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。
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");
}
}
}代码解释：
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();
}
});
});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。
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");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。
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();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();
}
}代码解释：
本教程提供了一种在Android应用内实现HTTP服务器并与AlertDialog交互的方法。通过选择合适的线程同步机制，可以有效地管理并发，并提供良好的用户体验。
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