Question

我正在制作一个健身应用程序，允许用户制作健身活动列表。制作新活动时的其中一个选项是使用Google地图选择位置。这将打开一个新片段，并使当前片段上的所有值都重置。为了防止这种情况发生，我保存了使用onSaveInstanceState（）设置的所有值：

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    if (mEventStr != null)
        outState.putString("event", mEventStr);
    if (mSelectStartDateTxtVw != null)
        outState.putString("startDate", mSelectStartDateTxtVw.getText().toString());
    if (mSelectStartTimeTxtVw != null)
        outState.putString("startTime", mSelectStartTimeTxtVw.getText().toString());
    if (mSelectEndDateTxtVw != null)
        outState.putString("endDate", mSelectEndDateTxtVw.getText().toString());
    if (mSelectEndTimeTxtVw != null)
        outState.putString("endTime", mSelectEndTimeTxtVw.getText().toString());
    if (mEventType != null)
        outState.putString("eventType", mEventType);
    if (mEventDescriptionEdTxt != null)
        outState.putString("eventDescription", mEventDescriptionEdTxt.getText().toString());
}

然后，当用户从Google Map返回时，我会在onCreateView（）中恢复这些值：

if (savedInstanceState != null) {
    mEventStr = savedInstanceState.getString("event");
    mSelectStartDateTxtVw.setText(savedInstanceState.getString("startDate"));
    mSelectStartTimeTxtVw.setText(savedInstanceState.getString("startTime"));
    mSelectEndDateTxtVw.setText(savedInstanceState.getString("endDate"));
    mSelectEndTimeTxtVw.setText(savedInstanceState.getString("endTime"));
    mEventType = savedInstanceState.getString("eventType");
    mEventDescriptionEdTxt.setText(savedInstanceState.getString("eventDescription"));
}

然而，这似乎不起作用。有没有人知道为什么会这样？

Answer 1

在方法结束时调用import MapKit let kEarthRadius = 6378137.0 // CLLocationCoordinate2D uses degrees but we need radians func radians(degrees: Double) -> Double { return degrees * M_PI / 180; } func regionArea(locations: [CLLocationCoordinate2D]) -> Double { guard locations.count > 2 else { return 0 } var area = 0.0 for i in 0..<locations.count { let p1 = locations[i > 0 ? i - 1 : locations.count - 1] let p2 = locations[i] area += radians(degrees: p2.longitude - p1.longitude) * (2 + sin(radians(degrees: p1.latitude)) + sin(radians(degrees: p2.latitude)) ) } area = -(area * kEarthRadius * kEarthRadius / 2); return max(area, -area) // In order not to worry about is polygon clockwise or counterclockwise defined. }

Answer 2

我通过将所选值传递给Google Map片段，然后将这些值传递回原始片段来修复此问题：

// CreateEventFragment.java
Bundle bundle = new Bundle();
if (mEventStr != null)
    outState.putString("event", mEventStr);
if (mSelectStartDateTxtVw != null)
    outState.putString("startDate", mSelectStartDateTxtVw.getText().toString());
if (mSelectStartTimeTxtVw != null)
    outState.putString("startTime", mSelectStartTimeTxtVw.getText().toString());
if (mSelectEndDateTxtVw != null)
    outState.putString("endDate", mSelectEndDateTxtVw.getText().toString());
if (mSelectEndTimeTxtVw != null)
    outState.putString("endTime", mSelectEndTimeTxtVw.getText().toString());
if (mEventType != null)
    outState.putString("eventType", mEventType);
if (mEventDescriptionEdTxt != null)
    outState.putString("eventDescription", mEventDescriptionEdTxt.getText().toString());

// GoogleMapFragment.java
Bundle inBundle = getArguments();
Bundle outBundle = new Bundle();
outBundle.putString("event", inBundle.getString("event"));
outBundle.putString("startDate", inBundle.getString("startDate"));
outBundle.putString("startTime", inBundle.getString("startTime"));
outBundle.putString("endDate", inBundle.getString("endDate"));
outBundle.putString("endTime", inBundle.getString("endTime"));
outBundle.putString("eventType", inBundle.getString("eventType"));
outBundle.putString("eventDescription", inBundle.getString("eventDescription"));

我知道这不是最优雅的解决方案，但它确实有效。

为什么我的savedInstanceState Bundle不保留值？

2 个答案: