Android将char数组发送到JNI C ++

Question

Good day

I have a question how to send my char array to jni c++ code? I know how send int number only..

A have this array char[] chars = password.toCharArray();

and private native void JNIEncrypt(char[] chars);

My JNI method look like this

Java_com_kru13_ndkdemos_MainActivity_JNIEncrypt( JNIEnv* env, jobject  obj, ?????)

I would like to ask how it should look JNI method? I need use char array in c++ code

than you

Answer 1

It would be:

Java_com_kru13_ndkdemos_MainActivity_JNIEncrypt( JNIEnv* env, jobject  obj, jcharArray array)

Inside the function you will have to use env->GetCharArrayElements(...) .

Answer 2

Why not just pass it as a String , which is jstring in JNI:

// Java side
private native void JNIEncrypt(String password);

// Native JNI side
Java_com_kru13_ndkdemos_MainActivity_JNIEncrypt(JNIEnv* env, jobject thiz, jstring password);

You can then access the string JNI side via GetStringChars () and related or GetStringUTFChars (). For example:

const char* utf8 = env->GetStringUTFChars(password, NULL);
// do something with utf8
env->ReleaseStringUTFChars(password, utf8);

Answer 3

toCharArray gets you the sequence of Unicode/UTF-16 code-units from the string. On Android, You will probably want Unicode/UTF-8 on the C++ side, but that depends on the C++ libraries you want to use. Once, you know, use the Java String class to get the bytes.

Note: GetStringUTFChars gives you modified UTF-8 code-units, which Unicode-compliant libraries reject for many characters.

private void JNIEncrypt(String string) {
    JNIEncrypt(string.getBytes("UTF-8")); 
    // Or, for the OS default, string.getBytes()
}

private native void JNIEncrypt(byte[] chars);