Android开发TextvView实现镂空字体效果

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自定义TextView

public class HollowTextView extends AppCompatTextView {
    private Paint mTextPaint, mBackgroundPaint;
    private Bitmap mBackgroundBitmap,mTextBitmap;
    private Canvas mBackgroundCanvas,mTextCanvas;
    private RectF mBackgroundRect;
    private int mBackgroundColor;
    private float mCornerRadius;

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

    public HollowTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initAttrs(attrs,0);
        initPaint();
    }

    public HollowTextView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initAttrs(attrs,defStyleAttr);
        initPaint();
    }


    private void initAttrs(AttributeSet attrs,int defStyleAttr){
        if(attrs == null){
            return;
        }
        TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.HollowTextView, defStyleAttr, 0);
        mBackgroundColor = typedArray.getColor(R.styleable.HollowTextView_hollowTextView_background_color, Color.TRANSPARENT);
        mCornerRadius = typedArray.getDimension(R.styleable.HollowTextView_hollowTextView_corner_radius,0);
        typedArray.recycle();
    }

    /***
     * 初始化画笔属性
     */
    private void initPaint() {
        //画文字的paint
        mTextPaint = new Paint();
        //这是镂空的关键
        mTextPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        mTextPaint.setAntiAlias(true);
        mBackgroundPaint = new Paint();
        mBackgroundPaint.setColor(mBackgroundColor);
        mBackgroundPaint.setAntiAlias(true);

    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mBackgroundBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_4444);
        mBackgroundCanvas = new Canvas(mBackgroundBitmap);
        mTextBitmap = Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_4444);
        mTextCanvas = new Canvas(mTextBitmap);
        mBackgroundRect = new RectF(0,0,getWidth(),getHeight());
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //这里给super传入的是mTextCanvas，把一些基本属性都支持进去
        super.onDraw(mTextCanvas);
        drawBackground(mBackgroundCanvas);
        int sc;
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP ){
            sc = canvas.saveLayer(0,0,getMeasuredWidth(),getMeasuredHeight(),null);
        }else {
            sc = canvas.saveLayer(0,0,getMeasuredWidth(),getMeasuredHeight(),null,Canvas.ALL_SAVE_FLAG);
        }
        canvas.drawBitmap(mBackgroundBitmap,0,0,null);
        canvas.drawBitmap(mTextBitmap, 0, 0, mTextPaint);
        canvas.restoreToCount(sc);
    }

    private void drawBackground(Canvas canvas){
        if(mCornerRadius > 0){
            canvas.drawRoundRect(mBackgroundRect,mCornerRadius,mCornerRadius, mBackgroundPaint);
        }else {
            canvas.drawColor(mBackgroundColor);
        }
    }public clas