自定义圆形背景的TextView

继承TextView类,

首先是构造方法, 两参()构造是解析布局文件时调用的, 所以相关的操作在这个方法中定义.

在onDraw()方法里,

1. 使用canvas.drawCircle(float cx, float cy, float radius, Paint paint)方法绘制一个圆. 圆的颜色由Paint参数决定. 在初始化以及设置颜色的方法中设置Paint的颜色参数. 
2. 使用canvas.drawBitmap(Bitmat bitmap, float left, float top, Paint paint); 方法绘制背景之上的图案.

使用validate()方法会造成View的重绘, 并重新调用onDraw方法.

附上完整代码:

public class MyTextView extends TextView {
    private static final String NAME_SPACE = "http://demo.com/src";
	private Paint mBgPaint = new Paint();
	private Bitmap mForePic;
	private float mBgRadius = -1;

	public MyTextView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		init();
	}

	public MyTextView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
		mBgPaint.setColor(attrs.getAttributeIntValue(NAME_SPACE, "backgroundColor", Color.TRANSPARENT));
		int forePicId = attrs.getAttributeResourceValue(NAME_SPACE, "forepic", -1);
		mBgRadius = attrs.getAttributeIntValue(NAME_SPACE, "bgraidus", -1);
		setForePic(forePicId);
		setBackgroundRadius(mBgRadius);
	}

	public MyTextView(Context context) {
		super(context);
		init();
	}

	private void init() {
		mBgPaint.setColor(Color.TRANSPARENT);
		mBgPaint.setAntiAlias(true);
		this.setGravity(Gravity.CENTER);
	}

	@Override
	public void setBackgroundColor(int color) {
		mBgPaint.setColor(color);
	}
	
	@Override
	public void onDraw(Canvas canvas) {
		//如果没有设置半径, 默认为View的宽高的一半
		if (mBgRadius == -1) {
			mBgRadius = Math.max(getWidth(), getHeight()) / 2;
		}
		canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBgRadius, mBgPaint);
		if (mForePic != null) {
			super.setText("");
			canvas.drawBitmap(mForePic,
					(getMeasuredWidth() - mForePic.getWidth()) / 2,
					(getMeasuredHeight() - mForePic.getHeight()) / 2, null);
		}
		super.onDraw(canvas);
	}

	/**
	 * 设置前景图片
	 * 
	 * @param resId
	 *            图片资源的id
	 */
	public void setForePic(int resId) {
		mForePic = BitmapFactory.decodeResource(getResources(), resId);
		//invalidate();
	}

	/**
	 * 设置前景图片
	 * 
	 * @param drawable
	 */
	public void setForePic(Drawable drawable) {
		mForePic = ((BitmapDrawable) drawable).getBitmap();
		invalidate();
	}

	/**
	 * 设置背景圆形的半径
	 * @param radius
	 */
	public void setBackgroundRadius(float radius) {
		this.mBgRadius = radius;
	}