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 = ;
    jint wordcnt = ;
    unsigned char buf[];

    //fd_dev = open("/dev/wordcount2", O_RDONLY);
    fd_dev = open("/data/local/jnitest.txt", O_RDONLY);
    read(fd_dev, buf, );

    num =     ((int) buf[]) <<  |
            ((int) buf[]) <<  |
            ((int) buf[]) <<   |
            ((int) buf[]) ;
    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 > ) {
        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- is larger than android:minSdkVersion 

　　[ Fix ]

$ vim /home/linx/Software/Android/ndk/build/core/add-$ application.mk
// add the android-8 following android-14
APP_PLATFORM := android-
APP_PLATFORM := android-

　　[ 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.