Android中保存Activity状态的多种实现方式

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    // 保存简单数据类型
    outState.putString("KEY_TEXT", editText.getText().toString());
    outState.putInt("KEY_SCORE", currentScore);
}

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

    if (savedInstanceState != null) {
        // 恢复数据
        String savedText = savedInstanceState.getString("KEY_TEXT");
        int savedScore = savedInstanceState.getInt("KEY_SCORE", 0);
        editText.setText(savedText);
        currentScore = savedScore;
    }
}

// 或专门使用恢复方法
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    String savedText = savedInstanceState.getString("KEY_TEXT");
    // ... 恢复操作
}

// 保存
SharedPreferences prefs = getPreferences(MODE_PRIVATE);
prefs.edit().putInt("HIGH_SCORE", 100).apply();

// 读取
int highScore = prefs.getInt("HIGH_SCORE", 0);

// ViewModel 保存非界面数据
public class MyViewModel extends ViewModel {
    public LiveData<List<User>> users;
    // ...
}

// Activity 中
viewModel = ViewModelProviders.of(this).get(MyViewModel.class);

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private int score;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        editText = findViewById(R.id.editText);
        
        // 恢复保存的状态
        if (savedInstanceState != null) {
            editText.setText(savedInstanceState.getString("SAVED_TEXT"));
            score = savedInstanceState.getInt("SCORE", 0);
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("SAVED_TEXT", editText.getText().toString());
        outState.putInt("SCORE", score);
    }

    // 可选：专门恢复方法
    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);
        // 系统会自动恢复View状态（如EditText文本）
    }
}