笔记：Android判断版本并根据版本使用不同的代码以及旧版本XML问题

Android provides a unique code for each platform version in the Build constants class. Use these codes within your app to build conditions that ensure the code that depends on higher API levels is executed only when those APIs are available on the system.

private void setUpActionBar() {    // Make sure we're running on Honeycomb or higher to use ActionBar APIs    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {        ActionBar actionBar = getActionBar();        actionBar.setDisplayHomeAsUpEnabled(true);    }}

在我们自己开发应用过程中，常常使用如下的代码形式判断运行新API还是旧的API:

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) 
    {
            // 包含新API的代码块
    }
    else
    {
            // 包含旧的API的代码块
    }

Note: When parsing XML resources, Android ignores XML attributes that aren’t supported by the current device. So you can safely use XML attributes that are only supported by newer versions without worrying about older versions breaking when they encounter that code. For example, if you set thetargetSdkVersion="11", your app includes the ActionBar by default on Android 3.0 and higher. To then add menu items to the action bar, you need to set android:showAsAction="ifRoom" in your menu resource XML. It's safe to do this in a cross-version XML file, because the older versions of Android simply ignore theshowAsAction attribute (that is, you do not need a separate version in res/menu-v11/).