android.apis.graphics 画图（引）

  //设置Path路径
      private static void makePath(Path p) {
          p.moveTo(10, 0);
          p.cubicTo(100, -50, 200, 50, 300, 0);//贝赛尔曲线
     }

  private float[] buildTextPositions(String text, float y, Paint paint) {
          float[] widths = new float[text.length()];
          // initially get the widths for each char
          int n = paint.getTextWidths(text, widths);
          // now popuplate the array, interleaving spaces for the Y values X值为字符的宽
          float[] pos = new float[n * 2];
          float accumulatedX = 0;
          for (int i = 0; i < n; i++) {
              pos[i * 2 + 0] = accumulatedX;
              pos[i * 2 + 1] = y;
              accumulatedX += widths[i];
          }
          return pos;
      }

  p.setColor(0x80FF0000);
              canvas.drawLine(x, y, x, y + DY * 3, p);//(x,y)为基准线
              p.setColor(Color.BLACK);
  
              canvas.translate(0, DY);
              p.setTextAlign(Paint.Align.LEFT);
              canvas.drawText(TEXT_L, x, y, p);//以（x,y）点Paint.Align.LEFT，

  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);
      }
      p.setColor(Color.BLACK);
  
      p.setTextAlign(Paint.Align.LEFT);
      canvas.drawPosText(POSTEXT, pos, p);

  canvas.drawPath(mPath, mPathPaint);
              p.setTextAlign(Paint.Align.LEFT);
              canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p);
  
             canvas.translate(0, DY * 1.5f);
               canvas.drawPath(mPath, mPathPaint);
              p.setTextAlign(Paint.Align.CENTER);
             canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p);
 
              canvas.translate(0, DY * 1.5f);
              canvas.drawPath(mPath, mPathPaint);
              p.setTextAlign(Paint.Align.RIGHT);
              canvas.drawTextOnPath(TEXTONPATH, mPath, 0, 0, p);

  mFace = Typeface.createFromAsset(getContext().getAssets(),
              "fonts/samplefont.ttf");

  @Override
         protected void onDraw(Canvas canvas) {
              canvas.drawColor(Color.WHITE);
  
              mPaint.setTypeface(null);
              canvas.drawText("Default", 10, 100, mPaint);
              mPaint.setTypeface(mFace);
             canvas.drawText("Custom", 10, 200, mPaint);
          }

  static Bitmap makeDst(int w, int h) {
          Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
          Canvas c = new Canvas(bm);
          Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
          p.setColor(0xFFFFCC44);
          c.drawOval(new RectF(0, 0, w * 3 / 4, h * 3 / 4), p);
          return bm;
      }

  static Bitmap makeSrc(int w, int h) {
          Bitmap bm = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
          Canvas c = new Canvas(bm);
          Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
  
          p.setColor(0xFF66AAFF);
          c.drawRect(w / 3, h / 3, w * 19 / 20, h * 19 / 20, p);
          return bm;
     }

  Bitmap bm = Bitmap.createBitmap(new int[] { 0xFFFFFFFF, 0xFFCCCCCC,
                  0xFFCCCCCC, 0xFFFFFFFF }, 2, 2, Bitmap.Config.RGB_565);
              mBG = new BitmapShader(bm, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
              Matrix m = new Matrix();
              m.setScale(6, 6);// 放大6倍
              mBG.setLocalMatrix(m);

  private static final Xfermode[] sModes = {
              new PorterDuffXfermode(PorterDuff.Mode.CLEAR),
              new PorterDuffXfermode(PorterDuff.Mode.SRC),
              new PorterDuffXfermode(PorterDuff.Mode.DST),
              new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER),
              new PorterDuffXfermode(PorterDuff.Mode.DST_OVER),
              new PorterDuffXfermode(PorterDuff.Mode.SRC_IN),
              new PorterDuffXfermode(PorterDuff.Mode.DST_IN),
              new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT),
              new PorterDuffXfermode(PorterDuff.Mode.DST_OUT),
              new PorterDuffXfermode(PorterDuff.Mode.SRC_ATOP),
              new PorterDuffXfermode(PorterDuff.Mode.DST_ATOP),
              new PorterDuffXfermode(PorterDuff.Mode.XOR),
              new PorterDuffXfermode(PorterDuff.Mode.DARKEN),
              new PorterDuffXfermode(PorterDuff.Mode.LIGHTEN),
              new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY),
              new PorterDuffXfermode(PorterDuff.Mode.SCREEN) };

   @Override
           protected void onDraw(Canvas canvas) {
               canvas.drawColor(Color.WHITE);
   
               Paint labelP = new Paint(Paint.ANTI_ALIAS_FLAG);
               labelP.setTextAlign(Paint.Align.CENTER);
   
               Paint paint = new Paint();
               paint.setFilterBitmap(false);
  
              canvas.translate(15, 35);
  
              int x = 0;
              int y = 0;
              for (int i = 0; i < sModes.length; i++) {
                  // draw the border
                  paint.setStyle(Paint.Style.STROKE);
                  paint.setShader(null);// Pass null to clear any previous shader
                  canvas.drawRect(x - 0.5f, y - 0.5f, x + W + 0.5f, y + H + 0.5f, paint);
  
                  // draw the checker-board pattern
                  paint.setStyle(Paint.Style.FILL);
                  paint.setShader(mBG);
                  canvas.drawRect(x, y, x + W, y + H, paint);
  
                  // draw the src/dst example into our offscreen bitmap
                  int sc = canvas.saveLayer(x, y, x + W, y + H, null,
                      Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG
                          | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
                          | Canvas.FULL_COLOR_LAYER_SAVE_FLAG
                          | Canvas.CLIP_TO_LAYER_SAVE_FLAG);
                  // canvas.save();
                  canvas.translate(x, y);
                  canvas.drawBitmap(mDstB, 0, 0, paint);
                  paint.setXfermode(sModes[i]);
                  canvas.drawBitmap(mSrcB, 0, 0, paint);