Android Open Source - MockGPSPath Draggable Layout

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License

The source code is released under:

GNU General Public License

Java Source Code

package com.rc.mockgpspath;
//from  w  ww .java  2s  . c o m
import java.util.ArrayList;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Transformation;
import android.widget.RelativeLayout;

/**
 * Special layout which allows for dragging of children. Catches touch events
 * and determines if they are drags or not. Uses spacial transforms in the
 * getChildStaticTransformation to have the dragged object follow the user's
 * finger.
 * 
 * @author Ryan
 * 
 */
public class DraggableLayout extends RelativeLayout {

  private ArrayList<Draggable> draggables = new ArrayList<Draggable>();
  private Rect mRect = new Rect();
  private Draggable currentDraggable = null;
  private DragListener dragListener = null;

  private void init() {
    setStaticTransformationsEnabled(true);
    setChildrenDrawingCacheEnabled(true);
    setChildrenDrawnWithCacheEnabled(true);
  }

  public DraggableLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
  }

  public DraggableLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }

  public DraggableLayout(Context context) {
    super(context);
    init();
  }

  @Override
  protected boolean getChildStaticTransformation(View child, Transformation t) {
    for (Draggable draggable : draggables) {
      if (child == draggable.child) {
        t.getMatrix().setTranslate(-draggable.x, -draggable.y);
        return true;
      }
    }
    return super.getChildStaticTransformation(child, t);
  }

  @Override
  public boolean onInterceptTouchEvent(MotionEvent event) {
    if (event.getAction() == MotionEvent.ACTION_DOWN) {
      for (Draggable draggable : draggables) {
        if (draggable.child.getVisibility() != View.VISIBLE)
          continue;

        draggable.child.getHitRect(mRect);
        if (mRect.contains((int) event.getX(), (int) event.getY())) {
          return true;
        }
      }
    }
    return super.onInterceptTouchEvent(event);
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    if (event.getAction() == MotionEvent.ACTION_DOWN) {
      for (Draggable draggable : draggables) {
        if (draggable.child.getVisibility() != View.VISIBLE)
          continue;

        draggable.child.getHitRect(mRect);
        if (mRect.contains((int) event.getX(), (int) event.getY())) {
          currentDraggable = draggable;
          currentDraggable.x = 0;
          currentDraggable.y = 0;
          currentDraggable.touchStartX = event.getX();
          currentDraggable.touchStartY = event.getY();
          currentDraggable.touchStartXinChild = event.getX() - currentDraggable.child.getLeft();
          currentDraggable.touchStartYinChild = event.getY() - currentDraggable.child.getTop();
          currentDraggable.child.bringToFront();
          if (dragListener != null) {
            dragListener.DragBegun(currentDraggable.child);
          }
          return true;
        }
      }
      return false;
    }
    if (event.getAction() != MotionEvent.ACTION_MOVE) {
      if (currentDraggable != null) {
        if (dragListener != null) {
          dragListener.DragFinished(currentDraggable.child, event.getX(), event.getY(), currentDraggable.touchStartXinChild, currentDraggable.touchStartYinChild);
        }
        currentDraggable.x = 0;
        currentDraggable.y = 0;
        currentDraggable = null;
        invalidate();
      }
      return true;
    } else {
      if (currentDraggable != null) {
        currentDraggable.x = currentDraggable.touchStartX - event.getX();
        currentDraggable.y = currentDraggable.touchStartY - event.getY();
        invalidate();
      }
    }

    return true;
  }

  /**
   * Mark a view as being draggable. By default, all views are undraggable
   * until this method is called on them.
   * 
   * @param v
   *            The view to mark as draggable
   */
  public void addDraggable(View v) {
    Draggable draggable = new Draggable();
    draggable.child = v;
    draggables.add(draggable);
  }

  public void setDragListener(DragListener dragListener) {
    this.dragListener = dragListener;
  }

  /**
   * Helper class to store information on any views in the container that are
   * draggable.
   * 
   * @author Ryan
   * 
   */
  private static class Draggable {
    View child;
    float x, y;
    float touchStartX, touchStartY;
    float touchStartXinChild, touchStartYinChild;
  }

  /**
   * Interface that can be passed to setDragListener to be notified of drag
   * events.
   * 
   * @author Ryan
   * 
   */
  public interface DragListener {
    /**
     * Called when a drag event begins.
     * 
     * @param view
     *            The view that is being dragged.
     */
    public void DragBegun(View view);

    /**
     * Called when a view has been dragged into a new position and the user
     * has released it.
     * 
     * @param view
     *            The view that has been dragged.
     * @param xInScreen
     *            The X position of the user's finger when released.
     * @param yInScreen
     *            The Y position of the user's finger when released.
     * @param touchStartXinChild
     *            The X position of the user's finger inside the view when
     *            he began to drag the view. This is the offset to use when
     *            considering things like points in the map pin.
     * @param touchStartYinChild
     *            The Y position of the user's finger inside the view when
     *            he began to drag the view. This is the offset to use when
     *            considering things like points in the map pin.
     */
    public void DragFinished(View view, float xInScreen, float yInScreen, float touchStartXinChild, float touchStartYinChild);
  }
}

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