DragActivity.java

package com.esfoo.drag;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.esfoo.R;

/**
 * This activity presents two images and a text view and allows them to be dragged around.
 * Press and hold on a view initiates a drag. 
 *
 * <p> This activity is derviced from the Android Launcher class.
 * 
 */

public class DragActivity extends Activity 
    implements View.OnLongClickListener, View.OnClickListener
{


private DragController mDragController;   // Object that sends out drag-drop events while a view is being moved.
private DragLayer mDragLayer;             // The ViewGroup that supports drag-drop.

public static final boolean Debugging = false;

/**
 * onCreate - called when the activity is first created.
 * 
 * Creates a drag controller and sets up three views so click and long click on the views are sent to this activity.
 * The onLongClick method starts a drag sequence.
 *
 */

 protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    mDragController = new DragController(this);

    setContentView(R.layout.main);
    setupViews ();
}

/**
 * Handle a click on a view.
 *
 */    

public void onClick(View v) 
{

    toast ("You clicked. Try a long click");
}

/**
 * Handle a long click.
 *
 * @param v View
 * @return boolean - true indicates that the event was handled
 */    

public boolean onLongClick(View v) 
{
    trace ("onLongClick in view: " + v);

    // Make sure the drag was started by a long press as opposed to a long click.
    // (Note: I got this from the Workspace object in the Android Launcher code. 
    //  I think it is here to ensure that the device is still in touch mode as we start the drag operation.)
    if (!v.isInTouchMode()) {
       toast ("isInTouchMode returned false. Try touching the view again.");
       return false;
    }
    return startDrag (v);
}

/**
 * Start dragging a view.
 *
 */    

public boolean startDrag (View v)
{
    // Let the DragController initiate a drag-drop sequence.
    // I use the dragInfo to pass along the object being dragged.
    // I'm not sure how the Launcher designers do this.
    Object dragInfo = v;
    mDragController.startDrag (v, mDragLayer, dragInfo, DragController.DRAG_ACTION_MOVE);
    return true;
}

/**
 * Finds all the views we need and configure them to send click events to the activity.
 *
 */
private void setupViews() 
{
    DragController dragController = mDragController;

    mDragLayer = (DragLayer) findViewById(R.id.drag_layer);
    mDragLayer.setDragController(dragController);
    dragController.addDropTarget (mDragLayer);

    ImageView i1 = (ImageView) findViewById (R.id.Image1);
    ImageView i2 = (ImageView) findViewById (R.id.Image2);

    i1.setOnClickListener(this);
    i1.setOnLongClickListener(this);

    i2.setOnClickListener(this);
    i2.setOnLongClickListener(this);

    TextView tv = (TextView) findViewById (R.id.Text1);
    tv.setOnLongClickListener(this);

    Toast.makeText (getApplicationContext(), 
                    "Press and hold to drag a view", Toast.LENGTH_LONG).show ();

}

/**
 * Show a string on the screen via Toast.
 * 
 * @param msg String
 * @return void
 */

public void toast (String msg)
{
    Toast.makeText (getApplicationContext(), msg, Toast.LENGTH_SHORT).show ();
} // end toast

/**
 * Send a message to the debug log and display it using Toast.
 */

public void trace (String msg) 
{
    if (!Debugging) return;
    Log.d ("DragActivity", msg);
    toast (msg);
}

} // end class