Activity被系统销毁造成的Fragment混乱的问题

た入场券 2022-06-06 03:30 298阅读 0赞

大多数App主页底部都会有几个tab页面，用Activity+Fragment或者Activity+Vierpager+Fragment来管理Tab页面（由于viewpager的加载机制所以不会出现这个问题），当程序长期在后台由于系统资源不足就把MainActivity回收了或者从MainActivity点进去的activity报错了点击back回到MainActivity fragment也会混乱，主要是由于fragment的状态还保存着，但是add()和hide() show()方法已经失效了，分析好原因，我们就可以解决了。

在MainActivity被销毁或者在后台等情况下会调用onSaveInstanceState方法来保存状态，所以做个标记outState.putBoolean("isMainActivityDestroy",true);应为被销毁会重新调用onCreate方法，所以你if(savedInstanceState!=null&&savedInstanceState.getBoolean("isMainActivityDestroy",false))满足这个条件就去移除之前fragment状态，重新add fragment。看代码你会更了解；

protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            fragmentManager = getSupportFragmentManager();
            if(savedInstanceState!=null&&savedInstanceState.getBoolean("isMainActivityDestroy",false)){
                //当activity被系统销毁，获取到之前的fragment，并且移除之前的fragment的状态
                indexFragment = (IndexFragment) fragmentManager.findFragmentByTag("flag1");
                buyGoldFragment = (BuyGoldFragment) fragmentManager.findFragmentByTag("flag2");
                discoveryFragment = (DiscoveryFragment) fragmentManager.findFragmentByTag("flag3");
                mineFragment = (MineFragment) fragmentManager.findFragmentByTag("flag4");
                fragmentManager.beginTransaction().remove(indexFragment).commit();
                fragmentManager.beginTransaction().remove(buyGoldFragment).commit();
                fragmentManager.beginTransaction().remove(discoveryFragment).commit();
                fragmentManager.beginTransaction().remove(mineFragment).commit();
            }
    
            setContentView(R.layout.activity_main);
           
            //创建fragment，并且全部add一遍
            indexFragment = new IndexFragment();
            buyGoldFragment = new BuyGoldFragment();
            discoveryFragment = new DiscoveryFragment();
            mineFragment = new MineFragment();
            fragmentManager.beginTransaction().add(R.id.linear_fragment, indexFragment,"flag1").commit();
            fragmentManager.beginTransaction().add(R.id.linear_fragment, buyGoldFragment,"flag2").hide(buyGoldFragment).
                    add(R.id.linear_fragment, discoveryFragment,"flag3").hide(discoveryFragment).
                    add(R.id.linear_fragment, mineFragment,"flag4").hide(mineFragment).commit();
        }

@Override
        protected void onSaveInstanceState(Bundle outState) {
           super.onSaveInstanceState(outState);
           outState.putBoolean("isMainActivityDestroy",true);
        }

这样就会重新创建Fragment的状态，add（） show（） hide（） 也就重新起作用了