android判断一个功能是否可用

[code]Device features

In order for you to manage your app’s availability based on device features, Android defines feature IDs for any hardware or software feature that may not be available on all devices. For instance, the feature ID for the compass sensor is FEATURE_SENSOR_COMPASS and the feature ID for app widgets is FEATURE_APP_WIDGETS.

If necessary, you can prevent users from installing your app when their devices don't provide a given feature by declaring it with a <uses-feature> element in your app's manifest file.

For example, if your app does not make sense on a device that lacks a compass sensor, you can declare the compass sensor as required with the following manifest tag:

<manifest ... >
    <uses-feature android:name="android.hardware.sensor.compass"
                  android:required="true" />
    ...
</manifest>
Google Play Store compares the features your app requires to the features available on each user's device to determine whether your app is compatible with each device. If the device does not provide all the features your app requires, the user cannot install your app.

However, if your app's primary functionality does not require a device feature, you should set the required attribute to "false" and check for the device feature at runtime. If the app feature is not available on the current device, gracefully degrade the corresponding app feature. For example, you can query whether a feature is available by calling hasSystemFeature() like this:

PackageManager pm = getPackageManager();
if (!pm.hasSystemFeature(PackageManager.FEATURE_SENSOR_COMPASS)) {
    // This device does not have a compass, turn off the compass feature
    disableCompassFeature();
}