在另一个活动中加载 SharedPreferences答案

【问题标题】：Loading SharedPreferences in another activity在另一个活动中加载 SharedPreferences
【发布时间】：2017-02-25 12:12:46
【问题描述】：

这就是问题所在。在我的第二堂课中，我正在尝试加载 SharedPreferences。下面我还将包括我的第一堂课。

//set label for journal questions
public TextView journalQuestionLabel;
public int counter = 0;
SharedPreferences preferences;


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

    //TODO: Send saved preferences here
    preferences = getSharedPreferences("grammarOption", MODE_PRIVATE);
    int selection = preferences.getInt("grammarOption", -1);
    Log.d("in onCreate", "preferences = " + selection);

}

当我测试它时，我的调试日志总是打印 -1。它不会加载我的共享首选项。我究竟做错了什么？

我已经尝试过这里和每个教程的其他答案，但它们不起作用。这是我设置和保存微调器首选项的代码。我已经检查过了，它正在工作。

    private void setupSpinner() {
    // Create adapter for spinner. The list options are from the String array it will use
    // the spinner will use the default layout
    final ArrayAdapter grammarSpinnerAdapter = ArrayAdapter.createFromResource(this, R.array.array_grammar_options,
            android.R.layout.simple_spinner_dropdown_item);

    // Specify dropdown layout style - simple list view with 1 item per line
    grammarSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);

    //Apply the adapter to the spinner
    grammarChoiceSpinner.setAdapter(grammarSpinnerAdapter);

    //Create shared preferences to store the spinner selection
    SharedPreferences preferences = getApplicationContext().getSharedPreferences
            ("Selection", MODE_PRIVATE);

    editor = preferences.edit();

    // Create the intent to save the position
    grammarChoiceSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

            //receive the string of the option and store it
            int grammarOptionPosition = grammarChoiceSpinner.getSelectedItemPosition();
            //put the string in the editor
            editor.putInt("grammarOption", grammarOptionPosition);
            editor.commit();
            //make a toast so the user knows if it's not "select"
            if (grammarOptionPosition != 0) {
                Toast.makeText(getApplicationContext(), "Choice saved.",
                        Toast.LENGTH_SHORT).show();
            }
        }

        // Because AdapterView is an abstract class, onNothingSelected must be defined
        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            mGrammar = 0;
        }
    });
}

这里在onCreate()中调用

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_opening);

    //find the spinner to read user input
    grammarChoiceSpinner = (Spinner) findViewById(R.id.spinner);

    setupSpinner();

【问题讨论】：

标签： android sharedpreferences spinner

【解决方案1】：

您在getSharedPreferences(String, int) 中传递了错误的字符串。

preferences = getSharedPreferences("Selection", MODE_PRIVATE);
int selection = preferences.getInt("grammarOption", -1);
Log.d("in onCreate", "preferences = " + selection);

试试这个。

希望对你有帮助。

【讨论】：

是的！如此简单的解决方案 - 已解决，谢谢！

【解决方案2】：

确保您的 SharedPreference 密钥在两个班级甚至整个应用程序中都相同。
在保存的同时做喜欢 -

SharedPreferences preferences = getSharedPreferences("MY_PREFS", MODE_PRIVATE);
preferences.edit().putInt("grammerOption", 1).apply();

虽然从首选项中获取数据确实如此 -

SharedPreferences preferences = getSharedPreferences("MY_PREFS", MODE_PRIVATE);
int option = preference.getInt("grammerOption", -1);

附言，偏好键（此处为MY_PREFS）必须相同。

【讨论】：