ok6410 android driver(7)

　　This article talk about how to test device driver on JNI.

　　There are two ways to test the device driver : 

　　(1) Create methods to control devices in .c/.cpp file, the .java call the methods in .c/.cpp :

　　This way is call JNI (Java Native Interface), means java works via native interface in C/C++.

　　(2) .java control devices via the class in FileInputStream and FileOutputStream.

 

　　TIPS : 

I test these two methods in eclipse ADT.

If you don't know how to write android application program, I think you'd better take some reading in books about android app design and do some practice firstly.

　　Error TIPS:

If there "R cannot be resolved to a variable" error in your project when created, try "Project -> clean"

 

　　1、JNI

　　(1) Create android project

File -> New -> Android Application Project

　　(2) Create jni native support

　　You must get the ndk work tools already and prefix the ndk path :

Windows -> Preferences -> Android -> NDK

　　Right click the project name :

Android Tools -> Add Native Support

　　There will be a new directory in project :

jni ——- Andoid.mk

       |—-  wordcntjni.cpp

　　(3) string.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>



    <string name="app_name">wordcntjni</string>

    <string name="action_settings">Settings</string>

    <string name="wcstring">JNI test app.</string>

    <string name="wcwrite">Write</string>

    <string name="wcread">Read</string>



</resources>

　　(4) activity_main.xml

　　Graphical Layout :

　　xml :

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >



    <EditText

        android:id="@+id/editText_wc"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:inputType="text"

        android:layout_alignParentLeft="true"

        android:layout_alignParentRight="true"

        android:layout_alignParentTop="true"

        android:ems="10" >



        <requestFocus />

    </EditText>



    <Button

        android:id="@+id/onClick_wcRead"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignRight="@+id/editText_wc"

        android:layout_below="@+id/editText_wc"

        android:onClick="onClick_wcRead"

        android:text="@string/wcread" />



    <Button

        android:id="@+id/onClick_wcWrite"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@+id/editText_wc"

        android:layout_toLeftOf="@+id/onClick_wcRead"

        android:onClick="onClick_wcWrite"

        android:text="@string/wcwrite" />



    <TextView

        android:id="@+id/textView_wc"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@+id/editText_wc"

        android:layout_below="@+id/onClick_wcWrite"

        android:text="@string/wcstring" />



</RelativeLayout>

　　(5) MainActivity.java

package com.example.wordcntjni;



import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.widget.EditText;

import android.widget.TextView;



public class MainActivity extends Activity {

    private TextView tv_wc;

    private EditText et_wc;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        tv_wc = (TextView) findViewById(R.id.textView_wc);

        et_wc = (EditText) findViewById(R.id.editText_wc);

    }

    

    public void onClick_wcRead (View view) {

        tv_wc.setText("Read words :" + String.valueOf(readWordCnt()));

    }

    public void onClick_wcWrite (View view) {

        tv_wc.setText("Words write success.");

        writeWordCnt(et_wc.getText().toString());

    }

    

    public native int readWordCnt();

    public native void writeWordCnt(String str);

    static {

        System.loadLibrary("wordcntjni");

    }



    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }



}

　　(6) wordcntjni.cpp wordcntjni.h

　　Before we edit wordcntjni.cpp, we should create wordcntjni.h first :

$ pwd

~/Software/ADT/project/wordcntjni/jni



$ javah -classpath ../bin/classes/ -jni -o wordcntjni.h com.example.wordcntjni.MainActivity

　　Project clean the eclipse and we would find a new file wordcntjni.h in dir jni.

　　Finaly, we can edit the wordcntjni.cpp :

#include <jni.h>

#include <string.h>

#include <fcntl.h>

#include <stdio.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>

#include <stdlib.h>



#include "wordcntjni.h"



JNIEXPORT jint JNICALL Java_com_example_wordcntjni_MainActivity_readWordCnt

  (JNIEnv *env, jobject thiz)

{

    int fd_dev;

    int num = 0;

    jint wordcnt = 0;

    unsigned char buf[4];



    //fd_dev = open("/dev/wordcount2", O_RDONLY);

    fd_dev = open("/data/local/jnitest.txt", O_RDONLY);

    read(fd_dev, buf, 4);



    num =     ((int) buf[0]) << 24 |

            ((int) buf[1]) << 16 |

            ((int) buf[2]) << 8  |

            ((int) buf[3]) ;

    wordcnt = (jint) num;



    close(fd_dev);



    return wordcnt;

}



char* jstring_to_pchar(JNIEnv* env, jstring str)

{

    char* pstr = NULL;



    jclass clsstring = env->FindClass("java/lang/String");

    jstring strencode = env->NewStringUTF("utf-8");

    jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");

    jbyteArray byteArray = (jbyteArray) (env->CallObjectMethod(str, mid, strencode));

    jsize size = env->GetArrayLength(byteArray);

    jbyte* pbyte = env->GetByteArrayElements(byteArray, JNI_FALSE);



    if (size > 0) {

        pstr = (char*) malloc(size);

        memcpy(pstr, pbyte, size);

    }

    return pstr;

}



JNIEXPORT void JNICALL Java_com_example_wordcntjni_MainActivity_writeWordCnt

  (JNIEnv *env, jobject thiz, jstring str)

{

    int fd_dev;



    //fd_dev = open("/dev/wordcount2", O_WRONLY);

    fd_dev = open("/data/local/jnitest.txt", O_WRONLY);

    char* pstr = jstring_to_pchar(env, str);

    if (pstr != NULL) {

        write(fd_dev, pstr, strlen(pstr));

    }



    close(fd_dev);

}

　　When compilier the application, the following errors may occur :

　　[ error1 ] 

Android NDK: WARNING: APP_PLATFORM android-14 is larger than android:minSdkVersion 8

　　[ Fix ] 

$ vim /home/linx/Software/Android/ndk/build/core/add-$ application.mk 

// add the android-8 following android-14

APP_PLATFORM := android-14

APP_PLATFORM := android-8

　　[ error2 ]

There still the read error couldn't fix yet.

The file writing is ok.

If you have any idea about this error.

I am very please to receive your reply.

 

　　2、Java FileStream 

　　We don't need to create the jni files anymore by this way, just test the device in android application.

　　(1) string.xml

<?xml version="1.0" encoding="utf-8"?>

<resources>



    <string name="app_name">file_test</string>

    <string name="action_settings">Settings</string>

    <string name="hello_world">Hello, Press button to write file.</string>

    <string name="wstring">Write</string>

    <string name="rstring">Read</string>

</resources>

　　(2) activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context=".MainActivity" >



    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world" />



    <Button

        android:id="@+id/button2"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentRight="true"

        android:layout_below="@+id/textView1"

        android:layout_marginRight="14dp"

        android:onClick="onClick_button2"        

        android:text="@string/rstring" />



    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignBaseline="@+id/button2"

        android:layout_alignBottom="@+id/button2"

        android:layout_toLeftOf="@+id/button2"

        android:onClick="onClick_button1"

        android:text="@string/wstring" />



</RelativeLayout>

　　(3) MainActivity.java

package com.example.file_test;



import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.nio.ByteBuffer;



import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.widget.TextView;



public class MainActivity extends Activity {

    public TextView fstream; 



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        fstream = (TextView) findViewById(R.id.textView1);

    }

    

    public void onClick_button1 (View view) {

        writeFile("File text strings.");

        fstream.setText("File write success.");

    }

    public void onClick_button2 (View view) {

        fstream.setText("File read :" + String.valueOf(readFile()));

    }

    private int readFile () {

        byte[] buffer = new byte[4];

        int num = 0;

        try {



            FileInputStream fis = new FileInputStream("/data/local/jnitest.txt");

            //FileInputStream fis = new FileInputStream("/dev/wordcount2");

            fis.read(buffer);

            ByteBuffer bbuf = ByteBuffer.wrap(buffer);

            num = bbuf.getInt();

            

            

//            num =    (int)((buffer[0]) & 0xff)     << 24     |

//                    (int)((buffer[1]) & 0xff)     << 16     |

//                    (int)((buffer[2]) & 0xff)     << 8       |

//                    (int)((buffer[3]) & 0xff)    ;

            

            fis.close();

        } catch (Exception e) {

        }

        return num;

    }



    private void writeFile (String str) {

        try { 

            FileOutputStream fos = new FileOutputStream("/data/local/jnitest.txt");

            //FileOutputStream fos = new FileOutputStream("/dev/wordcount2");

            fos.write(str.getBytes("iso-8859-1"));

            fos.close();

        } catch (Exception e) {

        }

    }



    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.main, menu);

        return true;

    }



}

　　[error]

This file does't fix the read error too, and the write is also ok.

If you have any idea about this error.

I am very please to receive your reply.