Dagger 2 在Android中的使用——将Dagger2相关逻辑抽离出来的小技巧

Dagger2_with_android_part3_1.kt

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cf.android666.myapplication.dagger2.dagger2xandroid

import android.app.Activity
import android.app.Application
import android.content.Context
import android.os.Bundle
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentActivity
import androidx.fragment.app.FragmentManager
import dagger.android.AndroidInjection
import dagger.android.HasFragmentInjector
import dagger.android.support.AndroidSupportInjection

/**
 * Helper class to automatically inject fragments if they implement [Injectable].
 * 在Google源码上做了一些小修改以适应本例
 */
object AppInjector {
    fun init(githubApp: MainApplication) {
      //这步直接写在MainApplication也可以
        DaggerAppComponent.create().inject(githubApp)
        githubApp
            .registerActivityLifecycleCallbacks(object : Application.ActivityLifecycleCallbacks {
                override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
                    handleActivity(activity)
                }

                override fun onActivityStarted(activity: Activity) {

                }

                override fun onActivityResumed(activity: Activity) {

                }

                override fun onActivityPaused(activity: Activity) {

                }

                override fun onActivityStopped(activity: Activity) {

                }

                override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle?) {

                }

                override fun onActivityDestroyed(activity: Activity) {

                }
            })
    }

  /**
  * 关键的方法就在这里
  */
    private fun handleActivity(activity: Activity) {
      /**
      * 针对Activity
      * 判断条件有两个
      * 1 如果Activity实现了HasFragmentInjector，说明Fragment的@Module在Activity中
      * 2 如果Activity实现了Injectable，说明Activity和Fragment的@Module在Application中
      */
        if (activity is HasFragmentInjector|| activity is Injectable) {
            AndroidInjection.inject(activity)
        }
        //  下面是针对两种Fragment的
        if (activity is FragmentActivity) {
            activity.supportFragmentManager
                .registerFragmentLifecycleCallbacks(
                    object : FragmentManager.FragmentLifecycleCallbacks() {
                        override fun onFragmentCreated(
                            fm: FragmentManager,
                            f: Fragment,
                            savedInstanceState: Bundle?
                        ) {
                            if (f is Injectable) {
                                AndroidSupportInjection.inject(f)
                            }
                        }
                    }, true
                )

            activity.fragmentManager.registerFragmentLifecycleCallbacks(
                object : android.app.FragmentManager.FragmentLifecycleCallbacks(){

                    override fun onFragmentCreated(
                        fm: android.app.FragmentManager?,
                        f: android.app.Fragment?,
                        savedInstanceState: Bundle?
                    ) {
                        if (f is Injectable) {
                            AndroidInjection.inject(f)
                        }
                    }
                },true
            )
        }
    }
}

/**
*用来标记那些需要依赖注入的类
*/
interface Injectable 

Dagger2_with_android_part3_2.kt

/**
 * author: jixiaoyong
 * email: jixiaoyong1995@gmail.com
 * website: https://jixiaoyong.github.io
 * date: 2019/1/27
 * description: MainApplication现在只需要调用AppInjector.init(this)就可以了
 * 在其他将@Module放到MainApplication的@Component中的Fragment、Activity等都只需要实现
  Injectable接口就可以了，不用再去调用AndroidInjection.inject(this)
 */
class MainApplication : HasActivityInjector, HasFragmentInjector, Application() {


    override fun onCreate() {
        super.onCreate()
        AppInjector.init(this)
//        DaggerAppComponent.create().inject(this)
    }

    @Inject
    lateinit var dispatchActivityInjector: DispatchingAndroidInjector<Activity>
    @Inject
    lateinit var dispatchingFragmentInject: DispatchingAndroidInjector<Fragment>

    override fun activityInjector() = dispatchActivityInjector

    override fun fragmentInjector() = dispatchingFragmentInject
}

Dagger2_with_android_part3_3.kt

/**
 * author: jixiaoyong
 * email: jixiaoyong1995@gmail.com
 * website: https://jixiaoyong.github.io
 * date: 2019/1/27
 * description: 本例中Fragment和Activity的@Module都是在Application中
 * 下面只需要在需要实现Injectable接口就可以了
 * 这里为了使Activity中的依赖也可以被注入，给Activity也实现了Injectable接口
 */
class MainActivity : AppCompatActivity(),Injectable {

    @Inject
    lateinit var waitForInjectClass: WaitForInjectClass

    override fun onCreate(savedInstanceState: Bundle?) {
//        AndroidInjection.inject(this)
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_dagger2_x_android_main)

        Log.d("TAG", "The Class is $waitForInjectClass")
    }
}

class MainFragment : Fragment(), Injectable {

    @Inject
    lateinit var waitForInjectClass: WaitForInjectClassForFragment


    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        Log.d("TAG", "Fragment class is $waitForInjectClass")
        return inflater?.inflate(R.layout.fragment_dagger2_android_main, container, false)
    }
}