1、实现代码

  • 一般在首页复写OnKeyDown方法

    1. public class MainActivity extends AppCompatActivity {
    3.   private static final String TAG = "MainActivity";
    5.   private WifiAdmin wifiAdmin;
    7.   @Override
    8.   protected void onCreate(Bundle savedInstanceState) {
    9.       super.onCreate(savedInstanceState);
    10.       setContentView(R.layout.activity_main);
    12.       wifiAdmin = WifiAdmin.getInstance(this);
    13.       Log.e(TAG, "onCreate:" + wifiAdmin.mWifiInfo);
    14.   }
    16.   //上次点击返回键的时间
    17.   private long mExitTime = 0;
    19.   @Override
    20.   public boolean onKeyDown(int keyCode, KeyEvent event) {
    21.       if (keyCode == KeyEvent.KEYCODE_BACK){
    22.           if ((System.currentTimeMillis() - mExitTime) > 2000){
    23.               Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
    24.               mExitTime = System.currentTimeMillis();
    25.           }else {
    26.               System.exit(0);//返回0表示正常退出程序
    27.           }
    28.           return true;
    29.       }
    30.       return super.onKeyDown(keyCode, event);
    31.   }
    32. }