Android Embedding PR 9: Introduce an AndroidTouchProcessor to convert...

Android Embedding PR 9: Introduce an AndroidTouchProcessor to convert MotionEvents to Flutter touch data. (#7947)

ci/licenses_golden/licenses_flutter

@@ -473,6 +473,7 @@ FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/Flutte
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/FlutterShellArgs.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/android/AndroidKeyProcessor.java
+FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/android/AndroidTouchProcessor.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/android/FlutterActivity.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/android/FlutterFragment.java
 FILE: ../../../flutter/shell/platform/android/io/flutter/embedding/engine/android/FlutterSurfaceView.java

shell/platform/android/BUILD.gn

@@ -113,6 +113,7 @@ java_library("flutter_shell_java") {
     "io/flutter/embedding/engine/FlutterJNI.java",
     "io/flutter/embedding/engine/FlutterShellArgs.java",
     "io/flutter/embedding/engine/android/AndroidKeyProcessor.java",
+    "io/flutter/embedding/engine/android/AndroidTouchProcessor.java",
     "io/flutter/embedding/engine/android/FlutterActivity.java",
     "io/flutter/embedding/engine/android/FlutterFragment.java",
     "io/flutter/embedding/engine/android/FlutterSurfaceView.java",

shell/platform/android/io/flutter/embedding/engine/android/AndroidTouchProcessor.java

+package io.flutter.embedding.engine.android;
+
+import android.support.annotation.NonNull;
+import android.view.MotionEvent;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+import io.flutter.embedding.engine.renderer.FlutterRenderer;
+
+/**
+ * Sends touch information from Android to Flutter in a format that Flutter
+ * understands.
+ */
+public class AndroidTouchProcessor {
+
+  // Must match the PointerChange enum in pointer.dart.
+  // TODO(mattcarroll): convert these to an IntDef
+  private static final int POINTER_CHANGE_CANCEL = 0;
+  private static final int POINTER_CHANGE_ADD = 1;
+  private static final int POINTER_CHANGE_REMOVE = 2;
+  private static final int POINTER_CHANGE_HOVER = 3;
+  private static final int POINTER_CHANGE_DOWN = 4;
+  private static final int POINTER_CHANGE_MOVE = 5;
+  private static final int POINTER_CHANGE_UP = 6;
+
+  // Must match the PointerDeviceKind enum in pointer.dart.
+  // TODO(mattcarroll): convert these to an IntDef
+  private static final int POINTER_DEVICE_KIND_TOUCH = 0;
+  private static final int POINTER_DEVICE_KIND_MOUSE = 1;
+  private static final int POINTER_DEVICE_KIND_STYLUS = 2;
+  private static final int POINTER_DEVICE_KIND_INVERTED_STYLUS = 3;
+  private static final int POINTER_DEVICE_KIND_UNKNOWN = 4;
+
+  // Must match the unpacking code in hooks.dart.
+  private static final int POINTER_DATA_FIELD_COUNT = 19;
+  private static final int BYTE_PER_FIELD = 8;
+
+  @NonNull
+  private final FlutterRenderer renderer;
+
+  /**
+   * Constructs an {@code AndroidTouchProcessor} that will send touch event data
+   * to the Flutter execution context represented by the given {@link FlutterRenderer}.
+   */
+  // TODO(mattcarroll): consider moving packet behavior to a FlutterInteractionSurface instead of FlutterRenderer
+  public AndroidTouchProcessor(@NonNull FlutterRenderer renderer) {
+    this.renderer = renderer;
+  }
+
+  /**
+   * Sends the given {@link MotionEvent} data to Flutter in a format that
+   * Flutter understands.
+   */
+  public boolean onTouchEvent(MotionEvent event) {
+    int pointerCount = event.getPointerCount();
+
+    // Prepare a data packet of the appropriate size and order.
+    ByteBuffer packet = ByteBuffer.allocateDirect(
+        pointerCount * POINTER_DATA_FIELD_COUNT * BYTE_PER_FIELD
+    );
+    packet.order(ByteOrder.LITTLE_ENDIAN);
+
+    int maskedAction = event.getActionMasked();
+    // ACTION_UP, ACTION_POINTER_UP, ACTION_DOWN, and ACTION_POINTER_DOWN
+    // only apply to a single pointer, other events apply to all pointers.
+    if (maskedAction == MotionEvent.ACTION_UP || maskedAction == MotionEvent.ACTION_POINTER_UP
+        || maskedAction == MotionEvent.ACTION_DOWN || maskedAction == MotionEvent.ACTION_POINTER_DOWN) {
+      addPointerForIndex(event, event.getActionIndex(), packet);
+    } else {
+      // ACTION_MOVE may not actually mean all pointers have moved
+      // but it's the responsibility of a later part of the system to
+      // ignore 0-deltas if desired.
+      for (int p = 0; p < pointerCount; p++) {
+        addPointerForIndex(event, p, packet);
+      }
+    }
+
+    // Verify that the packet is the expected size.
+    assert packet.position() % (POINTER_DATA_FIELD_COUNT * BYTE_PER_FIELD) == 0;
+
+    // Send the packet to Flutter.
+    renderer.dispatchPointerDataPacket(packet, packet.position());
+
+    return true;
+  }
+
+  // TODO(mattcarroll): consider creating a PointerPacket class instead of using a procedure that mutates inputs.
+  private void addPointerForIndex(MotionEvent event, int pointerIndex, ByteBuffer packet) {
+    int pointerChange = getPointerChangeForAction(event.getActionMasked());
+    if (pointerChange == -1) {
+      return;
+    }
+
+    int pointerKind = getPointerDeviceTypeForToolType(event.getToolType(pointerIndex));
+
+    long timeStamp = event.getEventTime() * 1000; // Convert from milliseconds to microseconds.
+
+    packet.putLong(timeStamp); // time_stamp
+    packet.putLong(pointerChange); // change
+    packet.putLong(pointerKind); // kind
+    packet.putLong(event.getPointerId(pointerIndex)); // device
+    packet.putDouble(event.getX(pointerIndex)); // physical_x
+    packet.putDouble(event.getY(pointerIndex)); // physical_y
+
+    if (pointerKind == POINTER_DEVICE_KIND_MOUSE) {
+      packet.putLong(event.getButtonState() & 0x1F); // buttons
+    } else if (pointerKind == POINTER_DEVICE_KIND_STYLUS) {
+      packet.putLong((event.getButtonState() >> 4) & 0xF); // buttons
+    } else {
+      packet.putLong(0); // buttons
+    }
+
+    packet.putLong(0); // obscured
+
+    // TODO(eseidel): Could get the calibrated range if necessary:
+    // event.getDevice().getMotionRange(MotionEvent.AXIS_PRESSURE)
+    packet.putDouble(event.getPressure(pointerIndex)); // pressure
+    packet.putDouble(0.0); // pressure_min
+    packet.putDouble(1.0); // pressure_max
+
+    if (pointerKind == POINTER_DEVICE_KIND_STYLUS) {
+      packet.putDouble(event.getAxisValue(MotionEvent.AXIS_DISTANCE, pointerIndex)); // distance
+      packet.putDouble(0.0); // distance_max
+    } else {
+      packet.putDouble(0.0); // distance
+      packet.putDouble(0.0); // distance_max
+    }
+
+    packet.putDouble(event.getToolMajor(pointerIndex)); // radius_major
+    packet.putDouble(event.getToolMinor(pointerIndex)); // radius_minor
+
+    packet.putDouble(0.0); // radius_min
+    packet.putDouble(0.0); // radius_max
+
+    packet.putDouble(event.getAxisValue(MotionEvent.AXIS_ORIENTATION, pointerIndex)); // orientation
+
+    if (pointerKind == POINTER_DEVICE_KIND_STYLUS) {
+      packet.putDouble(event.getAxisValue(MotionEvent.AXIS_TILT, pointerIndex)); // tilt
+    } else {
+      packet.putDouble(0.0); // tilt
+    }
+  }
+
+  private int getPointerChangeForAction(int maskedAction) {
+    // Primary pointer:
+    if (maskedAction == MotionEvent.ACTION_DOWN) {
+      return POINTER_CHANGE_DOWN;
+    }
+    if (maskedAction == MotionEvent.ACTION_UP) {
+      return POINTER_CHANGE_UP;
+    }
+    // Secondary pointer:
+    if (maskedAction == MotionEvent.ACTION_POINTER_DOWN) {
+      return POINTER_CHANGE_DOWN;
+    }
+    if (maskedAction == MotionEvent.ACTION_POINTER_UP) {
+      return POINTER_CHANGE_UP;
+    }
+    // All pointers:
+    if (maskedAction == MotionEvent.ACTION_MOVE) {
+      return POINTER_CHANGE_MOVE;
+    }
+    if (maskedAction == MotionEvent.ACTION_CANCEL) {
+      return POINTER_CHANGE_CANCEL;
+    }
+    return -1;
+  }
+
+  // TODO(mattcarroll): introduce IntDef for toolType.
+  private int getPointerDeviceTypeForToolType(int toolType) {
+    switch (toolType) {
+      case MotionEvent.TOOL_TYPE_FINGER:
+        return POINTER_DEVICE_KIND_TOUCH;
+      case MotionEvent.TOOL_TYPE_STYLUS:
+        return POINTER_DEVICE_KIND_STYLUS;
+      case MotionEvent.TOOL_TYPE_MOUSE:
+        return POINTER_DEVICE_KIND_MOUSE;
+      case MotionEvent.TOOL_TYPE_ERASER:
+        return POINTER_DEVICE_KIND_INVERTED_STYLUS;
+      default:
+        // MotionEvent.TOOL_TYPE_UNKNOWN will reach here.
+        return POINTER_DEVICE_KIND_UNKNOWN;
+    }
+  }
+}