android 签字版

public class DrawLineLayout extends View {
    private static final float STROKE_WIDTH = 5f;

    /** Need to track this so the dirty region can accommodate the stroke. **/
    private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;

    private Paint paint = new Paint();
    private Path path = new Path();

    /**
     * Optimizes painting by invalidating the smallest possible area.
     */
    private float lastTouchX;
    private float lastTouchY; 
    private final RectF dirtyRect = new RectF();
    private Bitmap cachebBitmap;

    public DrawLineLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

        paint.setAntiAlias(true);
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeWidth(STROKE_WIDTH);
    }

    /**
     * 用于清空你已经绘制好的图
     */
    public void clear() {
        path.reset();

        // Repaints the entire view.
        invalidate();//重新调用绘制
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawPath(path, paint);
    }

//更加触摸点绘制线
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float eventX = event.getX();
        float eventY = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                path.moveTo(eventX, eventY);
                lastTouchX = eventX;
                lastTouchY = eventY;
                // There is no end point yet, so don't waste cycles invalidating.
                return true;

            case MotionEvent.ACTION_MOVE:
            case MotionEvent.ACTION_UP:
                // Start tracking the dirty region.
                resetDirtyRect(eventX, eventY);

                // When the hardware tracks events faster than they are delivered, the
                // event will contain a history of those skipped points.
                int historySize = event.getHistorySize();
                for (int i = 0; i < historySize; i++) {
                    float historicalX = event.getHistoricalX(i);
                    float historicalY = event.getHistoricalY(i);
                    expandDirtyRect(historicalX, historicalY);
                    path.lineTo(historicalX, historicalY);
                }

                // After replaying history, connect the line to the touch point.
                path.lineTo(eventX, eventY);
                break;

            default:

                return false;
        }

        // Include half the stroke width to avoid clipping.
        invalidate(
                (int) (dirtyRect.left - HALF_STROKE_WIDTH),
                (int) (dirtyRect.top - HALF_STROKE_WIDTH),
                (int) (dirtyRect.right + HALF_STROKE_WIDTH),
                (int) (dirtyRect.bottom + HALF_STROKE_WIDTH));

        lastTouchX = eventX;
        lastTouchY = eventY;

        return true;
    }

    /**
     * Called when replaying history to ensure the dirty region includes all
     * points.
     */
    private void expandDirtyRect(float historicalX, float historicalY) {
        if (historicalX < dirtyRect.left) {
            dirtyRect.left = historicalX;
        } else if (historicalX > dirtyRect.right) {
            dirtyRect.right = historicalX;
        }
        if (historicalY < dirtyRect.top) {
            dirtyRect.top = historicalY;
        } else if (historicalY > dirtyRect.bottom) {
            dirtyRect.bottom = historicalY;
        }
    }

    /**
     * Resets the dirty region when the motion event occurs.
     */
    private void resetDirtyRect(float eventX, float eventY) {

        // The lastTouchX and lastTouchY were set when the ACTION_DOWN
        // motion event occurred.
        dirtyRect.left = Math.min(lastTouchX, eventX);
        dirtyRect.right = Math.max(lastTouchX, eventX);
        dirtyRect.top = Math.min(lastTouchY, eventY);
        dirtyRect.bottom = Math.max(lastTouchY, eventY);
    }
    /**
     * 保存view视图的bitmap信息
     * @return bitmap数据
     */
    public Bitmap getImage() {
        Bitmap bitmap = Bitmap.createBitmap(1920, 1080, Bitmap.Config.RGB_565);
        Canvas canvas = new Canvas(bitmap);
        /**
         * 绘制背景
         */
        Drawable bgDrawable = getBackground();
        if (bgDrawable != null)
            bgDrawable.draw(canvas);
        else
            canvas.drawColor(Color.WHITE);
        draw(canvas);// 绘制view视图的内容
        return bitmap;
    }
    /**
     * 将图像保存到文件
     * @return 返回false表示保存失败
     */
    public boolean saveImageToFile(String filePath) {
        try {
            File file = new File(filePath);
            if (!file.exists()) {
                file.createNewFile();
            }
            FileOutputStream fos = new FileOutputStream(file);
            getImage().compress(Bitmap.CompressFormat.PNG, 100, fos);
            fos.flush();
            fos.close();
//            Toast.makeText(getContext(),"wanc",Toast.LENGTH_SHORT).show();
            return true;
        } catch (FileNotFoundException e) {
            return false;
        } catch (IOException e) {
            return false;
        }
    }

}