手势密码View 的 onDraw实现

@Override
    protected void onDraw(Canvas canvas) {
        final ArrayList<Cell> pattern = mPattern;
        final int count = pattern.size();
        final boolean[][] drawLookup = mPatternDrawLookup;

        if (mPatternDisplayMode == DisplayMode.Animate) {

            // figure out which circles to draw

            // + 1 so we pause on complete pattern
            final int oneCycle = (count + 1) * MILLIS_PER_CIRCLE_ANIMATING;
            final int spotInCycle = (int) (SystemClock.elapsedRealtime() -
                    mAnimatingPeriodStart) % oneCycle;
            final int numCircles = spotInCycle / MILLIS_PER_CIRCLE_ANIMATING;

            clearPatternDrawLookup();
            for (int i = 0; i < numCircles; i++) {
                final Cell cell = pattern.get(i);
                drawLookup[cell.getRow()][cell.getColumn()] = true;
            }

            // figure out in progress portion of ghosting line

            final boolean needToUpdateInProgressPoint = numCircles > 0
                    && numCircles < count;

            if (needToUpdateInProgressPoint) {
                final float percentageOfNextCircle =
                        ((float) (spotInCycle % MILLIS_PER_CIRCLE_ANIMATING)) /
                                MILLIS_PER_CIRCLE_ANIMATING;

                final Cell currentCell = pattern.get(numCircles - 1);
                final float centerX = getCenterXForColumn(currentCell.column);
                final float centerY = getCenterYForRow(currentCell.row);

                final Cell nextCell = pattern.get(numCircles);
                final float dx = percentageOfNextCircle *
                        (getCenterXForColumn(nextCell.column) - centerX);
                final float dy = percentageOfNextCircle *
                        (getCenterYForRow(nextCell.row) - centerY);
                mInProgressX = centerX + dx;
                mInProgressY = centerY + dy;
            }
            // TODO: Infinite loop here...
            invalidate();
        }

        final Path currentPath = mCurrentPath;
        currentPath.rewind();

        // draw the circles
        for (int i = 0; i < 3; i++) {
            float centerY = getCenterYForRow(i);
            for (int j = 0; j < 3; j++) {
                CellState cellState = mCellStates[i][j];
                float centerX = getCenterXForColumn(j);
                float translationY = cellState.translationY;
                if (isHardwareAccelerated() && cellState.hwAnimating) {
                    DisplayListCanvas displayListCanvas = (DisplayListCanvas) canvas;
                    displayListCanvas.drawCircle(cellState.hwCenterX, cellState.hwCenterY,
                            cellState.hwRadius, cellState.hwPaint);
                } else {
                    drawCircle(canvas, (int) centerX, (int) centerY + translationY,
                            cellState.radius, drawLookup[i][j], cellState.alpha);

                }
            }
        }

        // TODO: the path should be created and cached every time we hit-detect a cell
        // only the last segment of the path should be computed here
        // draw the path of the pattern (unless we are in stealth mode)
        final boolean drawPath = !mInStealthMode;

        if (drawPath) {
            mPathPaint.setColor(getCurrentColor(true /* partOfPattern */));

            boolean anyCircles = false;
            float lastX = 0f;
            float lastY = 0f;
            for (int i = 0; i < count; i++) {
                Cell cell = pattern.get(i);

                // only draw the part of the pattern stored in
                // the lookup table (this is only different in the case
                // of animation).
                if (!drawLookup[cell.row][cell.column]) {
                    break;
                }
                anyCircles = true;

                float centerX = getCenterXForColumn(cell.column);
                float centerY = getCenterYForRow(cell.row);
                if (i != 0) {
                    CellState state = mCellStates[cell.row][cell.column];
                    currentPath.rewind();
                    currentPath.moveTo(lastX, lastY);
                    if (state.lineEndX != Float.MIN_VALUE && state.lineEndY != Float.MIN_VALUE) {
                        currentPath.lineTo(state.lineEndX, state.lineEndY);
                    } else {
                        currentPath.lineTo(centerX, centerY);
                    }
                    canvas.drawPath(currentPath, mPathPaint);
                }
                lastX = centerX;
                lastY = centerY;
            }

            // draw last in progress section
            if ((mPatternInProgress || mPatternDisplayMode == DisplayMode.Animate)
                    && anyCircles) {
                currentPath.rewind();
                currentPath.moveTo(lastX, lastY);
                currentPath.lineTo(mInProgressX, mInProgressY);

                mPathPaint.setAlpha((int) (calculateLastSegmentAlpha(
                        mInProgressX, mInProgressY, lastX, lastY) * 255f));
                canvas.drawPath(currentPath, mPathPaint);
            }
        }
    }