ActivityDragImage.java - Drag image horizontally and scale it.

ActivityDragImage.java

package com.example.androidtests;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.RelativeLayout;

import com.nineoldandroids.view.ViewPropertyAnimator;

public class ActivityDragImage extends Activity
{
	private ImageView mImage;

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);

		RelativeLayout mainLayout = new RelativeLayout(this);
		setContentView(mainLayout);

		mImage = new ImageView(this);
		RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
		lp.addRule(RelativeLayout.CENTER_IN_PARENT);
		mainLayout.addView(mImage, lp);

		mImage.setImageResource(R.drawable.square400px);
		mImage.setOnTouchListener(mTouchListener);
	}

	private View.OnTouchListener mTouchListener = new View.OnTouchListener()
	{
		private float mStartX;

		@Override
		public boolean onTouch(View v, MotionEvent event)
		{
			switch (event.getActionMasked())
			{
				case MotionEvent.ACTION_DOWN :
					mStartX = event.getRawX();
					return true;

				case MotionEvent.ACTION_MOVE :
					float currentX = event.getRawX();
					animateTo(currentX - mStartX, true); // Snap to drag
					return true;

				case MotionEvent.ACTION_UP :
				case MotionEvent.ACTION_CANCEL :
					animateTo(0, false); // Ease back
					return true;
			}

			return false;
		}
	};

	private void animateTo(float displacement, boolean immediate)
	{
		final int EASE_BACK_DURATION = 300; // ms
		int duration = (immediate ? 0 : EASE_BACK_DURATION);

		Display display = getWindowManager().getDefaultDisplay();
		int totalWidth = display.getWidth();
		float scale = 1.0f - Math.abs(displacement / totalWidth);

		ViewPropertyAnimator.animate(mImage)
			.translationX(displacement)
			.scaleX(scale)
			.scaleY(scale)
			.setDuration(duration)
			.start();
	}
}