Android判断网络连接状态及双击退出APP

这次是安卓常用的两个小功能，一个是判断网络是否连接，另一个是双击返回键退出APP，这两个类都是放到代码里都能用

判断网络的实体化类

public void getNetInfor() {
        //首先是获取网络连接管理者
        ConnectivityManager manager = (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = manager.getActiveNetworkInfo();
        //网络状态存在并且是已连接状态
        if (info != null && info.isConnected()) {
            Toast.makeText(ShouyeActivity.this, "网络已连接", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(ShouyeActivity.this, "网络连接失败", Toast.LENGTH_SHORT).show();
            //下面的这种写法你应该看得懂
            new AlertDialog.Builder(ShouyeActivity.this)
                    .setTitle("请检查网络连接")
                    .setNegativeButton("确定", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            if (android.os.Build.VERSION.SDK_INT > 10) {
                                //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
                                startActivity(new Intent(android.provider.Settings.ACTION_SETTINGS));
                            } else {
                                startActivity(new Intent(android.provider.Settings.ACTION_WIRELESS_SETTINGS));
                            }
                        }
                    })
                    .show();
        }
    }

下面是双击退出APP 也是个实体化类

//点击两次返回键退出APP
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        long secondTime = System.currentTimeMillis();
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if (secondTime - firstTime < 2000) {
                System.exit(0);
            } else {
                Toast.makeText(getApplicationContext(), "再按一次返回键退出", Toast.LENGTH_SHORT).show();
                firstTime = System.currentTimeMillis();
            }
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }