Android 直接通过JNI访问驱动

package com.yang.jniaccesshardware;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.Toast;
import com.yang.hardlibrary.HardControl;
public class MainActivity extends AppCompatActivity {

    private boolean led_on = false;
    private Button button;
    private CheckBox led1;
    private CheckBox led2;
    private CheckBox led3;
    private CheckBox led4;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=(Button)findViewById(R.id.BUTTON);
        HardControl.ledOpen();
        led1=(CheckBox)findViewById(R.id.led1);
        led2=(CheckBox)findViewById(R.id.led2);
        led3=(CheckBox)findViewById(R.id.led3);
        led4=(CheckBox)findViewById(R.id.led4);

        button.setOnClickListener(new MyButtonListener());
    }
    class MyButtonListener implements View.OnClickListener {
        @Override
        public void onClick(View v) {

            HardControl hardControl = new HardControl();//依赖硬件

            led_on = !led_on;
            if (led_on) {
                button.setText("ALL OFF");
                led1.setChecked(true);
                led2.setChecked(true);
                led3.setChecked(true);
                led4.setChecked(true);
                for (int i = 0; i < 4; i++)
                    HardControl.ledCtrl(i, 1);
            }
            else {
                button.setText("ALL ON");
                led1.setChecked(false);
                led2.setChecked(false);
                led3.setChecked(false);
                led4.setChecked(false);
                for (int i = 0; i < 4; i++)
                    HardControl.ledCtrl(i, 0);
            }
        }
    }
    public void onCheckboxClicked(View view) {
        // Is the view now checked?
        boolean checked = ((CheckBox) view).isChecked();

        // Check which checkbox was clicked
        switch(view.getId()) {
            case R.id.led1:
                if (checked)
                {
                    Toast.makeText(getApplicationContext(),"led1_on",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(1, 1);
                }
                else
                {
                    Toast.makeText(getApplicationContext(),"led1_off",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(1, 0);
                }
                break;
            case R.id.led2:
                if (checked)
                {
                    Toast.makeText(getApplicationContext(),"led1_on",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(2, 1);
                }
                else
                {
                    Toast.makeText(getApplicationContext(),"led1_off",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(2, 0);
                }
                break;
            case R.id.led3:

                if (checked)
                {
                    Toast.makeText(getApplicationContext(),"led1_on",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(3, 1);
                }
                else
                {
                    Toast.makeText(getApplicationContext(),"led1_off",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(3, 0);
                }
                break;
            case R.id.led4:
                if (checked)
                {
                    Toast.makeText(getApplicationContext(),"led1_on",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(4, 1);
                }
                else
                {
                    Toast.makeText(getApplicationContext(),"led1_off",Toast.LENGTH_LONG).show();
                    HardControl.ledCtrl(4, 0);
                }
                break;
        }
    }
}

package com.yang.hardlibrary;
public class HardControl {
    public static native int ledCtrl(int which, int status);
    public static native int ledOpen();
    public static native void ledClose();//申明三个本地方法。

    static {
        try {
            System.loadLibrary("hardcontrol");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

#include <jni.h>  /* /usr/lib/jvm/java-1.7.0-openjdk-amd64/include/ */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>

#include <android/log.h>  /* liblog */

//__android_log_print(ANDROID_LOG_DEBUG, "JNIDemo", "native add ...");

#if 0
typedef struct {
    char *name;          /* Java里调用的函数名 */
    char *signature;    /* JNI字段描述符, 用来表示Java里调用的函数的参数和返回值类型 */
    void *fnPtr;          /* C语言实现的本地函数 */
} JNINativeMethod;
#endif

static jint fd;

jint ledOpen(JNIEnv *env, jobject cls)
{
    fd = open("/dev/leds", O_RDWR);
    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledOpen : %d", fd);
    if (fd >= )
        return ;
    else
        return -;
}

void ledClose(JNIEnv *env, jobject cls)
{
    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledClose ...");
    close(fd);
}

jint ledCtrl(JNIEnv *env, jobject cls, jint which, jint status)
{
    int ret = ioctl(fd, status, which);
    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledCtrl : %d, %d, %d", which, status, ret);
    return ret;
}

static const JNINativeMethod methods[] = {
    {"ledOpen", "()I", (void *)ledOpen},
    {"ledClose", "()V", (void *)ledClose},
    {"ledCtrl", "(II)I", (void *)ledCtrl},
};

/* System.loadLibrary */
JNIEXPORT jint JNICALL
JNI_OnLoad(JavaVM *jvm, void *reserved)
{
    JNIEnv *env;
    jclass cls;

    if ((*jvm)->GetEnv(jvm, (void **)&env, JNI_VERSION_1_4)) {
        return JNI_ERR; /* JNI version not supported */
    }
    cls = (*env)->FindClass(env, "com/yang/hardlibrary/HardControl");
    if (cls == NULL) {
        return JNI_ERR;
    }
    /* 2. map java hello <-->c c_hello */
    if ((*env)->RegisterNatives(env, cls, methods, sizeof(methods)/sizeof(methods[])) < )
        return JNI_ERR;

    return JNI_VERSION_1_4;
}