Android应用内HTTP服务器：AlertDialog交互与响应处理-java教程-PHP中文网

android应用内http服务器：alertdialog交互与响应处理

本文档介绍了如何在Android应用内部署HTTP服务器，并在接收到请求时通过AlertDialog与用户交互。通过监听AlertDialog的按钮点击事件，服务器能够根据用户的选择向客户端发送响应。同时，提供了一种简单的阻塞方法，确保用户交互完成后再发送响应，并讨论了潜在的性能影响。

在Android应用中集成HTTP服务器，并根据用户在AlertDialog中的选择来响应客户端请求，这涉及到多线程、UI交互和网络编程。以下将详细介绍实现步骤和注意事项。

创建HTTP服务器

首先，需要创建一个HTTP服务器。可以使用Java自带的HttpServer类来实现。

import com.sun.net.httpserver.HttpServer;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpExchange;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.URI;
import java.util.HashMap;
import java.util.Map;
import android.os.Handler;
import android.os.Looper;
import android.app.AlertDialog;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.TextView;
import androidx.appcompat.widget.AppCompatButton;
import android.widget.LinearLayout;
import android.util.Log;

public class HttpServerManager {

    private static final String TAG = "HttpServerManager";
    private HttpServer httpServer;
    private AlertDialog adminRegisterDialog;
    private View adminRegisterView;

    private static HttpServerManager instance;

    public static HttpServerManager getInstance() {
        if (instance == null) {
            instance = new HttpServerManager();
        }
        return instance;
    }

    private HttpServerManager() {
        try {
            InetSocketAddress address = new InetSocketAddress(8080);
            httpServer = HttpServer.create(address, 0);

            httpServer.createContext("/getDeviceRegister", new EchoGetHandlerForDeviceRegister());

            httpServer.setExecutor(null); // Use the default executor
            httpServer.start();

            Log.i(TAG, "HttpServer Start");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    static void parseQuery(String query, Map<String, Object> parameters) {
        if (query != null) {
            String pairs[] = query.split("[&]");
            for (String pair : pairs) {
                String param[] = pair.split("[=]");
                if (param.length > 1) {
                    parameters.put(param[0], param[1]);
                }
            }
        }
    }

    class EchoGetHandlerForDeviceRegister implements HttpHandler {

        @Override
        public void handle(HttpExchange he) throws IOException {
            // parse request
            Map<String, Object> parameters = new HashMap<>();
            URI requestedUri = he.getRequestURI();
            String query = requestedUri.getRawQuery();

            parseQuery(query, parameters);

            // Flag to control the while loop
            final boolean[] isClick = {false};
            final AppCompatButton[] allowButtonHolder = {null};


            new Handler(Looper.getMainLooper()).post(() -> {
                //SHOW DIALOG HERE
                AdminRegisterDialogResult result = showAdminRegisterDialog(he.getRemoteAddress());
                allowButtonHolder[0] = result.getAllowButton();

                //ALERT DILOG CLICK LISTENER
                result.getAllowButton().setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Log.i(TAG,"allowButton");
                        isClick[0] = true;
                        adminRegisterDialog.dismiss();
                    }
                });

                result.getNotAllowButton().setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Log.i(TAG,"not allowButton");
                        isClick[0] = true;
                        adminRegisterDialog.dismiss();
                    }
                });

            });

            // This is a busy-wait loop.  Consider alternatives.
            while (!isClick[0]) {
                Log.i(TAG, "in while loop");
                try {
                    Thread.sleep(100); // Avoid busy-waiting, but be careful with sleep in a handler
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            Log.i(TAG, "out while loop");

            // send response
            String response = "<h1>Alert Dialog Clicked</h1>";
            for (String key : parameters.keySet())
                response += key + " = " + parameters.get(key) + "\n";
            he.sendResponseHeaders(200, response.length());
            OutputStream os = he.getResponseBody();
            os.write(response.toString().getBytes());
            os.close();
        }
    }

    public class AdminRegisterDialogResult {
        private AppCompatButton allowButton;
        private AppCompatButton notAllowButton;

        public AdminRegisterDialogResult(AppCompatButton allowButton, AppCompatButton notAllowButton) {
            this.allowButton = allowButton;
            this.notAllowButton = notAllowButton;
        }

        public AppCompatButton getAllowButton() {
            return allowButton;
        }

        public AppCompatButton getNotAllowButton() {
            return notAllowButton;
        }
    }

    public AdminRegisterDialogResult showAdminRegisterDialog(InetSocketAddress clientAdress){
        Log.i(TAG, "showAdminRegisterDialog()");
        if (adminRegisterDialog != null)
            adminRegisterDialog.cancel();

        Context context = MainActivity.instance();

        AlertDialog.Builder builder = new AlertDialog.Builder(context);

        LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        adminRegisterView = li.inflate(R.layout.register_dialog, null);


        builder.setView(adminRegisterView);
        builder.setCancelable(false);

        TextView deviceNameText = adminRegisterView.findViewById(R.id.deviceNameText);
        TextView infoText = adminRegisterView.findViewById(R.id.infoText);

        deviceNameText.setText(clientAdress.toString());
        infoText.setText(R.string.register_admin_allow_text);

        AppCompatButton allowButton = adminRegisterView.findViewById(R.id.allowButton);
        AppCompatButton notAllowButton = adminRegisterView.findViewById(R.id.notAllowButton);

        adminRegisterDialog = builder.create();
        adminRegisterDialog.show();
        adminRegisterDialog.getWindow().setLayout(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

        return new AdminRegisterDialogResult(allowButton, notAllowButton);

    }

    public void stop() {
        if (httpServer != null) {
            httpServer.stop(0);
            Log.i(TAG, "HttpServer Stop");
        }
    }
}

登录后复制

代码解释：

HttpServerManager 类负责创建和管理 HTTP 服务器实例。
EchoGetHandlerForDeviceRegister 类实现了 HttpHandler 接口，用于处理 /getDeviceRegister 路径的请求。
parseQuery 方法用于解析 URL 中的查询参数。
showAdminRegisterDialog 方法用于显示 AlertDialog，等待用户交互。
isClick 标志位用于控制 while 循环，确保用户点击按钮后才发送响应。

显示AlertDialog并等待用户交互

在 EchoGetHandlerForDeviceRegister 的 handle 方法中，使用 Handler 将显示 AlertDialog 的操作切换到主线程。这非常重要，因为UI操作必须在主线程中进行。

new Handler(Looper.getMainLooper()).post(() -> {
    //SHOW DIALOG HERE
    AdminRegisterDialogResult result = showAdminRegisterDialog(he.getRemoteAddress());

    //ALERT DILOG CLICK LISTENER
    result.getAllowButton().setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Log.i(TAG,"allowButton");
            isClick[0] = true;
            adminRegisterDialog.dismiss();
        }
    });

    result.getNotAllowButton().setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Log.i(TAG,"not allowButton");
            isClick[0] = true;
            adminRegisterDialog.dismiss();
        }
    });

});

登录后复制

使用while循环阻塞直到用户交互

为了确保在用户点击AlertDialog上的按钮后再发送响应，可以使用一个 while 循环进行阻塞。

Hour One

AI文字到视频生成

查看详情

final boolean[] isClick = {false};

while (!isClick[0]) {
    Log.i(TAG, "in while loop");
    try {
        Thread.sleep(100); // Avoid busy-waiting, but be careful with sleep in a handler
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

Log.i(TAG, "out while loop");

登录后复制

注意： 这种方法使用了忙等待（busy-waiting），会消耗CPU资源。虽然添加了Thread.sleep(100)来降低CPU占用，但仍然不是最佳实践。在实际应用中，应该考虑使用更高效的线程同步机制，如 CountDownLatch 或 Semaphore。

发送响应

在 while 循环结束后，表示用户已经进行了交互，此时可以构建并发送响应。

// send response
String response = "<h1>Alert Dialog Clicked</h1>";
for (String key : parameters.keySet())
    response += key + " = " + parameters.get(key) + "\n";
he.sendResponseHeaders(200, response.length());
OutputStream os = he.getResponseBody();
os.write(response.toString().getBytes());
os.close();

登录后复制

替代方案：使用 CountDownLatch

CountDownLatch 是一种更优雅的线程同步方式，可以避免忙等待。

import java.util.concurrent.CountDownLatch;

class EchoGetHandlerForDeviceRegister implements HttpHandler {

    @Override
    public void handle(HttpExchange he) throws IOException {
        // parse request
        Map<String, Object> parameters = new HashMap<>();
        URI requestedUri = he.getRequestURI();
        String query = requestedUri.getRawQuery();

        parseQuery(query, parameters);

        final CountDownLatch latch = new CountDownLatch(1);

        new Handler(Looper.getMainLooper()).post(() -> {
            //SHOW DIALOG HERE
            AdminRegisterDialogResult result = showAdminRegisterDialog(he.getRemoteAddress());

            //ALERT DILOG CLICK LISTENER
            result.getAllowButton().setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Log.i(TAG,"allowButton");
                    latch.countDown(); // Signal that the button has been clicked
                    adminRegisterDialog.dismiss();
                }
            });

            result.getNotAllowButton().setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Log.i(TAG,"not allowButton");
                    latch.countDown(); // Signal that the button has been clicked
                    adminRegisterDialog.dismiss();
                }
            });
        });

        try {
            latch.await(); // Wait for the latch to be counted down
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // send response
        String response = "<h1>Alert Dialog Clicked</h1>";
        for (String key : parameters.keySet())
            response += key + " = " + parameters.get(key) + "\n";
        he.sendResponseHeaders(200, response.length());
        OutputStream os = he.getResponseBody();
        os.write(response.toString().getBytes());
        os.close();
    }
}

登录后复制

代码解释：

CountDownLatch latch = new CountDownLatch(1); 创建一个计数器，初始值为1。
在按钮的 OnClickListener 中，调用 latch.countDown(); 将计数器减1，当计数器为0时，latch.await(); 会立即返回。
latch.await(); 会阻塞当前线程，直到计数器为0。