Android 如何使用OnsavedInstance保存微调器及其适配器，并在保存后进行恢复？

我在应用程序中处理两个微调器的onSavedInstance和onRestoreInstance时遇到问题

我有两个SpinnerAdapter，可以用一对ArrayAdapter动态填充-adapter1/adapter2和adapter3/adapter4

在onCreate method应用程序中，为它们创建4个适配器，当用户按下按钮1时，它会用适配器1和适配器2填充喷丝头From和喷丝头To，当按钮2分别用适配器3和适配器4填充喷丝头

正如我所理解的生命周期——当屏幕旋转时，android会破坏应用程序，然后从一开始就恢复它

所以在onSavedInstancei我把我的纺纱机放进一捆

savedInstanceState.putInt("from",spinnerFrom.getSelectedItemPosition);
savedInstanceState.putInt("to",spinnertTo.getSelectedItemPosition());

在恢复时，我从bundle中检索它们：

spinnerFrom.setSelection(savedInstanceState.getInt("from"));
spinnertTo.setSelection(savedInstanceState.getInt("to"));

问题是：当应用程序还原时，它会丢失我的适配器，它们会得到空值

为了检查它，我创建了技术按钮和下一个代码：

 protected void checkAdapter () {
       //get Adapter from spinners
        SpinnerAdapter valueAdapter = spinnerFrom.getAdapter();
        SpinnerAdapter resultAdapter = spinnertTo.getAdapter();

    if (valueAdapter == null | resultAdapter== null) {
                Toast.makeText(this, “adapter null” , Toast.LENGTH_SHORT).show();
    }
    else{
    Toast.makeText(this, “adapters not null” , Toast.LENGTH_SHORT).show();
    }
    }

// here i saving arraylist that ussualy i get from resources.
 savedInstanceState.putStringArray(ADAPTER_TO,getStringArray(spinnerFrom.getAdapter()));
            savedInstanceState.putStringArray(ADAPTER_FROM,getStringArray(spinnerFrom.getAdapter()));

问题：如何正确地将AdroidSpinner及其适配器放入OnSavedInstance捆绑包中，然后在RestoreInstance上恢复它，以防它不是在onCreate中而是在onClick方法中填充？ 提前谢谢

应用程序java代码：

      import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.ArrayAdapter;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.RadioGroup;
    import android.widget.Spinner;
    import android.widget.SpinnerAdapter;
    import android.widget.TextView;
    import android.widget.Toast;

    import butterknife.BindView;
    import butterknife.ButterKnife;
    import butterknife.OnClick;


    public class MainActivity extends AppCompatActivity  {
        protected double getEnteredValue;
        protected SpinnerAdapter checkAdapter;
        protected int pos;
   protected ArrayAdapter<String> adapter 1, adapter2, adapter3,
                adapter4;

//butterknife bindings
@BindView(R.id.unit_From_spinner)Spinner spinnerFrom;
@BindView(R.id.unit_To_spinner)Spinner spinnertTo;
@BindView(R.id.radio_result_group) RadioGroup resultGroup;
@BindView(R.id.radio_value_gropu) RadioGroup valueGroup;
@BindView(R.id.valueEditTextView) EditText valueEdit;
@BindView(R.id.resultView) TextView resultView;
@BindView(R.id.conver_button) Button  convertButton;

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
         savedInstanceState.putString("result",resultView.getText().toString());          savedInstanceState.putString("value",valueEdit.getText().toString());         savedInstanceState.putInt("from",spinnerFrom.getSelectedItemPosition);
savedInstanceState.putInt("to",spinnertTo.getSelectedItemPosition());
savedInstanceState.putInt("radGroup1",resultGroup.getCheckedRadioButtonId());
savedInstanceState.putInt("radGroup2", valueGroup.getCheckedRadioButtonId());
super.onSaveInstanceState(savedInstanceState);

        }


@Override
protected void onCreate(Bundle savedInstanceState)  {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.unifiedlayout);
            ButterKnife.bind(this);

//adapters for spinners 
adapter1 = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item,getResources().getStringArray( R.array.adapter_1) );
adapter2 = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item,getResources().getStringArray(R.array. adapter_2));
adapter3 = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item,getResources().getStringArray( R.array. adapter_3) );
adapter4 = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item,getResources().getStringArray(R.array. adapter_4));}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
            resultView.setText(savedInstanceState.getString("result"));
            valueEdit.setText(savedInstanceState.getString("value"));
            spinnerFrom.setSelection(savedInstanceState.getInt("from"));
            spinnertTo.setSelection(savedInstanceState.getInt("to"));


            super.onSaveInstanceState(savedInstanceState);
        }

//OnClick
@OnClick({R.id.button1, R.id.button2,R.id.button3,R.id.button4} )
public void setViewOnClickEvent(View view){
    switch(view.getId()){
        case R.id. button1:
        fillSpinner(adapter1, adapter2); // fill spinner with values
                break;
            case R.id. button2:
                fillSpinner(adapter3,
                        adapter4);
                break;
        //button for check if any adapter active
         case R.id.buttonAdapter:
        checkAdapter () ;   
               break;   
       }
    }

//fill spinners when user checks radiobutton in radiogroups
protected void fillSpinner (final ArrayAdapter<String> spinnerToAdapter,
                                final ArrayAdapter<String> spinnerFromAdapter){

        valueGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup valueGroup, int checkedId) {
                pos = valueGroup.indexOfChild(findViewById(checkedId));
                switch (pos) {
                    case 0:
                        spinnerFrom.setAdapter(spinnerToAdapter);
                        break;
                    case 1:
                        spinnerFrom.setAdapter(spinnerFromAdapter);
                        break;
                }
            }
        });
        resultGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup resultGroup, int checkedId) {
                pos = resultGroup.indexOfChild(findViewById(checkedId));
                switch (pos) {
                    case 0:
                        spinnertTo.setAdapter(spinnerToAdapter);
                        break;
                    case 1:
                        spinnertTo.setAdapter(spinnerFromAdapter);
                        break;
                }
            }
        });
    }

//simple method for check if both spinners has null value
protected void checkAdapter () {
   //get Adapter from spinners
    SpinnerAdapter valueAdapter = spinnerFrom.getAdapter();
    SpinnerAdapter resultAdapter = spinnertTo.getAdapter();

if (valueAdapter == null | resultAdapter== null) {
            Toast.makeText(this, “adapter null” , Toast.LENGTH_SHORT).show();
}
else{
Toast.makeText(this, “adapters not null” , Toast.LENGTH_SHORT).show();
}

}

3.在restoreInstance中，创建新适配器，用值填充微调器，并使用savedInstanceState.getStringArrayADAPTER_填充保存的值：

toAdapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item, savedInstanceState.getStringArray(ADAPTER_TO));
fromAdapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_spinner_item, savedInstanceState.getStringArray(ADAPTER_FROM));
     //use spinner.setAdapter to set created adapter.
    spinnerFrom.setAdapter (fromAdapter)
    spinnerTo.setAdapter (toAdapter)

这仍然不能像我所希望的那样正常工作，但是如果你想在旋转屏幕上保存微调器状态，你可以尝试使用这个逻辑。

Spnner有onNothingSelected方法。 在该方法中，尝试使用spinneradapter.getLastVisiblePosition。 当你关闭应用程序时，保存最后一个位置，当你回来时，使用最后一个位置。

---

希望有帮助。

您可以使用两种方法来实现这一点。1建议使用ViewModels架构组件2使用保存和还原状态

一,。您可以创建viewModel，并且每当用户选择某个对象时，都可以使用指定的值调用viewModel。通过观察ViewModel，即使在旋转更改之后，也可以获得该值的最新更改，因为ViewModel将保持活动状态

3将用户的选择保留在“活动”中的局部变量中，然后在“保存和还原”中，按如下方式放置和获取值：

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
  super.onSaveInstanceState(savedInstanceState);
  savedInstanceState.putInt("firstSpinnerPosition", variableThatHasTheChangedPosition);
  savedInstanceState.putInt("secondSpinnerPosition", variableThatHasTheChangedPositionForSecond);
  // other stuff.
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);
  variableThatHasTheChangedPosition = savedInstanceState.getInt("firstSpinnerPosition");
  variableThatHasTheChangedPositionForSecond = savedInstanceState.getInt("secondSpinnerPosition");
//notify your adapter of the changes

}

---

我不能理解最后一个，它不等于我在代码中写的吗？正如我所写的-当用户单击按钮时，适配器会被填充，当屏幕旋转后，微调器中的任何活动适配器都会变为空。因此，我必须将适配器保存在onSaveInstanceState中，并在应用程序调用onRestoreInstanceState时调用spinner.setAdapter？您确定您有自己的项目，并且在调用onRestoreInstanceState时您的适配器已准备好使用吗？如果没有，则必须将从onRestoreInstanceState获取的信息放入某个变量中，然后在初始化和填充适配器后，相应地设置它们的值。是否确实已准备好项目，并且在调用onRestoreInstanceState时适配器已准备好使用？-不，当应用程序恢复自身时-它看不到任何适配器，因为它们不会创建onCreate memthod，所以即使使用保存的getSelectedItemPosition，它也不会执行任何操作。所以我必须保存活动适配器，比如adapter adapter=spinnerfrom.getAdapter？然后将保存的适配器设置为onRestoreInstanceState？您需要以某种方式保存项目，而不是保存适配器本身-使用捆绑包或任何可以保存项目并使用项目创建适配器的东西。如果您不能这样做，您可以将所选位置保存在变量中，并在数据准备就绪时使用它。很高兴你明白了。

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
  super.onSaveInstanceState(savedInstanceState);
  savedInstanceState.putInt("firstSpinnerPosition", variableThatHasTheChangedPosition);
  savedInstanceState.putInt("secondSpinnerPosition", variableThatHasTheChangedPositionForSecond);
  // other stuff.
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);
  variableThatHasTheChangedPosition = savedInstanceState.getInt("firstSpinnerPosition");
  variableThatHasTheChangedPositionForSecond = savedInstanceState.getInt("secondSpinnerPosition");
//notify your adapter of the changes

}