CODEWITHSUNDEEP
androidcanvas
Liron Navon
Liron Navon

Reputation: 1097

android canvas draw shapes with ghost

I am trying to create a simple drawing app I which the user can press a point of my custom view and drag it to create a rectangle or a circle, I managed to do it quite easily.

The problem arose when I try showing the user the progress of move their shape as it grow bigger or smaller.

To explain it simply I want the same effect as on windows if you click and drag your mouse on the desktop.

This is my onTouchEvent method, how do I do it?

if (chosenShape.equals("rectangle")) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN: // user start pressing
            //starting point - one side of the rect
            starting_X = touchX;
            starting_Y = touchY;
            break;
        case MotionEvent.ACTION_MOVE: // user move while pressing

            break;
        case MotionEvent.ACTION_UP: // user release
            //ending point - thie side of the circle
            ending_X = touchX;
            ending_Y = touchY;
            // draw the rectangle - opposite side of the rect
            drawCanvas.drawRect(starting_X, starting_Y, ending_X, ending_Y, drawPaint);
            chosenShape = ""; // reseting the shape to keep drawing
            break;
        default:
            return false;

    }
} else {
    switch (event.getAction()) {

        case MotionEvent.ACTION_DOWN:
            drawPath.moveTo(touchX, touchY);
            break;
        case MotionEvent.ACTION_MOVE:
            drawPath.lineTo(touchX, touchY);
            break;
        case MotionEvent.ACTION_UP:
            drawCanvas.drawPath(drawPath, drawPaint);
            drawPath.reset();
            break;
        default:
            return false;
    }
}

Upvotes: 0

Views: 95

Answers (1)

ScouseChris
ScouseChris

Reputation: 4397

In your case MotionEvent.ACTION_MOVE: you need to set the ending_X and ending_Y values.

Better yet would be to track intermediate_x and intermediate_y so you can draw a different effect, for example a dashed line instead of solid.

You're probably best storing all the shapes a user has drawn and refreshing the canvas each time a touch event comes in, otherwise you'll get the shapes drawn over each other as you drag ad they won't be cleared.

Upvotes: 1

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