判断网络状态

1.  
2. public class MainActivity extends AppCompatActivity{  
3.     @Override  
4.     protected void onCreate(Bundle savedInstanceState) {  
5.         super.onCreate(savedInstanceState);  
6.         setContentView(R.layout.activity_main);  
7.         getNetInfor();  
8.     }  
9.     public void getNetInfor() {  
10.         //首先是获取网络连接管理者  
11.         ConnectivityManager manager = (ConnectivityManager)  
12.                 getSystemService(Context.CONNECTIVITY_SERVICE);  
13.         NetworkInfo info = manager.getActiveNetworkInfo();  
14.         //网络状态存在并且是已连接状态  
15.         if (info != null && info.isConnected()) {  
16.             Toast.makeText(MainActivity.this, "网络已连接", Toast.LENGTH_SHORT).show();  
17.         } else {  
18.             Toast.makeText(MainActivity.this, "网络连接失败", Toast.LENGTH_SHORT).show();  
19.             //下面的这种写法你应该看得懂  
20.             new AlertDialog.Builder(MainActivity.this)  
21.             .setTitle("请检查网络连接")  
22.             .setNegativeButton("确定", new DialogInterface.OnClickListener() {  
23.                 @Override  
24.                 public void onClick(DialogInterface dialog, int which) {  
25.                     if (android.os.Build.VERSION.SDK_INT > 10) {  
26.                         //安卓系统3.0以上打开设置界面，也可以直接用ACTION_WIRELESS_SETTINGS打开到wifi界面  
27.                         startActivity(new Intent(android.provider.Settings.ACTION_SETTINGS));  
28.                     } else {  
29.                         startActivity(new Intent(android.provider.Settings.ACTION_WIRELESS_SETTINGS));  
30.                     }  
31.                 }  
32.             })  
33.             .show();  
34.         }  
35.     }  
36. }