example.myview.MyView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
          android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
         />