Android应用程序:(jni方式)控制LED/GPIO

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publicstaticnativeintled(inti,intj);

led.java:

[java] view plain copy

packagecom.example.led;
importandroid.os.Bundle;
importandroid.app.Activity;
importandroid.view.Menu;
publicclassLEDextendsActivity{
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.led);
}
@Override
publicbooleanonCreateOptionsMenu(Menumenu){
getMenuInflater().inflate(R.menu.led,menu);
returntrue;
}
<spanstyle="color:#ff6666;">publicstaticnativeintled(inti,intj);</span>
}

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-classpathbin/classes-djnicom.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<jni.h>
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/ioctl.h>
#include<android/log.h>
#defineLOG_TAG"LED"//androidlogcat
#defineLOGI(...)__android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#defineLOGE(...)__android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
//intmain(intargc,char**argv)
jintJNICALLJava_com_example_led_Led_led(JNIEnv*env,jclassthiz,jintled_nu,jinton)
{
intfd;
fd=open("/dev/leds0",O_RDWR);
if(fd<0)
printf("Can'topen/dev/leds!\n");
ioctl(fd,on,led_nu);
LOGI("led_nu=%d,state=%d\n",led_nu,on);
close(fd);
return0;
}

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:=$(callmy-dir)
include$(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

packagecom.example.led;
importandroid.os.Bundle;
importandroid.app.Activity;
importandroid.view.Menu;
publicclassLEDextendsActivity{
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.led);
}
@Override
publicbooleanonCreateOptionsMenu(Menumenu){
getMenuInflater().inflate(R.menu.led,menu);
returntrue;
}
publicstaticnativeintled(inti,intj);
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

<LinearLayoutxmlns: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="led1on"
android:textOff="led1off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn2"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led2on"
android:textOff="led2off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn3"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led3on"
android:textOff="led3off"
android:layout_gravity="center_horizontal"
/>
<ToggleButton
android:id="@+id/btn4"
android:layout_width="140dip"
android:layout_height="wrap_content"
android:textOn="led4on"
android:textOff="led4off"
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

packagecom.example.led;
importandroid.app.Activity;
importandroid.content.Intent;
importandroid.net.Uri;
importandroid.os.Bundle;
importandroid.view.View;
importandroid.widget.Button;
importandroid.widget.ToggleButton;
importandroid.util.Log;
importandroid.widget.CompoundButton.OnCheckedChangeListener;
publicclassLedextendsActivity{
privatestaticfinalStringTAG="LED";
privateToggleButtonbutton1;
privateToggleButtonbutton2;
privateToggleButtonbutton3;
privateToggleButtonbutton4;
@Override
publicvoidonCreate(BundlesavedInstanceState){
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(newButton.OnClickListener()
{
publicvoidonClick(Viewv)
{
if(button1.isChecked())
{
Log.w(TAG,"----led1on");
led(0,1);
}
else
{
Log.w(TAG,"----led1off");
led(0,0);
}
}
});
button2.setOnClickListener(newButton.OnClickListener()
{
publicvoidonClick(Viewv)
{
if(button2.isChecked())
{
Log.w(TAG,"----led2on");
led(1,1);
}
else
{
Log.w(TAG,"----led2off");
led(1,0);
}
}
});
button3.setOnClickListener(newButton.OnClickListener()
{
publicvoidonClick(Viewv)
{
if(button3.isChecked())
{
Log.w(TAG,"----led3on");
led(2,1);
}
else
{
Log.w(TAG,"----led3off");
led(2,0);
}
}
});
button4.setOnClickListener(newButton.OnClickListener()
{
publicvoidonClick(Viewv)
{
if(button4.isChecked())
{
Log.w(TAG,"----led4on");
led(3,1);
}
else
{
Log.w(TAG,"-----led4off");
led(3,0);
}
}
});
}
publicstaticnativeintled(inti,intj);
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.

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