how to rotate canvas android

To rotate a canvas in Android using C++, you can follow these steps:

  1. Get the current transformation matrix: Use the getMatrix() method of the Canvas class to retrieve the current transformation matrix.

  2. Save the current state: Save the current state of the canvas using the save() method of the Canvas class. This allows you to restore the canvas to its original state after applying the rotation.

  3. Apply the rotation: Use the rotate() method of the Matrix class to apply the desired rotation to the transformation matrix. The rotate() method takes the rotation angle in degrees as a parameter.

  4. Set the new transformation matrix: Use the setMatrix() method of the Canvas class to set the modified transformation matrix as the new transformation matrix for the canvas.

  5. Draw on the canvas: Perform any drawing operations on the canvas using the modified transformation matrix. The drawings will now be rotated according to the applied rotation.

  6. Restore the original state: After drawing on the canvas, use the restore() method of the Canvas class to restore the canvas to its original state before the rotation was applied.

Here is an example code snippet to rotate a canvas in Android using C++:

// Get the current transformation matrix
SkMatrix currentMatrix = canvas->getTotalMatrix();

// Save the current state
canvas->save();

// Apply the rotation
float rotationAngle = 45.0f; // Set the desired rotation angle
currentMatrix.rotate(rotationAngle);

// Set the new transformation matrix
canvas->setMatrix(currentMatrix);

// Draw on the canvas
// ...

// Restore the original state
canvas->restore();

Please note that this example assumes you already have a Canvas object available. You'll need to modify the code to fit your specific use case.