/*
* 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 java.util.ArrayList;
import android.util.AndroidRuntimeException;
import android.util.Config;
import android.util.Log;
import com.android.internal.os.RuntimeInit;
/**
* Low-level class holding the list of messages to be dispatched by a
* {@link Looper}. Messages are not added directly to a MessageQueue,
* but rather through {@link Handler} objects associated with the Looper.
*
* <p>You can retrieve the MessageQueue for the current thread with
* {@link Looper#myQueue() Looper.myQueue()}.
*/
public class MessageQueue {
Message mMessages;
private final ArrayList mIdleHandlers = new ArrayList();
private boolean mQuiting = false;
boolean mQuitAllowed = true;
/**
* Callback interface for discovering when a thread is going to block
* waiting for more messages.
*/
public static interface IdleHandler {
/**
* Called when the message queue has run out of messages and will now
* wait for more. Return true to keep your idle handler active, false
* to have it removed. This may be called if there are still messages
* pending in the queue, but they are all scheduled to be dispatched
* after the current time.
*/
boolean queueIdle();
}
/**
* Add a new {@link IdleHandler} to this message queue. This may be
* removed automatically for you by returning false from
* {@link IdleHandler#queueIdle IdleHandler.queueIdle()} when it is
* invoked, or explicitly removing it with {@link #removeIdleHandler}.
*
* <p>This method is safe to call from any thread.
*
* @param handler The IdleHandler to be added.
*/
public final void addIdleHandler(IdleHandler handler) {
if (handler == null) {
throw new NullPointerException("Can't add a null IdleHandler");
}
synchronized (this) {
mIdleHandlers.add(handler);
}
}
/**
* Remove an {@link IdleHandler} from the queue that was previously added
* with {@link #addIdleHandler}. If the given object is not currently
* in the idle list, nothing is done.
*
* @param handler The IdleHandler to be removed.
*/
public final void removeIdleHandler(IdleHandler handler) {
synchronized (this) {
mIdleHandlers.remove(handler);
}
}
MessageQueue() {
}
final Message next() {
boolean tryIdle = true;
while (true) {
long now;
Object[] idlers = null;
// Try to retrieve the next message, returning if found.
synchronized (this) {
now = SystemClock.uptimeMillis();
Message msg = pullNextLocked(now);
if (msg != null) return msg;
if (tryIdle && mIdleHandlers.size() > 0) {
idlers = mIdleHandlers.toArray();
}
}
// There was no message so we are going to wait... but first,
// if there are any idle handlers let them know.
boolean didIdle = false;
if (idlers != null) {
for (Object idler : idlers) {
boolean keep = false;
try {
didIdle = true;
keep = ((IdleHandler)idler).queueIdle();
} catch (Throwable t) {
Log.e("MessageQueue",
"IdleHandler threw exception", t);
RuntimeInit.crash("MessageQueue", t);
}
if (!keep) {
synchronized (this) {
mIdleHandlers.remove(idler);
}
}
}
}
// While calling an idle handler, a new message could have been
// delivered... so go back and look again for a pending message.
if (didIdle) {
tryIdle = false;
continue;
}
synchronized (this) {
// No messages, nobody to tell about it... time to wait!
try {
if (mMessages != null) {
if (mMessages.when-now > 0) {
Binder.flushPendingCommands();
this.wait(mMessages.when-now);
}
} else {
Binder.flushPendingCommands();
this.wait();
}
}
catch (InterruptedException e) {
}
}
}
}
final Message pullNextLocked(long now) {
Message msg = mMessages;
if (msg != null) {
if (now >= msg.when) {
mMessages = msg.next;
if (Config.LOGV) Log.v(
"MessageQueue", "Returning message: " + msg);
return msg;
}
}
return null;
}
final boolean enqueueMessage(Message msg, long when) {
if (msg.when != 0) {
throw new AndroidRuntimeException(msg
+ " This message is already in use.");
}
if (msg.target == null && !mQuitAllowed) {
throw new RuntimeException("Main thread not allowed to quit");
}
synchronized (this) {
if (mQuiting) {
RuntimeException e = new RuntimeException(
msg.target + " sending message to a Handler on a dead thread");
Log.w("MessageQueue", e.getMessage(), e);
return false;
} else if (msg.target == null) {
mQuiting = true;
}
msg.when = when;
//Log.d("MessageQueue", "Enqueing: " + msg);
Message p = mMessages;
if (p == null || when == 0 || when < p.when) {
msg.next = p;
mMessages = msg;
this.notify();
} else {
Message prev = null;
while (p != null && p.when <= when) {
prev = p;
p = p.next;
}
msg.next = prev.next;
prev.next = msg;
this.notify();
}
}
return true;
}
final boolean removeMessages(Handler h, int what, Object object,
boolean doRemove) {
synchronized (this) {
Message p = mMessages;
boolean found = false;
// Remove all messages at front.
while (p != null && p.target == h && p.what == what
&& (object == null || p.obj == object)) {
if (!doRemove) return true;
found = true;
Message n = p.next;
mMessages = n;
p.recycle();
p = n;
}
// Remove all messages after front.
while (p != null) {
Message n = p.next;
if (n != null) {
if (n.target == h && n.what == what
&& (object == null || n.obj == object)) {
if (!doRemove) return true;
found = true;
Message nn = n.next;
n.recycle();
p.next = nn;
continue;
}
}
p = n;
}
return found;
}
}
final void removeMessages(Handler h, Runnable r, Object object) {
if (r == null) {
return;
}
synchronized (this) {
Message p = mMessages;
// Remove all messages at front.
while (p != null && p.target == h && p.callback == r
&& (object == null || p.obj == object)) {
Message n = p.next;
mMessages = n;
p.recycle();
p = n;
}
// Remove all messages after front.
while (p != null) {
Message n = p.next;
if (n != null) {
if (n.target == h && n.callback == r
&& (object == null || n.obj == object)) {
Message nn = n.next;
n.recycle();
p.next = nn;
continue;
}
}
p = n;
}
}
}
final void removeCallbacksAndMessages(Handler h, Object object) {
synchronized (this) {
Message p = mMessages;
// Remove all messages at front.
while (p != null && p.target == h
&& (object == null || p.obj == object)) {
Message n = p.next;
mMessages = n;
p.recycle();
p = n;
}
// Remove all messages after front.
while (p != null) {
Message n = p.next;
if (n != null) {
if (n.target == h && (object == null || n.obj == object)) {
Message nn = n.next;
n.recycle();
p.next = nn;
continue;
}
}
p = n;
}
}
}
/*
private void dumpQueue_l()
{
Message p = mMessages;
System.out.println(this + " queue is:");
while (p != null) {
System.out.println(" " + p);
p = p.next;
}
}
*/
void poke()
{
synchronized (this) {
this.notify();
}
}
}
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