Prefer ScopedUtfChars where possible

Minor refactor of input-related files to use safer ScopedUtfChars
constructs.

Fixes: 119214506
Test: make sure the device boots with an -eng build
Change-Id: I7980100be616c921d522484277444546ebdab56b

core/jni/android_hardware_input_InputApplicationHandle.cpp

@@ -17,6 +17,7 @@
 #define LOG_TAG "InputApplicationHandle"
 
 #include <nativehelper/JNIHelp.h>
+#include "core_jni_helpers.h"
 #include "jni.h"
 #include <android_runtime/AndroidRuntime.h>
 #include <utils/threads.h>
@@ -63,16 +64,7 @@ bool NativeInputApplicationHandle::updateInfo() {
         mInfo = new InputApplicationInfo();
     }
 
-    jstring nameObj = jstring(env->GetObjectField(obj,
-            gInputApplicationHandleClassInfo.name));
-    if (nameObj) {
-        const char* nameStr = env->GetStringUTFChars(nameObj, NULL);
-        mInfo->name = nameStr;
-        env->ReleaseStringUTFChars(nameObj, nameStr);
-        env->DeleteLocalRef(nameObj);
-    } else {
-        mInfo->name = "<null>";
-    }
+    mInfo->name = getStringField(env, obj, gInputApplicationHandleClassInfo.name, "<null>");
 
     mInfo->dispatchingTimeout = env->GetLongField(obj,
             gInputApplicationHandleClassInfo.dispatchingTimeoutNanos);

core/jni/android_hardware_input_InputWindowHandle.cpp

@@ -17,6 +17,7 @@
 #define LOG_TAG "InputWindowHandle"
 
 #include <nativehelper/JNIHelp.h>
+#include "core_jni_helpers.h"
 #include "jni.h"
 #include <android_runtime/AndroidRuntime.h>
 #include <utils/threads.h>
@@ -86,24 +87,14 @@ bool NativeInputWindowHandle::updateInfo() {
 
     mInfo.touchableRegion.clear();
 
-    jobject tokenObj = env->GetObjectField(obj,
-            gInputWindowHandleClassInfo.token);
+    jobject tokenObj = env->GetObjectField(obj, gInputWindowHandleClassInfo.token);
     if (tokenObj) {
         mInfo.token = ibinderForJavaObject(env, tokenObj);
     } else {
         mInfo.token.clear();
     }
 
-    jstring nameObj = jstring(env->GetObjectField(obj,
-            gInputWindowHandleClassInfo.name));
-    if (nameObj) {
-        const char* nameStr = env->GetStringUTFChars(nameObj, NULL);
-        mInfo.name = nameStr;
-        env->ReleaseStringUTFChars(nameObj, nameStr);
-        env->DeleteLocalRef(nameObj);
-    } else {
-        mInfo.name = "<null>";
-    }
+    mInfo.name = getStringField(env, obj, gInputWindowHandleClassInfo.name, "<null>");
 
     mInfo.layoutParamsFlags = env->GetIntField(obj,
             gInputWindowHandleClassInfo.layoutParamsFlags);
@@ -241,8 +232,7 @@ int register_android_view_InputWindowHandle(JNIEnv* env) {
     GET_FIELD_ID(gInputWindowHandleClassInfo.ptr, clazz,
             "ptr", "J");
 
-    GET_FIELD_ID(gInputWindowHandleClassInfo.inputApplicationHandle,
-            clazz,
+    GET_FIELD_ID(gInputWindowHandleClassInfo.inputApplicationHandle, clazz,
             "inputApplicationHandle", "Landroid/view/InputApplicationHandle;");
 
     GET_FIELD_ID(gInputWindowHandleClassInfo.token, clazz,

core/jni/android_view_InputChannel.cpp

@@ -17,7 +17,7 @@
 #define LOG_TAG "InputChannel-JNI"
 
 #include <nativehelper/JNIHelp.h>
-
+#include "nativehelper/scoped_utf_chars.h"
 #include <android_runtime/AndroidRuntime.h>
 #include <binder/Parcel.h>
 #include <utils/Log.h>
@@ -123,9 +123,8 @@ static jobject android_view_InputChannel_createInputChannel(JNIEnv* env,
 
 static jobjectArray android_view_InputChannel_nativeOpenInputChannelPair(JNIEnv* env,
         jclass clazz, jstring nameObj) {
-    const char* nameChars = env->GetStringUTFChars(nameObj, NULL);
-    std::string name = nameChars;
-    env->ReleaseStringUTFChars(nameObj, nameChars);
+    ScopedUtfChars nameChars(env, nameObj);
+    std::string name = nameChars.c_str();
 
     sp<InputChannel> serverChannel;
     sp<InputChannel> clientChannel;

core/jni/core_jni_helpers.h

@@ -18,6 +18,8 @@
 #define CORE_JNI_HELPERS
 
 #include <nativehelper/JNIHelp.h>
+#include <nativehelper/scoped_local_ref.h>
+#include <nativehelper/scoped_utf_chars.h>
 #include <android_runtime/AndroidRuntime.h>
 
 namespace android {
@@ -72,6 +74,20 @@ static inline int RegisterMethodsOrDie(JNIEnv* env, const char* className,
     return res;
 }
 
+/**
+ * Read the specified field from jobject, and convert to std::string.
+ * If the field cannot be obtained, return defaultValue.
+ */
+static inline std::string getStringField(JNIEnv* env, jobject obj, jfieldID fieldId,
+        const char* defaultValue) {
+    ScopedLocalRef<jstring> strObj(env, jstring(env->GetObjectField(obj, fieldId)));
+    if (strObj != nullptr) {
+        ScopedUtfChars chars(env, strObj.get());
+        return std::string(chars.c_str());
+    }
+    return std::string(defaultValue);
+}
+
 }  // namespace android
 
 #endif  // CORE_JNI_HELPERS