硬件访问服务2之让Android应用程序访问C库

安卓应用程序访问c库流程：
1、编译so文件
上传hardcontrol.c到服务器然后
执行：
arm-linux-gcc -fPIC -shared hardcontrol.c -o libhardcontrol.so -I /usr/lib/jvm/java-1.7.0-openjdk-amd64/include/
得到.so文件
2、将.so文件放入app/libs下建armeabi子目录
3、修改build.gradle
加上：

sourceSets{    main{        jniLibs.srcDirs = ['libs']    }}

4、找不到”libc.so.6”
解决方法：
修改编译选项

   arm-linux-gcc -fPIC -shared hardcontrol.c -o libhardcontrol.so -I /usr/lib/jvm/java-1.7.0-openjdk-amd64/include/-nostdlib /work/android-5.0.2/prebuilts/ndk/9/platforms/android-19/arch-arm/usr/lib/libc.so

5、在c库中添加打印信息：

#include <android/log.h> /*liblog*/               __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledOpen ...");

   然后修改编译选项：

     arm-linux-gcc -fPIC -shared hardcontrol.c -o libhardcontrol.so -I /usr/lib/jvm/java-1.7.0-openjdk-amd64/include/ -nostdlib /work/android-5.0.2/prebuilts/ndk/9/platforms/android-19/arch-arm/usr/lib/libc.so -I /work/android-5.0.2/prebuilts/ndk/9/platforms/android-19/arch-arm/usr/include /work/android-5.0.2/prebuilts/ndk/9/platforms/android-19/arch-arm/usr/lib/liblog.so

程序源码：

MainActivity.java

package com.example.dongxiem.app_0001_leddemo;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.Button;import android.view.View;import android.widget.CheckBox;import android.widget.Checkable;import android.widget.Toast;import com.example.dongxiem.hardlibrary.*;public class MainActivity extends AppCompatActivity {    private Button button = null;    private boolean ledon = false;    private CheckBox checkBoxLed1 = null;    private CheckBox checkBoxLed2 = null;    private CheckBox checkBoxLed3 = null;    private CheckBox checkBoxLed4 = null;    class MyButtonListener implements View.OnClickListener{        @Override        public void onClick(View v) {            ledon = !ledon;            if (ledon) {                button.setText("ALL OFF");                checkBoxLed1.setChecked(true);                checkBoxLed2.setChecked(true);                checkBoxLed3.setChecked(true);                checkBoxLed4.setChecked(true);                for (int i = 0; i < 4; i++)                HardControl.ledCtrl(i,1);            }            else {                button.setText("ALL ON");                checkBoxLed1.setChecked(false);                checkBoxLed2.setChecked(false);                checkBoxLed3.setChecked(false);                checkBoxLed4.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) {                    // Put some meat on the sandwich                    Toast.makeText(getApplicationContext(), "LED1 ON", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(0,1);                }            else {                    // Remove the meat                    Toast.makeText(getApplicationContext(), "LED1 OFF", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(0,0);                }                break;            case R.id.LED2:                if (checked) {                    // Put some meat on the sandwich                    Toast.makeText(getApplicationContext(), "LED2 ON", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(1,1);                }                else {                    // Remove the meat                    Toast.makeText(getApplicationContext(), "LED2 OFF", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(1,0);                }                break;            case R.id.LED3:                if (checked) {                    // Put some meat on the sandwich                    Toast.makeText(getApplicationContext(), "LED3 ON", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(2,1);                }                else {                    // Remove the meat                    Toast.makeText(getApplicationContext(), "LED3 OFF", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(2,0);                }                break;            case R.id.LED4:                if (checked) {                    // Put some meat on the sandwich                    Toast.makeText(getApplicationContext(), "LED4 ON", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(3,1);                }                else {                    // Remove the meat                    Toast.makeText(getApplicationContext(), "LED4 OFF", Toast.LENGTH_SHORT).show();                    HardControl.ledCtrl(3,0);                }                break;            // TODO: Veggie sandwich        }    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button)findViewById(R.id.BUTTON);        HardControl.ledOpen();        checkBoxLed1 = (CheckBox)findViewById(R.id.LED1);        checkBoxLed2 = (CheckBox)findViewById(R.id.LED2);        checkBoxLed3 = (CheckBox)findViewById(R.id.LED3);        checkBoxLed4 = (CheckBox)findViewById(R.id.LED4);        button.setOnClickListener(new MyButtonListener());/* button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // Perform action on click ledon = !ledon; if (ledon) button.setText("ALL OFF"); else button.setText("ALL ON"); } }); */    }}

HardControl.java:

package com.example.dongxiem.hardlibrary;public class HardControl {    public static native int ledCtrl(int which, int status);    public static native int ledOpen();    public static native int ledClose();    static {        try {            System.loadLibrary("hardcontrol");        } catch (Exception e) {            e.printStackTrace();        }    }}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.example.dongxiem.app_0001_leddemo.MainActivity" android:orientation="vertical" >    <TextView  android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello Garmen!This is my LedDemo" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" />    <Button  android:id="@+id/BUTTON" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="ALL ON" />    <CheckBox  android:id="@+id/LED1" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="LED1" android:onClick="onCheckboxClicked" />    <CheckBox  android:id="@+id/LED2" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="LED2" android:onClick="onCheckboxClicked" />    <CheckBox  android:id="@+id/LED3" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="LED3" android:onClick="onCheckboxClicked" />    <CheckBox  android:id="@+id/LED4" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="LED4" android:onClick="onCheckboxClicked" /></LinearLayout>

Hardcontrol.c:

#include <jni.h> /* /usr/lib/jvm/java-1.7.0-openjdk-amd64/include/ */#include <stdio.h>#include <stdlib.h>#include <android/log.h> /*liblog*/#if 0typedef 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;#endifjint ledOpen(JNIEnv *env, jobject cls){    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledOpen ...");    return 0;}void ledClose(JNIEnv *env, jobject cls){    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledClose ...");    return 0;}jint ledCtrl(JNIEnv *env, jobject cls, jint which, jint status){    __android_log_print(ANDROID_LOG_DEBUG, "LEDDemo", "native ledCtrl : %d, %d", which, status);    return 0;}static const JNINativeMethod methods[] = {    {"ledOpen", "()I", (void *)ledOpen},    {"ledClose", "()V", (void *)ledClose},    {"ledCtrl", "(II)I", (void *)ledCtrl},};/* System.loadLibrary */JNIEXPORT jint JNICALLJNI_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/example/dongxiem/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[0]) ) < 0)        return JNI_ERR;    return JNI_VERSION_1_4;}

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