折线在模拟器上崩溃

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我正在尝试在地图上绘制折线

导入com.google.android.gms.maps.model.Polyline;导入com.google.android.gms.maps.model.PolylineOptions;

import java.util.ArrayList;导入java.util.List;

公共类MainActivity扩展了AppCompatActivity，它实现了OnMapReadyCallback，SeekBar.OnSeekBarChangeListener {//初始化变量

GoogleMap gMap;
SeekBar seekWidth, seekBlue, seekGreen, seekRed;
Button btClear, btDraw;

Polyline polyline = null;
List<LatLng> latLngList = new ArrayList<>();
List<Marker> markerList = new ArrayList<>();

PolylineOptions polylineOptions = null;

int red = 0, green= 0, blue=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    //Assign variable
    seekWidth = findViewById(R.id.seek_width);
    seekRed = findViewById(R.id.seek_red);
    seekGreen = findViewById(R.id.seek_green);
    seekBlue = findViewById(R.id.seek_blue);
    btDraw=findViewById(R.id.bt_draw);
    btClear=findViewById(R.id.bt_clear);

    /*Initialise SupportMapFragment
    SupportMapFragment supportMapFragment = (SupportMapFragment)getSupportFragmentManager()
            .findFragmentById(R.id.google_map);
    supportMapFragment.getMapAsync(this);

    btDraw.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Draw Polyline on Map
            if (polyline!=null) polyline.remove();
            //Create PolylineOptions
            PolylineOptions polylineOptions = new PolylineOptions()
                    .addAll(latLngList).clickable(true);
            polyline = gMap.addPolyline(polylineOptions);

            setWidth();

        }
    });*/

    //Initialise SupportMapFragment
    SupportMapFragment supportMapFragment = (SupportMapFragment)getSupportFragmentManager()
            .findFragmentById(R.id.google_map);
    supportMapFragment.getMapAsync(this);

    btDraw.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            //Draw Polyline on Map
            if (polyline!=null) polyline.remove();
            if(polylineOptions!=null){
                //Create PolylineOptions
                polyline = gMap.addPolyline(polylineOptions);

                setWidth();
            }
        }
    });

    btClear.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Clear All
            if (polyline!=null) polyline.remove();
            for(Marker marker: markerList) marker.remove();
            latLngList.clear();
            markerList.clear();
            seekWidth.setProgress(3);
            seekBlue.setProgress(0);
            seekGreen.setProgress(0);
            seekRed.setProgress(0);

        }
    });

    seekRed.setOnSeekBarChangeListener(this);
    seekGreen.setOnSeekBarChangeListener(this);
    seekBlue.setOnSeekBarChangeListener(this);


}

private void setWidth() {
    seekWidth.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            //Get Seekbar Progress
            int width = seekWidth.getProgress();
            if (polyline != null) {
                //Set Polyline Width
                polyline.setWidth(width);
            }
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {

        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
    });
}

/*@Override
public void onMapReady(GoogleMap googleMap) {
    /*gMap= googleMap;
    gMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng latLng) {
            //Create MarkerOptions
            MarkerOptions markerOptions = new MarkerOptions().position(latLng);
            //Create Marker
            Marker marker = gMap.addMarker(markerOptions);
            //Add Latlng and Marker
            latLngList.add(latLng);
            markerList.add(marker);
        }
    });

}*/

    public void onMapReady(GoogleMap googleMap) {
        gMap= googleMap;
        gMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
            @Override
            public void onMapClick(LatLng latLng) {
                //Create MarkerOptions
                MarkerOptions markerOptions = new MarkerOptions().position(latLng);
                //Create Marker
                Marker marker = gMap.addMarker(markerOptions);
                //Add Latlng and Marker
                latLngList.add(latLng);
                markerList.add(marker);

                polylineOptions = new PolylineOptions().addAll(latLngList).clickable(true);
            }
        });
    }

@Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
    switch (seekBar.getId()){
        case R.id.seek_red:
            red = i;
            break;
        case R.id.seek_green:
            green = i;
            break;
        case R.id.seek_blue:
            blue= i;
            break;

    }
    if(polyline !=null){
    //Set Polyline Color
        polyline.setColor(Color.rgb(red,green,blue));
    }


}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {

}

}

错误如下：] >>

2019-11-29 13：39：40.391 20694-20694 / com.example.poly E / AndroidRuntime：致命异常：主要流程：com.example.poly，PID：20694java.lang.NullPointerException：尝试在计算机上调用虚拟方法'void com.google.android.gms.maps.model.Polyline.setColor（int）'空对象引用

在com.example.poly.MainActivity.onProgressChanged（MainActivity.java:149）在android.widget.SeekBar.onProgressRefresh（SeekBar.java:93）在android.widget.ProgressBar.doRefreshProgress（ProgressBar.java:1327）在android.widget.ProgressBar.refreshProgress（ProgressBar.java:1382）在android.widget.ProgressBar.setProgressInternal（ProgressBar.java:1447）在android.widget.AbsSeekBar.trackTouchEvent（AbsSeekBar.java:850）在android.widget.AbsSeekBar.onTouchEvent（AbsSeekBar.java:760）在android.view.View.dispatchTouchEvent（View.java:9943）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2669）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2358）在com.android.internal.policy.DecorView.superDispatchTouchEvent（DecorView.java:411）在com.android.internal.policy.PhoneWindow.superDispatchTouchEvent（PhoneWindow.java:1810）在android.app.Activity.dispatchTouchEvent（Activity.java:3061）在androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent（WindowCallbackWrapper.java:69）在com.android.internal.policy.DecorView.dispatchTouchEvent（DecorView.java:373）在android.view.View.dispatchPointerEvent（View.java:10163）在android.view.ViewRootImpl $ ViewPostImeInputStage.processPointerEvent（ViewRootImpl.java:4434）在android.view.ViewRootImpl $ ViewPostImeInputStage.onProcess（ViewRootImpl.java:4302）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3849）在android.view.ViewRootImpl $ InputStage.onDeliverToNext（ViewRootImpl.java:3902）在android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java:3868）在android.view.ViewRootImpl $ AsyncInputStage.forward（ViewRootImpl.java:3995）在android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:3876）在android.view.ViewRootImpl $ AsyncInputStage.apply（ViewRootImpl.java:4052）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3849）在android.view.ViewRootImpl $ InputStage.onDeliverToNext（ViewRootImpl.java:3902）在android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java:3868）在android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:3876）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3849）在android.view.ViewRootImpl.deliverInputEvent（ViewRootImpl.java:6210）在android.view.ViewRootImpl.doProcessInputEvents（ViewRootImpl.java:6184）在android.view.ViewRootImpl.enqueueInputEvent（ViewRootImpl.java:6145）在android.view.ViewRootImpl $ WindowInputEventReceiver.onInputEvent（ViewRootImpl.java:6313）在android.view.InputEventReceiver.dispatchInputEvent（InputEventReceiver.java:185）在android.view.InputEventReceiver.nativeConsumeBatchedInputEvents（Native方法）在android.view.InputEventReceiver.consumeBatchedInputEvents（InputEventReceiver.java:176）在android.view.ViewRootImpl.doConsumeBatchedInput（ViewRootImpl.java:6284）在android.view.ViewRootImpl $ ConsumeBatchedInputRunnable.run（ViewRootImpl.java:6336）

我正在尝试在地图导入com.google.android.gms.maps.model.Polyline上绘制折线；导入com.google.android.gms.maps.model.PolylineOptions;导入java.util.ArrayList;导入java.util ....

答案

这实际上可能是临时修复程序或永久修复程序，具体取决于折线为何仍为null的根本原因，但下面应该解决您的崩溃问题。

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