Question

尝试使用broadCastReceiver测试ConnectivityManager.CONNECTIVITY_ACTION时，应用程序崩溃，logcat说Error receiving broadcast Intent。请让我知道我错过了什么。

代码：

public class wifi_socket_01 extends Activity {

TextView tv_conn_status;
TextView tv_conn_ssid;
TextView tv_conn_speed;
TextView tv_conn_strengt;
TextView tv_conn_ip;

EditText et_ip;
ToggleButton tobBtn_connect;
EditText et_msg;
Button btn_send;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    SetUpAllViews(R.layout.activity_main);
    displayWiFiStates();

    this.registerReceiver(this.myWiFiReceiver, 
            new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
}

private BroadcastReceiver myWiFiReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        NetworkInfo networkInfo = intent.getParcelableExtra(ConnectivityManager.EXTRA_EXTRA_INFO);
        if (networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
            displayWiFiStates();
        }
    }
};

private void SetUpAllViews(int layout) {
    // TODO Auto-generated method stub
    setContentView(layout);

    tv_conn_status = (TextView) findViewById(R.id.tv_conn_status);
    tv_conn_ssid = (TextView) findViewById(R.id.tv_conn_ssid);
    tv_conn_speed = (TextView) findViewById(R.id.tv_conn_speed);
    tv_conn_strengt = (TextView) findViewById(R.id.tv_conn_strength);
    tv_conn_ip = (TextView) findViewById(R.id.tv_conn_ip);
    et_ip = (EditText) findViewById(R.id.et_ip);
    tobBtn_connect = (ToggleButton) findViewById(R.id.togbtn_connect);
    et_msg = (EditText) findViewById(R.id.et_msg);
    btn_send = (Button) findViewById(R.id.btn_send);
}

protected void displayWiFiStates() {
    // TODO Auto-generated method stub
    String service = Context.CONNECTIVITY_SERVICE;
    ConnectivityManager myConnManager = (ConnectivityManager) getSystemService(service);
    NetworkInfo myNetworkInfo = myConnManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    WifiManager myWifiManager = (WifiManager)getSystemService(Context.WIFI_SERVICE);
    WifiInfo myWiFiInfo = myWifiManager.getConnectionInfo();

    if(myNetworkInfo.isConnected()) {
        tv_conn_ip.setText("IP: "+myWiFiInfo.getIpAddress());
    }else {
        tv_conn_status.setText("Disconnected");
    }
}

}

logcat的：

11-08 10:26:57.645: E/AndroidRuntime(15348): FATAL EXCEPTION: main
11-08 10:26:57.645: E/AndroidRuntime(15348): Process: com.example.wifi_socket_01, PID:   
15348
11-08 10:26:57.645: E/AndroidRuntime(15348): java.lang.RuntimeException: Error 
receiving broadcast Intent { act=android.net.conn.CONNECTIVITY_CHANGE flg=0x4000010   
(has extras) } in com.example.wifi_socket_01.MainActivity$1@4302f638
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:782)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at a
ndroid.os.Handler.handleCallback(Handler.java:733)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
 android.os.Handler.dispatchMessage(Handler.java:95)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
android.os.Looper.loop(Looper.java:157)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
android.app.ActivityThread.main(ActivityThread.java:5293)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at  
java.lang.reflect.Method.invokeNative(Native Method)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at   
java.lang.reflect.Method.invoke(Method.java:515)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at   
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at    
dalvik.system.NativeStart.main(Native Method)
11-08 10:26:57.645: E/AndroidRuntime(15348): Caused by: java.lang.NullPointerException
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
com.example.wifi_socket_01.MainActivity$1.onReceive(MainActivity.java:48)
11-08 10:26:57.645: E/AndroidRuntime(15348):    at 
android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:772)

Answer 1

试试这个：

改变你的

NetworkInfo networkInfo = intent.getParcelableExtra(ConnectivityManager.EXTRA_EXTRA_INFO);

到

ConnectivityManager cm =
        (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = cm.getActiveNetworkInfo();

来自文档： EXTRA_EXTRA_INFO

提供可选提供的额外字符串的字符串的查找键   有关网络状态的信息。

提供可选提供的额外字符串的字符串的查找键   有关网络状态的信息。信息可能会被传递   来自较低的网络层，其含义可能是特定于a   特定的网络类型。使用getStringExtra（String）检索它。

常数值：＆＃34; extraInfo＆＃34;

所以我们找到了问题根源的解释，它实际上从未实际返回networkInfo。它完全与网络状态有关。

希望它有所帮助：）

Answer 2

您可能在AndroidManifest中错过了正确的Android权限：

def avgs = sums.collect{patient, value -> (value / counts[patient]) }

Answer 3

我遇到了同样的问题，结果是onReceive函数中的空指针，我通过改变来修复它

    Boolean up = cm.getActiveNetworkInfo().isConnected();

到

    NetworkInfo info = cm.getActiveNetworkInfo();
    boolean up = false;
    if(info != null && info.isConnected()){
        up = true;
    }

我也在Android N上，这是在UI线程上运行的服务上发生的

收到broadCast Intent时出错

3 个答案: