我正在尝试在按下按钮时从另一个Activity更改trx的值，我尝试的是
ScoresActivity.kt ：
class ScoresActivity : AppCompatActivity(), View.OnClickListener {
var trx = 0
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scores)
}
}
其他课程
override fun onClick(p0: View?) {
when(p0){
button_1 -> {
ScoresActivity().trx = 5
}
}
但每当我打印trx的值时，它就是0。
答案 0 :(得分：4)
问题：
当您致电ScoresActivity()时，您将创建ScoresActivity课程的新实例。由于您没有保存此实例，因此值trx的设置将丢失。
解决方案：
我不确定trx应该代表什么，但由于Activity名称给出了一个提示，我认为它是某种分数（然后可以在全球范围内使用）。
一种方法是将trx放在companion object中，而class ScoresActivity: Activity() {
// ...
companion object {
var trx: Int = 0
}
}
本身就在ScoresActivity中。
ScoresActivity.trx = 5
用法（来自任何活动）：
trx其他方式是另一个类，它是一个单例（Kotlin中的object）并表示构成游戏状态的值，或者通过活动之间的意图传递 var logoElement = document.createElement ('a');
logoElement.href = 'http://www.schienenpost.de/';
logoElement.target = '_blank';
var logoImage = document.createElement ('img');
logoImage.src = 'http://www.schienenpost.de/schienenpost.png';
logoElement.appendChild (logoImage);
var iconStyle = new ol.style.Style ({
image: new ol.style.Icon (/** @type {olx.style.IconOptions} */ ({
anchor: [0.5, 1.0],
src: 'http://www.schienenpost.de/marker/marker.png'
}))
});
var scaleLineControl = new ol.control.ScaleLine();
var markerStartEnd = function (layer,feature) {
var i, iconFeature, iconFeatures = [], coordinates, nameLine;
coordinates = feature.getGeometry ().getCoordinates ();
nameLine = feature.getProperties () ['name'];
i = 0;
iconFeature = new ol.Feature ({
geometry: new ol.geom.Point (coordinates[i]),
name: 'Start'+nameLine,
});
iconFeature.setStyle (iconStyle);
iconFeatures.push (iconFeature);
i = coordinates.length - 1;
iconFeature = new ol.Feature ({
geometry: new ol.geom.Point (coordinates[i]),
name: 'End'+nameLine,
});
iconFeature.setStyle (iconStyle);
iconFeatures.push (iconFeature);
layer.getSource ().addFeatures (iconFeatures);
};
var layerLines = new ol.layer.Vector ({
source: new ol.source.Vector ({
format: new ol.format.GeoJSON (),
url: 'schienenpost.geojson',
useSpatialIndex: false
}),
style: new ol.style.Style ({stroke: new ol.style.Stroke ({color : 'red', width: 3})}),
});
var layerMarker = new ol.layer.Vector ({
title: 'Marker',
source: new ol.source.Vector ()
});
var element = document.getElementById ('popup');
var popup = new ol.Overlay ({
element: element,
positioning: 'bottom-center',
stopEvent: false,
offset: [0, -0]
});
var map = new ol.Map ({
controls: ol.control.defaults ()
.extend ([
new ol.control.OverviewMap (),
new ol.control.FullScreen (),
scaleLineControl
]),
//target 'map',
target: document.getElementById ('map'),
layers: [
new ol.layer.Tile ({
source: new ol.source.OSM ()
}),
],
view: new ol.View ({
center: ol.proj.fromLonLat ([10.627, 53.620]),
zoom: 8
}),
logo: logoElement
});
map.addOverlay (popup);
map.addLayer (layerLines);
map.addLayer (layerMarker);
map.once ('moveend', function(e) {
layerLines.getSource ().getFeaturesCollection ().forEach (function (feature) {
markerStartEnd (layerMarker,feature);
});
});
map.on ('click', function (evt) {
var feature = map.forEachFeatureAtPixel (evt.pixel,
function (feature) {
return feature;
});
if (feature) {
var coordinates = feature.getGeometry ().getCoordinates ();
var clickpoint = map.getCoordinateFromPixel (evt.pixel);
if (!isNaN (coordinates [0])) { // Punkt
popup.setPosition (coordinates);
} else if (!isNaN (coordinates [0][0])) { // Linie
popup.setPosition (clickpoint);
} else { // kein brauchbares feature
$ (element).popover ('destroy');
return;
}
$ (element).popover ({
'placement': 'top',
'html': true,
'content': feature.get ('name')
});
$ (element).popover ().data ('bs.popover').options.content = feature.get ('name');
$ (element).popover ('show');
} else {
$ (element).popover ('hide');
}
});
map.on ('pointermove', function(e) {
if (e.dragging) {
$ (element).popover ('destroy');
return;
}
var pixel = map.getEventPixel (e.originalEvent);
var hit = map.hasFeatureAtPixel (pixel);
map.getTarget ().style.cursor = hit ? 'pointer' : '';
});
值。
答案 1 :(得分：1)