java - 如何保存字符串？

Question

我正在编写一个简单的应用程序，它有两个 Activity 。我可以通过单击 OptionMenu 中的项目来切换到 Activity。

现在，我想保存实例。当我在 Activity 1 的 EditText 中写入内容并更改为 Activity 2，然后再次切换回 Activity 1 时，我希望在 EditText 中恢复数据(字符串)。

我该怎么做？

这是 Activity 1 的代码:

public class ActivityA extends Activity {

private String txt1;
private String txt2;
private String txt3;
private String txt4;

private EditText edText1;
private EditText edText2;
private EditText edText3;
private EditText edText4;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity_a); 
    setTitle(R.string.activity1_title);  

    txt1 = "-";
    txt2 = "-";
    txt3 = "-";
    txt4 = "-";

    if (savedInstanceState != null){
        txt1 = savedInstanceState.getString("Value1");
        txt2 = savedInstanceState.getString("Value2");
        txt3 = savedInstanceState.getString("Value3");
        txt4 = savedInstanceState.getString("Value4");
    }

    edText1 = (EditText) findViewById(R.id.editText);
    edText1.setText(""+txt1);

    edText2 = (EditText) findViewById(R.id.editText2);
    edText2.setText(""+txt2);

    edText3 = (EditText) findViewById(R.id.editText3);
    edText3.setText(""+txt3);

    edText4 = (EditText) findViewById(R.id.editText4);
    edText4.setText(""+txt4);
}

public void onSaveInstanceState(Bundle savedInstanceState) {
    super.onSaveInstanceState(savedInstanceState);
    savedInstanceState.putString("Value1",txt1);
    savedInstanceState.putString("Value2",txt2);
    savedInstanceState.putString("Value3",txt3);
    savedInstanceState.putString("Value4",txt4);

}

public void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    txt1 = savedInstanceState.getString("Value1");
    txt2 = savedInstanceState.getString("Value2");
    txt3 = savedInstanceState.getString("Value3");
    txt4 = savedInstanceState.getString("Value4");

}
}

问题是它不保存字符串，我不知道为什么。
有人有想法吗？

Answer 1

共享首选项是存储和检索简单数据的方法。当您离开第一个 Activity 时存储它，并在用户返回该 Activity 时在 onCreate 中恢复它。