java - NullPointerException java，即使显示值？

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What is a NullPointerException, and how do I fix it?
                                
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我不明白我的代码发生了什么...我在一个值上得到一个空指针异常，甚至认为在我的日志中该行之前也显示了相同的值。我不知道错误还会从何而来。这是我的代码：

 private Map<String,Double> isRecordValid(RecordObject record, RecordObject previousRecord, int counterElevationArrayFilligness) {
        Map<String,Double> values = null;
        boolean SPEED_OK = true;
        boolean DISTANCE_OK = false;
        boolean ELEVATION_OK = false;

        // SPEED
        // has to be greater then the average Human walking: 1.4 m/s
        if(record.getSpeed() > 1.4){
            values.put("Speed", record.getSpeed());
            Log.d("DEBUG", "SPEED OK");
            SPEED_OK = true;
        }

        // DISTANCE
        // Check if the distance record we are checking and the last one, is above the average accuracy of both.
        // This is done to avoid having loads of reccords stacking up when the phone is not moving and therefore lots of Flase Postivie values
        float[] distanceBetweenResults = new float[1];
        LatLng latLongA = new LatLng(record.getLatitude(), record.getLongitude());
        LatLng latLongB = new LatLng(previousRecord.getLatitude(), previousRecord.getLongitude());
        Location.distanceBetween(latLongA.latitude, latLongA.longitude, latLongB.latitude, latLongB.longitude, distanceBetweenResults);
        double distanceBetweenAB = distanceBetweenResults[0];

        int accuracyA = record.getAccuracy();
        int accuracyB = previousRecord.getAccuracy();
        int averageAccuracy = (accuracyA + accuracyB) / 2;

        Log.d("DEBUG", "" + distanceBetweenAB);
        if (SPEED_OK) {
            if (distanceBetweenAB > averageAccuracy) {
                values.put("Distance", distanceBetweenAB);
                Log.d("DEBUG", "DISTANCE OK");
                DISTANCE_OK = true;
            }
        }

        // ELEVATION
        // fill in an array to calculate the average altitude over 4 reocrds, this is done because the alitude in an android phone
        // is really inacurate unless the phone has a barometer, which most don't.
        for (int e=0; e < elevationArray.length; e++) {
            if(elevationArray[e] == null){
                elevationArray[e] = record.getAltitude();
                Log.d("DEBUG", "FIRST ELEVATION OK");
                ELEVATION_OK = true;
            } else {
                counterElevationArrayFilligness ++;
            }
        }

        if(elevationArray[3] != null){ //Once the array is filled with value
            int sum = 0;
            for (double value:elevationArray) {
                sum += value;
            }
            double averageElevation = sum / 4; //this is the average of all the 4 values

            int interval = Double.compare(averageElevation, BASE_ELEVATION); //this returns the interval between 2 doubles
            if (interval > 1 || interval < -1){ // check if the difference is at least 1m
                values.put("Elevation", averageElevation);
                Log.d("DEBUG", "ELEVATION OK");
                ELEVATION_OK = true;
            }
        }

        if(DISTANCE_OK && ELEVATION_OK && SPEED_OK){
            return values;
        } else {
            return null;
        }
    }

错误在线：values.put（“ Distance”，distanceBetweenAB）;
但是，在IF函数之前会显示distanceBetweenAB值
这是我得到的错误：

FATAL EXCEPTION: main
                  Process: com.example.rtuya.myfitnesstracker, PID: 6406
                  java.lang.RuntimeException: Error receiving broadcast Intent { act=UPDATE_UI flg=0x10 } in com.example.rtuya.myfitnesstracker.MainActivity$1@e47673d
                      at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:891)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                   Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.Map.put(java.lang.Object, java.lang.Object)' on a null object reference
                      at com.example.rtuya.myfitnesstracker.Service.TrackerService.isRecordValid(TrackerService.java:347)
                      at com.example.rtuya.myfitnesstracker.Service.TrackerService.calculateUptoNowValues(TrackerService.java:216)
                      at com.example.rtuya.myfitnesstracker.Service.TrackerService.updateHistoryTable(TrackerService.java:143)
                      at com.example.rtuya.myfitnesstracker.MainActivity.getValuesFromService(MainActivity.java:98)
                      at com.example.rtuya.myfitnesstracker.MainActivity$1.onReceive(MainActivity.java:72)
                      at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:881)

最佳答案

NullPointerException是由于values变量引起的。不是因为distanceBetweenAB。
您需要初始化值。

例如：

Map<String,Double> values = new HashMap<>();