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/*
* Copyright 2017 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.webkit;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.os.Handler;
/**
* Manages tracing of WebViews. In particular provides functionality for the app
* to enable/disable tracing of parts of code and to collect tracing data.
* This is useful for profiling performance issues, debugging and memory usage
* analysis in production and real life scenarios.
* <p>
* The resulting trace data is sent back as a byte sequence in json format. This
* file can be loaded in "chrome://tracing" for further analysis.
* <p>
* Note: All methods in this class must be called on the UI thread. All callbacks
* are also called on the UI thread.
* <p>
* Example usage:
* <pre class="prettyprint">
* TracingController tracingController = TracingController.getInstance();
* tracingController.start(new TraceConfig(CATEGORIES_WEB_DEVELOPER));
* [..]
* tracingController.stopAndFlush(new TraceFileOutput("trace.json"), null);
* </pre></p>
*/
public abstract class TracingController {
/**
* Interface for capturing tracing data.
*/
public interface TracingOutputStream {
/**
* Will be called to return tracing data in chunks.
* Tracing data is returned in json format an array of bytes.
*/
void write(byte[] chunk);
/**
* Called when tracing is finished and the data collection is over.
* There will be no calls to #write after #complete is called.
*/
void complete();
}
/**
* Returns the default TracingController instance. At present there is
* only one TracingController instance for all WebView instances,
* however this restriction may be relaxed in the future.
*
* @return the default TracingController instance
*/
@NonNull
public static TracingController getInstance() {
return WebViewFactory.getProvider().getTracingController();
}
/**
* Starts tracing all webviews. Depeding on the trace mode in traceConfig
* specifies how the trace events are recorded.
*
* For tracing modes {@link TracingConfig#RECORD_UNTIL_FULL},
* {@link TracingConfig#RECORD_CONTINUOUSLY} and
* {@link TracingConfig#RECORD_UNTIL_FULL_LARGE_BUFFER} the events are recorded
* using an internal buffer and flushed to the outputStream when
* {@link #stopAndFlush(TracingOutputStream, Handler)} is called.
*
* @param tracingConfig configuration options to use for tracing
* @return false if the system is already tracing, true otherwise.
*/
public abstract boolean start(TracingConfig tracingConfig);
/**
* Stops tracing and discards all tracing data.
*
* This method is particularly useful in conjunction with the
* {@link TracingConfig#RECORD_TO_CONSOLE} tracing mode because tracing data is logged to
* console and not sent to an outputStream as with
* {@link #stopAndFlush(TracingOutputStream, Handler)}.
*
* @return false if the system was not tracing at the time of the call, true
* otherwise.
*/
public abstract boolean stop();
/**
* Stops tracing and flushes tracing data to the specifid outputStream.
*
* Note that if the {@link TracingConfig#RECORD_TO_CONSOLE} tracing mode is used
* nothing will be sent to the outputStream and no TracingOuputStream methods will be
* called. In that case it is more convenient to just use {@link #stop()} instead.
*
* @param outputStream the output steam the tracing data will be sent to.
* @param handler the {@link android.os.Handler} on which the outputStream callbacks
* will be invoked. If the handler is null the current thread's Looper
* will be used.
* @return false if the system was not tracing at the time of the call, true
* otherwise.
*/
public abstract boolean stopAndFlush(TracingOutputStream outputStream,
@Nullable Handler handler);
/** True if the system is tracing */
public abstract boolean isTracing();
// TODO: consider adding getTraceBufferUsage, percentage and approx event count.
// TODO: consider adding String getCategories(), for obtaining the actual list
// of categories used (given that presets are ints).
}
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