Dot.java

package com.google.mcommerce.sample.android.chapter08.dragAndDrop;

// This file is Dot.java
import android.content.ClipData;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.DragEvent;
import android.view.View;

import com.google.mcommerce.sample.android.R;

public class Dot extends View implements View.OnDragListener {
	private static final int DEFAULT_RADIUS = 20;
	private static final int DEFAULT_COLOR = Color.WHITE;
	private static final int SELECTED_COLOR = Color.MAGENTA;
	protected static final String DOTTAG = "DragDot";
	private Paint mNormalPaint;
	private Paint mDraggingPaint;
	private int mColor = DEFAULT_COLOR;
	private int mRadius = DEFAULT_RADIUS;
	private boolean inDrag;

	public Dot(Context context, AttributeSet attrs) {
		super(context, attrs);

		// Apply attribute settings from the layout file.
		// Note: these could change on a reconfiguration
		// such as a screen rotation.
		TypedArray myAttrs = context.obtainStyledAttributes(attrs,
				R.styleable.Dot);

		final int numAttrs = myAttrs.getIndexCount();
		for (int i = 0; i < numAttrs; i++) {
			int attr = myAttrs.getIndex(i);
			switch (attr) {
			case R.styleable.Dot_radius:
				mRadius = myAttrs.getDimensionPixelSize(attr, DEFAULT_RADIUS);
				break;
			case R.styleable.Dot_color:
				mColor = myAttrs.getColor(attr, DEFAULT_COLOR);
				break;
			}
		}
		myAttrs.recycle();

		// Setup paint colors
		mNormalPaint = new Paint();
		mNormalPaint.setColor(mColor);
		mNormalPaint.setAntiAlias(true);

		mDraggingPaint = new Paint();
		mDraggingPaint.setColor(SELECTED_COLOR);
		mDraggingPaint.setAntiAlias(true);

		// Start a drag on a long click on the dot
		setOnLongClickListener(lcListener);
		setOnDragListener(this);
	}

	private static View.OnLongClickListener lcListener = new View.OnLongClickListener() {
		private boolean mDragInProgress;

		public boolean onLongClick(View v) {
			ClipData data = ClipData.newPlainText("DragData",
					(String) v.getTag());
			mDragInProgress = v.startDrag(data, new View.DragShadowBuilder(v),
					(Object) v, 0);
			Log.v((String) v.getTag(), "starting drag? " + mDragInProgress);
			return true;
		}
	};

	@Override
	protected void onMeasure(int widthSpec, int heightSpec) {
		int size = 2 * mRadius + getPaddingLeft() + getPaddingRight();
		setMeasuredDimension(size, size);
	}

	// The dragging functionality
	public boolean onDrag(View v, DragEvent event) {
		String dotTAG = (String) getTag();
		// Only worry about drag events if this is us being dragged
		if (event.getLocalState() != this) {
			Log.v(dotTAG, "This drag event is not for us");
			return false;
		}
		boolean result = true;

		// get event values to work with
		int action = event.getAction();
		float x = event.getX();
		float y = event.getY();

		switch (action) {
		case DragEvent.ACTION_DRAG_STARTED:
			Log.v(dotTAG, "drag started. X: " + x + ", Y: " + y);
			inDrag = true; // used in draw() below to change color
			break;
		case DragEvent.ACTION_DRAG_LOCATION:
			Log.v(dotTAG, "drag proceeding... At: " + x + ", " + y);
			break;
		case DragEvent.ACTION_DRAG_ENTERED:
			Log.v(dotTAG, "drag entered. At: " + x + ", " + y);
			break;
		case DragEvent.ACTION_DRAG_EXITED:
			Log.v(dotTAG, "drag exited. At: " + x + ", " + y);
			break;
		case DragEvent.ACTION_DROP:
			Log.v(dotTAG, "drag dropped. At: " + x + ", " + y);
			// Return false because we don't accept the drop in Dot.
			result = false;
			break;
		case DragEvent.ACTION_DRAG_ENDED:
			Log.v(dotTAG, "drag ended. Success? " + event.getResult());
			inDrag = false; // change color of original dot back
			break;
		default:
			Log.v(dotTAG, "some other drag action: " + action);
			result = false;
			break;
		}
		return result;
	}

	// Here is where we draw our dot, and where we change the color if
	// we're in the process of being dragged. Note: the color change affects
	// the original dot only, not the shadow.
	public void draw(Canvas canvas) {
		float cx = this.getWidth() / 2 + getLeftPaddingOffset();
		float cy = this.getHeight() / 2 + getTopPaddingOffset();
		Paint paint = mNormalPaint;
		if (inDrag)
			paint = mDraggingPaint;
		canvas.drawCircle(cx, cy, mRadius, paint);
		invalidate();
	}
}