Fragment详解（二）

Fragment详解（一）

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1. Fragment中getActivity()为null 的问题
2. 向一个Fragment传递参数

package com.example.test0508.fragment;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.example.test0508.R;

public class ContainerActivity extends AppCompatActivity {

    private AFragment aFragment;
    private Button mBtnChange;
    private BFragment bFragment;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_container);
        mBtnChange = findViewById(R.id.btn_change);
        mBtnChange.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //点击之后替换Fragment
                if (bFragment == null){
                    //需要实例化
                    bFragment = new BFragment();
                }
                getSupportFragmentManager().beginTransaction().replace(R.id.fl_container,bFragment).commitAllowingStateLoss();
            }
        });

        //实例化AFragment，这里传递参数
        aFragment = AFragment.newInstance("我是修改后的标题");
        //把AFragment添加到Activity中
        getSupportFragmentManager().beginTransaction().add(R.id.fl_container,aFragment).commitAllowingStateLoss();


    }
}

package com.example.test0508.fragment;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.example.test0508.R;

public class AFragment extends Fragment {
    private TextView mTvTitle;
    private Activity mActivity;

    //想要可以传参，写一个静态方法
    public static AFragment newInstance(String title){
        AFragment fragment = new AFragment();
        Bundle bundle = new Bundle();
        bundle.putString("title",title);
        fragment.setArguments(bundle);
        return fragment;
    }

    /**
     * 设置布局文件
     */
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_a,container,false);
        return view;
    }

    /**
     * findViewById 就可以做其他事情
     */
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        mTvTitle = view.findViewById(R.id.tv_fragment_a);
        if (getArguments() != null){
            mTvTitle.setText(getArguments().getString("title"));
        }
    }



    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
//        mActivity = (Activity) context;

    }
    /**
     * 当Activity为null的时候，必然经历过这个方法
     */
    @Override
    public void onDetach() {
        super.onDetach();

    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        //取消异步
    }
}