如何在安卓的文本视图周围设置边框？

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public class BorderedTextView extends TextView {
        private Paint paint = new Paint();
        public static final int BORDER_TOP = 0x00000001;
        public static final int BORDER_RIGHT = 0x00000002;
        public static final int BORDER_BOTTOM = 0x00000004;
        public static final int BORDER_LEFT = 0x00000008;

        private Border[] borders;

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

        public BorderedTextView(Context context, AttributeSet attrs) {
            super(context, attrs);
            init();
        }

        public BorderedTextView(Context context) {
            super(context);
            init();
        }
        private void init(){
            paint.setStyle(Paint.Style.STROKE);
            paint.setColor(Color.BLACK);
            paint.setStrokeWidth(4);        
        }
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            if(borders == null) return;

            for(Border border : borders){
                paint.setColor(border.getColor());
                paint.setStrokeWidth(border.getWidth());

                if(border.getStyle() == BORDER_TOP){
                    canvas.drawLine(0, 0, getWidth(), 0, paint);                
                } else
                if(border.getStyle() == BORDER_RIGHT){
                    canvas.drawLine(getWidth(), 0, getWidth(), getHeight(), paint);
                } else
                if(border.getStyle() == BORDER_BOTTOM){
                    canvas.drawLine(0, getHeight(), getWidth(), getHeight(), paint);
                } else
                if(border.getStyle() == BORDER_LEFT){
                    canvas.drawLine(0, 0, 0, getHeight(), paint);
                }
            }
        }

        public Border[] getBorders() {
            return borders;
        }

        public void setBorders(Border[] borders) {
            this.borders = borders;
        }
}

public class Border {
    private int orientation;
    private int width;
    private int color = Color.BLACK;
    private int style;
    public int getWidth() {
        return width;
    }
    public void setWidth(int width) {
        this.width = width;
    }
    public int getColor() {
        return color;
    }
    public void setColor(int color) {
        this.color = color;
    }
    public int getStyle() {
        return style;
    }
    public void setStyle(int style) {
        this.style = style;
    }
    public int getOrientation() {
        return orientation;
    }
    public void setOrientation(int orientation) {
        this.orientation = orientation;
    }
    public Border(int Style) {
        this.style = Style;
    }
}

@Override
public void draw(Canvas canvas, MapView mapView, boolean shadow) {

Paint strokePaint = new Paint();
strokePaint.setARGB(255, 0, 0, 0);
strokePaint.setTextAlign(Paint.Align.CENTER);
strokePaint.setTextSize(16);
strokePaint.setTypeface(Typeface.DEFAULT_BOLD);
strokePaint.setStyle(Paint.Style.STROKE);
strokePaint.setStrokeWidth(2);

Paint textPaint = new Paint();
textPaint.setARGB(255, 255, 255, 255);
textPaint.setTextAlign(Paint.Align.CENTER);
textPaint.setTextSize(16);
textPaint.setTypeface(Typeface.DEFAULT_BOLD);

canvas.drawText("Some Text", 100, 100, strokePaint);
canvas.drawText("Some Text", 100, 100, textPaint);

super.draw(canvas, mapView, shadow); 
}

public static GradientDrawable backgroundWithoutBorder(int color) {

    GradientDrawable gdDefault = new GradientDrawable();
    gdDefault.setColor(color);
    gdDefault.setCornerRadii(new float[] { radius, radius, 0, 0, 0, 0,
                                           radius, radius });
    return gdDefault;
}

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ImageView selectionBorder = BorderDrawer.generateBorderImageView(context, borderWidth, borderHeight, thickness, Color.Blue);

/**
 * Because creating a border is Rocket Science in Android.
 */
public class BorderDrawer
{
    public static ImageView generateBorderImageView(Context context, int borderWidth, int borderHeight, int borderThickness, int color)
    {
        ImageView mask = new ImageView(context);

        // Create the square to serve as the mask
        Bitmap squareMask = Bitmap.createBitmap(borderWidth - (borderThickness*2), borderHeight - (borderThickness*2), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(squareMask);

        Paint paint = new Paint();
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(color);
        canvas.drawRect(0.0f, 0.0f, (float)borderWidth, (float)borderHeight, paint);

        // Create the darkness bitmap
        Bitmap solidColor = Bitmap.createBitmap(borderWidth, borderHeight, Bitmap.Config.ARGB_8888);
        canvas = new Canvas(solidColor);

        paint.setStyle(Paint.Style.FILL);
        paint.setColor(color);
        canvas.drawRect(0.0f, 0.0f, borderWidth, borderHeight, paint);

        // Create the masked version of the darknessView
        Bitmap borderBitmap = Bitmap.createBitmap(borderWidth, borderHeight, Bitmap.Config.ARGB_8888);
        canvas = new Canvas(borderBitmap);

        Paint clearPaint = new Paint();
        clearPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

        canvas.drawBitmap(solidColor, 0, 0, null);
        canvas.drawBitmap(squareMask, borderThickness, borderThickness, clearPaint);

        clearPaint.setXfermode(null);

        ImageView borderView = new ImageView(context);
        borderView.setImageBitmap(borderBitmap);

        return borderView;
    }
}

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<selector xmlns:android="http://schemas.android.com/apk/res/android">

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