Question

我正在尝试将API 21+的功能添加到支持18的应用程序中。我有检查以确保运行应用程序的手机在API 21上用于各种方法，但我需要声明一个我的活动顶部的对象，这阻止了应用程序在旧的API手机上工作。是否有任何用于包装该对象的模式，以便它只为运行API 21+的设备创建，并为低于此值的任何内容返回null？对于上下文，这适用于蓝牙广告客户，我需要此对象来创建/停止广告：

private AdvertiseCallback mAdvertisingCallback = new AdvertiseCallback() {
    @Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
        super.onStartSuccess(settingsInEffect);
    }

    @Override
    public void onStartFailure(int errorCode) {
        super.onStartFailure(errorCode);
    }
};

而我的广告数据是一种方法：

private void advertise( String stufftoadvertise ) {
    if( Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && BluetoothAdapter.getDefaultAdapter().isMultipleAdvertisementSupported() ) {
        BluetoothLeAdvertiser advertiser = BluetoothAdapter.getDefaultAdapter().getBluetoothLeAdvertiser();

        AdvertiseSettings settings = new AdvertiseSettings.Builder()
                .setAdvertiseMode( AdvertiseSettings.ADVERTISE_MODE_LOW_POWER )
                .setTxPowerLevel( AdvertiseSettings.ADVERTISE_TX_POWER_LOW )
                .setConnectable( false )
                .build();

        UUID uuid = UUID.fromString( getString( R.string.uuid_advertise ));
        ParcelUuid pUuid = new ParcelUuid( uuid );

        AdvertiseData data = new AdvertiseData.Builder()
                .setIncludeDeviceName( true )
                .addServiceUuid( pUuid )
                .addServiceData( pUuid, stufftoadvertise.getBytes( Charset.forName("UTF-8") ) )
                .build();

        advertiser.startAdvertising(settings, data, mAdvertisingCallback);
    }
}

Answer 1

不确定这是否是最好的解决方案，但我确实找到了一种方法来实现这一目标。我刚刚创建了一个静态类，它返回一个回调的单例，并且只在API为21或更高时才调用该类

@TargetApi(21)
public class AdvertiseCallbackCreator {

private static final AdvertiseCallback mAdvertisingCallback = new AdvertiseCallback() {
    @Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
        super.onStartSuccess(settingsInEffect);
    }

    @Override
    public void onStartFailure(int errorCode) {
        super.onStartFailure(errorCode);
    }
};

public static AdvertiseCallback getAdvertiseCallback() {
    if( Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && BluetoothAdapter.getDefaultAdapter().isMultipleAdvertisementSupported() ) {
        return mAdvertisingCallback;
    } else return null;
}
}

Answer 2

除非你是API 21+，否则不要实例化对象。例如，不要这样做：

android.*

但是，请执行此操作：

private AdvertiseCallback mAdvertisingCallback = new AdvertiseCallback() {
    @Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
        super.onStartSuccess(settingsInEffect);
    }

    @Override
    public void onStartFailure(int errorCode) {
        super.onStartFailure(errorCode);
    }
};

然后当你需要使用它时，只需在那里初始化它：

private class CustomAdvertiseCallback implements AdvertiseCallback {
    @Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
        super.onStartSuccess(settingsInEffect);
    }

    @Override
    public void onStartFailure(int errorCode) {
        super.onStartFailure(errorCode);
    }
}

在支持旧版Android时使用新API

2 个答案: