public	void	onSaveInstanceState(Bundle	savedInstanceState)	{
//	Save	the	user's	current	game	state
	savedInstanceState.putInt(STATE_SCORE,	mCurrentScore);
        savedInstanceState.putInt(STATE_LEVEL,	mCurrentLevel);
	super.onSaveInstanceState(savedInstanceState);
}

    public void onRestoreInstanceState(Bundle savedInstanceState) {
        //	Always	call	the	superclass	so	it	can	restore	the	view	hierarchy
        super.onRestoreInstanceState(savedInstanceState);
        //	Restore	state	members	from	saved	instance
        mCurrentScore = savedInstanceState.getInt(STATE_SCORE);
        mCurrentLevel = savedInstanceState.getInt(STATE_LEVEL);
    }

PackageManager packageManager = getPackageManager();
List<ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0);
boolean isIntentSafe = activities.size() > 0;

// Build the intent
Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);
// Verify it resolves
PackageManager packageManager = getPackageManager();
List<ResolveInfo> activities = packageManager.queryIntentActivities(mapIntent, 0);
boolean isIntentSafe = activities.size() > 0;
// Start an activity if it's safe
if (isIntentSafe) {
    startActivity(mapIntent);
}

Intent intent = new Intent(Intent.ACTION_SEND);
...
// Always use string resources for UI text. This says something like "Share this photo with"
String title = getResources().getText(R.string.chooser_title);
// Create and start the chooser
Intent chooser = Intent.createChooser(intent, title);
startActivity(chooser);

			<fragment	android:name="com.example.android.fragments.ArticleFragment"
					android:id="@+id/article_fragment"
					android:layout_weight="2"
					android:layout_width="0dp"
					android:layout_height="match_parent"	/>

    public class HeadlinesFragment extends ListFragment {
        OnHeadlineSelectedListener mCallback;

        //	Container	Activity	must	implement	this	interface
        public interface OnHeadlineSelectedListener {
            public void onArticleSelected(int position);
        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            try {
                mCallback = (OnHeadlineSelectedListener) activity;
            } catch (ClassCastException e) {
                throw new ClassCastException(activity.toString()
                        + "	must	implement	OnHeadlineSelectedListener");
            }
        }
                ...
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        mCallback.onArticleSelected(position);
    }

    public static class MainActivity extends Activity
            implements HeadlinesFragment.OnHeadlineSelectedListener {
                ...

        public void onArticleSelected(int position) {
            //	The	user	selected	the	headline	of	an	article	from	the	HeadlinesFragment
            //	Do	something	here	to	display	that	article
        }
    }

    // 设置内容View为0%的不透明度，但是状态为“可见”，
    // 因此在动画过程中是一直可见的（但是为全透明）。
    mContentView.setAlpha(0f);
    mContentView.setVisibility(View.VISIBLE);
    // 开始动画内容View到100%的不透明度，然后清除所有设置在View上的动画监听器。
    mContentView.animate()
            .alpha(1f)
            .setDuration(mShortAnimationDuration)
            .setListener(null);
    // 加载View开始动画逐渐变为0%的不透明度，
    // 动画结束后，设置可见性为GONE（消失）作为一个优化步骤
    //（它将不再参与布局的传递等过程）
    mLoadingView.animate()
            .alpha(0f)
            .setDuration(mShortAnimationDuration)
            .setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mLoadingView.setVisibility(View.GONE);
                }
            });

public boolean isOnline() {
    ConnectivityManager connMgr = (ConnectivityManager)
            getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
    return (networkInfo != null && networkInfo.isConnected());
}

private static final String DEBUG_TAG = "NetworkStatusExample";
...
    ConnectivityManager connMgr = (ConnectivityManager)
        getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    boolean isWifiConn = networkInfo.isConnected();
    networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
    boolean isMobileConn = networkInfo.isConnected();
    Log.d(DEBUG_TAG, "Wifi connected: " + isWifiConn);
    Log.d(DEBUG_TAG, "Mobile connected: " + isMobileConn);