Android NDK:how to impliment java api function in c/C++

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C++

Linux

Hi all,
i am working in android ndk using java api.Please help me.
My code in NativeLib.java

package com.marakana;
import android.R.bool;
import android.content.Context;
import android.view.inputmethod.InputMethodManager;
public class NativeLib {
static {
    System.loadLibrary("ndk_demo");
}
Context mContext;
 public NativeLib(NDKDemo ndkDemo) {
	}
public  void Keyboard(Context mContext){
	       this.mContext = mContext;
	  }
 public  void  getSystemService(bool makevisible){
     if(makevisible != null){
	        InputMethodManager m = (InputMethodManager)mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
	        m.toggleSoftInput(InputMethodManager.SHOW_FORCED, 0);
     }
     else
     {
    	 InputMethodManager m = (InputMethodManager)mContext.getSystemService(Context.INPUT_METHOD_SERVICE);
	        m.toggleSoftInput(0, 0);
     }
     }
  public native void  openKeyBoard();
 }

com_marakana_NativeLib.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_marakana_NativeLib */

#ifndef _Included_com_marakana_NativeLib
#define _Included_com_marakana_NativeLib
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_marakana_NativeLib
 * Method:    add
 * Signature: (II)I
 */

JNIEXPORT jstring JNICALL Java_com_marakana_NativeLib_openKeyBoard
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

1.How to impliment java function in c/c++
2.how to call c++ function by java for display keyboard.

Please help me.

Thanks in advace.