- 新建Java JNI 类 MyJni.java，并编写JNI native方法。
public class MyJNI {
static {
System.loadLibrary("jni_native");
}
public static native String getStringFromNative();
public static native int OpenDeviceNode();
public static native int CloseDeviceNode();
public static native int IICWriteRead(byte[] wBuf, int wLen, byte[] rBuf, int rLen);
}
- 生成头文件，cmd进入到工程路径 NdkDemoappsrcmainjava，执行命令生成.h头文件。
javah -classpath . -jni com.csu.jni.MyJNI
在MyJNI.java文件的同级目录（mainjavacom.csu.jni）生成一个.h的头文件com_csu_jni_MyJNI.h。
#include#include #include #include #include #include #include #include #include #include #ifndef _Included_com_csu_jni_MyJNI #define _Included_com_csu_jni_MyJNI #ifdef __cplusplus extern "C" { #endif JNIEXPORT jstring JNICALL Java_com_csu_jni_MyJNI_getStringFromNative (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_OpenDeviceNode (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_CloseDeviceNode (JNIEnv *, jclass); JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_IICWriteRead (JNIEnv *, jclass, jbyteArray, jint, jbyteArray, jint); #ifdef __cplusplus } #endif #endif
- main下java同级目录新建jni目录，将step6生成的.h文件拷贝到jni目录，然后新建com_csu_jni_MyJNI.c文件，实现.h文件中的方法。
//
// Created by Admin on 2021/11/17.
//
#include "com_csu_jni_MyJNI.h"
#define LOG_TAG "MyJNI"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
#define DEVICE_NAME "/dev/myjni"
static int fd = -1;
int file_read(jbyte *rbuf, jint rlen) {
int ret;
if (fd < 0) {
LOGE("file_read(), JNI IS NOT OPENEDn");
}
LOGI("JNI file_read(), rlen=%d, rbuf=%dn", rlen, rbuf[0]);
ret = read(fd, rbuf, rlen);
if (ret < 0) {
LOGE("JNI read failed, ret=%dn", ret);
}
LOGI("JNI read success, ret=%dn", ret);
return ret;
}
int file_write(jbyte *wbuf, jint wlen) {
int ret;
if (fd < 0) {
LOGE("file_write(), JNI IS NOT OPENEDn");
}
LOGI("JNI file_write(), wlen=%d, wbuf=%dn", wlen, wbuf[0]);
ret = write(fd, wbuf, wlen);
if (ret < 0) {
LOGE("JNI write failed, ret=%dn", ret);
}
LOGI("JNI write success, ret=%dn", ret);
return ret;
}
JNIEXPORT jstring JNICALL Java_com_csu_jni_MyJNI_getStringFromNative(JNIEnv *env, jclass clazz) {
return (*env)->NewStringUTF(env, "My JNI string");
}
JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_OpenDeviceNode(JNIEnv *env, jclass clazz) {
fd = open(DEVICE_NAME, O_RDWR|O_NONBLOCK);
if (fd < 0) {
LOGE("MyJNI open device failed, fd =%dn", fd);
}
LOGI("MyJNI open device Success, fd =%dn", fd);
return fd;
}
JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_CloseDeviceNode(JNIEnv *env, jclass clazz) {
close(fd);
return 0;
}
JNIEXPORT jint JNICALL Java_com_csu_jni_MyJNI_IICWriteRead(JNIEnv *env, jclass clazz, jbyteArray wBuf, jint wLen, jbyteArray rBuf, jint rLen) {
int ret = 0;
// 将Java层的数据拷到缓冲区
jbyte* bufw = (*env)->GetByteArrayElements(env, wBuf, NULL);
//jbyte* bufr = (*env)->GetByteArrayElements(env, rBuf, NULL);
//jint wlen = (*env)->GetArrayLength(env, wBuf);
jint len = (*env)->GetArrayLength(env, rBuf);
// 驱动会把要读取数据的寄存器放在首位返回，所以从驱动获取的数据buf长度要+1
len = len + 1;
// 新建一个数组，用于将驱动数据拷贝到缓冲区
jbyteArray jarr = (*env)->NewByteArray(env, len);
jbyte* jbuf = (*env)->GetByteArrayElements(env, jarr, NULL);
LOGI("JNI IICWriteRead(), wlen=%d, rlen=%dn", wLen, rLen);
if (wLen > 1) {
ret = file_write(bufw, wLen);
LOGI("JNI IICWriteRead(), wlen=%d, ret=%dn", wLen, ret);
}
// get register addr
jbuf[0] = bufw[0];
if (rLen > 0) {
ret = file_read(jbuf, rLen);
LOGI("JNI IICWriteRead(), rlen=%d, ret=%d, rbuf=%d.%d.%d.%dn", rLen, ret, jbuf[1], jbuf[2], jbuf[3], jbuf[4]);
// 驱动返回缓存区的数据，首位为寄存器地址，真正获取的数据从下标1开始
memcpy(jbuf, jbuf + 1, len - 1);
// 将缓冲区的数据返回给Java形参
(*env)->SetByteArrayRegion(env, rBuf, 0, rLen, jbuf);
}
// 释放资源，避免内存泄漏
(*env)->ReleaseByteArrayElements(env, rBuf, jbuf, 0);
(*env)->DeleteLocalRef(env, jarr);
LOGI("JNI IICWriteRead(), ret=%dn", ret);
return ret;
}
- jni目录下新建Android.mk文件。
LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := jni_native LOCAL_SRC_FILES := com_csu_jni_MyJNI.c LOCAL_LDLIBS :=-llog APP_ABI := all include $(BUILD_SHARED_LIBRARY)
- cmd进入到工程路径 NdkDemoappsrcmainjava，执行命令编译生成.so文件。
ndk-build
在jni同级目录下会生成两个文件夹libs和obj。
-
将libs文件夹下的内容拷贝到module项目名下的libs目录。
-
module的build.gradle 文件的android{}节点中添加对libs的引用：
sourceSets {
main {
jniLibs.srcDirs = ['libs']
}
}
- Activity中调用JNI方法
MainActivity.java
public class MainActivity extends AppCompatActivity {
private static final String TAG = "lxy";
private TextView tvInfo;
private int id = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String str = MyJNI.getStringFromNative();
Log.i(TAG, "onCreate: rs = " + str);
Button btnOpen = findViewById(R.id.btn_open);
Button btnClose = findViewById(R.id.btn_close);
Button btnFwVersion = findViewById(R.id.btn_read_fw_version);
Button btnWrite = findViewById(R.id.btn_write);
Button btnRead = findViewById(R.id.btn_read);
tvInfo = findViewById(R.id.tv_info);
btnOpen.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (id > 0) {
Log.i(TAG, "onClick: device is opened!!!");
updateTextInfo("device is opened!!!");
} else {
id = MyJNI.OpenDeviceNode();
updateTextInfo("device open, id = " + id);
Log.i(TAG, "onClick: device open id = " + id);
}
}
});
btnClose.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (id > 0) {
int rs = MyJNI.CloseDeviceNode();
Log.i(TAG, "onClick: close device rs = " + rs);
updateTextInfo("close device, rs = " + rs);
id = 0;
} else {
Log.i(TAG, "onClick: device is not open");
updateTextInfo("device is not open");
}
}
});
btnFwVersion.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (id > 0) {
byte[] wBuf = {0x10};
byte[] rBuf = new byte[256];
int rs = MyJNI.IICWriteRead(wBuf, 1, rBuf, 4);
Log.i(TAG, "onClick: ret = " + rs + ",rBuf= "
+ rBuf[0] + "." + rBuf[1] + "." + rBuf[2] + "." + rBuf[3]);
updateTextInfo("ret = " + rs + ",rBuf= "
+ rBuf[0] + "." + rBuf[1] + "." + rBuf[2] + "." + rBuf[3]);
}
}
});
btnWrite.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (id > 0) {
write();
}
}
});
btnRead.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (id > 0) {
read();
}
}
});
}
@Override
protected void onDestroy() {
super.onDestroy();
int rs = MyJNI.CloseDeviceNode();
Log.i(TAG, "onClick: close device rs = " + rs);
}
private void write() {
byte[] wbuf = {0x00, 0x00, 0x01, 0x02, 0x03};
byte[] rbuf = new byte[10];
int rs = MyJNI.IICWriteRead(wbuf, 5, rbuf, 0);
Log.i(TAG, "write(): ret=" + rs);
updateTextInfo("write to fw : " + Arrays.toString(wbuf));
}
private void read() {
byte[] wbuf = {0x00};
byte[] rbuf = new byte[256];
int rs = MyJNI.IICWriteRead(wbuf, 1, rbuf, 6);
Log.i(TAG, "read(): ret=" + rs + ", rbuf = " + Arrays.toString(rbuf));
updateTextInfo("read from fw : " + Arrays.toString(Arrays.copyOf(rbuf, 6)));
}
private void updateTextInfo(final String s) {
runOnUiThread(new Runnable() {
@Override
public void run() {
tvInfo.setText(s);
}
});
}
}
布局xml文件：
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