Question

我有一个列表视图，其中包含位置坐标（纬度，经度），并且我正尝试将其传递给地图活动以在地图上显示

这是在android studio和Kotlin上

listView.setOnItemClickListener { parent, view, position, id ->

        val time = usersList.get(position).time
        val long:String = usersList.get(position).long
        val late :String = usersList.get(position).late
startActivity(Intent(this, MapsActivity2::class.java).putExtra("long",long).putExtra("late",late))
}

class MapsActivity2 : AppCompatActivity(), OnMapReadyCallback {

private lateinit var mMap: GoogleMap

var long:String = intent.getStringExtra("long")
var late:String = intent.getStringExtra("late")


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_maps2)


    // Obtain the SupportMapFragment and get notified when the map is ready to be used.
    val mapFragment = supportFragmentManager
        .findFragmentById(R.id.map) as SupportMapFragment
    mapFragment.getMapAsync(this)
}


override fun onMapReady(googleMap: GoogleMap) {
    mMap = googleMap

    // Add a marker in Sydney and move the camera
    val sydney = LatLng(long.toDouble(), late.toDouble())
    mMap.addMarker(MarkerOptions().position(sydney).title("jh"))
    mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney))
}
}

进程：com.example.firebase，PID：32463 java.lang.RuntimeException：无法实例化活动ComponentInfo {com.example.firebase / com.example.firebase.MapsActivity2}：java.lang.NullPointerException：尝试调用虚拟方法'java.lang.String android.content.Intent。 getStringExtra（java.lang.String）'上的空对象引用在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:3289）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:3548）在android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:86）在android.app.servertransaction.TransactionExecutor.executeCallbacks（TransactionExecutor.java:108）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:2155）在android.os.Handler.dispatchMessage（Handler.java:109）在android.os.Looper.loop（Looper.java:207）在android.app.ActivityThread.main（ActivityThread.java:7539）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:524）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:958）原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'java.lang.String android.content.Intent.getStringExtra（java.lang.String）' 在com.example.firebase.MapsActivity2。（MapsActivity2.kt：19）在java.lang.Class.newInstance（本地方法）在android.app.AppComponentFactory.instantiateActivity（AppComponentFactory.java:69）在android.support.v4.app.CoreComponentFactory.instantiateActivity（CoreComponentFactory.java:43）在android.app.Instrumentation.newActivity（Instrumentation.java:1224）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:3274）

Answer 1

var long:String = intent.getStringExtra("long")
var late:String = intent.getStringExtra("late")

以上代码应位于onCreate（）;

Answer 2

无法在intent之前获得onCreate，因此请尝试将其放入onCreate中。这是因为Intent在final void attach(.....)

之前没有初始化

 lateinit var longStr : String 
 lateinit var late : String

 override onCreate(....) {
    longStr = intent.getStringExtra("long")
    late = intent.getStringExtra("late")
 }

Answer 3

   include code inside onCreate() also check if it contain the extra

oncreate(){
if(getIntent.hasExtra("long")){
var long:String = intent.getStringExtra("long")
}
if(getIntent.hasExtra("late")){
var late:String = intent.getStringExtra("late")
}
}

Answer 4

您可以在onCreate（）之后获得意图价值，如下所示：我还建议避免像long这样的预定义关键字，因为long被定义为数据类型

var long:String = intent.getStringExtra("long")
var late:String = intent.getStringExtra("late")

尝试将位置坐标从列表视图传递到地图活动时发生错误

4 个答案: