[英]Android : Need to create Shared Preferences object in c++ NDK and Store some Boolean value
我是新手,不知道如何開始,
我創建了一個使用 Android.mk 鏈接到 C++ 的項目
因此,當我從 Java 調用方法時,它應該將布爾值存儲到我的共享首選項對象中。
這是我的 JNI 方法
extern "C"
JNIEXPORT void JNICALL
Java_com_example_sample_storeBoolean(JNIEnv *env,jobject instance){
//TODO
const char *name ="hello";
__android_log_print(ANDROID_LOG_ERROR, "TRACKERS", "***** %s *****", name);
}
我打印的正常日志現在正在工作只需要創建 sharepreference 對象並設置布爾值
SharedPreferences prefs = context.getSharedPreferences("myprefdata", Context.MODE_PRIVATE);
prefs.edit().putBoolean("settingnootification", true).commit();
請指導我該怎么做。 謝謝
public abstract SharedPreferences getSharedPreferences(String name, int mode);
需要在c++中使用這個方法
我剛剛在 JNI 的 MainActivity 中調用saveBoolean(boolean bool)
並保存了值。 這是代碼:MainActivity
public class MainActivity extends AppCompatActivity {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
stringFromJNI(this);
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native void stringFromJNI(MainActivity mainActivity);
public void saveBoolean(boolean bool){
SharedPreferences sharedPreferences = this.getSharedPreferences("Test", Context.MODE_PRIVATE);
sharedPreferences.edit().putBoolean("testBool",bool).commit();
Log.d("MainActivity","saveBoolean Called "+bool);
}
}
#include <jni.h>
#include <string>
extern "C"
JNIEXPORT void JNICALL
Java_com_android_techgig_sharedpref_MainActivity_stringFromJNI(JNIEnv *env,jobject obj /* this */) {
jclass cls = (env)->GetObjectClass(obj); //for getting class
jmethodID mid = (env)->GetMethodID(cls, "saveBoolean", "(Z)V"); //for getting method signature, Z for boolean
if (mid == 0)
return;
//will return 0 in case of class not found
(env)->CallVoidMethod(obj, mid, true); //now calling actual method
printf("native called");
}
這是方法簽名類型
Signature Java Type
Z boolean
B byte
C char
S short
I int
J long
F float
D double
這是探索更多的鏈接..
編碼快樂!!!
我猜您想從您的代碼中調用 Java 類。 我建議從您的 C++ 代碼中調用 Java。
看看這里:
https://github.com/mkowsiak/jnicookbook/tree/master/recipes/recipeNo032
在此示例中,您要做的是:
您可能需要一些輔助類來簡化事情。 例如 PreferencesStorer - 您將在其中獲得適當的首選項類並傳遞要存儲的值。
看看這里:
public static int fun() {
System.out.println("From JVM");
return 0;
}
這是您要調用的方法,但您希望它是:store(String value, int mode)。
在您的代碼(Java 中)中,您需要創建此對象並將其作為參數傳遞給您的 C++ 代碼。 在 C++ 中,您想調用此對象的方法。 在 JVM 內部,它將已經存在——准備好被調用。
如果這不是您想要的,我認為您需要提供更多信息以使整個用例更加清晰。
玩得開心 JNI
我需要調用 getSharedPreferences() 方法,那么如何調用它並存儲布爾值。
因此,我創建了兩個用於在 NDK C++ 中存儲和檢索布爾值的簡單方法
主活動.java
public class MainActivity extends Activity {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("Native");
}
private Activity activity;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
activity=MainActivity.this;
setStoreBoolValues(activity, true);
if (getStoreValues(activity))
Log.e("Store Value", " ** true **");
else
Log.e("Store Value", " ** false **");
}
public native boolean getStoreValues(Activity activity);
public native void setStoreBoolValues(Activity activity, boolean flag);
}
在 MainActivity 中聲明了 Native Method,也調用了 my.so 文件
本機類.Cpp
jobject mainClass;
jstring spname(JNIEnv *env) {
return env->NewStringUTF("sharedstore");
}
jstring objectname(JNIEnv *env) {
return env->NewStringUTF("boolvaluestore");
}
extern "C"
JNIEXPORT jboolean JNICALL
Java_com_ebizzinfotech_amjad_contentresolverproj_MainActivity_getStoreValues(JNIEnv *env,
jobject instance,
jobject activity) {
jclass spcls = env->FindClass("android/content/SharedPreferences");
jclass contextcls = env->FindClass("android/content/Context");
mainClass = env->NewGlobalRef(activity);
jmethodID mid = env->GetMethodID(contextcls, "getSharedPreferences",
"(Ljava/lang/String;I)Landroid/content/SharedPreferences;");
jmethodID midbool = env->GetMethodID(spcls, "getBoolean",
"(Ljava/lang/String;Z)Z");
jobject jobjectshared = env->CallObjectMethod(mainClass, mid, spname(env), 0);
// jobject jobjectsharededit = env->CallObjectMethod(jobjectshared,midedit);
jboolean jboolean1 = env->CallBooleanMethod(jobjectshared, midbool,objectname(env), JNI_FALSE);
env->DeleteLocalRef(spcls);
env->DeleteLocalRef(contextcls);
return jboolean1;
}
extern "C"
JNIEXPORT void JNICALL
Java_com_ebizzinfotech_amjad_contentresolverproj_MainActivity_setStoreBoolValues(JNIEnv *env,
jobject instance,
jobject activity,
jboolean flag) {
jclass spcls = env->FindClass("android/content/SharedPreferences");
jclass speditorcls = env->FindClass("android/content/SharedPreferences$Editor");
jclass contextcls = env->FindClass("android/content/Context");
mainClass = env->NewGlobalRef(activity);
jmethodID mid = env->GetMethodID(contextcls, "getSharedPreferences",
"(Ljava/lang/String;I)Landroid/content/SharedPreferences;");
jmethodID midedit = env->GetMethodID(spcls, "edit",
"()Landroid/content/SharedPreferences$Editor;");
jmethodID midputbool = env->GetMethodID(speditorcls, "putBoolean",
"(Ljava/lang/String;Z)Landroid/content/SharedPreferences$Editor;");
jmethodID midapply = env->GetMethodID(speditorcls, "apply",
"()V");
jobject jobjectshared = env->CallObjectMethod(mainClass, mid,spname(env), 0);
jobject jobjectsharededit = env->CallObjectMethod(jobjectshared, midedit);
env->CallVoidMethod(env->CallObjectMethod(jobjectsharededit, midputbool, objectname(env), flag),
midapply);
env->DeleteLocalRef(spcls);
env->DeleteLocalRef(contextcls);
env->DeleteLocalRef(speditorcls);
}
我創建了兩個.cpp 類:用於讀取的SharedPreferences和用於寫入的SharedPreferences_Editor它們不需要任何特殊的Java 代碼,您應該能夠通過復制粘貼輕松地將它們包含在您的項目中。
//
// Created by Constantin on 24.10.2017.
//
#ifndef FPV_VR_HELPER_SHARED_PREFERENCES_HPP
#define FPV_VR_HELPER_SHARED_PREFERENCES_HPP
#include <jni.h>
#include <android/log.h>
#include <string>
///Example reading values
///SharedPreferences sharedPref(env,context,"pref_telemetry");
///T_Protocol=sharedPref.getInt(IDT::T_Protocol);
///Example writing values
///SharedPreferences_Editor editor=sharedPref.edit();
///editor.putString("MY_KEY","HELLO");
///editor.commit();
class SharedPreferences_Editor{
public:
SharedPreferences_Editor(JNIEnv* env,const jobject joSharedPreferences_Edit):env(env),joSharedPreferences_Edit(joSharedPreferences_Edit){
//find the methods for putting values into Shared preferences via the editor
jclass jcSharedPreferences_Editor = env->GetObjectClass(joSharedPreferences_Edit);
jmPutBoolean=env->GetMethodID(jcSharedPreferences_Editor,"putBoolean","(Ljava/lang/String;Z)Landroid/content/SharedPreferences$Editor;");
jmPutInt=env->GetMethodID(jcSharedPreferences_Editor,"putInt","(Ljava/lang/String;I)Landroid/content/SharedPreferences$Editor;");
jmPutString=env->GetMethodID(jcSharedPreferences_Editor,"putString","(Ljava/lang/String;Ljava/lang/String;)Landroid/content/SharedPreferences$Editor;");
jmCommit=env->GetMethodID(jcSharedPreferences_Editor,"commit","()Z");
}
//return itself for method chaining
const SharedPreferences_Editor& putBoolean(const char* key,const bool value)const{
env->CallObjectMethod(joSharedPreferences_Edit,jmPutBoolean,env->NewStringUTF(key),(jboolean)value);
return *this;
}
const SharedPreferences_Editor& putInt(const char* key,const int value)const{
env->CallObjectMethod(joSharedPreferences_Edit,jmPutInt,env->NewStringUTF(key),(jint)value);
return *this;
}
const SharedPreferences_Editor& putString(const char* key,const char* value)const{
env->CallObjectMethod(joSharedPreferences_Edit,jmPutString,env->NewStringUTF(key),env->NewStringUTF(value));
return *this;
}
bool commit()const{
return (bool)env->CallBooleanMethod(joSharedPreferences_Edit,jmCommit);
}
private:
JNIEnv* env;
jobject joSharedPreferences_Edit;
jmethodID jmPutBoolean;
jmethodID jmPutInt;
jmethodID jmPutString;
jmethodID jmCommit;
};
class SharedPreferences {
public:
SharedPreferences(SharedPreferences const &) = delete;
void operator=(SharedPreferences const &)= delete;
public:
//Note: Per default, this doesn't keep the reference to the sharedPreferences java object alive
//longer than the lifetime of the JNIEnv.
//With keepReference=true the joSharedPreferences is kept 'alive' and you can still use the class after the original JNIEnv* has become invalid -
//but make sure to refresh the JNIEnv* object with a new valid reference via replaceJNI()
SharedPreferences(JNIEnv *env, jobject androidContext,const char* name,const bool keepReference=false){
this->env=env;
//Find the 2 java classes we need to make calls with
jclass jcContext = env->FindClass("android/content/Context");
jclass jcSharedPreferences = env->FindClass("android/content/SharedPreferences");
//jclass jcSharedPreferences_Editor=env->FindClass("android/content/SharedPreferences$Editor");
if(jcContext==nullptr || jcSharedPreferences== nullptr){
__android_log_print(ANDROID_LOG_DEBUG, "SharedPreferences","Cannot find classes");
}
//find the 3 functions we need to get values from an SharedPreferences instance
jmGetBoolean=env->GetMethodID(jcSharedPreferences,"getBoolean","(Ljava/lang/String;Z)Z");
jmGetInt=env->GetMethodID(jcSharedPreferences,"getInt","(Ljava/lang/String;I)I");
jmGetFloat=env->GetMethodID(jcSharedPreferences,"getFloat","(Ljava/lang/String;F)F");
jmGetString=env->GetMethodID(jcSharedPreferences,"getString","(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;");
//find the 1 function we need to create the SharedPreferences.Editor object
jmEdit=env->GetMethodID(jcSharedPreferences,"edit", "()Landroid/content/SharedPreferences$Editor;");
//create a instance of SharedPreferences and store it in @joSharedPreferences
jmethodID jmGetSharedPreferences=env->GetMethodID(jcContext,"getSharedPreferences","(Ljava/lang/String;I)Landroid/content/SharedPreferences;");
joSharedPreferences=env->CallObjectMethod(androidContext,jmGetSharedPreferences,env->NewStringUTF(name),MODE_PRIVATE);
//jmEdit_commit=env->GetMethodID(jcSharedPreferences_Editor,"putString","(Ljava/lang/String;Ljava/lang/String;)Landroid/content/SharedPreferences$Editor;");
if(keepReference){
joSharedPreferences=env->NewWeakGlobalRef(joSharedPreferences);
}
}
void replaceJNI(JNIEnv* newEnv){
env=newEnv;
}
private:
JNIEnv* env;
jobject joSharedPreferences;
jmethodID jmGetBoolean;
jmethodID jmGetInt;
jmethodID jmGetFloat;
jmethodID jmGetString;
jmethodID jmEdit;
public:
bool getBoolean(const char* id,bool defaultValue=false)const{
return (bool)(env->CallBooleanMethod(joSharedPreferences,jmGetBoolean,env->NewStringUTF(id),(jboolean)defaultValue));
}
int getInt(const char* id,int defaultValue=0)const{
return (int)(env->CallIntMethod(joSharedPreferences,jmGetInt,env->NewStringUTF(id),(jint)defaultValue));
}
float getFloat(const char* id,float defaultValue=0.0f)const{
return (float)(env->CallFloatMethod(joSharedPreferences,jmGetFloat,env->NewStringUTF(id),(jfloat)defaultValue));
}
std::string getString(const char* id,const char* defaultValue="")const{
auto value=(jstring)(env->CallObjectMethod(joSharedPreferences,jmGetString,env->NewStringUTF(id),env->NewStringUTF(defaultValue)));
const char* valueP = env->GetStringUTFChars(value, nullptr);
const std::string ret=std::string(valueP);
env->ReleaseStringUTFChars(value,valueP);
//__android_log_print(ANDROID_LOG_DEBUG, "SharedPreferences","%s",ret.c_str());
return ret;
}
SharedPreferences_Editor edit()const{
//create a instance of SharedPreferences.Editor and store it in @joSharedPreferences_Edit
jobject joSharedPreferences_Edit=env->CallObjectMethod(joSharedPreferences,jmEdit);
SharedPreferences_Editor editor(env,joSharedPreferences_Edit);
return editor;
}
private:
static constexpr const int MODE_PRIVATE = 0; //taken directly from java, assuming this value stays constant in java
};
#endif //FPV_VR_HELPER_SHARED_PREFERENCES_HPP
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