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Android example source code file (ViewServer.java)

This example Android source code file (ViewServer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, bufferedreader, bufferedwriter, command_protocol_version, could, io, ioexception, net, network, outputstream, remote, serversocket, string, thread, util, utilities, value_protocol_version, value_server_version, view_server_default_port, viewserver

The ViewServer.java Android example source code

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.server;

import android.util.Slog;

import java.net.ServerSocket;
import java.net.Socket;
import java.net.InetAddress;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;

/**
 * The ViewServer is local socket server that can be used to communicate with the
 * views of the opened windows. Communication with the views is ensured by the
 * {@link com.android.server.WindowManagerService} and is a cross-process operation.
 *
 * {@hide}
 */
class ViewServer implements Runnable {
    /**
     * The default port used to start view servers.
     */
    public static final int VIEW_SERVER_DEFAULT_PORT = 4939;

    // Debug facility
    private static final String LOG_TAG = "ViewServer";

    private static final String VALUE_PROTOCOL_VERSION = "2";
    private static final String VALUE_SERVER_VERSION = "3";

    // Protocol commands
    // Returns the protocol version
    private static final String COMMAND_PROTOCOL_VERSION = "PROTOCOL";
    // Returns the server version
    private static final String COMMAND_SERVER_VERSION = "SERVER";
    // Lists all of the available windows in the system
    private static final String COMMAND_WINDOW_MANAGER_LIST = "LIST";

    private ServerSocket mServer;
    private Thread mThread;

    private final WindowManagerService mWindowManager;
    private final int mPort;

    /**
     * Creates a new ViewServer associated with the specified window manager.
     * The server uses the default port {@link #VIEW_SERVER_DEFAULT_PORT}. The server
     * is not started by default.
     *
     * @param windowManager The window manager used to communicate with the views.
     *
     * @see #start()
     */
    ViewServer(WindowManagerService windowManager) {
        this(windowManager, VIEW_SERVER_DEFAULT_PORT);
    }

    /**
     * Creates a new ViewServer associated with the specified window manager on the
     * specified local port. The server is not started by default.
     *
     * @param windowManager The window manager used to communicate with the views.
     * @param port The port for the server to listen to.
     *
     * @see #start()
     */
    ViewServer(WindowManagerService windowManager, int port) {
        mWindowManager = windowManager;
        mPort = port;
    }

    /**
     * Starts the server.
     *
     * @return True if the server was successfully created, or false if it already exists.
     * @throws IOException If the server cannot be created.
     *
     * @see #stop()
     * @see #isRunning()
     * @see WindowManagerService#startViewServer(int)
     */
    boolean start() throws IOException {
        if (mThread != null) {
            return false;
        }

        mServer = new ServerSocket(mPort, 1, InetAddress.getLocalHost());
        mThread = new Thread(this, "Remote View Server [port=" + mPort + "]");
        mThread.start();

        return true;
    }

    /**
     * Stops the server.
     *
     * @return True if the server was stopped, false if an error occured or if the
     *         server wasn't started.
     *
     * @see #start()
     * @see #isRunning()
     * @see WindowManagerService#stopViewServer()
     */
    boolean stop() {
        if (mThread != null) {
            mThread.interrupt();
            mThread = null;
            try {
                mServer.close();
                mServer = null;
                return true;
            } catch (IOException e) {
                Slog.w(LOG_TAG, "Could not close the view server");
            }
        }
        return false;
    }

    /**
     * Indicates whether the server is currently running.
     *
     * @return True if the server is running, false otherwise.
     *
     * @see #start()
     * @see #stop()
     * @see WindowManagerService#isViewServerRunning()  
     */
    boolean isRunning() {
        return mThread != null && mThread.isAlive();
    }

    /**
     * Main server loop.
     */
    public void run() {
        final ServerSocket server = mServer;

        while (Thread.currentThread() == mThread) {
            Socket client = null;
            // Any uncaught exception will crash the system process
            try {
                client = server.accept();

                BufferedReader in = null;
                try {
                    in = new BufferedReader(new InputStreamReader(client.getInputStream()), 1024);

                    final String request = in.readLine();

                    String command;
                    String parameters;

                    int index = request.indexOf(' ');
                    if (index == -1) {
                        command = request;
                        parameters = "";
                    } else {
                        command = request.substring(0, index);
                        parameters = request.substring(index + 1);
                    }

                    boolean result;
                    if (COMMAND_PROTOCOL_VERSION.equalsIgnoreCase(command)) {
                        result = writeValue(client, VALUE_PROTOCOL_VERSION);
                    } else if (COMMAND_SERVER_VERSION.equalsIgnoreCase(command)) {
                        result = writeValue(client, VALUE_SERVER_VERSION);
                    } else if (COMMAND_WINDOW_MANAGER_LIST.equalsIgnoreCase(command)) {
                        result = mWindowManager.viewServerListWindows(client);
                    } else {
                        result = mWindowManager.viewServerWindowCommand(client,
                                command, parameters);
                    }

                    if (!result) {
                        Slog.w(LOG_TAG, "An error occured with the command: " + command);
                    }
                } finally {
                    if (in != null) {
                        in.close();
                    }
                }
            } catch (Exception e) {
                Slog.w(LOG_TAG, "Connection error: ", e);
            } finally {
                if (client != null) {
                    try {
                        client.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    private static boolean writeValue(Socket client, String value) {
        boolean result;
        BufferedWriter out = null;
        try {
            OutputStream clientStream = client.getOutputStream();
            out = new BufferedWriter(new OutputStreamWriter(clientStream), 8 * 1024);
            out.write(value);
            out.write("\n");
            out.flush();
            result = true;
        } catch (Exception e) {
            result = false;
        } finally {
            if (out != null) {
                try {
                    out.close();
                } catch (IOException e) {
                    result = false;
                }
            }
        }
        return result;
    }
}

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