不推荐使用getIntent()、getStringExtra()

// 扩展函数，提供更安全的 getStringExtra 方法
inline fun <reified T : Any> Intent.getStringExtra(key: String): T? {
    return when (T::class) {
        String::class -> this.getStringExtra(key) as? T
        // 可以添加更多类型的支持
        else -> throw IllegalArgumentException("Unsupported type")
    }
}

// 使用示例
val myString: String? = intent.getStringExtra("my_key")

public class IntentUtils {
    public static String getStringExtra(Intent intent, String key) {
        return intent.getStringExtra(key);
    }

    // 可以添加更多类型的方法
}

String myString = IntentUtils.getStringExtra(intent, "my_key");

if (getIntent() != null) {
    String myString = getIntent().getStringExtra("my_key");
    // 处理 myString
} else {
    // 处理 getIntent() 为 null 的情况
}

val myString = intent?.getStringExtra("my_key")
if (myString != null) {
    // 使用 myString
} else {
    // 处理 myString 为 null 的情况
}

class MyViewModel : ViewModel() {
    private val _data = MutableLiveData<String>()
    val data: LiveData<String> get() = _data

    fun setData(value: String) {
        _data.value = value
    }
}

class MyActivity : AppCompatActivity() {
    private lateinit var viewModel: MyViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        viewModel = ViewModelProvider(this).get(MyViewModel::class.java)

        // 观察数据变化
        viewModel.data.observe(this, Observer { data ->
            // 更新 UI
        })
    }
}

class MyFragment : Fragment() {
    private lateinit var viewModel: MyViewModel

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view = inflater.inflate(R.layout.fragment_my, container, false)

        viewModel = ViewModelProvider(requireActivity()).get(MyViewModel::class.java)

        // 设置数据
        viewModel.setData("Hello from Fragment")

        return view
    }
}

plugins {
    id 'androidx.navigation.safeargs.kotlin' // 如果使用 Kotlin
    // 或者对于 Java
    // id 'androidx.navigation.safeargs'
}

dependencies {
    def nav_version = "2.7.7" // 使用最新版本
    implementation "androidx.navigation:navigation-fragment-ktx:$nav_version"
    implementation "androidx.navigation:navigation-ui-ktx:$nav_version"
}

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/nav_graph"
    app:startDestination="@id/destinationA">

    <fragment
        android:id="@+id/destinationA"
        android:name="com.example.app.DestinationA"
        android:label="Destination A">
        <action
            android:id="@+id/action_destinationA_to_destinationB"
            app:destination="@id/destinationB" />
    </fragment>

    <fragment
        android:id="@+id/destinationB"
        android:name="com.example.app.DestinationB"
        android:label="Destination B">
        <argument
            android:name="myArg"
            app:argType="string" />
    </fragment>
</navigation>

val action = DestinationADirections.actionDestinationAToDestinationB("Hello from A")
findNavController().navigate(action)

private val args: DestinationBArgs by navArgs()

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    val myArg = args.myArg
    // 使用 myArg
}

// 在 SenderActivity 中
Intent intent = new Intent(SenderActivity.this, ReceiverActivity.class);
Bundle bundle = new Bundle();
bundle.putString("my_key", "Hello, World!");
intent.putExtras(bundle);
startActivity(intent);

// 在 ReceiverActivity 中
Bundle bundle = getIntent().getExtras();
if (bundle != null) {
    String myString = bundle.getString("my_key");
    if (myString != null) {
        // 使用 myString
    }
}

public class DataHolder {
    private static final DataHolder instance = new DataHolder();
    private String sharedData;

    private DataHolder() {}

    public static DataHolder getInstance() {
        return instance;
    }

    public void setSharedData(String data) {
        this.sharedData = data;
    }

    public String getSharedData() {
        return sharedData;
    }
}

// 在 SenderActivity 中
DataHolder.getInstance().setSharedData("Hello, World!");
Intent intent = new Intent(SenderActivity.this, ReceiverActivity.class);
startActivity(intent);

// 在 ReceiverActivity 中
String myString = DataHolder.getInstance().getSharedData();
if (myString != null) {
    // 使用 myString
}