Add ID to InputEvent.

The interaction between Java and native code for KeyEvent and
MotionEvent is different, so I used different arrangement to pass
sequence number across JNI that keeps the consistency with other
metadata.

Unfortunately this new ID doesn't have absolute uniqueness guarantee so
it can't replace InputEvent#getSequenceNumber() which is used with a
strict in-process uniqueness assumption. Therefore only convert systrace
related use to ID.

Also expose ID generator through a static function in InputEvent so that
everyone can use it. InputReader and InputDispatcher will use different
instances.

Bug: 144889238
Test: Build and run.
Test: atest FrameworksCoreTests:KeyEventTest
Test: atest FrameworksCoreTests:MotionEventTest
Change-Id: Icbdcaee1d98948c05484865a4e15e55161ecfa69
Merged-In: Icbdcaee1d98948c05484865a4e15e55161ecfa69
(cherry picked from 29d21d4062f90a1c79971e5380426fc54b307807)

1 files changed, 15 insertions, 0 deletions

diff --git a/core/java/android/view/InputEvent.java b/core/java/android/view/InputEvent.java
index 5f9c4801ee66..cb9e746543f6 100644
--- a/core/java/android/view/InputEvent.java
+++ b/core/java/android/view/InputEvent.java
@@ -233,6 +233,21 @@ public abstract class InputEvent implements Parcelable {
         return mSeq;
     }
 
+    /**
+     * Gets the ID of this event. This is generated when an event is created and preserved until its
+     * last stage. It won't change just because the event crosses process boundary, but should
+     * change when making a copy with modifications.
+     * <p>
+     * To avoid exposing app usage to other processes this ID is generated from a CSPRNG. Therefore
+     * there isn't 100% guarantee on the uniqueness of this ID, though the chance of ID collisions
+     * is considerably low. The rule of thumb is not to rely on the uniqueness for production logic,
+     * but a good source for tracking an event (e.g. logging and profiling).
+     *
+     * @return The ID of this event.
+     * @hide
+     */
+    public abstract int getId();
+
     public int describeContents() {
         return 0;
     }