java - 当我尝试使用 ImageButton 获取当前位置时收到错误消息

Question

我创建了一个 Google Maps 项目，当我尝试运行应用程序时，在 Logcat 中出现此错误：

2021-05-04 23:04:43.119 30960-30960/com.example.googlemaps E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.googlemaps, PID: 30960
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.googlemaps/com.example.googlemaps.MainActivity}: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.ImageButton
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3792)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:246)
        at android.app.ActivityThread.main(ActivityThread.java:8506)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1139)
     Caused by: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.ImageButton
        at com.example.googlemaps.MainActivity.onCreate(MainActivity.java:55)
        at android.app.Activity.performCreate(Activity.java:8198)
        at android.app.Activity.performCreate(Activity.java:8182)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3765)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:246) 
        at android.app.ActivityThread.main(ActivityThread.java:8506) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1139) 

这是我在 xml 文件中的 ImageButton。

<ImageButton
        android:id="@+id/gpsBtn"
        android:layout_width="55dp"
        android:layout_height="53dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.224"
        app:srcCompat="@mipmap/gps" />

这就是我在 MainActivity.java 中使用它的方式。

gpsImageBtn = (ImageButton) findViewById(R.id.gpsBtn);
@Override
    public void onMapReady(GoogleMap googleMap) {
        map = googleMap;

        gpsImageBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                    getCurrentLocation();
                } else {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 44);
                }
            }
        });
    }

private void getCurrentLocation() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        Task<Location> task = client.getLastLocation();
        task.addOnSuccessListener(new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                if (location != null) {
                    supportMapFragment.getMapAsync(new OnMapReadyCallback() {
                        @Override
                        public void onMapReady(@NonNull GoogleMap googleMap) {
                            LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
                            MarkerOptions options = new MarkerOptions().position(latLng).title("We are here");
                            googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(latLng, 10));
                            googleMap.addMarker(options);
                        }
                    });
                }
            }
        });
    }
@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == 44) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                getCurrentLocation();
            }
        }
    }

我希望我的 ImageButton 能够在 Google 地图上获取我的当前位置。

2021-05-05 09:14:18.437 28109-28109/com.example.googlemaps E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.googlemaps, PID: 28109
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at com.example.googlemaps.MainActivity.onMapReady(MainActivity.java:128)
        at com.example.googlemaps.-$$Lambda$LoyQsFFqrj9dAHwAkAA_9-9Ps-k.onMapReady(Unknown Source:2)
        at com.google.android.gms.maps.zzat.zzb(com.google.android.gms:play-services-maps@@17.0.1:1)
        at com.google.android.gms.maps.internal.zzaq.zza(com.google.android.gms:play-services-maps@@17.0.1:6)
        at com.google.android.gms.internal.maps.zzb.onTransact(com.google.android.gms:play-services-maps@@17.0.1:3)
        at android.os.Binder.transact(Binder.java:1043)
        at cx.b(:com.google.android.gms.dynamite_mapsdynamite@201817052@20.18.17 (040700-0):2)
        at com.google.maps.api.android.lib6.impl.be.run(:com.google.android.gms.dynamite_mapsdynamite@201817052@20.18.17 (040700-0):2)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

我想尝试让自己成为某种实际 Google 地图的副本。

标签： javaxmlandroid-studio