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POOne finger zoom + rotate in Android
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copied!<p>I was developing a zoom control in android based on the tutorial: <a href="http://blogs.sonyericsson.com/developerworld/2010/07/07/android-one-finger-zoom-tutorial-part-4/" rel="nofollow">Android one finger zoom tutorial</a></p> <pre><code>public abstract class Dynamics { /** * The maximum delta time, in milliseconds, between two updates */ private static final int MAX_TIMESTEP = 50; /** The current position */ protected float mPosition; /** The current velocity */ protected float mVelocity; /** The current maximum position */ protected float mMaxPosition = Float.MAX_VALUE; /** The current minimum position */ protected float mMinPosition = -Float.MAX_VALUE; /** The time of the last update */ protected long mLastTime = 0; /** * Sets the state of the dynamics object. Should be called before starting * to call update. * * @param position The current position. * @param velocity The current velocity in pixels per second. * @param now The current time */ public void setState(final float position, final float velocity, final long now) { mVelocity = velocity; mPosition = position; mLastTime = now; } /** * Returns the current position. Normally used after a call to update() in * order to get the updated position. * * @return The current position */ public float getPosition() { return mPosition; } /** * Gets the velocity. Unit is in pixels per second. * * @return The velocity in pixels per second */ public float getVelocity() { return mVelocity; } /** * Used to find out if the list is at rest, that is, has no velocity and is * inside the the limits. Normally used to know if more calls to update are * needed. * * @param velocityTolerance Velocity is regarded as 0 if less than * velocityTolerance * @param positionTolerance Position is regarded as inside the limits even * if positionTolerance above or below * * @return true if list is at rest, false otherwise */ public boolean isAtRest(final float velocityTolerance, final float positionTolerance) { final boolean standingStill = Math.abs(mVelocity) < velocityTolerance; final boolean withinLimits = mPosition - positionTolerance < mMaxPosition && mPosition + positionTolerance > mMinPosition; return standingStill && withinLimits; } /** * Sets the maximum position. * * @param maxPosition The maximum value of the position */ public void setMaxPosition(final float maxPosition) { mMaxPosition = maxPosition; } /** * Sets the minimum position. * * @param minPosition The minimum value of the position */ public void setMinPosition(final float minPosition) { mMinPosition = minPosition; } /** * Updates the position and velocity. * * @param now The current time */ public void update(final long now) { int dt = (int)(now - mLastTime); if (dt > MAX_TIMESTEP) { dt = MAX_TIMESTEP; } onUpdate(dt); mLastTime = now; } /** * Gets the distance to the closest limit (max and min position). * * @return If position is more than max position: distance to max position. If * position is less than min position: distance to min position. If * within limits: 0 */ protected float getDistanceToLimit() { float distanceToLimit = 0; if (mPosition > mMaxPosition) { distanceToLimit = mMaxPosition - mPosition; } else if (mPosition < mMinPosition) { distanceToLimit = mMinPosition - mPosition; } return distanceToLimit; } /** * Updates the position and velocity. * * @param dt The delta time since last time */ abstract protected void onUpdate(int dt); } </code></pre> <hr> <pre><code>public class SpringDynamics extends Dynamics { /** Friction factor */ private float mFriction; /** Spring stiffness factor */ private float mStiffness; /** Spring damping */ private float mDamping; /** * Set friction parameter, friction physics are applied when inside of snap * bounds. * * @param friction Friction factor */ public void setFriction(float friction) { mFriction = friction; } /** * Set spring parameters, spring physics are applied when outside of snap * bounds. * * @param stiffness Spring stiffness * @param dampingRatio Damping ratio, < 1 underdamped, > 1 overdamped */ public void setSpring(float stiffness, float dampingRatio) { mStiffness = stiffness; mDamping = dampingRatio * 2 * (float)Math.sqrt(stiffness); } /** * Calculate acceleration at the current state * * @return Current acceleration */ private float calculateAcceleration() { float acceleration; final float distanceFromLimit = getDistanceToLimit(); if (distanceFromLimit != 0) { acceleration = distanceFromLimit * mStiffness - mDamping * mVelocity; } else { acceleration = -mFriction * mVelocity; } return acceleration; } @Override protected void onUpdate(int dt) { // Calculate dt in seconds as float final float fdt = dt / 1000f; // Calculate current acceleration final float a = calculateAcceleration(); // Calculate next position based on current velocity and acceleration mPosition += mVelocity * fdt + .5f * a * fdt * fdt; // Update velocity mVelocity += a * fdt; } } </code></pre> <p>Can someone give me some idea as to how to incorporate rotation of image into this as well (similar to the iphone pinch)?</p> <p>Thanks</p>

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