/*
* 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.util.TimeUtils;
/**
*
* Defines a message containing a description and arbitrary data object that can be
* sent to a {@link Handler}. This object contains two extra int fields and an
* extra object field that allow you to not do allocations in many cases.
*
* <p class="note">While the constructor of Message is public, the best way to get
* one of these is to call {@link #obtain Message.obtain()} or one of the
* {@link Handler#obtainMessage Handler.obtainMessage()} methods, which will pull
* them from a pool of recycled objects.</p>
*/
public final class Message implements Parcelable {
/**
* User-defined message code so that the recipient can identify
* what this message is about. Each {@link Handler} has its own name-space
* for message codes, so you do not need to worry about yours conflicting
* with other handlers.
*/
public int what;
/**
* arg1 and arg2 are lower-cost alternatives to using
* {@link #setData(Bundle) setData()} if you only need to store a
* few integer values.
*/
public int arg1;
/**
* arg1 and arg2 are lower-cost alternatives to using
* {@link #setData(Bundle) setData()} if you only need to store a
* few integer values.
*/
public int arg2;
/**
* An arbitrary object to send to the recipient. When using
* {@link Messenger} to send the message across processes this can only
* be non-null if it contains a Parcelable of a framework class (not one
* implemented by the application). For other data transfer use
* {@link #setData}.
*
* <p>Note that Parcelable objects here are not supported prior to
* the {@link android.os.Build.VERSION_CODES#FROYO} release.
*/
public Object obj;
/**
* Optional Messenger where replies to this message can be sent. The
* semantics of exactly how this is used are up to the sender and
* receiver.
*/
public Messenger replyTo;
/**
* Optional field indicating the uid that sent the message. This is
* only valid for messages posted by a {@link Messenger}; otherwise,
* it will be -1.
*/
public int sendingUid = -1;
/** If set message is in use.
* This flag is set when the message is enqueued and remains set while it
* is delivered and afterwards when it is recycled. The flag is only cleared
* when a new message is created or obtained since that is the only time that
* applications are allowed to modify the contents of the message.
*
* It is an error to attempt to enqueue or recycle a message that is already in use.
*/
/*package*/ static final int FLAG_IN_USE = 1 << 0;
/** If set message is asynchronous */
/*package*/ static final int FLAG_ASYNCHRONOUS = 1 << 1;
/** Flags to clear in the copyFrom method */
/*package*/ static final int FLAGS_TO_CLEAR_ON_COPY_FROM = FLAG_IN_USE;
/*package*/ int flags;
/*package*/ long when;
/*package*/ Bundle data;
/*package*/ Handler target;
/*package*/ Runnable callback;
// sometimes we store linked lists of these things
/*package*/ Message next;
private static final Object sPoolSync = new Object();
private static Message sPool;
private static int sPoolSize = 0;
private static final int MAX_POOL_SIZE = 50;
private static boolean gCheckRecycle = true;
/**
* Return a new Message instance from the global pool. Allows us to
* avoid allocating new objects in many cases.
*/
public static Message obtain() {
synchronized (sPoolSync) {
if (sPool != null) {
Message m = sPool;
sPool = m.next;
m.next = null;
m.flags = 0; // clear in-use flag
sPoolSize--;
return m;
}
}
return new Message();
}
/**
* Same as {@link #obtain()}, but copies the values of an existing
* message (including its target) into the new one.
* @param orig Original message to copy.
* @return A Message object from the global pool.
*/
public static Message obtain(Message orig) {
Message m = obtain();
m.what = orig.what;
m.arg1 = orig.arg1;
m.arg2 = orig.arg2;
m.obj = orig.obj;
m.replyTo = orig.replyTo;
m.sendingUid = orig.sendingUid;
if (orig.data != null) {
m.data = new Bundle(orig.data);
}
m.target = orig.target;
m.callback = orig.callback;
return m;
}
/**
* Same as {@link #obtain()}, but sets the value for the <em>target</em> member on the Message returned.
* @param h Handler to assign to the returned Message object's <em>target</em> member.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h) {
Message m = obtain();
m.target = h;
return m;
}
/**
* Same as {@link #obtain(Handler)}, but assigns a callback Runnable on
* the Message that is returned.
* @param h Handler to assign to the returned Message object's <em>target</em> member.
* @param callback Runnable that will execute when the message is handled.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h, Runnable callback) {
Message m = obtain();
m.target = h;
m.callback = callback;
return m;
}
/**
* Same as {@link #obtain()}, but sets the values for both <em>target</em> and
* <em>what</em> members on the Message.
* @param h Value to assign to the <em>target</em> member.
* @param what Value to assign to the <em>what</em> member.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h, int what) {
Message m = obtain();
m.target = h;
m.what = what;
return m;
}
/**
* Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>, and <em>obj</em>
* members.
* @param h The <em>target</em> value to set.
* @param what The <em>what</em> value to set.
* @param obj The <em>object</em> method to set.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h, int what, Object obj) {
Message m = obtain();
m.target = h;
m.what = what;
m.obj = obj;
return m;
}
/**
* Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>,
* <em>arg1</em>, and <em>arg2</em> members.
*
* @param h The <em>target</em> value to set.
* @param what The <em>what</em> value to set.
* @param arg1 The <em>arg1</em> value to set.
* @param arg2 The <em>arg2</em> value to set.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h, int what, int arg1, int arg2) {
Message m = obtain();
m.target = h;
m.what = what;
m.arg1 = arg1;
m.arg2 = arg2;
return m;
}
/**
* Same as {@link #obtain()}, but sets the values of the <em>target</em>, <em>what</em>,
* <em>arg1</em>, <em>arg2</em>, and <em>obj</em> members.
*
* @param h The <em>target</em> value to set.
* @param what The <em>what</em> value to set.
* @param arg1 The <em>arg1</em> value to set.
* @param arg2 The <em>arg2</em> value to set.
* @param obj The <em>obj</em> value to set.
* @return A Message object from the global pool.
*/
public static Message obtain(Handler h, int what,
int arg1, int arg2, Object obj) {
Message m = obtain();
m.target = h;
m.what = what;
m.arg1 = arg1;
m.arg2 = arg2;
m.obj = obj;
return m;
}
/** @hide */
public static void updateCheckRecycle(int targetSdkVersion) {
if (targetSdkVersion < Build.VERSION_CODES.LOLLIPOP) {
gCheckRecycle = false;
}
}
/**
* Return a Message instance to the global pool.
* <p>
* You MUST NOT touch the Message after calling this function because it has
* effectively been freed. It is an error to recycle a message that is currently
* enqueued or that is in the process of being delivered to a Handler.
* </p>
*/
public void recycle() {
if (isInUse()) {
if (gCheckRecycle) {
throw new IllegalStateException("This message cannot be recycled because it "
+ "is still in use.");
}
return;
}
recycleUnchecked();
}
/**
* Recycles a Message that may be in-use.
* Used internally by the MessageQueue and Looper when disposing of queued Messages.
*/
void recycleUnchecked() {
// Mark the message as in use while it remains in the recycled object pool.
// Clear out all other details.
flags = FLAG_IN_USE;
what = 0;
arg1 = 0;
arg2 = 0;
obj = null;
replyTo = null;
sendingUid = -1;
when = 0;
target = null;
callback = null;
data = null;
synchronized (sPoolSync) {
if (sPoolSize < MAX_POOL_SIZE) {
next = sPool;
sPool = this;
sPoolSize++;
}
}
}
/**
* Make this message like o. Performs a shallow copy of the data field.
* Does not copy the linked list fields, nor the timestamp or
* target/callback of the original message.
*/
public void copyFrom(Message o) {
this.flags = o.flags & ~FLAGS_TO_CLEAR_ON_COPY_FROM;
this.what = o.what;
this.arg1 = o.arg1;
this.arg2 = o.arg2;
this.obj = o.obj;
this.replyTo = o.replyTo;
this.sendingUid = o.sendingUid;
if (o.data != null) {
this.data = (Bundle) o.data.clone();
} else {
this.data = null;
}
}
/**
* Return the targeted delivery time of this message, in milliseconds.
*/
public long getWhen() {
return when;
}
public void setTarget(Handler target) {
this.target = target;
}
/**
* Retrieve the a {@link android.os.Handler Handler} implementation that
* will receive this message. The object must implement
* {@link android.os.Handler#handleMessage(android.os.Message)
* Handler.handleMessage()}. Each Handler has its own name-space for
* message codes, so you do not need to
* worry about yours conflicting with other handlers.
*/
public Handler getTarget() {
return target;
}
/**
* Retrieve callback object that will execute when this message is handled.
* This object must implement Runnable. This is called by
* the <em>target</em> {@link Handler} that is receiving this Message to
* dispatch it. If
* not set, the message will be dispatched to the receiving Handler's
* {@link Handler#handleMessage(Message Handler.handleMessage())}.
*/
public Runnable getCallback() {
return callback;
}
/**
* Obtains a Bundle of arbitrary data associated with this
* event, lazily creating it if necessary. Set this value by calling
* {@link #setData(Bundle)}. Note that when transferring data across
* processes via {@link Messenger}, you will need to set your ClassLoader
* on the Bundle via {@link Bundle#setClassLoader(ClassLoader)
* Bundle.setClassLoader()} so that it can instantiate your objects when
* you retrieve them.
* @see #peekData()
* @see #setData(Bundle)
*/
public Bundle getData() {
if (data == null) {
data = new Bundle();
}
return data;
}
/**
* Like getData(), but does not lazily create the Bundle. A null
* is returned if the Bundle does not already exist. See
* {@link #getData} for further information on this.
* @see #getData()
* @see #setData(Bundle)
*/
public Bundle peekData() {
return data;
}
/**
* Sets a Bundle of arbitrary data values. Use arg1 and arg2 members
* as a lower cost way to send a few simple integer values, if you can.
* @see #getData()
* @see #peekData()
*/
public void setData(Bundle data) {
this.data = data;
}
/**
* Sends this Message to the Handler specified by {@link #getTarget}.
* Throws a null pointer exception if this field has not been set.
*/
public void sendToTarget() {
target.sendMessage(this);
}
/**
* Returns true if the message is asynchronous, meaning that it is not
* subject to {@link Looper} synchronization barriers.
*
* @return True if the message is asynchronous.
*
* @see #setAsynchronous(boolean)
*/
public boolean isAsynchronous() {
return (flags & FLAG_ASYNCHRONOUS) != 0;
}
/**
* Sets whether the message is asynchronous, meaning that it is not
* subject to {@link Looper} synchronization barriers.
* <p>
* Certain operations, such as view invalidation, may introduce synchronization
* barriers into the {@link Looper}'s message queue to prevent subsequent messages
* from being delivered until some condition is met. In the case of view invalidation,
* messages which are posted after a call to {@link android.view.View#invalidate}
* are suspended by means of a synchronization barrier until the next frame is
* ready to be drawn. The synchronization barrier ensures that the invalidation
* request is completely handled before resuming.
* </p><p>
* Asynchronous messages are exempt from synchronization barriers. They typically
* represent interrupts, input events, and other signals that must be handled independently
* even while other work has been suspended.
* </p><p>
* Note that asynchronous messages may be delivered out of order with respect to
* synchronous messages although they are always delivered in order among themselves.
* If the relative order of these messages matters then they probably should not be
* asynchronous in the first place. Use with caution.
* </p>
*
* @param async True if the message is asynchronous.
*
* @see #isAsynchronous()
*/
public void setAsynchronous(boolean async) {
if (async) {
flags |= FLAG_ASYNCHRONOUS;
} else {
flags &= ~FLAG_ASYNCHRONOUS;
}
}
/*package*/ boolean isInUse() {
return ((flags & FLAG_IN_USE) == FLAG_IN_USE);
}
/*package*/ void markInUse() {
flags |= FLAG_IN_USE;
}
/** Constructor (but the preferred way to get a Message is to call {@link #obtain() Message.obtain()}).
*/
public Message() {
}
@Override
public String toString() {
return toString(SystemClock.uptimeMillis());
}
String toString(long now) {
StringBuilder b = new StringBuilder();
b.append("{ when=");
TimeUtils.formatDuration(when - now, b);
if (target != null) {
if (callback != null) {
b.append(" callback=");
b.append(callback.getClass().getName());
} else {
b.append(" what=");
b.append(what);
}
if (arg1 != 0) {
b.append(" arg1=");
b.append(arg1);
}
if (arg2 != 0) {
b.append(" arg2=");
b.append(arg2);
}
if (obj != null) {
b.append(" obj=");
b.append(obj);
}
b.append(" target=");
b.append(target.getClass().getName());
} else {
b.append(" barrier=");
b.append(arg1);
}
b.append(" }");
return b.toString();
}
public static final Parcelable.Creator<Message> CREATOR
= new Parcelable.Creator<Message>() {
public Message createFromParcel(Parcel source) {
Message msg = Message.obtain();
msg.readFromParcel(source);
return msg;
}
public Message[] newArray(int size) {
return new Message[size];
}
};
public int describeContents() {
return 0;
}
public void writeToParcel(Parcel dest, int flags) {
if (callback != null) {
throw new RuntimeException(
"Can't marshal callbacks across processes.");
}
dest.writeInt(what);
dest.writeInt(arg1);
dest.writeInt(arg2);
if (obj != null) {
try {
Parcelable p = (Parcelable)obj;
dest.writeInt(1);
dest.writeParcelable(p, flags);
} catch (ClassCastException e) {
throw new RuntimeException(
"Can't marshal non-Parcelable objects across processes.");
}
} else {
dest.writeInt(0);
}
dest.writeLong(when);
dest.writeBundle(data);
Messenger.writeMessengerOrNullToParcel(replyTo, dest);
dest.writeInt(sendingUid);
}
private void readFromParcel(Parcel source) {
what = source.readInt();
arg1 = source.readInt();
arg2 = source.readInt();
if (source.readInt() != 0) {
obj = source.readParcelable(getClass().getClassLoader());
}
when = source.readLong();
data = source.readBundle();
replyTo = Messenger.readMessengerOrNullFromParcel(source);
sendingUid = source.readInt();
}
}
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