Add @NonNull / @Nullable annotations to android.mtp API.

BUG=26758882

Change-Id: Ic86d2253114b487d68a069f3e63f19b200d6cb97

media/java/android/mtp/MtpDeviceInfo.java

@@ -16,6 +16,8 @@
 
 package android.mtp;
 
+import android.annotation.NonNull;
+
 /**
  * This class encapsulates information about an MTP device.
  * This corresponds to the DeviceInfo Dataset described in
@@ -39,7 +41,7 @@ public class MtpDeviceInfo {
      *
      * @return the manufacturer name
      */
-    public final String getManufacturer() {
+    public final @NonNull String getManufacturer() {
         return mManufacturer;
     }
 
@@ -48,7 +50,7 @@ public class MtpDeviceInfo {
      *
      * @return the model name
      */
-    public final String getModel() {
+    public final @NonNull String getModel() {
         return mModel;
     }
 
@@ -57,7 +59,7 @@ public class MtpDeviceInfo {
      *
      * @return the device version
      */
-    public final String getVersion() {
+    public final @NonNull String getVersion() {
         return mVersion;
     }
 
@@ -66,7 +68,7 @@ public class MtpDeviceInfo {
      *
      * @return the serial number
      */
-    public final String getSerialNumber() {
+    public final @NonNull String getSerialNumber() {
         return mSerialNumber;
     }
 
@@ -110,7 +112,7 @@ public class MtpDeviceInfo {
      * @see MtpConstants#OPERATION_SET_OBJECT_REFERENCES
      * @see MtpConstants#OPERATION_SKIP
      */
-    public final int[] getOperationsSupported() {
+    public final @NonNull int[] getOperationsSupported() {
         return mOperationsSupported;
     }
 
@@ -137,7 +139,7 @@ public class MtpDeviceInfo {
      * @see MtpEvent#EVENT_OBJECT_PROP_DESC_CHANGED
      * @see MtpEvent#EVENT_OBJECT_REFERENCES_CHANGED
      */
-    public final int[] getEventsSupported() {
+    public final @NonNull int[] getEventsSupported() {
         return mEventsSupported;
     }
 
@@ -163,7 +165,7 @@ public class MtpDeviceInfo {
      * Returns if the code set contains code.
      * @hide
      */
-    private static boolean isSupported(int[] set, int code) {
+    private static boolean isSupported(@NonNull int[] set, int code) {
         for (final int element : set) {
             if (element == code) {
                 return true;

media/java/android/mtp/MtpObjectInfo.java

@@ -16,8 +16,13 @@
 
 package android.mtp;
 
+import android.annotation.NonNull;
+import android.os.Build;
+
 import com.android.internal.util.Preconditions;
 
+import dalvik.system.VMRuntime;
+
 /**
  * This class encapsulates information about an object on an MTP device.
  * This corresponds to the ObjectInfo Dataset described in
@@ -40,10 +45,10 @@ public final class MtpObjectInfo {
     private int mAssociationType;
     private int mAssociationDesc;
     private int mSequenceNumber;
-    private String mName;
+    private String mName = "";
     private long mDateCreated;
     private long mDateModified;
-    private String mKeywords;
+    private String mKeywords = "";
 
     // only instantiated via JNI or via a builder
     private MtpObjectInfo() {
@@ -311,7 +316,7 @@ public final class MtpObjectInfo {
      *
      * @return the object's name
      */
-    public final String getName() {
+    public final @NonNull String getName() {
         return mName;
     }
 
@@ -340,7 +345,7 @@ public final class MtpObjectInfo {
      *
      * @return the object's keyword list
      */
-    public final String getKeywords() {
+    public final @NonNull String getKeywords() {
         return mKeywords;
     }
 
@@ -435,12 +440,20 @@ public final class MtpObjectInfo {
             return this;
         }
 
-        public Builder setKeywords(String value) {
+        public Builder setKeywords(@NonNull String value) {
+            if (VMRuntime.getRuntime().getTargetSdkVersion() > Build.VERSION_CODES.N_MR1) {
+                Preconditions.checkNotNull(value);
+            } else if (value == null) {
+                // Before N_MR1 we accept null value and it was regarded as an empty string in
+                // MtpDevice#sendObjectInfo.
+                value = "";
+            }
             mObjectInfo.mKeywords = value;
             return this;
         }
 
-        public Builder setName(String value) {
+        public Builder setName(@NonNull String value) {
+            Preconditions.checkNotNull(value);
             mObjectInfo.mName = value;
             return this;
         }

media/java/android/mtp/MtpStorageInfo.java

@@ -16,6 +16,8 @@
 
 package android.mtp;
 
+import android.annotation.NonNull;
+
 /**
  * This class encapsulates information about a storage unit on an MTP device.
  * This corresponds to the StorageInfo Dataset described in
@@ -68,7 +70,7 @@ public final class MtpStorageInfo {
      *
      * @return the storage unit description
      */
-    public final String getDescription() {
+    public final @NonNull String getDescription() {
         return mDescription;
     }
 
@@ -77,7 +79,7 @@ public final class MtpStorageInfo {
      *
      * @return the storage volume identifier
      */
-    public final String getVolumeIdentifier() {
+    public final @NonNull String getVolumeIdentifier() {
         return mVolumeIdentifier;
     }
 }