打算寫一個(gè)FbSetApp去操作framebuffer的設(shè)備文件，以便能夠去設(shè)置FB的一些參數(shù)。

新建兩個(gè)class

FbParams.java：

package org.trident.fbset;

public class FbParams {

int pos_x;

int pos_y;

int size_x;//Width

int size_y;//Height

}

用于傳遞FB起始位置和大小的參數(shù)。

FbSetControl.java：

package org.trident.fbset;

public class FbSetControl {

static {

System.loadLibrary("fbset");

}

public native int Init();

public native int SetPosition();

}

然后在FbSetApp下，執(zhí)行：

javac -d bin src\org\trident\app\FbParams.java

javac -d bin src\org\trident\app\FbSetControl.java

然后轉(zhuǎn)到FbSetApp\bin\classes下

javah -d ../../jni org.trident.app.FbSetControl

這樣就會在FbSetApp\jni目錄下生成org_trident_app_FbSetControl.h:

如果報(bào)文件無法訪問和找不到類，那么多半是環(huán)境變量設(shè)置有問題：

java_home：C:\Program Files\Java\jdk1.7.0_01(java安裝好后的路徑)，

Path變量中添加 %java_home%/bin，

classpath：.;%java_home%/lib

加入我們自己要用到的結(jié)構(gòu)cnxtfb_position

org_trident_app_FbSetControl.h：

/* DO NOT EDIT THIS FILE - it is machine generated */

#include

/* Header for class org_trident_fbset_FbSetControl */

#ifndef _Included_org_trident_fbset_FbSetControl

#define _Included_org_trident_fbset_FbSetControl

#ifdef __cplusplus

extern "C" {

#endif

/*

* Class:???? org_trident_fbset_FbSetControl

* Method:??? Init

* Signature: ()I

*/

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_Init

(JNIEnv *, jobject);

/*

* Class:???? org_trident_fbset_FbSetControl

* Method:??? GetResolution

* Signature: ()I

*/

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_GetResolution

(JNIEnv *, jobject, jobject tparam);

/*

* Class:???? org_trident_fbset_FbSetControl

* Method:??? SetPosition

* Signature: ()I

*/

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_SetPosition

(JNIEnv *, jobject, jobject tparam);

typedef struct _cnxtfb_position{

int nPosX;

int nPosY;

int nSizeX;

int nSizeY;

}cnxtfb_position;

typedef struct _cnxtfb_resolution{

int uWidth;

int uHeight;

}cnxtfb_resolution;

#ifdef __cplusplus

}

#endif

#endif

在FbSetApp/jni創(chuàng)建一個(gè)C文件，org_trident_fbset_FbSetControl.c:

#include

#include

#include

#include

#include

#include

#define? DEVICE_NAME? "/dev/fb0"? //device point

#define FBIO_SET_POSITION????? 0x4637

#define FBIO_GETFBRESOLUTION????? 0x4626

#define? OMX_HAL_IOCTL_SET_SCREEN_POS_HW_CURSOR 0x12

static cnxtfb_position fb_pos;

static cnxtfb_resolution fb_res;

//#define DBG 0

#define? LOG_TAG??? "fbset"

#define? printf(...)? __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)

#ifdef __cplusplus

extern "C" {

#endif

/*

* Class:???? FbSetControl

* Method:??? Init

* Signature: ()I

*/

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_Init

(JNIEnv * env, jobject? obj)

{

fb_pos.nPosX = 0;

fb_pos.nPosY = 0;

fb_pos.nSizeX = 0;

fb_pos.nSizeX = 0;

printf("%d %d,%d %d",fb_pos.nPosX,fb_pos.nPosY,fb_pos.nSizeX,fb_pos.nSizeY);

}

/*

* Class:???? FbSetControl

* Method:??? GetResolution

* Signature: ()I

*/

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_GetResolution

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

{

jfieldID fid;

jclass tprm = (*env)->GetObjectClass(env, tparam);

static int fbfd = -1;

if (fbfd < 0)

{

if ( ( fbfd = open( "/dev/fb0", O_RDWR ) ) < 0 )

{

printf(stderr, "open %s error!\n",DEVICE_NAME);

//return -1;

}

if (ioctl(fbfd, FBIO_GETFBRESOLUTION, &fb_res)) {

printf(stderr, "error FBIO_SET_POSITION screeninfo!\n");

//return -1;

}

fid = (*env)->GetFieldID(env, tprm, "width", "I");

(* env)->SetIntField(env,tparam, fid, fb_res.uWidth);

printf("uWidth is %d",fb_res.uWidth);

fid = (*env)->GetFieldID(env, tprm, "height", "I");

(* env)->SetIntField(env,tparam, fid, fb_res.uHeight);

printf("uHeight is %d",fb_res.uWidth);

close(fbfd);

fbfd=-1;

}

}

JNIEXPORT jint JNICALL Java_org_trident_fbset_FbSetControl_SetPosition

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

{

jfieldID fid;

jclass tprm = (*env)->GetObjectClass(env, tparam);

static int fbfd = -1;

static int cursorfd = -1;

fid = (*env)->GetFieldID(env, tprm, "pos_x", "I");

fb_pos.nPosX = (*env)->GetIntField(env, tparam, fid);

printf("nPosX is %d",fb_pos.nPosX);

fid = (*env)->GetFieldID(env, tprm, "pos_y", "I");

fb_pos.nPosY = (*env)->GetIntField(env, tparam, fid);

printf("nPosY is %d",fb_pos.nPosY);

fid = (*env)->GetFieldID(env, tprm, "size_x", "I");

fb_pos.nSizeX = (*env)->GetIntField(env, tparam, fid);

printf("nSizeX is %d",fb_pos.nSizeX);

fid = (*env)->GetFieldID(env, tprm, "size_y", "I");

fb_pos.nSizeY = (*env)->GetIntField(env, tparam, fid);

printf("%d %d,%d %d",fb_pos.nPosX,fb_pos.nPosY,fb_pos.nSizeX,fb_pos.nSizeY);

#ifdef DBG

//printf("%d %d,%d %d",fb_pos.nPosX,fb_pos.nPosY,fb_pos.nSizeX,fb_pos.nSizeY);

#else

if (fbfd < 0)

{

if ( ( fbfd = open( "/dev/fb0", O_RDWR ) ) < 0 )

{

printf(stderr, "open %s error!\n",DEVICE_NAME);

//return -1;

}

if (ioctl(fbfd, FBIO_SET_POSITION, &fb_pos)) {

printf(stderr, "error FBIO_SET_POSITION screeninfo!\n");

//return -1;

}

close(fbfd);

fbfd=-1;

}

if (cursorfd < 0)

{

if ((cursorfd = open("/dev/HW_CURSOR", O_RDWR))<0)

{

printf("Failed to open HD cursor node warnerye.\n");

//return ;

}

if(ioctl(cursorfd, OMX_HAL_IOCTL_SET_SCREEN_POS_HW_CURSOR, &fb_pos) < 0)

{

printf("change Cursor FB POSITION failed: %s\n", strerror(errno));

close(cursorfd);

cursorfd = -1;

//return;

}

close(cursorfd);

cursorfd=-1;

}

#endif

}

#ifdef __cplusplus

}

#endif

對于jni部分參數(shù)傳遞的方法，在此有必要說明一下：

jfieldID fid;

jclass tprm = (*env)->GetObjectClass(env, tparam);

作用是拿到傳遞的env中我們添加的tparam結(jié)構(gòu)的指針

fid = (*env)->GetFieldID(env, tprm, "pos_x", "I");

作用是拿到tparam結(jié)構(gòu)中pos_x的ID，"I"表示是int，如果我們要傳遞字符串變量，比如IP地址，可以這樣寫：

const char *ip;

jfieldID fid;

jstring jstr;

jclass tprm = (*env)->GetObjectClass(env, tparam);

fid = (*env)->GetFieldID(env, tparam, "ipadd", "Ljava/lang/String;");

jstr = (*env)->GetObjectField(env,tparam, fid);

ip = (*env)->GetStringUTFChars(env, jstr, NULL);

//strcpy(param.pszSrcAddr,ip);

(*env)->ReleaseStringUTFChars(env,jstr,ip);

printf("ip is %s",params.pszSrcAddr);

然后再增加一個(gè)Android.mk：

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE??? := fbset

LOCAL_SRC_FILES := org_trident_fbset_FbSetControl.c

LOCAL_C_INCLUDES := inc

LOCAL_LDLIBS??? := -lm -llog -ljnigraphics

LOCAL_LDLIBS??? += -LD:/Android/workspace/fbset/jni/lib

include $(BUILD_SHARED_LIBRARY)

然后就可以使用ndk-build編譯生成so，要做這一步，你需要安裝NDK，安裝步驟你可以參照：

安裝完成以后你就可以在cygwin下面編譯jni部分的代碼生成so文件了。

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