listView根本没有出现 . 安卓

listView根本没有出现（活动是白色的，我添加的东西很少（按钮）），我不知道它是否重要，但这不是我的主要活动 .

编辑：我为主要活动和项目添加了xml

public class CarsMenu extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cars_menu);
        runListView();
        clickFun();

    }
    private void clickFun() {
        ListView list = (ListView) findViewById(R.id.MlistView);
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View viewClicked, int position, long id) {
                TextView textView = (TextView) viewClicked;
                Toast.makeText(getApplicationContext(), "clicked", Toast.LENGTH_SHORT).show();              
            }
        });

    }
    private void runListView(){
        String[] getCars = {"blue", "green", "purple", "red"};
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.items,    getCars);
        ListView list = (ListView) findViewById(R.id.MlistView);
        list.setAdapter(adapter);

    }
}

活动xml

activity xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${packageName}.${activityClass}" >




        <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:onClick="btnCarClick"
            android:text="Refresh" />

        <ListView
            android:id="@+id/MlistView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/button1"
            android:layout_centerHorizontal="true" >

        </ListView>
</RelativeLayout>

items xml

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


</TextView>

android清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.http"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.http.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.http.Exception_Error"
            android:configChanges="orientation|keyboardHidden|screenSize"
            android:label="@string/title_activity_exception__error"
            android:theme="@style/FullscreenTheme" >
        </activity>
        <activity
            android:name="com.example.http.Menu_Activity"
            android:label="@string/title_activity_menu_" >
        </activity>
        <activity
            android:name="com.example.http.Dev"
            android:label="@string/title_activity_dev" >
        </activity>
        <activity
            android:name="com.example.http.AllCars"
            android:label="@string/title_activity_all_cars" >
        </activity>
        <activity
            android:name="com.example.http.Cars"
            android:label="@string/title_activity_cars" >
        </activity>
        <activity
            android:name="com.example.http.CarsMenu"
            android:label="@string/title_activity_cars_menu" >
        </activity>
    </application>

    <uses-permission android:name="android.permission.INTERNET" >
    </uses-permission>

</manifest>