java不兼容类型：MainActivity无法转换为LifecycleOwner

Question

MainActivity cannot be converted to LifecycleOwner 我用它作为LiveCycle的所有者，但是它被拒绝了，我得到了一个错误，正如你在图片中看到的。 我处理Api 25，我认为这个问题可能与这个版本有关 这是关于我的sdk的信息

compileSdkVersion 25
buildToolsVersion '25.0.2'

这是我的代码：

private void retrieveTasks() {
    Log.d(TAG, "Actively retrieving the tasks from the DataBase");
    // Extract all this logic outside the Executor and remove the Executor
    // Fix compile issue by wrapping the return type with LiveData
    LiveData<List<TaskEntry>> tasks = mDb.taskDao().loadAllTasks();
    // Observe tasks and move the logic from runOnUiThread to onChanged
    tasks.observe(this, new Observer<List<TaskEntry>>() {
        @Override
        public void onChanged(@Nullable List<TaskEntry> taskEntries) {
            Log.d(TAG, "Receiving database update from LiveData");
            mAdapter.setTasks(taskEntries);
        }
    });
}

我将LiveData依赖项放在我的Gradle

compile "安卓.arch.lifecycle:extensions:1.0.0"
annotationProcessor "安卓.arch.lifecycle:compiler:1.0.0"

如果有人知道问题的原因，请告诉我

Answer 1

我也犯了同样的错误。升级到androidx支持库修复了该问题。 在Android Studio内部选择：重构->；迁移到android x

Answer 2

正如您所看到的here，LifecycleOwner是在支持库26.1.0中添加的。解决问题的最简单方法是升级支持库版本

Answer 3

默认情况下，Support Library 26.1.0及更高版本中的片段和活动已经实现了LifecycleOwner接口

但在版本25中，您需要实现LifecycleOwner接口 比如说

public class MyActivity extends Activity implements LifecycleOwner {
    private LifecycleRegistry mLifecycleRegistry;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mLifecycleRegistry = new LifecycleRegistry(this);
        mLifecycleRegistry.markState(Lifecycle.State.CREATED);
    }

    @Override
    public void onStart() {
        super.onStart();
        mLifecycleRegistry.markState(Lifecycle.State.STARTED);
    }

    @NonNull
    @Override
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }
}

资料来源：Handling lifecycles with lifecycle-aware components