Creates a generic mechanism to dump app-side information.

Currently, 'dumpsys activity' can dump the state of some managers:
 - AutofillManager
 - ContentCapturemaanger
 - UiTranslationController

But the support for these custom dumping is hardcoded into
Activity itself, which makes it harder to extend. For example,
automotive builds provide an app-side Car object, which currently
cannot be dumped.

This CL makes the mechanism more flexible by providing a couple new
public / SystemAPIs that let Automotive (or other mainline modules)
extend it.

Examples:

$ adb shell dumpsys activity com.android.car.carlauncher/.CarLauncher --list-dumpables
$ adb shell dumpsys activity com.android.car.carlauncher/.CarLauncher --dump-dumpable CarUserManager
$ adb shell dumpsys activity service com.android.systemui/.SystemUIService CarUserManager

NOTE: this CL only adds the new APIs; a follow-up CL will change the
existing managers to use them.

Test: see above
Test: m update-api

Bug: 149254050
CTS-Coverage-Bug: 149254050

Change-Id: I6920ff3542d3d75edd667c2c7658e9d0a7af534f

2 files changed, 87 insertions, 0 deletions

diff --git a/core/java/android/util/Dumpable.java b/core/java/android/util/Dumpable.java
new file mode 100644
index 000000000000..79c576d08866
--- /dev/null
+++ b/core/java/android/util/Dumpable.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.util;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+
+import java.io.PrintWriter;
+
+/**
+ * Represents an object whose state can be dumped into a {@link PrintWriter}.
+ */
+public interface Dumpable {
+
+    /**
+     * Gets the name of the {@link Dumpable}.
+     *
+     * @return class name, by default.
+     */
+    @NonNull
+    default String getDumpableName() {
+        return getClass().getName();
+    }
+
+    //TODO(b/149254050): decide whether it should take a ParcelFileDescription as well.
+
+    /**
+     * Dumps the internal state into the given {@code writer}.
+     *
+     * @param writer writer to be written to
+     * @param args optional list of arguments
+     */
+    void dump(@NonNull PrintWriter writer, @Nullable String[] args);
+}
diff --git a/core/java/android/util/DumpableContainer.java b/core/java/android/util/DumpableContainer.java
new file mode 100644
index 000000000000..04d19dc41926
--- /dev/null
+++ b/core/java/android/util/DumpableContainer.java
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.util;
+
+import android.annotation.NonNull;
+
+/**
+ * Objects that contains a list of {@link Dumpable}, which will be dumped when the object itself
+ * is dumped.
+ */
+public interface DumpableContainer {
+
+    /**
+     * Adds the given {@link Dumpable dumpable} to the container.
+     *
+     * <p>If a dumpable with the same {@link Dumpable#getDumpableName() name} was added before, this
+     * call is ignored.
+     *
+     * @param dumpable dumpable to be added.
+     *
+     * @throws IllegalArgumentException if the {@link Dumpable#getDumpableName() dumpable name} is
+     * {@code null}.
+     *
+     * @return {@code true} if the dumpable was added, {@code false} if the call was ignored.
+     */
+    boolean addDumpable(@NonNull Dumpable dumpable);
+}