Question

当我将布局更改为横向时，我需要保存所有变量和文本视图以显示所有值。任何人都可以帮助我吗？我试图在onsavedInstanceState方法中保存一些东西，但它不会保存任何东西。这是我的代码。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    accu = (TextView) findViewById(R.id.accu);
    speed1 = (TextView)findViewById(R.id.speed);
    t = (TextView)findViewById(R.id.t);
    prevLatLon = (TextView) findViewById(R.id.prevLatLon);
    listView = (ListView)findViewById(R.id.listView);
    listText = (TextView)findViewById(R.id.listText);

    locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);

    locationListener = new LocationListener() {


public void onLocationChanged(Location loc) {
                  //locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0,  0, locationListener);
            accuracy = (int) loc.getAccuracy();

            listView.setAdapter(new ArrayAdapter<String>(MainActivity.this, R.layout.activity_simplelist, R.id.listText, list));

            accu.setText("Accuracy: " + accuracy);
            speed1.setText("Speed: " + speed);
            t.setText("Time: " + time);

            DateFormat format = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
            Date date = new Date(loc.getTime());
            String formatted = format.format(date);

            if(flag == 0){
                latitude =  loc.getLatitude();
                longitude = loc.getLongitude();
                speed = (int) loc.getSpeed();
                time = formatted;

                flag = 1;
                list.add("latitude: " + latitude + " longitude: " + longitude +
                        " \nspeed: " + speed + " Time: " +time);
            }
            else {
                prevLatitude = latitude;
                prevLongitude = longitude;
                prevSpeed = speed;
                prevTime = time;

                prevLatLon.setText("Previous Latitude: " + latitude + "\nPrevious Longitude: " + longitude +
                                    " \nPrevious speed: " + speed + " \nTime: " + time);
                latitude = loc.getLatitude();
                longitude = loc.getLongitude();
                speed = (int) loc.getSpeed();
                time = formatted;

                list.add("latitude: " + latitude + " longitude: " + longitude +
                        " \nspeed: " + speed + " Time: " + time);
                speed = prevSpeed + speed;
            }
            /*currentLocation = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            currentLat = currentLocation.getLatitude();
            currentLon = currentLocation.getLongitude();*/

            //list.add("speed: " + speed + " accuracy: " + accuracy);
            Toast.makeText(MainActivity.this, "Location Changed", Toast.LENGTH_SHORT).show();
        }

我试过这个

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    super.onSaveInstanceState(savedInstanceState);
    // Save UI state changes to the savedInstanceState.
    // This bundle will be passed to onCreate if the process is
    // killed and restarted.
        accu.setText("Accuracy: " + accuracy);
        speed1.setText("Speed: " + speed);
        t.setText("Time: " + time);

        prevLatLon.setText("Previous Latitude: " + latitude + "\nPrevious Longitude: " + longitude +
                " \nPrevious speed: " + speed + " \nTime: " + time);

        savedInstanceState.putDouble("latitude", latitude);
        savedInstanceState.putDouble("longitude", longitude);
        savedInstanceState.putDouble("prevLatitude", prevLatitude);
        savedInstanceState.putDouble("prevLongitude", prevLongitude);
        savedInstanceState.putDouble("speed", speed);
        savedInstanceState.putDouble("accuracy", accuracy);
        // etc.

}

Answer 1

当您使用onSaveInstanceState保存某些内容时，您应该稍后在onRestoreInstanceState上或使用onCreate(Bundle)检索它们。

在您的活动的onCreate上执行以下代码：

onCreate(Bundle bundle)
{
    /* ... */

    if (bundle == null)
    {
        //Initialize data
        data = 0;
    } else
    {
        //Load data from the bundle (the same way you saved them)
        data = bundle.getInt("MY_DATA", 0); //0 is default value
    }
}

或者，您可以使用onRestoreInstanceState(Bundle)方法保证bundle始终为非null。我不确定在哪种情况下哪两个更好，但两者都有效。

布局更改时保存活动状态

1 个答案: