Android example source code file (Registrant.java)

This example Android source code file (Registrant.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

android, asyncresult, handler, message, object, os, registrant, throwable, util, weakreference

The Registrant.java Android example source code

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.os;

import android.os.Handler;
import android.os.Message;

import java.lang.ref.WeakReference;
import java.util.HashMap;

/** @hide */
public class Registrant
{
    public
    Registrant(Handler h, int what, Object obj)
    {
        refH = new WeakReference(h);
        this.what = what;
        userObj = obj;
    }

    public void
    clear()
    {
        refH = null;
        userObj = null;
    }

    public void
    notifyRegistrant()
    {
        internalNotifyRegistrant (null, null);
    }
    
    public void
    notifyResult(Object result)
    {
        internalNotifyRegistrant (result, null);
    }

    public void
    notifyException(Throwable exception)
    {
        internalNotifyRegistrant (null, exception);
    }

    /**
     * This makes a copy of @param ar
     */
    public void
    notifyRegistrant(AsyncResult ar)
    {
        internalNotifyRegistrant (ar.result, ar.exception);
    }

    /*package*/ void
    internalNotifyRegistrant (Object result, Throwable exception)
    {
        Handler h = getHandler();

        if (h == null) {
            clear();
        } else {
            Message msg = Message.obtain();

            msg.what = what;
            
            msg.obj = new AsyncResult(userObj, result, exception);
            
            h.sendMessage(msg);
        }
    }

    /**
     * NOTE: May return null if weak reference has been collected
     */

    public Message
    messageForRegistrant()
    {
        Handler h = getHandler();

        if (h == null) {
            clear();

            return null;
        } else {
            Message msg = h.obtainMessage();

            msg.what = what;
            msg.obj = userObj;

            return msg;
        }
    }

    public Handler
    getHandler()
    {
        if (refH == null)
            return null;

        return (Handler) refH.get();
    }

    WeakReference   refH;
    int             what;
    Object          userObj;
}