3.自定义view-TextView变色

1.效果

2.实现原理

自定义Textview，重写onDraw方法，将画布分成两部分，用不同颜色的画笔画

核心代码：

    @Override
    protected void onDraw(Canvas canvas) {
//super.onDraw(canvas);
        int middle = (int) (mProcess * getWidth());
        if (mDirection == Direction.LEFT_TO_RIGHT) {
            //变色区域
            drawText(canvas, 0, middle, mChangePaint);
            //默认区域
            drawText(canvas, middle, getWidth(), mDefaultPaint);
        } else {
            //默认区域
            drawText(canvas, 0, getWidth() - middle, mDefaultPaint);
            //变色区域
            drawText(canvas, getWidth() - middle, getWidth(), mChangePaint);
        }    }

    /**
     * 裁剪画布->画文字
     *
     * @param canvas
     * @param start
     * @param end
     * @param paint
     */
    private void drawText(Canvas canvas, int start, int end, Paint paint) {
        canvas.save();
        //裁剪画布
        canvas.clipRect(start, 0, end, getHeight());
        String text = getText().toString();        //获取文字起点
        Rect bounds = new Rect();
        paint.getTextBounds(text, 0, text.length(), bounds);
        int x = getWidth() / 2 - bounds.width() / 2;        //获取基线
        Paint.FontMetricsInt fontMetrics = paint.getFontMetricsInt();
        int dy = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
        int baseLine = getHeight() / 2 + dy;        canvas.drawText(text, x, baseLine, paint);
        canvas.restore();    }

源码地址