Android应用程序:(jni方式)控制LED/GPIO

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前面文章介绍了如何编写 led 驱动模块 , 这里介绍如何编写一个 Android 应用程序去控制 LED/GPIO. 小弟不才 , 不会用 JAVA, 所以这个应用程序是用 C 写的 , 然后用 java 实现了几个按钮 , 代码和外观都比较丑陋 , 大家勿喷 ! 费话少说 , 贴代码 !

1.新建eclipse项目

2.在led.java中加入public static native int led(int i, int j);

led.java:

[java] view plain copy

package com.example.led;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class LED extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.led);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.led, menu);
return true;
}
"color:#ff6666;">public static native int led(int i, int j);
}

3.编译项目文件,bin目录下会生成led.apk.

5.利用javah命令生成头文件,该头文件中包含了符合jni格式的函数名,

javah -classpath bin/classes -d jni com.example.led.LED

6. jni目录下新建led.c

此c程序实际上是linux下的LED测试程序,函数入口更换为上面javah生成的函数名,以便java调用.

[cpp] view plain copy

#include
#include
#include
#include
#include
#include
#include
#define LOG_TAG "LED" //android logcat
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__ )
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS_ _)
//int main(int argc, char **argv)
jint JNICALL Java_com_example_led_Led_led(JNIEnv *env, jclass thiz, jint led_nu, jint on)
{
int fd;
fd = open("/dev/leds0", O_RDWR);
if(fd < 0)
printf("Can't open /dev/leds!\n");
ioctl(fd, on, led_nu);
LOGI("led_nu=%d,state=%d\n", led_nu, on);
close(fd);
return 0;
}

7. 在jni目录下新建Andorid.mk [实际上是为led.c编写makefile]

Android.mk:

[plain] view plain copy

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := LED
LOCAL_SRC_FILES := led.c
LOCAL_LDLIBS := -llog
LOCAL_C_INCLUDES := $(MY_ANDROID_SOURCE)/frameworks/base/core/jni/android/graphics \
include $(BUILD_SHARED_LIBRARY)

用ndk-build编译生成so库

8.回到eclipse中,将生成的so库添加进led.java中

led.java:

[java] view plain copy

package com.example.led;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class LED extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.led);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.led, menu);
return true;
}
public static native int led(int i, int j);
static
{
System.loadLibrary("LED");
}
}

9. 修改布局,在led.xml中为界面添加按钮

res --> layout --> led.xml:

[html] view plain copy

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ToggleButton
android:id="@+id/btn1"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led1 on"
android:textOff="led1 off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn2"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led2 on"
android:textOff="led2 off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn3"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led3 on"
android:textOff="led3 off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn4"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led4 on"
android:textOff="led4 off"
android:layout_gravity="center_horizontal"
/>
LinearLayout>

10. 在led.java中添加监听按键代码(最终的led.java)

[java] view plain copy

package com.example.led;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ToggleButton;
import android.util.Log;
import android.widget.CompoundButton.OnCheckedChangeListener;
public class Led extends Activity {
private static final String TAG = "LED";
private ToggleButton button1;
private ToggleButton button2;
private ToggleButton button3;
private ToggleButton button4;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.led);
Log.w(TAG,"layout");
button1 = (ToggleButton)findViewById(R.id.btn1);
button2 = (ToggleButton)findViewById(R.id.btn2);
button3 = (ToggleButton)findViewById(R.id.btn3);
button4 = (ToggleButton)findViewById(R.id.btn4);
Log.w(TAG,"button");
button1.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
if (button1.isChecked())
{
Log.w(TAG,"----led1 on");
led(0, 1);
}
else
{
Log.w(TAG,"----led1 off");
led(0, 0);
}
}
});
button2.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
if (button2.isChecked())
{
Log.w(TAG,"----led2 on");
led(1, 1);
}
else
{
Log.w(TAG,"----led2 off");
led(1, 0);
}
}
});
button3.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
if (button3.isChecked())
{
Log.w(TAG,"----led3 on");
led(2, 1);
}
else
{
Log.w(TAG,"----led3 off");
led(2, 0);
}
}
});
button4.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
if (button4.isChecked())
{
Log.w(TAG,"----led4 on");
led(3, 1);
}
else
{
Log.w(TAG,"-----led4 off");
led(3, 0);
}
}
});
}
public static native int led(int i, int j);
static
{
System.loadLibrary("LED");
}
}

11. 编译整个项目,在bin目录下生成led.apk, 拷贝到开发板中就可以安装运行了.

注意:安装led.apk前,请先加载led.ko模块,并确认编译模块所用的内核版本和android版本一至.另外,还需要通过串口修改 /dev/leds0 的权限为 777.(chmod 777 /dev/leds0),否则led.c中的open("/dev/leds0", o_RDWR)会失败.

Android应用程序:(jni方式)控制LED/GPIO

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