我喜欢 android,但不喜欢应用程序本身。我正在尝试使用 NDK -> MyczkowskiAdam/LuckyNumbersCppCMD 将我的学校作业重新创建为 Android 应用程序 从 C++ 打印输出到文本字段不是问题,但为了让我的程序工作,我必须将两个字符串(名字和姓氏)从文本字段输入传递到 C++ 并存储它们,以便主程序可以解释它,这就是我的意思真的很挣扎。
在我的 C++ 文件中,我必须将 FrNm 和 LstNm 传递给主程序进程:
int LuckyNumbersProcess(std::string FrNm, std::string LstNm) {
//stuff
//return LuckyNumber (int)
}
然后我有运行 LuckyNumbersProcess 并将 LuckyNumber 写入文本字段的 native 函数:
extern "C"
JNIEXPORT jstring JNICALL
Java_com_android_mycax_luckynumbers_MainActivity_Calculate (JNIEnv *env,
jobject ) {
LuckyNumbersProcess(FrNmFromJava, LstNmFromJava);
std::string sLuckyNumber = NumberToString(LuckyNumber);
return env->NewStringUTF(sLuckyNumber.c_str());
}
来自文本字段的输入显示存储在 FrNmFromJava 和 LstNmFromJava 中,但我该如何处理呢?
我试过这个方法:
extern "C"
JNIEXPORT void JNICALL
Java_com_android_mycax_luckynumbers_MainActivity_GetFirstName (JNIEnv * env,
jobject jobj) {
const char *str;
jclass myclass_class =(jclass) env->NewGlobalRef
(env->FindClass ("GetFirstNameFromField"));
// we need the MyClass constructor
jmethodID constructorID = env->GetMethodID
(myclass_class, "", "()V");
// and the sayHello() method
jmethodID methodID = env->GetMethodID
(myclass_class, "iFirstName", "()Ljava/lang/String;");
// instanciate a MyClass object
jobject myclass_object = env->NewObject
(myclass_class, constructorID);
// call the sayHello() method
jstring s = (jstring) env->CallObjectMethod
(myclass_object, methodID);
// convert the Java String to use it in C
str = env->GetStringUTFChars(s, 0);
//printf("%s" , str);
FrNmFromJava = str;
env->ReleaseStringUTFChars(s, str);
}
但它返回 JNI NewGlobalRef 调用时出现未决异常 java.lang.ClassNotFoundException: Did't find class "GetFirstNameFromField"on path:
这是我的 Java 文件:
public class MainActivity extends AppCompatActivity {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("luckynumbers");
}
EditText mFirstName;
EditText mLastName;
Button mButton;
GetFirstNameFromField gfn = new GetFirstNameFromField();
GetLastNameFromField gln = new GetLastNameFromField();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mFirstName = (EditText)findViewById(R.id.firstName);
mLastName = (EditText)findViewById(R.id.lastName);
mButton = (Button)findViewById(R.id.button);
mButton.setOnClickListener(
new View.OnClickListener()
{
public void onClick(View view)
{
gfn.iFirstName();
gln.iLastName();
GetFirstName();
GetLastName();
TextView tv = (TextView) findViewById(R.id.sample_text);
tv.setText(Calculate());
}
});
}
public class GetFirstNameFromField {
public String iFirstName() {
return mFirstName.getText().toString();
}
}
public class GetLastNameFromField {
public String iLastName() {
return mLastName.getText().toString();
}
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native String Calculate();
public native String GetFirstName();
public native String GetLastName();
}
任何帮助将不胜感激:)
最佳答案
好的,我知道了,现在一切正常。
在 java 中,我只是将两个字符串传递给本地方法
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mFirstName = (EditText)findViewById(R.id.firstName);
mLastName = (EditText)findViewById(R.id.lastName);
mButton = (Button)findViewById(R.id.button);
mButton.setOnClickListener(
new View.OnClickListener()
{
public void onClick(View view)
{
TextView tv = (TextView) findViewById(R.id.sample_text);
tv.setText(Calculate(mFirstName.getText().toString(),mLastName.getText().toString()));
}
});
}
public native String Calculate(String jFirstName, String jLastName);
在 C++ 中
extern "C"
JNIEXPORT jstring JNICALL
Java_com_android_mycax_luckynumbers_MainActivity_Calculate (JNIEnv *env, jobject, jstring cFirstName, jstring cLastName) {
const char *path = env->GetStringUTFChars(cFirstName, NULL);
const char *path2 = env->GetStringUTFChars(cLastName, NULL);
FrNmFromJava = ToString(path);
LstNmFromJava = ToString(path2);
LuckyNumbersProcess(FrNmFromJava, LstNmFromJava);
std::string sLuckyNumber = ToString(LuckyNumber);
ClearAll();
return env->NewStringUTF(sLuckyNumber.c_str());
}
关于java - NDK : Pass text field value to c++ string,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43309657/