如果两个位置点超过了当前地图的可视范围，会显示异常

Created by: RaySaii

屏幕最上方的位置点是在杭州

render() {
    return <MapView style={StyleSheet.absoluteFill}>
      <Marker
          active
          draggable
          title={'一个可拖拽的标记 ' + this.state.time.toLocaleTimeString()}
          onDragEnd={this._onDragEvent}
          onInfoWindowPress={this._onInfoWindowPress}
          coordinate={this._coordinates[0]}
      />
      <Marker
          icon='green'
          onInfoWindowPress={this._onCustomInfoWindowPress}
          coordinate={this._coordinates[1]}>
        <TouchableOpacity activeOpacity={0.9} onPress={this._onCustomInfoWindowPress}>
          <View style={styles.customInfoWindow}>
            <Text>Custom View InfoWindow</Text>
          </View>
        </TouchableOpacity>
      </Marker>
      <Marker
          icon={() =>
              <View style={styles.customIcon}>
                <Image style={styles.customIcon} />
              </View>
          }
          title='自定义图片'
          description="Sometimes you'll have some special properties that you need to expose for the native component, but don't actually want them as part of the API for the associated React component."
          coordinate={this._coordinates[2]}
      />
      <Marker
          title='自定义标记'
          icon={() =>
              <View style={styles.customMarker}>
                <Text style={styles.markerText}>{this.state.time.toLocaleTimeString()}</Text>
              </View>
          }
          coordinate={{latitude:30.182159,longitude:120.139843}}
      />
    </MapView>
  }