public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    return netInfo != null && netInfo.isConnectedOrConnecting();
}

在AndroidManifest.xml中添加下面权限:

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

Calendar c = Calendar.getInstance();

int seconds = c.get(Calendar.SECOND);

参考：Calendar class documentation

Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.google.com"));

startActivity(browserIntent);

在AndroidManifest.xml的activity里添加android:screenOrientation="portrait"

<activity android:name=".SomeActivity" android:label="@string/app_name" android:screenOrientation="portrait">

一样的。历史问题，API 8+用match_parent就可以了

<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:gravity="center"
    android:text="@string/**yourtextstring**"
/>

CTRL+F12

Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x;
int height = size.y;

如果不在Activity里：

WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();

import android.provider.Settings.Secure;

private String android_id = Secure.getString(getContext().getContentResolver(), Secure.ANDROID_ID);

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