Fix first batch of warnings in the Android embedding

shell/platform/android/io/flutter/embedding/android/FlutterView.java

@@ -876,7 +876,7 @@ public InputConnection onCreateInputConnection(@NonNull EditorInfo outAttrs) {
    * methods.
    */
   @Override
-  public boolean checkInputConnectionProxy(View view) {
+  public boolean checkInputConnectionProxy(@NonNull View view) {
     return flutterEngine != null
         ? flutterEngine.getPlatformViewsController().checkInputConnectionProxy(view)
         : super.checkInputConnectionProxy(view);
@@ -894,7 +894,7 @@ public boolean checkInputConnectionProxy(View view) {
    * previous {@code keyCode} to generate a unicode combined character.
    */
   @Override
-  public boolean dispatchKeyEvent(KeyEvent event) {
+  public boolean dispatchKeyEvent(@NonNull KeyEvent event) {
     if (event.getAction() == KeyEvent.ACTION_DOWN && event.getRepeatCount() == 0) {
       // Tell Android to start tracking this event.
       getKeyDispatcherState().startTracking(event, this);
@@ -1003,6 +1003,7 @@ public AccessibilityNodeProvider getAccessibilityNodeProvider() {
    * @return The view matching the accessibility id if any.
    */
   @SuppressLint("SoonBlockedPrivateApi")
+  @Nullable
   public View findViewByAccessibilityIdTraversal(int accessibilityId) {
     if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
       return findViewByAccessibilityIdRootedAtCurrentView(accessibilityId, this);
@@ -1349,7 +1350,7 @@ public void onFlutterUiNoLongerDisplayed() {
         });
   }
 
-  public void attachOverlaySurfaceToRender(FlutterImageView view) {
+  public void attachOverlaySurfaceToRender(@NonNull FlutterImageView view) {
     if (flutterEngine != null) {
       view.attachToRenderer(flutterEngine.getRenderer());
     }
@@ -1450,13 +1451,13 @@ private void sendViewportMetricsToFlutter() {
   }
 
   @Override
-  public void onProvideAutofillVirtualStructure(ViewStructure structure, int flags) {
+  public void onProvideAutofillVirtualStructure(@NonNull ViewStructure structure, int flags) {
     super.onProvideAutofillVirtualStructure(structure, flags);
     textInputPlugin.onProvideAutofillVirtualStructure(structure, flags);
   }
 
   @Override
-  public void autofill(SparseArray<AutofillValue> values) {
+  public void autofill(@NonNull SparseArray<AutofillValue> values) {
     textInputPlugin.autofill(values);
   }
 

shell/platform/android/io/flutter/embedding/android/KeyboardManager.java

@@ -79,7 +79,9 @@ public class KeyboardManager {
    *     dispatched to.
    */
   public KeyboardManager(
-      View view, @NonNull TextInputPlugin textInputPlugin, Responder[] responders) {
+      @NonNull View view,
+      @NonNull TextInputPlugin textInputPlugin,
+      @NonNull Responder[] responders) {
     this.view = view;
     this.textInputPlugin = textInputPlugin;
     this.responders = responders;
@@ -103,7 +105,7 @@ public KeyboardManager(
    */
   interface Responder {
     interface OnKeyEventHandledCallback {
-      void onKeyEventHandled(Boolean canHandleEvent);
+      void onKeyEventHandled(boolean canHandleEvent);
     }
 
     /**
@@ -122,7 +124,7 @@ private class Callback implements OnKeyEventHandledCallback {
       boolean isCalled = false;
 
       @Override
-      public void onKeyEventHandled(Boolean canHandleEvent) {
+      public void onKeyEventHandled(boolean canHandleEvent) {
         if (isCalled) {
           throw new IllegalStateException(
               "The onKeyEventHandledCallback should be called exactly once.");
@@ -140,7 +142,7 @@ public void onKeyEventHandled(Boolean canHandleEvent) {
       this.keyEvent = keyEvent;
     }
 
-    @NonNull final KeyEvent keyEvent;
+    final KeyEvent keyEvent;
     int unrepliedCount = responders.length;
     boolean isEventHandled = false;
 
@@ -149,9 +151,9 @@ public OnKeyEventHandledCallback buildCallback() {
     }
   }
 
-  @NonNull protected final Responder[] responders;
-  @NonNull private final HashSet<KeyEvent> redispatchedEvents = new HashSet<>();
-  @NonNull private final TextInputPlugin textInputPlugin;
+  protected final Responder[] responders;
+  private final HashSet<KeyEvent> redispatchedEvents = new HashSet<>();
+  private final TextInputPlugin textInputPlugin;
   private final View view;
 
   public boolean handleEvent(@NonNull KeyEvent keyEvent) {

shell/platform/android/io/flutter/embedding/android/MotionEventTracker.java

@@ -2,6 +2,7 @@
 
 import android.util.LongSparseArray;
 import android.view.MotionEvent;
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import java.util.PriorityQueue;
 import java.util.concurrent.atomic.AtomicLong;
@@ -18,10 +19,12 @@ private MotionEventId(long id) {
       this.id = id;
     }
 
+    @NonNull
     public static MotionEventId from(long id) {
       return new MotionEventId(id);
     }
 
+    @NonNull
     public static MotionEventId createUnique() {
       return MotionEventId.from(ID_COUNTER.incrementAndGet());
     }
@@ -35,6 +38,7 @@ public long getId() {
   private final PriorityQueue<Long> unusedEvents;
   private static MotionEventTracker INSTANCE;
 
+  @NonNull
   public static MotionEventTracker getInstance() {
     if (INSTANCE == null) {
       INSTANCE = new MotionEventTracker();
@@ -48,7 +52,8 @@ private MotionEventTracker() {
   }
 
   /** Tracks the event and returns a unique MotionEventId identifying the event. */
-  public MotionEventId track(MotionEvent event) {
+  @NonNull
+  public MotionEventId track(@NonNull MotionEvent event) {
     MotionEventId eventId = MotionEventId.createUnique();
     eventById.put(eventId.id, MotionEvent.obtain(event));
     unusedEvents.add(eventId.id);
@@ -61,7 +66,7 @@ public MotionEventId track(MotionEvent event) {
    * popped or discarded.
    */
   @Nullable
-  public MotionEvent pop(MotionEventId eventId) {
+  public MotionEvent pop(@NonNull MotionEventId eventId) {
     // remove all the older events.
     while (!unusedEvents.isEmpty() && unusedEvents.peek() < eventId.id) {
       eventById.remove(unusedEvents.poll());

shell/platform/android/io/flutter/embedding/engine/deferredcomponents/PlayStoreDeferredComponentManager.java

@@ -66,7 +66,7 @@ public class PlayStoreDeferredComponentManager implements DeferredComponentManag
 
   private class FeatureInstallStateUpdatedListener implements SplitInstallStateUpdatedListener {
     @SuppressLint("DefaultLocale")
-    public void onStateUpdate(SplitInstallSessionState state) {
+    public void onStateUpdate(@NonNull SplitInstallSessionState state) {
       int sessionId = state.sessionId();
       if (sessionIdToName.get(sessionId) != null) {
         switch (state.status()) {
@@ -231,7 +231,7 @@ private boolean verifyJNI() {
     return true;
   }
 
-  public void setDeferredComponentChannel(DeferredComponentChannel channel) {
+  public void setDeferredComponentChannel(@NonNull DeferredComponentChannel channel) {
     this.channel = channel;
   }
 
@@ -288,7 +288,7 @@ private void initLoadingUnitMappingToComponentNames() {
     }
   }
 
-  public void installDeferredComponent(int loadingUnitId, String componentName) {
+  public void installDeferredComponent(int loadingUnitId, @Nullable String componentName) {
     String resolvedComponentName =
         componentName != null ? componentName : loadingUnitIdToComponentNames.get(loadingUnitId);
     if (resolvedComponentName == null) {
@@ -357,7 +357,9 @@ public void installDeferredComponent(int loadingUnitId, String componentName) {
             });
   }
 
-  public String getDeferredComponentInstallState(int loadingUnitId, String componentName) {
+  @NonNull
+  public String getDeferredComponentInstallState(
+      int loadingUnitId, @Nullable String componentName) {
     String resolvedComponentName =
         componentName != null ? componentName : loadingUnitIdToComponentNames.get(loadingUnitId);
     if (resolvedComponentName == null) {
@@ -375,7 +377,7 @@ public String getDeferredComponentInstallState(int loadingUnitId, String compone
     return sessionIdToState.get(sessionId);
   }
 
-  public void loadAssets(int loadingUnitId, String componentName) {
+  public void loadAssets(int loadingUnitId, @NonNull String componentName) {
     if (!verifyJNI()) {
       return;
     }
@@ -393,7 +395,7 @@ public void loadAssets(int loadingUnitId, String componentName) {
     }
   }
 
-  public void loadDartLibrary(int loadingUnitId, String componentName) {
+  public void loadDartLibrary(int loadingUnitId, @NonNull String componentName) {
     if (!verifyJNI()) {
       return;
     }
@@ -478,7 +480,7 @@ public void loadDartLibrary(int loadingUnitId, String componentName) {
         loadingUnitId, searchPaths.toArray(new String[searchPaths.size()]));
   }
 
-  public boolean uninstallDeferredComponent(int loadingUnitId, String componentName) {
+  public boolean uninstallDeferredComponent(int loadingUnitId, @Nullable String componentName) {
     String resolvedComponentName =
         componentName != null ? componentName : loadingUnitIdToComponentNames.get(loadingUnitId);
     if (resolvedComponentName == null) {

shell/platform/android/io/flutter/embedding/engine/plugins/shim/ShimPluginRegistry.java

@@ -48,7 +48,8 @@ public ShimPluginRegistry(@NonNull FlutterEngine flutterEngine) {
   }
 
   @Override
-  public Registrar registrarFor(String pluginKey) {
+  @NonNull
+  public Registrar registrarFor(@NonNull String pluginKey) {
     Log.v(TAG, "Creating plugin Registrar for '" + pluginKey + "'");
     if (pluginMap.containsKey(pluginKey)) {
       throw new IllegalStateException("Plugin key " + pluginKey + " is already in use");
@@ -60,13 +61,13 @@ public Registrar registrarFor(String pluginKey) {
   }
 
   @Override
-  public boolean hasPlugin(String pluginKey) {
+  public boolean hasPlugin(@NonNull String pluginKey) {
     return pluginMap.containsKey(pluginKey);
   }
 
   @Override
   @SuppressWarnings("unchecked")
-  public <T> T valuePublishedByPlugin(String pluginKey) {
+  public <T> T valuePublishedByPlugin(@NonNull String pluginKey) {
     return (T) pluginMap.get(pluginKey);
   }
 

shell/platform/android/io/flutter/embedding/engine/renderer/SurfaceTextureWrapper.java

@@ -67,7 +67,7 @@ public void detachFromGLContext() {
 
   // Called by native.
   @SuppressWarnings("unused")
-  public void getTransformMatrix(float[] mtx) {
+  public void getTransformMatrix(@NonNull float[] mtx) {
     surfaceTexture.getTransformMatrix(mtx);
   }
 }

shell/platform/android/io/flutter/embedding/engine/systemchannels/LocalizationChannel.java

@@ -110,6 +110,7 @@ public interface LocalizationMessageHandler {
      * The Flutter application would like to obtain the string resource of given {@code key} in
      * {@code locale}.
      */
-    String getStringResource(@NonNull String key, String locale);
+    @NonNull
+    String getStringResource(@NonNull String key, @NonNull String locale);
   }
 }

shell/platform/android/io/flutter/embedding/engine/systemchannels/RestorationChannel.java

@@ -5,6 +5,7 @@
 package io.flutter.embedding.engine.systemchannels;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import io.flutter.Log;
 import io.flutter.embedding.engine.dart.DartExecutor;
 import io.flutter.plugin.common.MethodCall;
@@ -72,12 +73,13 @@ public RestorationChannel(
   private boolean frameworkHasRequestedData = false;
 
   /** Obtain the most current restoration data that the framework has provided. */
+  @Nullable
   public byte[] getRestorationData() {
     return restorationData;
   }
 
   /** Set the restoration data from which the framework will restore its state. */
-  public void setRestorationData(byte[] data) {
+  public void setRestorationData(@NonNull byte[] data) {
     engineHasProvidedData = true;
     if (pendingFrameworkRestorationChannelRequest != null) {
       // If their is a pending request from the framework, answer it.

shell/platform/android/io/flutter/embedding/engine/systemchannels/TextInputChannel.java

@@ -205,7 +205,7 @@ private static HashMap<Object, Object> createEditingDeltaJSON(
    */
   public void updateEditingState(
       int inputClientId,
-      String text,
+      @NonNull String text,
       int selectionStart,
       int selectionEnd,
       int composingStart,
@@ -235,7 +235,7 @@ public void updateEditingState(
   }
 
   public void updateEditingStateWithDeltas(
-      int inputClientId, ArrayList<TextEditingDelta> batchDeltas) {
+      int inputClientId, @NonNull ArrayList<TextEditingDelta> batchDeltas) {
 
     Log.v(
         TAG,
@@ -250,7 +250,7 @@ public void updateEditingStateWithDeltas(
   }
 
   public void updateEditingStateWithTag(
-      int inputClientId, HashMap<String, TextEditState> editStates) {
+      int inputClientId, @NonNull HashMap<String, TextEditState> editStates) {
     Log.v(
         TAG,
         "Sending message to update editing state for "
@@ -325,7 +325,8 @@ public void unspecifiedAction(int inputClientId) {
         Arrays.asList(inputClientId, "TextInputAction.unspecified"));
   }
 
-  public void performPrivateCommand(int inputClientId, String action, Bundle data) {
+  public void performPrivateCommand(
+      int inputClientId, @NonNull String action, @NonNull Bundle data) {
     HashMap<Object, Object> json = new HashMap<>();
     json.put("action", action);
     if (data != null) {
@@ -415,7 +416,7 @@ public interface TextInputMethodHandler {
      * @param transform a 4x4 matrix that maps the local paint coordinate system to coordinate
      *     system of the FlutterView that owns the current client.
      */
-    void setEditableSizeAndTransform(double width, double height, double[] transform);
+    void setEditableSizeAndTransform(double width, double height, @NonNull double[] transform);
 
     // TODO(mattcarroll): javadoc
     void setEditingState(@NonNull TextEditState editingState);
@@ -432,11 +433,12 @@ public interface TextInputMethodHandler {
      *     commands.
      * @param data Any data to include with the command.
      */
-    void sendAppPrivateCommand(String action, Bundle data);
+    void sendAppPrivateCommand(@NonNull String action, @NonNull Bundle data);
   }
 
   /** A text editing configuration. */
   public static class Configuration {
+    @NonNull
     public static Configuration fromJson(@NonNull JSONObject json)
         throws JSONException, NoSuchFieldException {
       final String inputActionName = json.getString("inputAction");
@@ -494,6 +496,7 @@ private static Integer inputActionFromTextInputAction(@NonNull String inputActio
     }
 
     public static class Autofill {
+      @NonNull
       public static Autofill fromJson(@NonNull JSONObject json)
           throws JSONException, NoSuchFieldException {
         final String uniqueIdentifier = json.getString("uniqueIdentifier");
@@ -729,6 +732,7 @@ static TextCapitalization fromValue(@NonNull String encodedName) throws NoSuchFi
 
   /** State of an on-going text editing session. */
   public static class TextEditState {
+    @NonNull
     public static TextEditState fromJson(@NonNull JSONObject textEditState) throws JSONException {
       return new TextEditState(
           textEditState.getString("text"),

shell/platform/android/io/flutter/plugin/common/JSONMessageCodec.java

@@ -4,6 +4,7 @@
 
 package io.flutter.plugin.common;
 
+import androidx.annotation.Nullable;
 import java.nio.ByteBuffer;
 import org.json.JSONException;
 import org.json.JSONObject;
@@ -28,7 +29,8 @@ public final class JSONMessageCodec implements MessageCodec<Object> {
   private JSONMessageCodec() {}
 
   @Override
-  public ByteBuffer encodeMessage(Object message) {
+  @Nullable
+  public ByteBuffer encodeMessage(@Nullable Object message) {
     if (message == null) {
       return null;
     }
@@ -41,7 +43,8 @@ public ByteBuffer encodeMessage(Object message) {
   }
 
   @Override
-  public Object decodeMessage(ByteBuffer message) {
+  @Nullable
+  public Object decodeMessage(@Nullable ByteBuffer message) {
     if (message == null) {
       return null;
     }