我制作了一个广播接收器，当连接到互联网时，它会在屏幕上显示消息。我的代码是 - ＆gt;
MainActivity.java
import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int PERMISSION_ALL = 1;
String[] PERMISSIONS = {Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.INTERNET, Manifest.permission.WRITE_SETTINGS, Manifest.permission.ACCESS_NETWORK_STATE};
if (!hasPermissions(this, PERMISSIONS)) {
ActivityCompat.requestPermissions(this, PERMISSIONS, PERMISSION_ALL);
}
}
public static boolean hasPermissions(Context context, String... permissions) {
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && context != null && permissions != null) {
for (String permission : permissions) {
if (ActivityCompat.checkSelfPermission(context, permission) != PackageManager.PERMISSION_GRANTED) {
return false;
}
}
}
return true;
}
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
清单
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<receiver
android:name=".NetworkChangeReceiver"
android:exported="true">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
<action android:name="android.net.wifi.WIFI_STATE_CHANGED" />
</intent-filter>
</receiver>
</application>
广播接收器
public class NetworkChangeReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
final ConnectivityManager connMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
final NetworkInfo activeNetwork = connMgr.getActiveNetworkInfo();
if(activeNetwork != null && activeNetwork.isConnected())
{
Toast.makeText(context, "Connected", Toast.LENGTH_SHORT).show();
}
/* if (activeNetwork.getType() == ConnectivityManager.TYPE_WIFI || activeNetwork.getType() == ConnectivityManager.TYPE_MOBILE) {
Toast.makeText(context, "Network Available", Toast.LENGTH_SHORT).show();
}*/
}
}
但是，它仅在应用程序打开时才有效。当应用程序关闭时，它不起作用，即使应用程序关闭，如何使其工作？
答案 0 :(得分：2)
首先将您的接收者声明为Menifest文件，
<receiver android:name=".services.ConnectivityBroadcastReceiver">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
</intent-filter>
</receiver>
ConnectivityBroadcastReceiver.java
public class ConnectivityBroadcastReceiver extends BroadcastReceiver {
static final String CONNECTIVITY_CHANGE_ACTION = "android.net.conn.CONNECTIVITY_CHANGE";
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (CONNECTIVITY_CHANGE_ACTION.equals(action)) {
//check internet connection
if (!ConnectionHelper.isConnectedOrConnecting(context)) {
if (context != null) {
boolean show = false;
if (ConnectionHelper.lastNoConnectionTs == -1) {//first time
show = true;
ConnectionHelper.lastNoConnectionTs = System.currentTimeMillis();
} else {
if (System.currentTimeMillis() - ConnectionHelper.lastNoConnectionTs > 1000) {
show = true;
ConnectionHelper.lastNoConnectionTs = System.currentTimeMillis();
}
}
if (show && ConnectionHelper.isOnline) {
ConnectionHelper.isOnline = false;
context.stopService(new Intent(context, SyncData.class));
Log.e("Connection lost.");
}
}
} else {
Log.e("Connected.");
// Perform your actions here
ConnectionHelper.isOnline = true;
}
}
}
}
ConnectionHelper.java
public class ConnectionHelper {
public static long lastNoConnectionTs = -1;
public static boolean isOnline = true;
public static boolean isConnected(Context context) {
ConnectivityManager cm =(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
return activeNetwork != null && activeNetwork.isConnected();
}
public static boolean isConnectedOrConnecting(Context context) {
ConnectivityManager cm =(ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
return activeNetwork != null &&
activeNetwork.isConnectedOrConnecting();
}
}
答案 1 :(得分：0)
您正在寻找的是Services。建议您阅读Android Studio here的文档。
服务将允许您的应用程序的特定部分始终存在。即使用户重新启动设备而又从未再次运行应用程序。关于服务有很多东西可以看，但目前我认为一段代码对你最有帮助，这里有一些代码，
首先在你的清单中
<!--notification-->
<service android:name="services.HelloService"
android:exported="false"
android:description="My notification Center"/>
<!--notification-->
第二
创建一个名为 HelloService
的类并使用正确的导入*
粘贴以下代码public class HelloService extends Service {
private Looper mServiceLooper;
private ServiceHandler mServiceHandler;
// Handler that receives messages from the thread
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
// Normally we would do some work here, like download a file.
// For our sample, we just sleep for 5 seconds.
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
// Restore interrupt status.
Thread.currentThread().interrupt();
}
// Stop the service using the startId, so that we don't stop
// the service in the middle of handling another job
stopSelf(msg.arg1);
}
}
@Override
public void onCreate() {
// Start up the thread running the service. Note that we create a
// separate thread because the service normally runs in the process's
// main thread, which we don't want to block. We also make it
// background priority so CPU-intensive work will not disrupt our UI.
HandlerThread thread = new HandlerThread("ServiceStartArguments",
Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
// Get the HandlerThread's Looper and use it for our Handler
mServiceLooper = thread.getLooper();
mServiceHandler = new ServiceHandler(mServiceLooper);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "servicestarting",Toast.LENGTH_SHORT).show();
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
mServiceHandler.sendMessage(msg);
// If we get killed, after returning from here, restart
return START_STICKY;
}
@Override
public IBinder onBind(Intent intent) {
// We don't provide binding, so return null
return null;
}
@Override
public void onDestroy() {
Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show();
}
}
在'handleMessage方法'中添加一些代码，例如;
@Override
public void handleMessage(Message msg) {
//... your bit of code goes here
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
// Restore interrupt status.
Thread.currentThread().interrupt();
}
//stopSelf(msg.arg1);
}
最后，要激活服务类，在您的函数中触发服务，首先导入HelloService.class，然后创建一个Intent并启动！
Intent intent = new Intent(this, HelloService.class);
startActivity(intent)