Recycler查看保证金

我正在开发家庭安全应用程序。必须实现的功能之一是能够查看已连接的设备（用于发送通知，阻止访问等）。到目前为止，我已经能够创建设备的RecyclerView列表，一切对我来说都是完美的，只是该列表中的卡之间没有间距。

现在的屏幕截图

device_data_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:cardview="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="80dp"
android:layout_margin="8dp">

<RelativeLayout
android:layout_width="match_parent"
android:layout_height="80dp">

<ImageView
    android:id="@+id/deviceIcon"
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:layout_alignParentLeft="true"
    android:layout_centerVertical="true"
    android:scaleType="centerCrop"
    android:layout_marginLeft="8dp" />

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="80dp"
    android:layout_alignBottom="@+id/deviceIcon"
    android:layout_toEndOf="@+id/deviceIcon">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Username"
        android:id="@+id/deviceUsername"
        android:layout_gravity="center_vertical"
        android:textColor="#000000"
        android:layout_marginLeft="5dp" />

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:layout_gravity="center_vertical"
        android:gravity="center_vertical|center_horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="25dp"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="Device Model"
            android:gravity="center_vertical|right"
            android:textColor="#000000"
            android:id="@+id/deviceModel"
            android:layout_marginLeft="5dp" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="25dp"
            android:textColor="#000000"
            android:textAppearance="?android:attr/textAppearanceSmall"
            android:text="Device Version"
            android:gravity="center_vertical|right"
            android:id="@+id/deviceVersion"
            android:layout_marginLeft="5dp" />
    </LinearLayout>
</LinearLayout>

devices_list.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="@dimen/activity_vertical_margin">

    <view
        android:id="@+id/connectedDevicesList"
        class="android.support.v7.widget.RecyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerInParent="true" />
</RelativeLayout>

查看持有人代码

import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.exampleapp.R;

public class DeviceViewHolder extends RecyclerView.ViewHolder {

    protected ImageView     deviceIcon;
    protected TextView      deviceUsername;
    protected TextView      deviceModel;
    protected TextView      deviceVersion;

    public DeviceViewHolder(View view) {
        super(view);
        this.deviceIcon         =   (ImageView) view.findViewById(R.id.deviceIcon);
        this.deviceUsername     =   (TextView)  view.findViewById(R.id.deviceUsername);
        this.deviceModel        =   (TextView)  view.findViewById(R.id.deviceModel);
        this.deviceVersion      =   (TextView)  view.findViewById(R.id.deviceVersion);
    }
}

RecyclerView适配器

import android.content.Context;
import android.support.v4.content.ContextCompat;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;

import com.exampleapp.API.AuthorizedDevice;
import com.exampleapp.R;

public class ConnectedDeviceAdapter extends RecyclerView.Adapter<DeviceViewHolder> {
    private List<AuthorizedDevice> devices;
    private Context mContext;

    public ConnectedDeviceAdapter(Context context, List<AuthorizedDevice> devices) {
        this.devices = devices;
        this.mContext = context;
    }

    @Override
    public DeviceViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.connected_devices_layout, null);

        DeviceViewHolder viewHolder = new DeviceViewHolder(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(DeviceViewHolder deviceViewHolder, int i) {
        AuthorizedDevice device = devices.get(i);

        if (device.getDeviceId().equals("0")) {
            deviceViewHolder.deviceIcon.setBackground(ContextCompat.getDrawable(mContext, R.drawable.android_icon));
        } else {
            deviceViewHolder.deviceIcon.setBackground(ContextCompat.getDrawable(mContext, R.drawable.apple_icon));
        }

        deviceViewHolder.deviceUsername.setText(device.getUsername());
        deviceViewHolder.deviceModel.setText(device.getDeviceName());
        deviceViewHolder.deviceVersion.setText(device.getDeviceVersion());
    }

    @Override
    public int getItemCount() {
        return (null != devices ? devices.size() : 0);
    }
}

谁能帮我解决这个问题？提前非常感谢您！