Question

我试图在用户点击屏幕时保存标记的位置，我已按照正确的步骤操作如何使用共享首选项并检索它们。但是当我绘制一个位置并关闭并重新打开应用程序时。该应用程序崩溃。

这是我的MapActivity：

//Keys for Sharedpreferences
public static final String SHARED_PREF_NAME = "plot";
public static final String LONGTITUDE = "long";
public static final String LATITUDE = "lat";
public static final String PLOTTED= "plotted";
private boolean plotted= false;

  @Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
    LatLng philippines = new LatLng(13, 123);
    mMap.moveCamera(CameraUpdateFactory.newLatLng(philippines));
    mMap.animateCamera(CameraUpdateFactory.zoomTo(5.0f));

    if (ActivityCompat.checkSelfPermission(mapsPage.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(mapsPage.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        return;
    }
    mMap.setMyLocationEnabled(true);

  mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
        @Override
        public void onMapClick(LatLng point) {
                mMap.clear();
                mMap.addMarker(new MarkerOptions().position(point).draggable(false));
                mMap.moveCamera(CameraUpdateFactory.newLatLng(point));

                String lat = Double.toString(point.latitude);
                String lon = Double.toString(point.longitude);

                SharedPreferences sharedPreferences = mapsPage.this.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putBoolean(LOGGEDIN_SHARED_PREF, true);
                editor.putString(LONGTITUDE, lon);
                editor.putString(LATITUDE, lat);
                editor.commit();
        }
    });
}

 @Override
protected void onResume() {
    super.onResume();

    SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
    checkedout = sharedPreferences.getBoolean(LOGGEDIN_SHARED_PREF, false);

    if(checkedout)
    {
        SharedPreferences sharedPreferencess = getSharedPreferences(mapsPage.SHARED_PREF_NAME, Context.MODE_PRIVATE);
        String lon = sharedPreferencess.getString(mapsPage.LONGTITUDE,"Not Available");
        String lat = sharedPreferencess.getString(mapsPage.LATITUDE,"Not Available");

        double lo = Double.parseDouble(lon);
        double la = Double.parseDouble(lat);

        LatLng resumedPosition = new LatLng(lo,la);

        mMap.clear();
        mMap.addMarker(new MarkerOptions().position(resumedPosition).draggable(false));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(resumedPosition));
    }
}

提前感谢您的帮助！：d

Answer 1

您似乎正在尝试在onResume()上移动地图，但我猜想在Android调用onResume()时地图尚未准备就绪。所以为了解决这个问题，我会将其移到onMapReady()方法上。

//Keys for Sharedpreferences
public static final String SHARED_PREF_NAME = "plot";
public static final String LONGTITUDE = "long";
public static final String LATITUDE = "lat";
public static final String PLOTTED= "plotted";
private boolean plotted= false;

@Override
public void onMapReady(GoogleMap googleMap) {
  mMap = googleMap;

  mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
  LatLng philippines = new LatLng(13, 123);
  mMap.moveCamera(CameraUpdateFactory.newLatLng(philippines));
  mMap.animateCamera(CameraUpdateFactory.zoomTo(5.0f));

  if (ActivityCompat.checkSelfPermission(mapsPage.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(mapsPage.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    return;
  }
  mMap.setMyLocationEnabled(true);

  mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
    @Override
    public void onMapClick(LatLng point) {
      mMap.clear();
      mMap.addMarker(new MarkerOptions().position(point).draggable(false));
      mMap.moveCamera(CameraUpdateFactory.newLatLng(point));

      String lat = Double.toString(point.latitude);
      String lon = Double.toString(point.longitude);

      SharedPreferences sharedPreferences = mapsPage.this.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
      SharedPreferences.Editor editor = sharedPreferences.edit();
      editor.putBoolean(LOGGEDIN_SHARED_PREF, true);
      editor.putString(LONGTITUDE, lon);
      editor.putString(LATITUDE, lat);
      editor.commit();
    }
  });

  SharedPreferences sharedPreferences = getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
  checkedout = sharedPreferences.getBoolean(LOGGEDIN_SHARED_PREF, false);

  if(checkedout)
  {
    SharedPreferences sharedPreferencess = getSharedPreferences(mapsPage.SHARED_PREF_NAME, Context.MODE_PRIVATE);
    String lon = sharedPreferencess.getString(mapsPage.LONGTITUDE,"Not Available");
    String lat = sharedPreferencess.getString(mapsPage.LATITUDE,"Not Available");

    double lo = Double.parseDouble(lon);
    double la = Double.parseDouble(lat);

    LatLng resumedPosition = new LatLng(lo,la);

    mMap.clear();
    mMap.addMarker(new MarkerOptions().position(resumedPosition).draggable(false));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(resumedPosition));
  }

}

@Override
protected void onResume() {
  super.onResume();


}

使用共享首选项在MapClick上保存地图标记位置

1 个答案: