判斷Adndroid手機的網絡連接狀態

        判斷手機的網絡狀態，需要使用ConnectivityManager。ConnectivityManager主要管理和網絡連接相關的操作 。 相關的TelephonyManager則管理和手機、運營商等的相關信息；WifiManager則管理和wifi相關的信息。NetworkInfo類包含了對wifi和mobile兩種網絡模式連接的詳細描述，通過其getState()方法獲取的State對象則代表着連接成功與否等狀態。 

Java代碼：

package com.lenovo.test.network;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo.State;
import android.os.Bundle;
import android.provider.Settings;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class JudgeNetworkActivity extends Activity {
	/** Called when the activity is first created. */
	private Button mButton = null;
	private TextView mTextView = null;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		mButton = (Button) findViewById(R.id.mbutton);
		mTextView = (TextView) findViewById(R.id.mtv);
		final Builder builder = new AlertDialog.Builder(this);
		mButton.setOnClickListener(new View.OnClickListener() {
			public void onClick(View v) {
				// TODO Auto-generated method stub
				ConnectivityManager conMan = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

				// mobile 3G Data Network
				State mobile = conMan.getNetworkInfo(
						ConnectivityManager.TYPE_MOBILE).getState();

				// wifi
				State wifi = conMan.getNetworkInfo(
						ConnectivityManager.TYPE_WIFI).getState();
				mTextView.setText("Moble Network:" + mobile.toString() + "\n"
						+ "WIFI Network:" + wifi.toString());
				// 如果3G網絡和wifi網絡都未連接，且不是處於正在連接狀態 則進入Network Setting界面 由用戶配置網絡連接
				if (!(mobile == State.CONNECTED || mobile == State.CONNECTING
						|| wifi == State.CONNECTED || wifi == State.CONNECTING)) {
					builder.setTitle("Message")
							.setMessage("沒有可用的網絡，請設置有效的網絡連接！")
							.setNegativeButton("確定",
									new DialogInterface.OnClickListener() {
										public void onClick(
												DialogInterface dialog,
												int which) {
											startActivity(new Intent(
													Settings.ACTION_WIRELESS_SETTINGS));// 進入無線網絡配置界面
											// startActivity(new
											// Intent(Settings.ACTION_WIFI_SETTINGS));
											// 進入手機中的wifi網絡設置界面
										}
									}).show();
				}
			}
		});
	}
}

在AndroidManifest.xml裏添加權限：

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

運行結果：