如何检查设备功能

Question

如何检查android cordova的设备功能？任何人都可以提供代码吗？上下文变量的错误..shows上下文变量在此位置为null，同时尝试在设备中运行显示强制关闭的代码！我正在尝试检查相机功能..请帮助...提前感谢

package com.troubling.android;
import org.apache.cordova.api.CallbackContext;
import org.apache.cordova.api.CordovaPlugin;
import org.json.JSONArray;
import org.json.JSONException;

import android.app.Activity;
import android.content.pm.PackageManager;
import android.content.Context;
import android.util.Log;

public class Echo extends CordovaPlugin {

    @Override
    public boolean execute(String action, JSONArray args, CallbackContext callbackContext) throws
    JSONException 
    {
        Context context = null;
        PackageManager  pm = this.cordova.getActivity().getPackageManager();


        if (pm.hasSystemFeature(PackageManager.FEATURE_CAMERA)) {


            Log.i("camera", "This device has camera!");
        }
        else{

            Log.i("camera", "This device has no camera!");
        }

return false;

    }

    private void echo(String message, CallbackContext callbackContext) {
        if (message != null && message.length() > 0) { 
            callbackContext.success(message);
        } else {
            callbackContext.error("Expected one non-empty string argument.");
        }
    }

}

Answer 1

试

PackageManager  pm = this.cordova.getActivity().getApplicationContext().getPackageManager();