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/*
* ConnectBot: simple, powerful, open-source SSH client for Android
* Copyright 2007 Kenny Root, Jeffrey Sharkey
*
* 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 org.connectbot.service;
import java.util.concurrent.Semaphore;
import android.os.Handler;
import android.os.Message;
/**
* Helps provide a relay for prompts and responses between a possible user
* interface and some underlying service.
*
* @author jsharkey
*/
public class PromptHelper {
private final Object tag;
private Handler handler = null;
private Semaphore promptToken;
private Semaphore promptResponse;
public String promptInstructions = null;
public String promptHint = null;
public Object promptRequested = null;
private Object response = null;
public PromptHelper(Object tag) {
this.tag = tag;
// Threads must acquire this before they can send a prompt.
promptToken = new Semaphore(1);
// Responses will release this semaphore.
promptResponse = new Semaphore(0);
}
/**
* Register a user interface handler, if available.
*/
public void setHandler(Handler handler) {
this.handler = handler;
}
/**
* Set an incoming value from an above user interface. Will automatically
* notify any waiting requests.
*/
public void setResponse(Object value) {
response = value;
promptRequested = null;
promptInstructions = null;
promptHint = null;
promptResponse.release();
}
/**
* Return the internal response value just before erasing and returning it.
*/
protected Object popResponse() {
Object value = response;
response = null;
return value;
}
/**
* Request a prompt response from parent. This is a blocking call until user
* interface returns a value.
* Only one thread can call this at a time. cancelPrompt() will force this to
* immediately return.
*/
private Object requestPrompt(String instructions, String hint, Object type) throws InterruptedException {
Object response = null;
promptToken.acquire();
try {
promptInstructions = instructions;
promptHint = hint;
promptRequested = type;
// notify any parent watching for live events
if (handler != null)
Message.obtain(handler, -1, tag).sendToTarget();
// acquire lock until user passes back value
promptResponse.acquire();
response = popResponse();
} finally {
promptToken.release();
}
return response;
}
/**
* Request a string response from parent. This is a blocking call until user
* interface returns a value.
* @param hint prompt hint for user to answer
* @return string user has entered
*/
public String requestStringPrompt(String instructions, String hint) {
String value = null;
try {
value = (String) requestPrompt(instructions, hint, String.class);
} catch (Exception e) {
}
return value;
}
/**
* Request a boolean response from parent. This is a blocking call until user
* interface returns a value.
* @param hint prompt hint for user to answer
* @return choice user has made (yes/no)
*/
public Boolean requestBooleanPrompt(String instructions, String hint) {
Boolean value = null;
try {
value = (Boolean) requestPrompt(instructions, hint, Boolean.class);
} catch (Exception e) {
}
return value;
}
/**
* Cancel an in-progress prompt.
*/
public void cancelPrompt() {
if (!promptToken.tryAcquire()) {
// A thread has the token, so try to interrupt it
response = null;
promptResponse.release();
} else {
// No threads have acquired the token
promptToken.release();
}
}
}
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