• Fragment中的getActivity()為null的問(wèn)題

• 向Fragment傳遞參數(shù)

1. 向Fragment傳遞參數(shù)第一步在AFragment中

java 代碼:AFragment.class

public class AFragment extends Fragment {
    private TextView mTvTitle;

    /**
     * 調(diào)用這個(gè)方法陨舱，可以的到一個(gè)已經(jīng)傳好參數(shù)的fragment
     * @param title
     * @return
     */
    public static AFragment newInstance(String title){
        AFragment fragment=new AFragment();
        Bundle bundle=new Bundle();
        bundle.putString("title",title);
        fragment.setArguments(bundle);
        //即使fragment重構(gòu)，也會(huì)通過(guò)反射的機(jī)制苛吱，把重新實(shí)例化的fragment設(shè)上參數(shù)title
        return fragment;
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //相當(dāng)于activity的onCreate里的setcontentView,給它一個(gè)布局文件返回一個(gè)視圖文件
        View view=inflater.inflate(R.layout.fragment_a,container,false);
        return view;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        //當(dāng)View創(chuàng)建完成后虫啥，這里有一個(gè)回調(diào)方法
        super.onViewCreated(view, savedInstanceState);
        mTvTitle=(TextView)view.findViewById(R.id.tv_title);
        if(getArguments()!=null){
            //獲取參數(shù)
            mTvTitle.setText(getArguments().getString("title"));
        }

    }

    @Override
    public void onAttach(@NonNull Context context) {
        //當(dāng)Fragment與Activity發(fā)生關(guān)聯(lián)時(shí)調(diào)用
        super.onAttach(context);
    }

    @Override
    public void onDetach() {
        //與onAttach相對(duì)應(yīng)镊逝，當(dāng)Fragment與Activity關(guān)聯(lián)被取消時(shí)調(diào)用
        //當(dāng)調(diào)用這個(gè)方法后触创，會(huì)出現(xiàn)getactivity()為空
        super.onDetach();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        //取消異步
    }
}

關(guān)鍵代碼1

1. 設(shè)一個(gè)靜態(tài)的構(gòu)造方法 AFragment newInstance(String title),返回一個(gè)已經(jīng)傳好參數(shù)的fragment
2. 通過(guò)Bundle傳參數(shù)
3. 調(diào)用setArguments()

public static AFragment newInstance(String title){
        AFragment fragment=new AFragment();
        Bundle bundle=new Bundle();
        bundle.putString("title",title);
        fragment.setArguments(bundle);
        //即使fragment重構(gòu)薪丁，也會(huì)通過(guò)反射的機(jī)制，把重新實(shí)例化的fragment設(shè)上參數(shù)title
        return fragment;
    }

關(guān)鍵代碼 2

1. 在id為tv_title的textview控件中獲取參數(shù)灭衷，即等會(huì)會(huì)在這個(gè)控件里顯示傳入的字符串title

  public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        //當(dāng)View創(chuàng)建完成后次慢，這里有一個(gè)回調(diào)方法
        super.onViewCreated(view, savedInstanceState);
        mTvTitle=(TextView)view.findViewById(R.id.tv_title);
        if(getArguments()!=null){
            //獲取參數(shù)
            mTvTitle.setText(getArguments().getString("title"));
        }
    }

java 代碼:ContainerActivity.class

public class ContainerActivity extends AppCompatActivity {
    private  AFragment aFragment;
    private  BFragment bFragment;

    private Button btn_change;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_container);
        btn_change = (Button) findViewById(R.id.btn_change);
        btn_change.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(bFragment == null){
                    bFragment=new BFragment();
                }
                getSupportFragmentManager().beginTransaction().replace(R.id.fl_container,bFragment).commitAllowingStateLoss();
            }
        });
        //R.id.fl_container:裝在fragment的容器
        //aFragment：要加載的fragment
//        aFragment=new AFragment();
        //調(diào)用Fragment的一個(gè)靜態(tài)方法newInstance
        aFragment=AFragment.newInstance("我是參數(shù)");
        //把AFragment添加到Activity中,記得調(diào)用commit
        getSupportFragmentManager().beginTransaction().add(R.id.fl_container,aFragment).commitAllowingStateLoss();
    }

2. 在Fragment中傳遞參數(shù)第二步：在ContainerActivity中調(diào)用AFragment的靜態(tài)方法newInstance(),寫入?yún)?shù)

關(guān)鍵代碼

//傳參數(shù)的時(shí)候：
aFragment=AFragment.newInstance("我是參數(shù)");

//不傳參數(shù)的時(shí)候
 aFragment=new AFragment();