Question

我正在开发一个与树莓派进行通信的应用程序。应用程序通过套接字连接与服务器通信。

我目前能够建立通信并将其保存在服务中。但我的目标是从活动A改为活动B.问题是，我的应用程序在切换活动时会破坏服务。有办法避免这种情况吗？

活动A启动服务，当我启动活动B时，我将其绑定到活动以调用服务类中的方法。但它不是同一个实例。

我怎么能解决这个问题？

代码

ConnectActivity

package com.example.domen.twitchdronev3;

import android.content.Intent;
import android.os.Parcelable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class ConnectActivity extends AppCompatActivity {

    private int port = 3000;
    private String ip = "localhost";
    private Intent serviceIntent, activityIntent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_connect);

        Toast.makeText(getApplicationContext(), "Starte App...", Toast.LENGTH_LONG).show();

        activityIntent = new Intent(this, ControllActivity.class);
        serviceIntent = new Intent(this, ClientService.class);

        serviceIntent.putExtra("ip", ip);
        serviceIntent.putExtra("port", port);

        Button btnActivity = (Button) findViewById(R.id.changeActivity);
        btnActivity.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startService(serviceIntent);
                activityIntent.putExtra("Intent", (Parcelable) serviceIntent);
                startActivity(activityIntent);
            }
        });
    }

    // destroys the Activity
    @Override
    public void onDestroy() {
        super.onDestroy();
        Toast.makeText(getApplicationContext(), "Destroy (ConnectActivity)", Toast.LENGTH_LONG).show();
    }

    // Activity stopping
    @Override
    protected void onStop() {
        super.onStop();
    }
}

ControllActivity

package com.example.domen.twitchdronev3;

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class ControllActivity extends AppCompatActivity {

    public static final String TAG = "ControllActivity";

    private ClientService clientservice;
    private Intent serviceIntent;
    private boolean isBound;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_controll);

        Bundle extras = getIntent().getExtras();
        serviceIntent = extras.getParcelable("Intent");

        Button btnDisconnect = (Button) findViewById(R.id.btnDisconnect);
        btnDisconnect.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view) {
                doBindToService();
            }
        });
    }

    // destroys the Activity
    @Override
    public void onDestroy(){
        super.onDestroy();
        Toast.makeText(getApplicationContext(), "Destroy (ControllActivity)", Toast.LENGTH_LONG).show();
        doUnbindToService();
        stopService(serviceIntent);
    }

    // Functions to BIND and UNBIND the SERVICE
    // bind to Service
    public void doBindToService(){
        if(!isBound) {
            Toast.makeText(this, "(doBindToService) Binding...", Toast.LENGTH_LONG).show();
            isBound = bindService(serviceIntent, myConnection, Context.BIND_AUTO_CREATE);
        }
    }

    // Unbind to Service
    public void doUnbindToService(){
        Toast.makeText(this, "(doUnbindToService) Unbinding...", Toast.LENGTH_LONG).show();
        unbindService(myConnection);
        isBound = false;
    }

    private ServiceConnection myConnection = new ServiceConnection(){
        public static final String TAG = "ConnectActivity";

        @Override
        public void onServiceConnected(ComponentName className, IBinder service){
            Log.i(TAG, "BOUND SERVICE CONNECTED");
            clientservice = ((ClientService.ClientBinder) service).getService();
            isBound = true;
        }

        @Override
        public void onServiceDisconnected(ComponentName name){
            Log.i(TAG, "BOUND SERVICE DISCONNECTED");
            clientservice = null;
            isBound = false;
        }
    };
}

ClientService

package com.example.domen.twitchdronev3;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;
import android.widget.Toast;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;

/**
 * Created by ViTrex on 12.02.2018.
 */

public class ClientService extends Service {

    private static final String TAG = "ClientService";
    private final IBinder mBinder = new ClientBinder();

    private PrintWriter out;
    private Socket socket;

    private String ip = "";
    private int port = 0;

    private Thread backgroundThread;

    // the class used for the client binder
    public class ClientBinder extends Binder {
        ClientService getService() {
            // returns the instance of ClientService
            // so the client can access the public methods
            return ClientService.this;
        }
    }

    //SETTER
    public void setIP(String ip) {
        this.ip = ip;
    }

    public void setPort(int port) {
        this.port = port;
    }

    //GETTER
    public String getIP() {
        return this.ip;
    }

    public int getPort() {
        return this.port;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG, "onCreate...");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Toast.makeText(this, "onStartCommand", Toast.LENGTH_LONG).show();

        if(intent != null){
            setIP(intent.getStringExtra("ip"));
            setPort(intent.getIntExtra("port", 3000));
        }

        return START_NOT_STICKY;
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.i(TAG, "onBind called...");
        Toast.makeText(this, getIP() + " " + getPort(), Toast.LENGTH_LONG).show();
        backgroundThread = new Thread(new Runnable() {
            @Override
            public void run() {
                buildConnection();
            }
        });
        backgroundThread.start();
        return mBinder;
    }

    private void buildConnection() {
        Log.i(TAG, "Try to build up a connection ...");
        synchronized (this) {
            try {
                this.socket = new Socket(getIP(), getPort());
                this.out = new PrintWriter(this.socket.getOutputStream(), true);
                Log.i(TAG, "Connected");
            } catch (IOException ioe) {
                Log.i(TAG, ioe.getMessage());
                this.socket = null;
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "Close Service");
        Thread dummy = backgroundThread;
        backgroundThread = null;
        if (dummy != null)
            dummy.interrupt();

        if (this.socket != null) {
            try {
                this.out.close();
                this.socket.close();
                Log.i(TAG, "Close Socket");
            } catch (IOException ioe) {
                Log.i(TAG, "ERROR: Close Socket");
            }
        }
    }
}

Answer 1

你说：

活动A启动服务，当我启动活动B时，我绑定它调用服务类中的方法的活动。但它不是同一个例子。

你怎么知道不 同一个实例（大概是你的意思 of < / em> service实例）？

我认为你的代码是o.k.要在旧设备上运行（它在我的设备上运行。pre-API26，我认为权限在此之后发生了变化，因此可能需要更多代码。请参阅注意在这个答案的最后）。

你不想要START_STICKY吗？

我会将此代码（请Intent data设置的Activity A）添加到您的ClientService.java：

@Override public int onStartCommand(Intent intent, int flags, int startId) { String a_ip = intent.getStringExtra("ip"); int a_port = intent.getIntExtra("port",-1); Log.i(TAG, "onStartCommand called...with " + "ip:" + a_ip + "and port:"+ a_port); setIP(a_ip); setPort(a_port); return START_NOT_STICKY;//don't you want START_STICKY ? }

注意：如果您的应用针对API级别26或更高级别，系统会强制执行除非应用程序限制使用或创建后台服务本身就在前台。如果应用需要创建前景服务，应用程序应调用StartForegroundService（）。那种方法创建后台服务，但该方法向系统发出信号该服务将自己推向前台。一旦服务已经创建，服务必须调用它的startForeground（）方法在五秒钟内。来自here

在两个活动之间共享一项服务而不破坏它？

1 个答案: