BaseActivity，LazyBaseFragment懶加載問題分析

時間  2020-10-22
標籤 java react android 緩存 ide 工具 this google scala code 欄目 Java 简体版
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compile

implementation 'com.android.support:support-v4:26.1.0'
    //    compile 'com.tbruyelle.rxpermissions2:rxpermissions:0.9.5@aar'
    compile 'com.tbruyelle.rxpermissions:rxpermissions:0.9.4@aar'
    compile 'io.reactivex.rxjava2:rxjava:2.1.8'
    compile 'com.squareup.retrofit2:converter-gson:2.3.0'
    compile 'com.squareup.retrofit2:adapter-rxjava2:2.3.0'
    //okhttp log 工具
    compile 'com.squareup.okhttp3:logging-interceptor:3.1.2'
    compile 'com.google.code.gson:gson:2.8.2'
    compile 'io.reactivex:rxandroid:1.1.0'
    compile 'com.squareup.retrofit2:retrofit:2.3.0'
    compile 'com.squareup.retrofit2:converter-scalars:2.3.0'
    compile 'com.google.dagger:dagger:2.12'
    annotationProcessor 'com.google.dagger:dagger-compiler:2.9'
    //適配的終極解決方案
    compile 'com.zhy:autolayout:1.4.5'
    // If you want to bind to Android-specific lifecycles
    compile 'com.trello.rxlifecycle2:rxlifecycle-android:2.2.1'
    // If you want pre-written Activities and Fragments you can subclass as providers
    compile 'com.trello.rxlifecycle2:rxlifecycle-components:2.2.1'
    implementation 'com.android.support:cardview-v7:26.1.0'

    implementation 'com.jakewharton:butterknife:8.8.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

    compile 'org.greenrobot:eventbus:3.1.1'

BaseActivity

public abstract class BaseActivity extends RxAppCompatActivity {
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(getLayoutId());
        init(savedInstanceState);
    }

    protected abstract void init(Bundle savedInstanceState);

    protected abstract @LayoutRes int getLayoutId();
}

LazyBaseFragment

/**
 * Created by PVer on 2018/3/24.
 */

public abstract class LazyBaseFragment extends RxFragment{

    protected boolean isFirstUserVisible = true;
    protected boolean isPrepared = false;
    private View targetView;
    private boolean isFirstUserInVisible = true;
    protected String TAG = "LazyBaseFragment";


    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        if (getLayoutId() != 0) {
            return inflater.inflate(getLayoutId(), container,false);
        } else {
            return super.onCreateView(inflater, container, savedInstanceState);
        }
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        initViewAndEvent(view,savedInstanceState);
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        initPrepare();
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);

        Log.v(TAG,"setUserVisibleHint:" + String.valueOf(isVisibleToUser));

        if(isVisibleToUser)
        {
            //可見
            if(isFirstUserVisible)
            {
                //第一次用戶可見
                isFirstUserVisible = false;
                initPrepare();
            }
            else
            {
                onUserVisible();
            }
        }
        else
        {
            //不可見
            if(isFirstUserInVisible)
            {
                isFirstUserInVisible = false;
                onFirstUserInvisible();
            }
            else
            {
                onUserInvisible();
            }
        }
    }


    private synchronized void initPrepare() {
        if (isPrepared) {
            onFirstUserVisible();
        } else {
            isPrepared = true;
        }
    }

    public View getTargetView() {
        return targetView;
    }

    public void setTargetView(View targetView) {
        this.targetView = targetView;
    }

    protected abstract @LayoutRes int getLayoutId();

    protected abstract void onFirstUserVisible();  //第一次用戶可見

    protected abstract void onUserVisible();

    private void onFirstUserInvisible(){}

    protected abstract void onUserInvisible();

    protected abstract void initViewAndEvent(View view,Bundle savedInstanceState);
}

對於LazyBaseFragment的說明

假設有四個界面，第一個界面爲Home,第二個爲Exchange,第三個爲Treat，第四個爲Mine。 他們的生命週期調用：java

1. Adapter 繼承的是FragmentStatePagerAdapter :

03-24 23:51:54.981 18649-18649/com.fai.tools V/HomeFragment: setUserVisibleHint:false
03-24 23:51:54.981 18649-18649/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
03-24 23:51:54.981 18649-18649/com.fai.tools V/HomeFragment: setUserVisibleHint:true
03-24 23:51:54.987 18649-18649/com.fai.tools V/HomeFragment: onCreateView
03-24 23:51:55.001 18649-18649/com.fai.tools V/HomeFragment: onActivityCreated
03-24 23:51:55.001 18649-18649/com.fai.tools V/ExchangeFragment: onCreateView
03-24 23:51:55.018 18649-18649/com.fai.tools V/ExchangeFragment: onActivityCreated

繼續滑動一下ViewPager到ExchangeFragment:react

03-24 23:57:37.090 18649-18649/com.fai.tools V/TreatFragment: setUserVisibleHint:false
03-24 23:57:37.091 18649-18649/com.fai.tools V/HomeFragment: setUserVisibleHint:false
03-24 23:57:37.091 18649-18649/com.fai.tools V/ExchangeFragment: setUserVisibleHint:true
03-24 23:57:37.095 18649-18649/com.fai.tools V/TreatFragment: onCreateView
03-24 23:57:37.132 18649-18649/com.fai.tools V/TreatFragment: onActivityCreated

繼續滑動一下ViewPager到TreatFragment:android

03-25 11:20:59.987 22856-22856/com.fai.tools V/MineFragment: setUserVisibleHint:false
03-25 11:20:59.987 22856-22856/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
03-25 11:20:59.987 22856-22856/com.fai.tools V/TreatFragment: setUserVisibleHint:true
03-25 11:20:59.989 22856-22856/com.fai.tools V/HomeFragment: onPause
03-25 11:20:59.989 22856-22856/com.fai.tools V/HomeFragment: onStop
03-25 11:20:59.991 22856-22856/com.fai.tools V/HomeFragment: onDestroy
03-25 11:20:59.992 22856-22856/com.fai.tools V/MineFragment: onCreateView
03-25 11:21:00.010 22856-22856/com.fai.tools V/MineFragment: onActivityCreated

繼續滑動一下ViewPager到MineFragment:緩存

03-25 11:22:25.521 22856-22856/com.fai.tools V/TreatFragment: setUserVisibleHint:false
03-25 11:22:25.521 22856-22856/com.fai.tools V/MineFragment: setUserVisibleHint:true
03-25 11:22:25.524 22856-22856/com.fai.tools V/ExchangeFragment: onPause
03-25 11:22:25.524 22856-22856/com.fai.tools V/ExchangeFragment: onStop
03-25 11:22:25.526 22856-22856/com.fai.tools V/ExchangeFragment: onDestroy

2.若增長代碼：ide

viewPager.setOffscreenPageLimit(pagerLimit);  

//這句話的代碼的做用就是在一開始ViewPager就緩存pagerLimit + 1個頁面， 無論是FragmentPagerStateAdapter仍是FragmentPagerAdapter都是同樣的緩存模式，一開始就緩存，pagerLimit + 1個頁面，log同樣 。
// 雖然FragmentPagerAdapter已經會緩存全部加載過的頁面，他的緩存和viewPager.setOffscreenPageLimit(pagerLimit);區別在於 
// 1. FragmentPagerAdapter不是一開始就緩存pagerLimit + 1  ,是加載一個緩存一個，都緩存下來
// 2.FragmentPagerAdapter會將加載過的暫時用不到的fragment進行onPause onStop操做，好比在第三個頁面的時候，會將第一個頁面進行onPause , onStop操做
04-22 17:07:47.110 5114-5114/com.fai.tools V/HomeFragment: setUserVisibleHint:false
04-22 17:07:47.110 5114-5114/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
04-22 17:07:47.110 5114-5114/com.fai.tools V/TreatFragment: setUserVisibleHint:false
04-22 17:07:47.110 5114-5114/com.fai.tools V/MineFragment: setUserVisibleHint:false
04-22 17:07:47.110 5114-5114/com.fai.tools V/HomeFragment: setUserVisibleHint:true

04-22 17:07:47.114 5114-5114/com.fai.tools V/HomeFragment: onCreateView
04-22 17:07:47.138 5114-5114/com.fai.tools V/HomeFragment: onActivityCreated
04-22 17:07:47.138 5114-5114/com.fai.tools V/ExchangeFragment: onCreateView
04-22 17:07:47.142 5114-5114/com.fai.tools V/ExchangeFragment: onActivityCreated
04-22 17:07:47.142 5114-5114/com.fai.tools V/TreatFragment: onCreateView
04-22 17:07:47.146 5114-5114/com.fai.tools V/TreatFragment: onActivityCreated
04-22 17:07:47.146 5114-5114/com.fai.tools V/MineFragment: onCreateView
04-22 17:07:47.149 5114-5114/com.fai.tools V/MineFragment: onActivityCreated

繼續滑動到下一個頁面 ExchangeFragment工具

04-22 17:12:59.569 5114-5114/com.fai.tools V/HomeFragment: setUserVisibleHint:false
04-22 17:12:59.569 5114-5114/com.fai.tools V/ExchangeFragment: setUserVisibleHint:true

繼續滑動到下一個頁面 TreatFragmentthis

04-22 17:14:27.757 5114-5114/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
04-22 17:14:27.757 5114-5114/com.fai.tools V/TreatFragment: setUserVisibleHint:true

繼續滑動到下一個頁面MineFragmentgoogle

04-22 17:15:23.909 5114-5114/com.fai.tools V/TreatFragment: setUserVisibleHint:false
04-22 17:15:23.909 5114-5114/com.fai.tools V/MineFragment: setUserVisibleHint:true

3.Adapter 繼承的是FragmentPagerAdapter :

03-25 11:07:57.600 18382-18382/com.fai.tools V/HomeFragment: setUserVisibleHint:false
03-25 11:07:57.600 18382-18382/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
03-25 11:07:57.600 18382-18382/com.fai.tools V/HomeFragment: setUserVisibleHint:true
03-25 11:07:57.604 18382-18382/com.fai.tools V/HomeFragment: onCreateView
03-25 11:07:57.609 18382-18382/com.fai.tools V/HomeFragment: onActivityCreated
03-25 11:07:57.610 18382-18382/com.fai.tools V/ExchangeFragment: onCreateView
03-25 11:07:57.614 18382-18382/com.fai.tools V/ExchangeFragment: onActivityCreated

繼續滑動到下一個頁面ExchangeFragment：scala

03-25 11:08:32.784 18382-18382/com.fai.tools V/TreatFragment: setUserVisibleHint:false
03-25 11:08:32.784 18382-18382/com.fai.tools V/HomeFragment: setUserVisibleHint:false
03-25 11:08:32.784 18382-18382/com.fai.tools V/ExchangeFragment: setUserVisibleHint:true
03-25 11:08:32.787 18382-18382/com.fai.tools V/TreatFragment: onCreateView
03-25 11:08:32.805 18382-18382/com.fai.tools V/TreatFragment: onActivityCreated

繼續滑動一下ViewPager到TreatFragment:code

03-25 11:08:52.785 18382-18382/com.fai.tools V/MineFragment: setUserVisibleHint:false
03-25 11:08:52.785 18382-18382/com.fai.tools V/ExchangeFragment: setUserVisibleHint:false
03-25 11:08:52.785 18382-18382/com.fai.tools V/TreatFragment: setUserVisibleHint:true
03-25 11:08:52.788 18382-18382/com.fai.tools V/HomeFragment: onPause
03-25 11:08:52.788 18382-18382/com.fai.tools V/HomeFragment: onStop
03-25 11:08:52.791 18382-18382/com.fai.tools V/MineFragment: onCreateView
03-25 11:08:52.806 18382-18382/com.fai.tools V/MineFragment: onActivityCreated

繼續滑動一下ViewPager到MineFragment:

03-25 11:09:13.006 18382-18382/com.fai.tools V/TreatFragment: setUserVisibleHint:false
03-25 11:09:13.006 18382-18382/com.fai.tools V/MineFragment: setUserVisibleHint:true
03-25 11:09:13.008 18382-18382/com.fai.tools V/ExchangeFragment: onPause
03-25 11:09:13.008 18382-18382/com.fai.tools V/ExchangeFragment: onStop

FragmentStatePagerAdapter和FragmentPagerAdapter的區別：

FragmentStatePagerAdapter不會保存全部Pager的狀態，最多保存上一個，本身，下一個。其餘的都會執行onDestroy方法

FragmentPagerAdapter不會執行onDestroy方法，會保存全部的狀態。

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