Fragment使用总结

• 一个Fragment不能脱离Activity而存在
• Activity是屏幕的主体，而Fragment是Activity的一个组成元素

静态加载

MainActivity

package com.example.fragmentdemo;

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


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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.textView).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //静态加载frament
                startActivity(new Intent(MainActivity.this,staticloadFragmentActivity.class));
            }
        });

    }
}
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activitymain.xml

<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
        android:id="@+id/textView"
        android:gravity="center"
        android:text="static load fragment"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        />

LinearLayout>
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ListFrament

package com.example.fragmentdemo;

import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

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

//列表fragment
public class ListFrament extends Fragment {
    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
    }

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

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

    //创建视图，主要方法
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_list, container, false);
        return view;
    }
}
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fragment_list.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="#E46CC6"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView2"
        android:textSize="22sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textColor="#ffffff"
        android:text="TextView" />
RelativeLayout>
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staticloadFragmentActivity

package com.example.fragmentdemo;

import android.os.Bundle;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

public class staticloadFragmentActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_static_load_fragment);
    }
}
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activity_static_load_fragment.xml

<RelativeLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <fragment
        android:layout_centerInParent="true"
        android:id="@+id/listFrament"
        android:name="com.example.fragmentdemo.ListFrament"
        android:layout_width="300dp"
        android:layout_height="200dp"/>

RelativeLayout>
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主线程点击textview触发

startActivity(new Intent(MainActivity.this,staticloadFragmentActivity.class));
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跳到staticloadFragmentActivity中，然后

setContentView(R.layout.activity_static_load_fragment);
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加载视图activity_static_load_fragment

<fragment
    android:layout_centerInParent="true"
    android:id="@+id/listFrament"
    android:name="com.example.fragmentdemo.ListFrament"
    android:layout_width="300dp"
    android:layout_height="200dp"/>
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该视图中fragment又绑定了 android:name=“com.example.fragmentdemo.ListFrament”

也就是ListFrament类

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

    View view = inflater.inflate(R.layout.fragment_list, container, false);
    return view;
}
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中又加载了视图layout.fragment_list

感觉上边过于繁琐于是修改代码

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_static_load_fragment);

    }
}
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直接指向fragment，fragment加载两个不同的视图

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

    <fragment
        android:layout_centerInParent="true"
        android:id="@+id/listFrament"
        android:name="com.example.fragmentdemo.ListFrament"
        android:layout_width="300dp"
        android:layout_height="200dp"/>
    <fragment
        android:id="@+id/listFrament2"
        android:name="com.example.fragmentdemo.ListFrament2"
        android:layout_width="300dp"
        android:layout_height="200dp"/>

</RelativeLayout>
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只需要定义视图加载的类，就可以自定义Fragment了

特点：

模块化 可重用 可适配屏幕尺寸 必须再activity中

动态加载

activity_main.xml

<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
        android:id="@+id/textView"
        android:gravity="center"
        android:text="static load fragment"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        />
        <LinearLayout
            android:orientation="horizontal"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
            <LinearLayout
                android:layout_margin="5dp"
                android:orientation="horizontal"
                android:id="@+id/listContainer"
                android:layout_width="150dp"
                android:layout_height="match_parent">
                
            LinearLayout>     
            <LinearLayout
                android:layout_margin="5dp"
                android:orientation="horizontal"
                android:id="@+id/detailContainer"
                android:layout_width="200dp"
                android:layout_height="match_parent">
            LinearLayout>
        LinearLayout>
LinearLayout>
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MainActivity

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ListFrament frament = new ListFrament();
        ListFrament2 frament1 = new ListFrament2();
        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.listContainer,frament)
                .commit();
        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.detailContainer,frament1)
                .commit();
    }
}
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一个fragment只能被动态加载一次

好处：

灵活 可以加判断语句等操作

传值

Activity向Fragment传值

1.setArguments

在ListFragment中添加静态方法

public static final String Boundler_TITLE = "title";
private String title = "Love";

public static ListFrament newInstance(String title){
    ListFrament frament = new ListFrament();
    Bundle bundle=new Bundle();
    bundle.putString(Boundler_TITLE,title);
    frament.setArguments(bundle);

    return frament;
}
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在oncreate中获取传入的值

public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if(getArguments()!=null){
        title = getArguments().getString(Boundler_TITLE);
    }
}
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在创建视图时使用这个值

//创建视图，主要方法
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fragment_list, container, false);
    TextView textview = view.findViewById(R.id.textView2);
    textview.setText(title);
    return view;
}
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MainActivity调用

getSupportFragmentManager()
        .beginTransaction()
        .add(R.id.listContainer,new ListFrament().newInstance("ABCD"))
        .commit();
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Fragment向Activity传值

使用回调

在ListFragment中创建接口

//2.定义全局变量
OnTitleClickListener onTitleClickListener;

//3.设置接口的方法
public void setOnTitleClickListener(OnTitleClickListener onTitleClickListener) {
    this.onTitleClickListener = onTitleClickListener;
}

//1.定义接口
public interface OnTitleClickListener{
    void onClick(String title);
}
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设置Fragment被点击的时候，使用回调函数

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

    View view = inflater.inflate(R.layout.fragment_list, container, false);
    TextView textview = view.findViewById(R.id.textView2);
    textview.setText(title);
    textview.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(onTitleClickListener!=null){
                onTitleClickListener.onClick(title);
            }
        }
    });
    return view;
}
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在MainActivity中实现这个接口

public class MainActivity extends AppCompatActivity implements ListFrament.OnTitleClickListener {

    public  ListFrament listFrament = new ListFrament().newInstance("ABCD");

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListFrament2 frament1 = new ListFrament2();
        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.listContainer, listFrament)
                .commit();
        listFrament.setOnTitleClickListener(this);
        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.detailContainer,frament1)
                .commit();
    }

    @Override
    public void onClick(String title) {
        setTitle(title);
    }
}
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点击fragment就会实现回调了

扩展 传对象

private User user;
public class User{

}
public void setUser(User user) {
    this.user = user;
}

public static ListFrament newInstance(String title,User user){
    ListFrament frament = new ListFrament();
    Bundle bundle=new Bundle();
    bundle.putString(Boundler_TITLE,title);
    frament.setArguments(bundle);
    frament.setUser(user);
    return frament;
}
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直接添加这个对象的set方法再调用即可

Fragment和Fragment之间传值，之间调用回调即可