Android - 在本机和Java应用程序之间使用管道 [英] Android - Using pipe between native and java apps

问题描述

我正在开发SGS2 api v.16

我有两个应用程序：native和Java

从本机应用程序我打开一个带有mkfifo（）函数的Unix管道并写一些字符串。

在java应用程序中我试图读取字符串，但不知何故应用程序块和我不知道为什么，没有迹象在logcat中为什么它被阻止。

这2个应用程序有android：sharedUserId清单中的my.Id，并且该份额肯定有效。

在logcat中我可以看到打开输入流日志，但之后没有日志那个..
是否有推荐的方法从Java中读取管道文件？
注意：如果我用open（...）打开常规文件而不是使用mkfifo（...）我成功从文件中读取，问题是只有当我打开一个管道文件时mkfifo（）

这是从原生应用程序运行的函数：

  jint Java_com_example_ndkfoo_NdkFooActivity_writeToPipe（JNIEnv * env，jobject javaThis）{
 const char * PATH =/ data / data / com.example.ndkfoo / v_pipe8; 
 char * line =Hello Pipe！; 
 int pipe; 
 errno = 0; 
 
 //打开命名管道
 mode_t mode = S_IRWXU | S_IRWXG | S_IRWXO; 
 pipe = mkfifo（PATH，mode）; 
 if（errno！= 0）{
 __android_log_write（ANDROID_LOG_ERROR，NDK_FOO_TAG，strerror（errno））; 
返回错误; 
} 
 __android_log_write（ANDROID_LOG_DEBUG，NDK_FOO_TAG，文件成功打开）; 
 
 //实际写出数据并关闭管道
 int err = write（pipe，line，strlen（line））; 
 
 //关闭管道
 close（管道）; 
返回错误; 
 
} 
  

这是试图从管道中读取的java

  package com.example.secondparty; 
 
 import java.io.FileDescriptor; 
 import java.io.FileInputStream; 
 
 import android.os.Bundle; 
 import android.app.Activity; 
 import android.util.Log; 
 import android.view.Menu; 
 
公共类MainActivity扩展Activity {
 private static final String TAG = MainActivity.class.getSimpleName（）; 
 // public final static String PATH2 =/ sdcard / fifo9001; 
 public final static String PATH =/ data / data / com.example.ndkfoo / v_pipe8; 
 
 @Override 
 public void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.main）; 
 
 readFromPipe（）; 
 
} 
 
 @Override 
 public boolean onCreateOptionsMenu（菜单菜单）{
 getMenuInflater（）。inflate（R.menu.main，menu）; 
返回true; 
} 
 
 private void readFromPipe（）{
 Log.i（TAG，Attempt started）; 
 FileInputStream fis; 
 String message =; 
 byte buffer [] = new byte [256]; 
 
 try {
 Log.i（TAG，openning input stream）; 
 fis = new FileInputStream（PATH）; 
 Log.i（TAG，输入流已打开）; 
 FileDescriptor fd = fis.getFD（）; 
 int len = 0; 
 do {
 len = fis.read（buffer）; 
 if（len> 0）{
 String newmessage = new String（buffer，0，len，US-ASCII）; 
 message + = newmessage; 
} 
} while（len == buffer.length）; 
 Log.i（TAG，message：+ message）; 
 fis.close（）; 
} catch（例外e）{
 e.printStackTrace（）; 
} 
 
 
} 
} 
  

BufferedReader 而不是`FileInputStream

I'm developing on SGS2 api v.16

I have two applications: native and Java

From the native app I open a Unix pipe with mkfifo() function and write some string to it.

And in the java app I'm trying to read the string, but somehow the app blocks and I don't know why, no indication in the logcat for why it blocked.

The 2 apps have android:sharedUserId="my.Id" in the manifest, and the share worked for sure.

In the logcat I can see the "opening input stream" log, but no log after that.. Is there a recommended way to read from a pipe file in Java? NOTE: if I open a regular file with open(...) instead of using mkfifo(...) I succeed to read from the file, the problem is only when I open a pipe file with mkfifo()

Here is the function runs from the native app:

jint Java_com_example_ndkfoo_NdkFooActivity_writeToPipe(JNIEnv* env, jobject javaThis) {
   const char* PATH = "/data/data/com.example.ndkfoo/v_pipe8";
   char* line = "Hello Pipe!";
   int pipe;
   errno = 0;

   // open a named pipe
   mode_t mode = S_IRWXU | S_IRWXG | S_IRWXO;
   pipe = mkfifo(PATH, mode);
   if(errno != 0) {
        __android_log_write(ANDROID_LOG_ERROR, "NDK_FOO_TAG", strerror(errno));
        return errno;
    }
    __android_log_write(ANDROID_LOG_DEBUG, "NDK_FOO_TAG", "file opened successfully");

   // actually write out the data and close the pipe
   int err = write(pipe, line, strlen(line));

    // close the pipe
   close(pipe);
   return err;

}

And here is the java that tries to read from the pipe

package com.example.secondparty;

import java.io.FileDescriptor;
import java.io.FileInputStream;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;

public class MainActivity extends Activity {
     private static final String TAG = MainActivity.class.getSimpleName();
     //public final static String PATH2 = "/sdcard/fifo9001";
     public final static String PATH = "/data/data/com.example.ndkfoo/v_pipe8";

     @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        readFromPipe();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    private void readFromPipe() {
        Log.i(TAG, "Attempt started");
        FileInputStream fis;
        String message = "";
        byte buffer[] = new byte[256];

        try {
            Log.i(TAG, "openning input stream");
            fis = new FileInputStream(PATH);
            Log.i(TAG, "input stream opened");
            FileDescriptor fd =  fis.getFD();
            int len = 0;
            do {
                len = fis.read(buffer);
                if(len > 0) {
                    String newmessage = new String(buffer,0, len, "US-ASCII");
                    message += newmessage;
                }
            } while (len == buffer.length);
            Log.i(TAG, "message: "+message);
            fis.close();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }
}

解决方案

Use BufferedReader instead `FileInputStream

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