java - 保持TextView文本、大小、旋转后的可见性

Question

所以我有一个非常基本的布局，在屏幕顶部有一个 EditText 和一个 Button。当有人点击按钮时，EditText 输入被保存到 TextView ，然后 EditText 和按钮一起被隐藏。这是我的代码:

public void setName(View view){
    EditText editText = (EditText) findViewById(R.id.getUserName);
    Button button = (Button) findViewById(R.id.setName);
    TextView textView = (TextView) findViewById(R.id.displayName);
    playerName = editText.getText().toString();
    textView.setText(playerName);
    editText.setVisibility(View.GONE);
    button.setVisibility(View.GONE);
    textView.setTextSize(40);
    textView.setVisibility(View.VISIBLE);
}

那么当屏幕旋转时，onCreate 会再次被调用，看起来像这样:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_score_keeper);
        // Identifies a textView
        TextView textView = (TextView) findViewById(R.id.displayName);
        // Hide that textView until later
        textView.setVisibility(View.GONE);
        // Set player name to default value
        playerName = "Player Name";
        // Set score to default value
        score = 0;

}

问题在于它失去了我隐藏 EditText 和 Button 的事实，并且还再次隐藏了 TextView。

如何使所有这些属性保持相同？ (例如，保持文本相同、文本大小、 View 的可见性等)；是否可以使用 onSaveInstanceState？

谢谢你们。

外贸工作组

Answer 1

您当然可以只在 Activity 的 savedInstanceState 上执行此操作，但我也建议(因为这可能是您在多个位置执行的操作)编写一个 View 的子类，它也将其可见性保存为状态，例如:

public class VisibiitySaveTextView extends TextView {
    //These are just keys to save and restore values from the state
    private static final String SUPER_STATE = "super_state";
    private static final String VISIBILITY = "visibility";

    //Constructors

    @Override
    public Parcelable onSaveInstanceState () {
        Bundle state = new Bundle();

        //Piggyback off of the View's implementation and store that
        //bundle of saved information in our container bundle
        state.putParcelable(SUPER_STATE, super.onSaveInstanceState());

        //Store the current visibility of the View in the saved state
        state.putInt(VISIBILITY, getVisibility());
        return state;
    }

    @Override
    public void onRestoreInstanceState (Parcelable state) {
        //state should always be an instance of Bundle since that's what
        //we're saving, but check for safety
        if (state instanceof Bundle) {
            Bundle savedState = (Bundle)state;

            //Set the visibility of the View to match the visibility that
            //we retained in onSavedInstanceState(), falling back to the 
            //current visibility as default if no state was saved
            setVisibility(savedState.getInt(VISIBILITY, getVisibility()));

            //Pull out the superclass state we saved, and let the superclass
            //handle restoring all of the other state
            Parcelable superState = savedState.getParcelable(SUPER_STATE);
            super.onRestoreInstanceState(superState);
        } else {
            //Nothing special to do here other than pass it up to the super
            super.onRestoreInstanceState(state);
        }
    }
}

编辑:让 Activity 处理状态的示例:

private static final String MY_EDIT_TEXT_VISIBILITY = "my_edit_text_visibility";
private static final String MY_TEXT_VIEW_VISIBILITY - "my_text_view_visibility";
private static final String MY_BUTTON_VISIBILITY - "my_button_visibility";

@Override
protected void onSaveInstanceState (Bundle outState) {
    super.onSaveInstanceState(outState);

    //Save the state of each of these. It's super important to add null checks here
    //(which is why I prefer to let the View handle it) as in some cases this can
    //get called after the Views have been destroyed.

    if (myEditText != null) {
        outState.putInt(MY_EDIT_TEXT_VISIBILITY, myEditText.getVisibility());
    }

    if (myTextView != null) {
        outState.putInt(MY_TEXT_VIEW_VISIBILITY, myTextView.getVisibility());
    }

    if (myButton != null) {
        outState.putInt(MY_BUTTON_VISIBILITY, myButton.getVisibility());
    }
}

@Override
protected void onRestoreInstanceState (Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);

    //Check if we have saved state, and restore the visibility 
    //to all of the Views we care about
    if (savedInstanceState != null) {
        myEditText.setVisibility(savedInstanceState.getInt(MY_EDIT_TEXT_VISIBILITY, myEditText.getVisibility()));
        myTextView.setVisibility(savedInstanceState.getInt(MY_TEXT_VIEW_VISIBILITY, myTextView.getVisibility()));
        myButton.setVisibility(savedInstanceState.getInt(MY_BUTTON_VISIBILITY, myButton.getVisibility()));
    }
}