Android FinDeviceWBYID返回null
我正试图基于hello地图教程构建一个简单的地图应用程序,但是使用Android FinDeviceWBYID返回null,android,Android,我正试图基于hello地图教程构建一个简单的地图应用程序,但是使用findViewById获得的MapView返回空值。但是,地图在模拟器中正确显示。因此,该应用程序可以工作,但我无法在代码中检索地图视图。我错过了什么 代码: 布局: <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" andro
findViewById
获得的MapView
返回空值。但是,地图在模拟器中正确显示。因此,该应用程序可以工作,但我无法在代码中检索地图视图。我错过了什么
代码:
布局:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/mainlayout"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<com.google.android.maps.MapView
android:id="@+id/mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:apiKey="the key"
/>
</RelativeLayout>
setContentView(R.layout.main)
应该在MapView MapView=(MapView)findViewById(R.id.MapView)之前出现代码>
@覆盖
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);//setContentView(R.layout.main)
必须添加到MapView
之前
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
MapView mapView = (MapView) findViewById(R.id.mapview);
if (mapView == null) {
Log.d("onCreate", "map is null"); //log shows that mapView is null
}
}
我建议您在呼叫后立即添加setContentView
super.onCreate(savedInstanceState)
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); //<----------------------------------------
MapView mapView = (MapView) findViewById(R.id.mapview);
if (mapView == null) {
Log.d("onCreate", "map is null"); //log shows that mapView is null
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
MapView mapView = (MapView) findViewById(R.id.mapview);
if (mapView == null) {
Log.d("onCreate", "map is null"); //log shows that mapView is null
}
}