Android 进程间通信，Ashmem共享内存基本使用_android ashmem通信实现

Android 提供了几种进程间通信的方式，除了Socket，基本都是基于binder实现的。为什么要用共享内存来实现呢？因为binder传输数据被限制在1M，在较大的数据交换一般会使用文件，但效率非常的低，因此使用共享内存是很好的方式。在内存中开辟一块空间，通过binder或者其他方式将fd（文件描述符）传递到客户端或服务端进程，从而实现大文件传输

其中Android提供了封装好的MemoryFile对象，供使用。

具体实现

一，服务端

1，首先在APP内部存储中存放一张图片:路径 data/data/com.example.ashmem_service/files/image.jpg
2，将文件写入到共享内存 并返回ParcelFileDescriptor
2，通过binder将返回的pfd传递给客户端

aidl文件

// IMyAidlInterface.aidl
package com.example.ashmem;

// Declare any non-default types here with import statements

interface IMyAidlInterface {
    ParcelFileDescriptor getPfd();
}
1
2
3
4
5
6
7
8

public class MyService extends Service {
    @Override
    public void onCreate() {
        super.onCreate();
    }

    IMyAidlInterface.Stub myAidlInterface=new IMyAidlInterface.Stub() {
        @Override
        public ParcelFileDescriptor getPfd() throws RemoteException {
            return createMemory();
        }
    };

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return myAidlInterface;
    }




    //创建共享内存区域
    private ParcelFileDescriptor createMemory() {
        MemoryFile memoryFile=null;
        byte[] bytes =readFile(new File(getFilesDir().getPath(),"image.jpg"));
        try {
       		//创建内存对象 参数一：name 参数二：开辟的内存大小
            memoryFile=new MemoryFile("test_memory",1024*4);
            //将数据写入到内存当中
            memoryFile.getOutputStream().write(bytes);
            //通过反射获取到getFileDescriptor方法,注意
            Method method = MemoryFile.class.getDeclaredMethod("getFileDescriptor");
            //得到文件描述符
            FileDescriptor fd = (FileDescriptor) method.invoke(memoryFile);
            //将文件描述符返回
            return ParcelFileDescriptor.dup(fd);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        return null;
    }


    //file文件读取成byte[]
    public static byte[] readFile(File file) {
        RandomAccessFile rf = null;
        byte[] data = null;
        try {
            rf = new RandomAccessFile(file, "r");
            data = new byte[(int) rf.length()];
            rf.readFully(data);
        } catch (Exception exception) {
            exception.printStackTrace();
        } finally {
            closeQuietly(rf);
        }
        return data;
    }
    //关闭读取file
    public static void closeQuietly(Closeable closeable) {
        try {
            if (closeable != null) {
                closeable.close();
            }
        } catch (Exception exception) {
            exception.printStackTrace();
        }
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76

二，客户端

拿到fd写入到文件中即可

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private static final String TAG = "MainActivity";
    IMyAidlInterface aidl;
    ParcelFileDescriptor pfd = null;
    private ServiceConnection connection;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String filePath = this.getFilesDir().getPath();
        File file = new File(filePath + "/image.jpg");
        connection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                aidl = IMyAidlInterface.Stub.asInterface(service);
                try {
                    pfd = aidl.getPfd();
                    FileDescriptor fileDescriptor = pfd.getFileDescriptor();
                    FileInputStream inputStream=new FileInputStream(fileDescriptor);
                    file.createNewFile();
                    FileOutputStream fo = new FileOutputStream(file);
                    int read = inputStream.read();
                    while (read != -1) {
                        fo.write(read);
                        read = inputStream.read();
                    }
                    //关闭流
                    fo.flush();
                    fo.close();
                    inputStream.close();

//                    Log.i(TAG,"接收到的数据："+new String(content,"UTF-8"));
                } catch (RemoteException | IOException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {

            }
        };
        findViewById(R.id.bindService).setOnClickListener(this);


    }

    private void bindService() {
        Intent intent = new Intent();
        intent.setComponent(new ComponentName("com.example.ashmem", "com.example.ashmem.MyService"));
        boolean isbind = bindService(intent, connection, Context.BIND_AUTO_CREATE);
        Log.i(TAG, "bindService: "+isbind);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bindService:
                bindService();
                break;
            default:
                break;
        }
    }
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67