如何检查 API 级别 21 以下的设备是否没有互联网

Question

这是我的 MainActivity，我已经在 onstart 中注册了我的网络回调。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，它将继续下一步 activity 如果互联网已连接，否则不会

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);
    }

此外 ConnectivityManager.requestNetwork(networkRequest, networkCallback, 3000) 此命令需要 Api 级别 21 + 超时 3 秒。

Answer 1

为了轻松检查互联网，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 已在 API 29 上弃用。

getAllNetworkInfo 已在 API 23 上弃用。

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}

如何检查 API 级别 21 以下的设备是否没有互联网

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