在方向变化时处理匕首组件

Question

假设这里已经说过,开发人员有责任保留组件实例以实现自己的范围逻辑(因为范围方法将为给定组件返回相同的实例).

通过活动生命周期保持此组件引用的干净方法是什么？

示例:您正在实施MVP模式,因此您需要在Activity中使用Presenter.此演示者可以执行网络操作来下载项目.当设备旋转时,您的Activity将被销毁并重新创建,但您希望保持网络运行并返回预旋转演示者.

在为Presenter提供自定义PerActivity范围的组件范围是解决方案,因此您必须通过此循环保持Component实例,以便在首次启动Activity时注入相同的Presenter实例.

我们怎么处理这个？我想到了一种组件缓存(如HashMap？),它可以由Application类中的Application Component提供.

Answer 1

您可以看到ribot/android-boilerplate展示应用程序的实现。static Map<Long, ConfigPersistentComponent>他们选择的解决方案是在 内部建立一个BaseActivity，所有活动都从该内部扩展。

public class BaseActivity extends AppCompatActivity {

    private static final AtomicLong NEXT_ID = new AtomicLong(0);
    private static final Map<Long, ConfigPersistentComponent> sComponentsMap = new HashMap<>();

    private ActivityComponent mActivityComponent;
    private long mActivityId;

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

        // Create the ActivityComponent and reuses cached ConfigPersistentComponent if this is
        // being called after a configuration change.
        mActivityId = savedInstanceState != null ?
                savedInstanceState.getLong(KEY_ACTIVITY_ID) : NEXT_ID.getAndIncrement();

        ConfigPersistentComponent configPersistentComponent;
        if (!sComponentsMap.containsKey(mActivityId)) {
            // Creating new component
            configPersistentComponent = DaggerConfigPersistentComponent.builder()
                    .applicationComponent(BoilerplateApplication.get(this).getComponent())
                    .build();
            sComponentsMap.put(mActivityId, configPersistentComponent);
        } else {
            // Reusing component
            configPersistentComponent = sComponentsMap.get(mActivityId);
        }
        mActivityComponent = configPersistentComponent.activityComponent(new ActivityModule(this));
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putLong(KEY_ACTIVITY_ID, mActivityId);
    }

    @Override
    protected void onDestroy() {
        if (!isChangingConfigurations()) {
            // Activity is finishing, removing the component
            sComponentsMap.remove(mActivityId);
        }
        super.onDestroy();
    }

    ...

}