如何使用OnsavedInstance保存Spinner及其适配器并在之后恢复?

问题描述 投票:0回答:2

我在app中为我的两个微调器处理onSavedInstanceonRestoreInstance时遇到问题。

我有两个SpinnerAdapter,可以动态填充一对ArrayAdapter<String>- adapter1 / adapter2和adapter3 / adapter4。

在onCreate方法app中为它们创建4个适配器,当用户按下button1时,它将spinnerFromspinnerTo与adapter1和adapter2一起填充,当button2分别用adapter3和adapter4填充微调器时。

据我了解生命周期 - 当屏幕旋转时,android会破坏应用程序,然后从头开始恢复它。

所以在onSavedInstancei把我的旋转器捆绑起来

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

在恢复时我从包中检索它们:

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

问题是:当应用程序恢复时,它会丢失我的适配器并且它们会获得空值。

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();
    }
    }

问题:如何正确地将AdroidSpinner及其适配器放入OnSavedInstance包中,然后将其恢复到onRestoreInstance,以防它在onCreate中填充但不在onClick方法中?提前致谢!

App 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();
}

}

编辑:答案是不完美的它不起作用我想要的,但这种方式让我有可能保存适配器:1.Create方法从适配器检索字符串数组,想要'保存:

public static String[] getStringArray(SpinnerAdapter adapter) {
        String[] a = new String[adapter.getCount()];

        for (int i = 0; i < a.length; i++)
            a[i] = adapter.getItem(i).toString();

        return a;
}

2.在onSavedInstanceState中输入下一个代码:

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

3.在restoreInstance中创建新的适配器,它将使用值填充您的微调器,并使用savedInstanceState.getStringArray(ADAPTER_TO)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)

这仍然无法正常工作,但如果您想在旋转屏幕上保存微调器状态,您可以尝试使用此逻辑。

android android-arrayadapter android-spinner onsaveinstancestate
2个回答
1
投票

您可以使用两种方法实现此目的。 1)(推荐)使用ViewModels(架构组件)2)使用保存和恢复状态。

1)。您可以创建viewModel,每当用户选择某些内容时,请使用指定的值调用ViewModel。通过观察ViewModel,您可以获得该值的最新更改(即使在轮换更改后),因为ViewModel将保持活动状态。

3)将用户的选择保存在活动内的局部变量中,然后在保存和恢复中,putget的值如下:

@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

}

0
投票

斯宾纳有onNothingSelected()方法。 在那种方法中,尝试使用spinneradapter.getLastVisiblePosition()。 当您离开应用程序时,保存最后一个位置,当您回来时,请使用最后一个位置。 希望能帮助到你。

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