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TracingController

public abstract class TracingController
extends Object

java.lang.Object
   ↳ android.webkit.TracingController


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.

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.

Example usage:

 TracingController tracingController = TracingController.getInstance();
 tracingController.start(new TracingConfig.Builder()
                  .addCategories(CATEGORIES_WEB_DEVELOPER).build());
 ...
 tracingController.stop(new FileOutputStream("trace.json"),
                        Executors.newSingleThreadExecutor());
 

Summary

Public constructors

TracingController()

Public methods

static TracingController getInstance()

Returns the default TracingController instance.

abstract boolean isTracing()

Returns whether the WebView framework is tracing.

abstract void start(TracingConfig tracingConfig)

Starts tracing all webviews.

abstract boolean stop(OutputStream outputStream, Executor executor)

Stops tracing and flushes tracing data to the specified outputStream.

Inherited methods

Public constructors

TracingController

added in API level 28
public TracingController ()

Public methods

getInstance

added in API level 28
public static TracingController getInstance ()

Returns the default TracingController instance. At present there is only one TracingController instance for all WebView instances, however this restriction may be relaxed in a future Android release.

Returns
TracingController The default TracingController instance.

This value will never be null.

isTracing

added in API level 28
public abstract boolean isTracing ()

Returns whether the WebView framework is tracing.

Returns
boolean True if tracing is enabled.

start

added in API level 28
public abstract void start (TracingConfig tracingConfig)

Starts tracing all webviews. Depending on the trace mode in traceConfig specifies how the trace events are recorded. For tracing modes TracingConfig.RECORD_UNTIL_FULL and TracingConfig.RECORD_CONTINUOUSLY the events are recorded using an internal buffer and flushed to the outputStream when stop(OutputStream, Executor) is called.

Parameters
tracingConfig TracingConfig: Configuration options to use for tracing.

This value must never be null.

Throws
IllegalStateException If the system is already tracing.
IllegalArgumentException If the configuration is invalid (e.g. invalid category pattern or invalid tracing mode).

stop

added in API level 28
public abstract boolean stop (OutputStream outputStream, 
                Executor executor)

Stops tracing and flushes tracing data to the specified outputStream. The data is sent to the specified output stream in json format typically in chunks by invoking OutputStream.write(byte[]). On completion the OutputStream.close() method is called.

Parameters
outputStream OutputStream: The output stream the tracing data will be sent to. If null the tracing data will be discarded.

executor Executor: The Executor on which the outputStream OutputStream.write(byte[]) and OutputStream.close() methods will be invoked.

This value must never be null.

Callback and listener events are dispatched through this Executor, providing an easy way to control which thread is used. To dispatch events through the main thread of your application, you can use Context.getMainExecutor(). To dispatch events through a shared thread pool, you can use AsyncTask.THREAD_POOL_EXECUTOR.

Returns
boolean False if the WebView framework was not tracing at the time of the call, true otherwise.