activity与fragment的通信

2023-11-06 14:48:46

它们两个是独立的类,都是用于展示ui的,那么必须会用到通信的

原生方案:Bundle

相当于是类之间的通信工具,用于保存数据的android的一个类

java语言中类与类自己通信常用方案:接口

其他方案: eventBus,LiveData

步骤:

创建一个待处理的fragment
获取fragmentManager,一般都是通过setSupportFragmentManager()
开启一个事物transcation,一般调用fragmentManager的beginTransaction()
使用transaction进行fragment替换
提交事务

上面的步骤是以往说过的

Bundle接口案例:

文件目录结构:

代码(注意,主要是看MainActivity.java中定义了通信,BlankFragment1.java中引用了通信):
BlankFragment1.java:

package com.example.myfragment3;

import android.os.Bundle;

import androidx.fragment.app.Fragment;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link BlankFragment1#newInstance} factory method to
 * create an instance of this fragment.
 */
public class BlankFragment1 extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";
    private static final String TAG = "BlankFragment1";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public BlankFragment1() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment BlankFragment1.
     */
    // TODO: Rename and change types and number of parameters
    public static BlankFragment1 newInstance(String param1, String param2) {
        BlankFragment1 fragment = new BlankFragment1();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getArguments();
        String string = bundle.getString("message");
        Log.e(TAG, "onCreate: " + string);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_blank1, container, false);
    }
}

ItemFragment.java:

package com.example.myfragment3;

import android.content.Context;
import android.os.Bundle;

import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.myfragment3.placeholder.PlaceholderContent;

/**
 * A fragment representing a list of Items.
 */
public class ItemFragment extends Fragment {

    // TODO: Customize parameter argument names
    private static final String ARG_COLUMN_COUNT = "column-count";
    // TODO: Customize parameters
    private int mColumnCount = 1;

    /**
     * Mandatory empty constructor for the fragment manager to instantiate the
     * fragment (e.g. upon screen orientation changes).
     */
    public ItemFragment() {
    }

    // TODO: Customize parameter initialization
    @SuppressWarnings("unused")
    public static ItemFragment newInstance(int columnCount) {
        ItemFragment fragment = new ItemFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_COLUMN_COUNT, columnCount);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (getArguments() != null) {
            mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_item_list, container, false);

        // Set the adapter
        if (view instanceof RecyclerView) {
            Context context = view.getContext();
            RecyclerView recyclerView = (RecyclerView) view;
            if (mColumnCount <= 1) {
                recyclerView.setLayoutManager(new LinearLayoutManager(context));
            } else {
                recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));
            }
            recyclerView.setAdapter(new MyItemRecyclerViewAdapter(PlaceholderContent.ITEMS));
        }
        return view;
    }
}

MainActivity.java:

package com.example.myfragment3;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;

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


public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.btn);
//        默认传入它集成的匿名内部类
        button.setOnClickListener(this);

        Button button2 = findViewById(R.id.btn2);
        button2.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.btn:
                Bundle bundle = new Bundle();
                bundle.putString("message", "我喜欢小学课堂");
                BlankFragment1 bf = new BlankFragment1();
                bf.setArguments(bundle);
                replaceFragment(bf);
                break;
            case R.id.btn2:
                replaceFragment(new ItemFragment());
                break;
        }
    }

    //    动态切换fragment
    private void replaceFragment(Fragment fragment) {
//        获取默认的fragment管理类
        FragmentManager fragmentManager = getSupportFragmentManager();
//        获取管理类中的触发器
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        transaction.replace(R.id.framelayout, fragment);
//        上面只是创建一个事物的动作,并没有提交,下面还需要提交才能执行
        transaction.commit();

    }
}

MyItemRecyclerViewAdapter.java:

package com.example.myfragment3;

import androidx.recyclerview.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.example.myfragment3.placeholder.PlaceholderContent.PlaceholderItem;
import com.example.myfragment3.databinding.FragmentItemBinding;

import java.util.List;

/**
 * {@link RecyclerView.Adapter} that can display a {@link PlaceholderItem}.
 * TODO: Replace the implementation with code for your data type.
 */
public class MyItemRecyclerViewAdapter extends RecyclerView.Adapter<MyItemRecyclerViewAdapter.ViewHolder> {

    private final List<PlaceholderItem> mValues;

    public MyItemRecyclerViewAdapter(List<PlaceholderItem> items) {
        mValues = items;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        return new ViewHolder(FragmentItemBinding.inflate(LayoutInflater.from(parent.getContext()), parent, false));

    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, int position) {
        holder.mItem = mValues.get(position);
        holder.mIdView.setText(mValues.get(position).id);
        holder.mContentView.setText(mValues.get(position).content);
    }

    @Override
    public int getItemCount() {
        return mValues.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public final TextView mIdView;
        public final TextView mContentView;
        public PlaceholderItem mItem;

        public ViewHolder(FragmentItemBinding binding) {
            super(binding.getRoot());
            mIdView = binding.itemNumber;
            mContentView = binding.content;
        }

        @Override
        public String toString() {
            return super.toString() + " '" + mContentView.getText() + "'";
        }
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="change"></Button>


    <Button
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="replace"></Button>

    <FrameLayout
        android:id="@+id/framelayout"
        android:layout_width="match_parent"
        android:background="@color/teal_200"
        android:layout_height="match_parent"></FrameLayout>

</LinearLayout>

fragment_blank1.xml:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BlankFragment1">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />
</FrameLayout>

fragment_item.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <TextView
        android:id="@+id/item_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/text_margin"
        android:textAppearance="?attr/textAppearanceListItem" />

    <TextView
        android:id="@+id/content"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/text_margin"
        android:textAppearance="?attr/textAppearanceListItem" />
</LinearLayout>

fragment_item_list.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/list"
    android:name="com.example.myfragment3.ItemFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginLeft="16dp"
    android:layout_marginRight="16dp"
    app:layoutManager="LinearLayoutManager"
    tools:context=".ItemFragment"
    tools:listitem="@layout/fragment_item" />

run:

点击第一个按钮:

我这里测试只是在控制台输出一下,并没有用到view中

码农公寓

Bundle接口案例:

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