速读原著-Android应用开发入门教程(文本的对齐方式)

    private static class SampleView extends View {
        private Paint mPaint;
        private float mX;
        private float[] mPos;

        private Path mPath;
        private Paint mPathPaint;

        private static final int DY = 30;
        private static final String TEXT_L = "Left";
        private static final String TEXT_C = "Center";
        private static final String TEXT_R = "Right";
        private static final String POSTEXT = "Positioned";
        private static final String TEXTONPATH = "Along a path";

        private static void makePath(Path p) {
            p.moveTo(10, 0);
            p.cubicTo(100, -50, 200, 50, 300, 0);
        }
        private float[] buildTextPositions(String text, float y, Paint paint) {
            // 省略，计算位置信息等内容
            return pos;
        }

        public SampleView(Context context) {
            super(context);
            setFocusable(true);
            mPaint = new Paint();
            mPaint.setAntiAlias(true);
            mPaint.setTextSize(30);
            mPaint.setTypeface(Typeface.SERIF);

            mPos = buildTextPositions(POSTEXT, 0, mPaint);
            mPath = new Path();
            makePath(mPath); // 建立路径
            mPathPaint = new Paint();
            mPathPaint.setAntiAlias(true);
            mPathPaint.setColor(0x800000FF);
            mPathPaint.setStyle(Paint.Style.STROKE);
        }
        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.WHITE);
            Paint p = mPaint; // 获得画笔
            float x = mX;
            float y = 0;
            float[] pos = mPos;
            // 绘制正常的字串
            p.setColor(0x80FF0000); // 绘制一条线
            canvas.drawLine(x, y, x, y+DY*3, p);
            p.setColor(Color.BLACK);
            canvas.translate(0, DY);
            p.setTextAlign(Paint.Align.LEFT); // 绘制左对齐的文本
            canvas.drawText(TEXT_L, x, y, p);
            canvas.translate(0, DY);
            p.setTextAlign(Paint.Align.CENTER); // 绘制中对齐的文本
            canvas.drawText(TEXT_C, x, y, p);
            canvas.translate(0, DY);
            p.setTextAlign(Paint.Align.RIGHT); // 绘制右对齐的文本
            canvas.drawText(TEXT_R, x, y, p);
            // 绘制根据位置的的字串
            canvas.translate(100, DY*2);
            p.setColor(0xBB00FF00);
            for (int i = 0; i < pos.length/2; i++) {
                canvas.drawLine(pos[i*2+0], pos[i*2+1]-DY,
                        pos[i*2+0], pos[i*2+1]+DY*2, p);
            } // 绘制若干条线
            p.setColor(Color.BLACK);
            p.setTextAlign(Paint.Align.LEFT);
            canvas.drawPosText(POSTEXT, pos, p); // 绘制左对齐的文本
            canvas.translate(0, DY);
            p.setTextAlign(Paint.Align.CENTER);
            canvas.drawPosText(POSTEXT, pos, p); // 绘制中对齐的文本
            canvas.translate(0, DY);
            p.setTextAlign(Paint.Align.RIGHT);
            canvas.drawPosText(POSTEXT, pos, p); // 绘制右对齐的文本

            // 绘制在路径上的的字串
            canvas.translate(-100, DY*2); // 重定画布的位置
            canvas.drawPath(mPath, mPathPaint);
            p.setTextAlign(Paint.Align.LEFT);
            canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p); // 绘制对齐路径的文本
            canvas.translate(0, DY*1.5f);
            canvas.drawPath(mPath, mPathPaint);
            p.setTextAlign(Paint.Align.CENTER);
            canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p); // 绘制对齐路径的文本
            canvas.translate(0, DY*1.5f);
            canvas.drawPath(mPath, mPathPaint);
            p.setTextAlign(Paint.Align.RIGHT);
            canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p); // 绘制对齐路径的文本
        }
        // 省略部分内容
    }