如何在 API 级别 21 以下的设备中检查 NO INTERNET

Question

这是我的 MainActivity，我已经在 onstart 中注册了我的网络调用。在此代码中，无论设备是否打开互联网 wifi，都不会调用 onUnavailable()。我想在点击一个按钮后检查互联网，如果互联网连接，它将继续下一个活动，否则没有

public class MainActivity extends AppCompatActivity {
    private TextView textView;
    ConnectivityManager.NetworkCallback networkCallback;
    ConnectivityManager manager;
    public static final String TAG = "bantai";
    private NetworkRequest networkRequest;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = findViewById(R.id.internetTextview);
        networkRequest = new NetworkRequest.Builder().build();
        manager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);


        networkCallback = new ConnectivityManager.NetworkCallback() {
            @Override
            public void onAvailable(@NonNull Network network) {
                super.onAvailable(network);
                Log.d(TAG, "onAvailable: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("onAvailable");
                    }
                });

            }

            @Override
            public void onLosing(@NonNull Network network, int maxMsToLive) {
                super.onLosing(network, maxMsToLive);
                Log.d(TAG, "onLosing: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("loosing");
                    }
                });
            }

            @Override
            public void onLost(@NonNull Network network) {
                super.onLost(network);
                Log.d(TAG, "onLost: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("lost");
                    }
                });            }

            @Override
            public void onUnavailable() {
                super.onUnavailable();
                Log.d(TAG, "onUnavailable: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("unavailable");
                    }
                });            }

            @Override
            public void onCapabilitiesChanged(@NonNull Network network, @NonNull NetworkCapabilities networkCapabilities) {
                super.onCapabilitiesChanged(network, networkCapabilities);
                Log.d(TAG, "onCapabilitiesChanged: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("capability");
                    }
                });            }

            @Override
            public void onLinkPropertiesChanged(@NonNull Network network, @NonNull LinkProperties linkProperties) {
                super.onLinkPropertiesChanged(network, linkProperties);
                Log.d(TAG, "onLinkPropertiesChanged: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("link");
                    }
                });            }

            @Override
            public void onBlockedStatusChanged(@NonNull Network network, boolean blocked) {
                super.onBlockedStatusChanged(network, blocked);
                Log.d(TAG, "onBlockedStatusChanged: ");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.d(TAG, "onAvailable: "+ Thread.currentThread().getName());
                        textView.setText("blocked");
                    }
                });            }
        };
    }

    @Override
    protected void onStart() {
        super.onStart();
        manager.requestNetwork(networkRequest,networkCallback);

    }

    @Override
    protected void onStop() {
        super.onStop();
        manager.unregisterNetworkCallback(networkCallback);
    }

还有ConnectivityManager.requestNetwork(networkRequest, networkCallback, 3000)这个命令需要Api level 21 +，超时3秒。

Answer 1

为了方便查看互联网，请使用此功能，它在 api 16 及更高版本上响应：

在 AndroidManifest.xml 中添加：

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

现在检查网络状态：

• getActiveNetworkInfo 在 API 29 上已弃用。

• getAllNetworkInfo 在 API 23 上已弃用。

  fun isConnected(): Boolean {
  
   val hasInternet: Boolean
  
   val connectivityManager =
       ctx.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
  
   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
       val networkCapabilities = connectivityManager.activeNetwork ?: return false
       val actNw =
           connectivityManager.getNetworkCapabilities(networkCapabilities) ?: return false
       hasInternet = when {
           actNw.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> true
           actNw.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> true
           actNw.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> true
           else -> false
       }
   } else {
       hasInternet = try {
           if (connectivityManager.activeNetworkInfo == null) {
               false
           } else {
               connectivityManager.activeNetworkInfo?.isConnected!!
           }
       } catch (e: Exception) {
           false
       }
   }
   return hasInternet}