Add ResourceId validation helper method

An invalid, 'null' resource ID is defined as 0. Apps often use -1.

Add a helper method that makes checking valid IDs easy and more
centralized.

Eventually make it public API.

Bug: 38393777
Test: manual
Change-Id: I969ec4a45e86bdab3d7f57d357d475b77c7f8a78

diff --git a/core/java/android/app/AlertDialog.java b/core/java/android/app/AlertDialog.java
index b7f1068..a44bd03 100644 (file)
--- a/core/java/android/app/AlertDialog.java
+++ b/core/java/android/app/AlertDialog.java
@@ -25,6 +25,7 @@ import android.annotation.StringRes;
 import android.annotation.StyleRes;
 import android.content.Context;
 import android.content.DialogInterface;
+import android.content.res.ResourceId;
 import android.database.Cursor;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
@@ -204,7 +205,7 @@ public class AlertDialog extends Dialog implements DialogInterface {
         mAlert = AlertController.create(getContext(), this, getWindow());
     }
 
-    static int resolveDialogTheme(Context context, int themeResId) {
+    static @StyleRes int resolveDialogTheme(Context context, @StyleRes int themeResId) {
         if (themeResId == THEME_TRADITIONAL) {
             return R.style.Theme_Dialog_Alert;
         } else if (themeResId == THEME_HOLO_DARK) {
@@ -215,7 +216,7 @@ public class AlertDialog extends Dialog implements DialogInterface {
             return R.style.Theme_DeviceDefault_Dialog_Alert;
         } else if (themeResId == THEME_DEVICE_DEFAULT_LIGHT) {
             return R.style.Theme_DeviceDefault_Light_Dialog_Alert;
-        } else if (Integer.compareUnsigned(themeResId, 0x01000000) >= 0) {
+        } else if (ResourceId.isValid(themeResId)) {
             // start of real resource IDs.
             return themeResId;
         } else {
@@ -450,7 +451,7 @@ public class AlertDialog extends Dialog implements DialogInterface {
          * @param context the parent context
          */
         public Builder(Context context) {
-            this(context, resolveDialogTheme(context, 0));
+            this(context, resolveDialogTheme(context, ResourceId.ID_NULL));
         }
 
         /**

diff --git a/core/java/android/app/Dialog.java b/core/java/android/app/Dialog.java
index 943c572..b162cb1 100644 (file)
--- a/core/java/android/app/Dialog.java
+++ b/core/java/android/app/Dialog.java
@@ -34,6 +34,7 @@ import android.content.ContextWrapper;
 import android.content.DialogInterface;
 import android.content.res.Configuration;
 import android.content.pm.ApplicationInfo;
+import android.content.res.ResourceId;
 import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.Bundle;
@@ -169,7 +170,7 @@ public class Dialog implements DialogInterface, Window.Callback,
 
     Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
         if (createContextThemeWrapper) {
-            if (themeResId == 0) {
+            if (themeResId == ResourceId.ID_NULL) {
                 final TypedValue outValue = new TypedValue();
                 context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true);
                 themeResId = outValue.resourceId;

diff --git a/core/java/android/appwidget/AppWidgetProviderInfo.java b/core/java/android/appwidget/AppWidgetProviderInfo.java
index 52fa8a6..fd1b0e0 100644 (file)
--- a/core/java/android/appwidget/AppWidgetProviderInfo.java
+++ b/core/java/android/appwidget/AppWidgetProviderInfo.java
@@ -20,6 +20,7 @@ import android.annotation.NonNull;
 import android.content.Context;
 import android.content.pm.ActivityInfo;
 import android.content.pm.PackageManager;
+import android.content.res.ResourceId;
 import android.content.res.Resources;
 import android.graphics.drawable.Drawable;
 import android.os.Parcel;
@@ -368,7 +369,7 @@ public class AppWidgetProviderInfo implements Parcelable {
         try {
             Resources resources = context.getPackageManager().getResourcesForApplication(
                     providerInfo.applicationInfo);
-            if (resourceId != 0) {
+            if (ResourceId.isValid(resourceId)) {
                 if (density < 0) {
                     density = 0;
                 }

diff --git a/core/java/android/content/res/ResourceId.java b/core/java/android/content/res/ResourceId.java
new file mode 100644 (file)
index 0000000..adb9cf1
--- /dev/null
+++ b/core/java/android/content/res/ResourceId.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2017 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.content.res;
+
+import android.annotation.AnyRes;
+
+/**
+ * Provides a set of utility methods for dealing with Resource IDs.
+ * @hide
+ */
+public final class ResourceId {
+
+    /**
+     * The {@code null} resource ID.
+     */
+    public static final @AnyRes int ID_NULL = 0;
+
+    /**
+     * Checks whether the integer {@code id} is a valid resource ID, as generated by AAPT.
+     * <p>Note that a negative integer is not necessarily an invalid resource ID, and custom
+     * validations that compare the {@code id} against {@code 0} are incorrect.</p>
+     * @param id The integer to validate.
+     * @return {@code true} if the integer is a valid resource ID.
+     */
+    public static boolean isValid(@AnyRes int id) {
+        // With the introduction of packages with IDs > 0x7f, resource IDs can be negative when
+        // represented as a signed Java int. Some legacy code assumes -1 is an invalid resource ID,
+        // despite the existing documentation.
+        return id != -1 && (id & 0xff000000) != 0 && (id & 0x00ff0000) != 0;
+    }
+}

diff --git a/core/java/android/content/res/Resources.java b/core/java/android/content/res/Resources.java
index e525ab3..60226d5 100644 (file)
--- a/core/java/android/content/res/Resources.java
+++ b/core/java/android/content/res/Resources.java
@@ -151,7 +151,7 @@ public class Resources {
     /** @hide */
     public static int selectSystemTheme(int curTheme, int targetSdkVersion, int orig, int holo,
             int dark, int deviceDefault) {
-        if (curTheme != 0) {
+        if (curTheme != ResourceId.ID_NULL) {
             return curTheme;
         }
         if (targetSdkVersion < Build.VERSION_CODES.HONEYCOMB) {