1.

VersionedGestureDetector.java

import android.content.Context;import android.os.Build;import android.util.Log;import android.view.MotionEvent;import android.view.ScaleGestureDetector;public abstract class VersionedGestureDetector { private static final String TAG = "VersionedGestureDetector"; OnGestureListener mListener; public static VersionedGestureDetector newInstance(Context context, OnGestureListener listener) { final int sdkVersion = Integer.parseInt(Build.VERSION.SDK); VersionedGestureDetector detector = null; if (sdkVersion < Build.VERSION_CODES.ECLAIR) { detector = new CupcakeDetector(); } else if (sdkVersion < Build.VERSION_CODES.FROYO) { detector = new EclairDetector(); } else { detector = new FroyoDetector(context); } Log.d(TAG, "Created new " + detector.getClass()); detector.mListener = listener; return detector; } public abstract boolean onTouchEvent(MotionEvent ev); public interface OnGestureListener { public void onDrag(float dx, float dy); public void onScale(float scaleFactor); } private static class CupcakeDetector extends VersionedGestureDetector { float mLastTouchX; float mLastTouchY; float getActiveX(MotionEvent ev) { return ev.getX(); } float getActiveY(MotionEvent ev) { return ev.getY(); } boolean shouldDrag() { return true; } @Override public boolean onTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: { mLastTouchX = getActiveX(ev); mLastTouchY = getActiveY(ev); break; } case MotionEvent.ACTION_MOVE: { final float x = getActiveX(ev); final float y = getActiveY(ev); if (shouldDrag()) { mListener.onDrag(x - mLastTouchX, y - mLastTouchY); } mLastTouchX = x; mLastTouchY = y; break; } } return true; } } private static class EclairDetector extends CupcakeDetector { private static final int INVALID_POINTER_ID = -1; private int mActivePointerId = INVALID_POINTER_ID; private int mActivePointerIndex = 0; @Override float getActiveX(MotionEvent ev) { return ev.getX(mActivePointerIndex); } @Override float getActiveY(MotionEvent ev) { return ev.getY(mActivePointerIndex); } @Override public boolean onTouchEvent(MotionEvent ev) { final int action = ev.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: mActivePointerId = ev.getPointerId(0); break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: mActivePointerId = INVALID_POINTER_ID; break; case MotionEvent.ACTION_POINTER_UP: final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mActivePointerId = ev.getPointerId(newPointerIndex); mLastTouchX = ev.getX(newPointerIndex); mLastTouchY = ev.getY(newPointerIndex); } break; } mActivePointerIndex = ev.findPointerIndex(mActivePointerId); return super.onTouchEvent(ev); } } private static class FroyoDetector extends EclairDetector { private ScaleGestureDetector mDetector; public FroyoDetector(Context context) { mDetector = new ScaleGestureDetector(context, new ScaleGestureDetector.SimpleOnScaleGestureListener() { @Override public boolean onScale(ScaleGestureDetector detector) { mListener.onScale(detector.getScaleFactor()); return true; } }); } @Override boolean shouldDrag() { return !mDetector.isInProgress(); } @Override public boolean onTouchEvent(MotionEvent ev) { mDetector.onTouchEvent(ev); return super.onTouchEvent(ev); } } }

 

2.

TouchExampleView.java

import android.content.Context;import android.graphics.Canvas;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View; public class TouchExampleView extends View { private Drawable mIcon; private float mPosX; private float mPosY; private VersionedGestureDetector mDetector; private float mScaleFactor = 1.f; public TouchExampleView(Context context) { this(context, null, 0); } public TouchExampleView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public TouchExampleView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); mIcon = context.getResources().getDrawable(R.drawable.icon); mIcon.setBounds(0, 0, mIcon.getIntrinsicWidth(), mIcon.getIntrinsicHeight()); mDetector = VersionedGestureDetector.newInstance(context, new GestureCallback()); } @Override public boolean onTouchEvent(MotionEvent ev) { mDetector.onTouchEvent(ev); return true; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.save(); canvas.translate(mPosX, mPosY); canvas.scale(mScaleFactor, mScaleFactor); mIcon.draw(canvas); canvas.restore(); } private class GestureCallback implements VersionedGestureDetector.OnGestureListener { public void onDrag(float dx, float dy) { mPosX += dx; mPosY += dy; invalidate(); } public void onScale(float scaleFactor) { mScaleFactor *= scaleFactor; // Don't let the object get too small or too large. mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 5.0f)); invalidate(); } } }