android - 如何在 Android 的自定义 View 上保存实例状态？

Question

我有一个扩展 LinearLayout 的自定义 View :

public class CustomEditTextLogin extends LinearLayout {
    public CustomEditTextLogin(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        initialize(context);
    }
    public CustomEditTextLogin(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        initialize(context);
    }
    private LinearLayout llParentCetL;
    private TextView txtAlertCs;
    private EditText edt;
    private ImageView img;
    public static final int TEXT = 0;
    public static final int EMAIL = 1;
    public static final int PASSWORD = 2;
    public static final int USERNAME = 3;
    private void initialize(Context context) {
        LayoutInflater mLayoutInflater = (LayoutInflater)
        context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = mLayoutInflater.inflate(R.layout.custom_edit_text_login, this, true);
        llParentCetL = (LinearLayout) view.findViewById(R.id.llParentCetL);
        txtAlertCs = (TextView) view.findViewById(R.id.txtAlertCetL);
        edt = (EditText) view.findViewById(R.id.edtCetL);
        img = (ImageView) view.findViewById(R.id.imgCetL);

        txtAlertCs.setVisibility(View.GONE);
        int imgMargin = (int) (UIHelpers.width *0.025);
        UIHelpers.setMargin(img, imgMargin, imgMargin, imgMargin, imgMargin);
        img.setOnClickListener(new OnClickListener() {   
            @Override
            public void onClick(View view) {
                setFocus();
            }
        });
        public CustomEditTextLogin setFocus(){
            if(edt != null){
                edt.setFocusableInTouchMode(true);
                edt.requestFocus();

                InputMethodManager imm = (InputMethodManager) App.context.getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.showSoftInput(edt, InputMethodManager.SHOW_IMPLICIT);
            }
            return this;
        }
    }

我想保存实例状态并恢复它，但是它和Activity的实例状态不同。

如何在 Android 中的自定义 View 上保存实例状态？

Answer 1

不确定我是否正确理解了您的意思。但是看起来您想独立于 Activity 实例保存 View 的状态并能够恢复它。您可以为此使用保留的 fragment 。

• 扩展 Fragment 类并声明对有状态的引用对象。
• 创建 fragment 时调用 setRetainInstance(boolean)。
• 将 fragment 添加到您的 Activity 中。

• 在 Activity 执行时使用 FragmentManager 检索 fragment 重新启动。

  public class RetainedFragment extends Fragment {
  
  // data object we want to retain
  private MyDataObject data;
  
  // this method is only called once for this fragment
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      // retain this fragment
      setRetainInstance(true);
  }
  
  public void setData(MyDataObject data) {
      this.data = data;
  }
  
  public MyDataObject getData() {
      return data;
  }
  

要恢复保存的对象，您可以使用 FragmentManager。

    public class MyActivity extends Activity {

    private RetainedFragment dataFragment;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // find the retained fragment on activity restarts
        FragmentManager fm = getFragmentManager();
        dataFragment = (DataFragment) fm.findFragmentByTag(“data”);

        // create the fragment and data the first time
        if (dataFragment == null) {
            // add the fragment
            dataFragment = new DataFragment();
            fm.beginTransaction().add(dataFragment, “data”).commit();
            // load the data from the web
            dataFragment.setData(loadMyData());
        }

        // the data is available in dataFragment.getData()
        ...
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // store the data in the fragment
        dataFragment.setData(collectMyLoadedData());
    }
}

在这里您可以找到更多相关信息:http://developer.android.com/guide/topics/resources/runtime-changes.html

希望这对您有所帮助。