如果您熟悉
实现自定义视图,您可以创建一个扩展
MapView
类的自定义视图,以完全控制在视图画布上的绘制。但是由于
MapView
扩展了
FrameLayout
,它是
ViewGroup
,因此您应该覆盖
dispatchDraw()
方法,而不是
onDraw()
并在其中实现雷达绘制。就像这样:
@Override
public void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
canvas.save();
drawRadarOverTheMap(canvas);
canvas.restore();
}
您需要在每次地图移动/缩放/旋转时通过
invalidate()
调用它。要检测地图的移动/缩放/旋转,您需要使用
GoogleMap
(确切地说是
GoogleMap.setOnCameraMoveListener()
方法)。您可以在自定义 MapView 类中声明
GoogleMap
对象并通过 setter 设置它,但最好是自定义 MapView 类实现
OnMapReadyCallback
接口并在
onMapReady()
回调中获取它。
基于
MapView
的自定义视图(例如
RadarMapView
)的完整源代码可能如下:
public class RadarMapView extends MapView implements OnMapReadyCallback {
private OnMapReadyCallback mMapReadyCallback;
private GoogleMap mGoogleMap;
private Marker mMarker;
private Paint mPaintRadar;
public RadarMapView(@NonNull Context context) {
super(context);
init();
}
public RadarMapView(@NonNull Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init();
}
public RadarMapView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
public RadarMapView(@NonNull Context context, @Nullable GoogleMapOptions options) {
super(context, options);
init();
}
@Override
public void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
canvas.save();
drawRadarOverTheMap(canvas);
canvas.restore();
}
private void drawRadarOverTheMap(Canvas canvas) {
if (mGoogleMap == null) {
return;
}
final float centerX = getX() + getWidth() / 2;
final float centerY = getY() + getHeight() / 2;
canvas.drawCircle(centerX, centerY, 150, mPaintRadar);
canvas.drawCircle(centerX, centerY, 300, mPaintRadar);
canvas.drawCircle(centerX, centerY, 450, mPaintRadar);
}
private void init() {
setWillNotDraw(false);
mPaintRadar = new Paint();
mPaintRadar.setColor(Color.GREEN);
mPaintRadar.setStyle(Paint.Style.STROKE);
mPaintRadar.setStrokeWidth(10);
}
@Override
public void getMapAsync(OnMapReadyCallback callback) {
mMapReadyCallback = callback;
super.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mGoogleMap = googleMap;
mGoogleMap.setOnCameraMoveListener(new GoogleMap.OnCameraMoveListener() {
@Override
public void onCameraMove() {
invalidate();
}
});
if (mMapReadyCallback != null) {
mMapReadyCallback.onMapReady(googleMap);
}
}
}
你可以在 .xml
文件中使用它:
<?xml version="1.0" encoding="utf-8"?>
<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="{your_package_name}.MainActivity">
<{your_package_name}.RadarMapView
android:id="@+id/mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
</RelativeLayout>
对于像 MainActivity
这样的:
public class MainActivity extends AppCompatActivity {
private static final String MAP_VIEW_BUNDLE_KEY = "MapViewBundleKey";
private GoogleMap mGoogleMap;
private RadarMapView mMapView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Bundle mapViewBundle = null;
if (savedInstanceState != null) {
mapViewBundle = savedInstanceState.getBundle(MAP_VIEW_BUNDLE_KEY);
}
mMapView = (RadarMapView) findViewById(R.id.mapview);
mMapView.onCreate(mapViewBundle);
mMapView.getMapAsync(new OnMapReadyCallback() {
@Override
public void onMapReady(GoogleMap googleMap) {
mGoogleMap = googleMap;
}
});
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Bundle mapViewBundle = outState.getBundle(MAP_VIEW_BUNDLE_KEY);
if (mapViewBundle == null) {
mapViewBundle = new Bundle();
outState.putBundle(MAP_VIEW_BUNDLE_KEY, mapViewBundle);
}
mMapView.onSaveInstanceState(mapViewBundle);
}
@Override
protected void onResume() {
super.onResume();
mMapView.onResume();
}
@Override
protected void onStart() {
super.onStart();
mMapView.onStart();
}
@Override
protected void onStop() {
super.onStop();
mMapView.onStop();
}
@Override
protected void onPause() {
mMapView.onPause();
super.onPause();
}
@Override
protected void onDestroy() {
mMapView.onDestroy();
super.onDestroy();
}
@Override
public void onLowMemory() {
super.onLowMemory();
mMapView.onLowMemory();
}
}
你应该得到类似于这样的东西:
![Radar MapView](https://istack.dev59.com/VR3IL.webp)
此外,您可以通过canvas.drawBitmap()
方法在自定义视图画布上绘制位图雷达图像。
您还可以将ImageView
放置在MapView
或MapFragment
上(例如在RelativeLayout
中)。
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<fragment
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.MapFragment"
/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:src="@drawable/radar"
/>
</RelativeLayout>
在
ImageView
上绘制(甚至只需设置)雷达图像。
RadarMapView.java
,并用答案中的代码替换MainActivity.java
和activity_main.xml
的代码。答案中的源代码是完整且已就绪的(除了{your_package_name}.MainActivity
- 您应该将其替换为自己的)。 - Andrii Omelchenko