Question

如何在android中保存对话框的状态？我有以下带有单选按钮的对话框，但无法弄清楚如何保存对话框的状态。谢谢你的帮助

final CharSequence[] items = {"Item 1", "Item 2", "Item 3"};
AlertDialog.Builder builder = new AlertDialog.Builder(Tweaks.this);
builder.setTitle("Pick an item");
builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
}).show();

Answer 1

您应该在用户点击时存储所选项目的位置。然后在显示列表时查找以前存储的索引。如果之前没有存储的值，则返回-1。

我有一个应用偏好帮助类......

public class AppPreferences {
     private static final String APP_SHARED_PREFS = "myApp_preferences"; //  Name of the file -.xml
     private SharedPreferences appSharedPrefs;
     private Editor prefsEditor;

     public AppPreferences(Context context)
     {
         this.appSharedPrefs = context.getSharedPreferences(APP_SHARED_PREFS, Activity.MODE_PRIVATE);
         this.prefsEditor = appSharedPrefs.edit();
     }

     public int getItemIndex() {
         return appSharedPrefs.getInt("itemIndex", -1);
     }

     public void saveItemIndex(int i) {
         prefsEditor.putInt("itemIndex", i);
         prefsEditor.commit();
     }
}

然后，在我的代码中，我创建了一个字段变量......

protected AppPreferences appPrefs;

在Activity onCreate（）...

中实例化它的实例

appPrefs = new AppPreferences(getApplicationContext());

然后用......替换你的“-1”

builder.setSingleChoiceItems(items, appPrefs.getItemIndex(), new DialogInterface.OnClickListener() {

在你的onClick（）中确保你......

appPrefs.saveItemIndex(item);

Answer 2

我将状态保存在DialogFragment中的成员变量中。以下代码在关闭对话框时保存状态，但在应用程序关闭时保存不。

public class MyDialogFragment extends DialogFragment {

    //this is the default value, set when the dialog is created
    private String myValue = "any initial String"; 
    private TextEdit myTextEdit;

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        //construct the dialog
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        LayoutInflater inflater = getActivity().getLayoutInflater();
        ViewGroup myView = (ViewGroup)inflater.inflate(R.layout.my_view, null);
        builder.setView(myView);

        //find the view and set the value
        myTextEdit = (TextView)myView.findViewById(R.id.my_text_edit);
        myTextEdit.setText(myValue);

        return builder.create();
    }

    @Override
    public void onDismiss(DialogInterface dialog) {
        super.onDismiss(dialog);

        //when the dialog is dismissed, save the users input and overwrite the initial value
        myValue = myTextEdit.getText();

    }
}

Answer 3

您可以使用首选项，但我建议使用新的androidx设计模式。基本上，关闭对话框状态不应在应用程序关闭时保存。那就是我们想要的（因此我们不需要首选项或类似的东西）。

您可以使用android视图模型和保存的状态来完成这项工作。

这里是显示要与gradle（https://developer.android.com/jetpack/androidx/releases/lifecycle）一起使用的依赖项和版本的链接

implementation 'androidx.lifecycle:lifecycle-viewmodel-savedstate:1.0.0-rc01'

您可以这样做。

public class HelloAndroidViewModel extends AndroidViewModel{
    private SavedStateHandle mState;

    public HelloAndroidViewModel(SavedStateHandle savedStateHandle) {
            mState = savedStateHandle;
    }

    public void saveParam(int param){
        mState.set("key", param);
    }

    public int getParam(){
        Integer param = mState.get("key");
        if(param != null){
            return param.intValue();
        }
        // default value
        else {
            return -1;
        }
    }
}

public class HelloAndroid extends Activity {

  HelloAndroidViewModel viewModel;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    viewModel = ViewModelProviders.of(this, new SavedStateViewModelFactory(getApplication(), this).get(AndroidViewModel.class);

 }

然后，您可以使用值来检索和存储对话框。

final CharSequence[] items = {"Item 1", "Item 2", "Item 3"};
AlertDialog.Builder builder = new AlertDialog.Builder(Tweaks.this);
builder.setTitle("Pick an item");
builder.setSingleChoiceItems(items, viewModel.getParam(), new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        // save ui state
        viewModel.setParam(item);
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
}).show();

对话框的Android保存状态

3 个答案: