java - Android绘图保存到数据库

Question

我的应用程序有签名板。我使用 DrawView 和 FrameLayout 来显示它。如何将签名保存在数据库中。下面是我的代码。非常感谢任何建议或帮助。

Summary.java

FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
DrawView drawView = new DrawView(this);
drawView.requestFocus();
preview.addView(drawView);

DrawView.java

public class DrawView 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();

    public DrawView(Context context) {
        super(context);

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

    /** Erases the signature. */
    public void clear() {
        path.reset();

        // Repaints the entire view.
        invalidate();
    }

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

    @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();
            // Logger.debug("historySize : " + historySize);
            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.
            // Logger.debug("eventX " + eventX);
            // Logger.debug("eventY " + eventX);
            //
            // Logger.debug("lastTouchX " + lastTouchX);
            // Logger.debug("lastTouchY " + lastTouchY);
            //
            // if (eventX == lastTouchX && eventY == lastTouchY) {
            //
            // path.addCircle(eventX, eventY, 20, Path.Direction.CW);
            //
            // }

            path.lineTo(eventX, eventY);

            break;

        default:
            // Logger.debug("Ignored touch event: " + event.toString());
            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);
    }
}

Answer 1

您可以这样获取签名图像数据:

// in Activity code, maybe on a button click or onSaveInstanceState
// get a reference to the view
View drawView = getMyDrawViewFromSomewhere();

// get signature as a bitmap
drawView.buildDrawingCache();
Bitmap signature = drawView.getDrawingCache();

// convert to byte[]
ByteArrayOutputStream stream = new ByteArrayOutputStream();
signature.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

然后将其保存到数据库中，如下所示:

// get your database
SQLiteDatabase db = getMySQLiteOpenHelperFromSomewhere().getWritableDatabase();
ContentValues values = new ContentValues();
// The column names here will depend on your schema, of course.
// This would work with:
// CREATE TABLE `signature_table` (`username` VARCHAR, `signature_image` BLOB);
values.put("username", getTheUserName());
values.put("signature_image", byteArray);
db.insert("signature_table", null, values);

不要忘记清理:

signature.recycle();
drawView.destroyDrawingCache();

有关数据库的更多基础知识(如果您尚未设置):http://developer.android.com/training/basics/data-storage/databases.html