System tracing shows you information about processes only at the system level, so it's sometimes difficult to know which of your app or game's methods were executing at a given time relative to system events.
Jetpack provides a tracing API that you can use to label a particular section of code. This information is then reported in traces captured on the device. Macrobenchmark captures traces with custom trace points automatically.
When using the systrace command line tool to capture traces, the -a
option is
required; without this option, your app's methods will not appear in a system
trace report.
Kotlin
class MyAdapter : RecyclerView.Adapter<MyViewHolder>() { override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder { trace("MyAdapter.onCreateViewHolder") { MyViewHolder.newInstance(parent) } } override fun onBindViewHolder(holder: MyViewHolder, position: Int) { trace("MyAdapter.onBindViewHolder") { trace("MyAdapter.queryDatabase") val rowItem = queryDatabase(position) dataset.add(rowItem) } holder.bind(dataset[position]) } } }
Java
Trace
class in the Jetpack tracing
library, as shown in the following code snippet.
Note: When you call beginSection()
multiple times,
calling endSection()
ends only the most-recently-called
beginSection()
method. So, for nested calls, such as those in the
following snippet, make sure that you properly match each call to
beginSection()
with a call to endSection()
.
Additionally, you cannot call beginSection()
on one thread and
end it from another thread; you must call both methods on the same thread.
public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> { @Override public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { Trace.beginSection("MyAdapter.onCreateViewHolder"); MyViewHolder myViewHolder; try { myViewHolder = MyViewHolder.newInstance(parent); } finally { // In try and catch statements, always call "endSection()" in a // "finally" block. That way, the method is invoked even when an // exception occurs. Trace.endSection(); } return myViewHolder; } @Override public void onBindViewHolder(MyViewHolder holder, int position) { Trace.beginSection("MyAdapter.onBindViewHolder"); try { try { Trace.beginSection("MyAdapter.queryDatabase"); RowItem rowItem = queryDatabase(position); dataset.add(rowItem); } finally { Trace.endSection(); } holder.bind(dataset.get(position)); } finally { Trace.endSection(); } } }
There is also an NDK API for custom trace events. You can find out more about using that API for your native code in the Custom trace events in native code documentation.
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