java - OnSaveInstanceState 和 OnRestoreInstanceState 不在应用程序退出时保存

Question

我正尝试使用 OnSaveInstanceState 和 OnRestoreInstanceState 保存我以编程方式创建的 CardView 和 TextView，如示例代码中所示。调试时，我注意到值已保存，但当我退出应用程序并重新打开它时，没有任何内容被恢复。我做错了什么？

**@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putString("key", userInput.getText().toString());
    savedInstanceState.putInt("LayoutId", mConstraintLayout.getId());
    super.onSaveInstanceState(savedInstanceState);
}
@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    savedInstanceState.getString("key");
    savedInstanceState.getInt("LayoutId");
}**

这是我在“OnCreate”之后使用的方法

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mContext = getApplicationContext();
    mConstraintLayout = findViewById(R.id.top_left);
    addButton = findViewById(R.id.add);
    addButton.setOnClickListener(new View.OnClickListener() {
                                     @Override
                                     public void onClick(View v) {
                                         View popup = findViewById(R.id.popup);
                                         popup.setVisibility(View.VISIBLE);

                                     }
                                 });

    mButton = (Button) findViewById(R.id.create);
    mButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final CardView sticker = new CardView(mContext);
            CardView.LayoutParams params = new CardView.LayoutParams(
                    CardView.LayoutParams.WRAP_CONTENT,
                    CardView.LayoutParams.WRAP_CONTENT
            );
            params.height=500;
            params.width=500;

            CheckBox privateCalendar = findViewById(R.id.checkPrivate);
            CheckBox workCalendar = findViewById(R.id.checkWork);
            CheckBox holidayCalendar = findViewById(R.id.checkHoliday);
            if (privateCalendar.isChecked()){
                sticker.setCardBackgroundColor(Color.parseColor("#FFCC00"));
            }
            else if (workCalendar.isChecked()){
                sticker.setCardBackgroundColor(Color.parseColor("#FF8080"));
            }
            else if (holidayCalendar.isChecked()){
                sticker.setCardBackgroundColor(Color.parseColor("#66B3FF"));
            }
            else{
                sticker.setCardBackgroundColor(Color.parseColor("#FFCC00"));
            }

            sticker.setId(CardView.generateViewId());
            sticker.getId();
            sticker.setTag(CARD_VIEW_TAG);
            sticker.setLayoutParams(params);

            sticker.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    ClipData.Item item = new ClipData.Item((CharSequence) sticker.getTag());
                    String[] mimeTypes = {ClipDescription.MIMETYPE_TEXT_PLAIN};
                    ClipData data = new ClipData(sticker.getTag().toString(), mimeTypes, item);
                    View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(sticker);
                    sticker.startDrag(data
                            , shadowBuilder
                            , sticker
                            , 0
                    );
                    sticker.setVisibility(View.INVISIBLE);
                    return true;



                }
            });

            TextView tv = new TextView(mContext);
            tv.setLayoutParams(params);
            tv.setBackgroundColor(Color.TRANSPARENT);
            tv.setGravity(Gravity.CENTER);
            userInput = findViewById(R.id.editText);
            tv.setText(userInput.getText());
            tv.setTextSize(TypedValue.COMPLEX_UNIT_DIP, 20);
            tv.setTextColor(Color.BLACK);
            sticker.addView(tv);
            mConstraintLayout.addView(sticker);
            View popup = findViewById(R.id.popup);
            popup.setVisibility(View.GONE);

        }
    });
}

Answer 1

SavedInstanceState 和 RestoreInstanceState 将在由于配置更改(如方向更改)或 android 系统由于内存问题而终止该 Activity 而重新创建 Activity 时起作用，然后只有 savedInstanceState 和 restoreInstanceState 发挥作用。

如果您自己完成 Activity 并再次开始 Activity ，则这些方法没有用处。