Fragment系列：使用FrameLayout动态加载

1. 动态加载的完整代码实现

上一篇写了：使用＜fragment＞标签静态加载Fragment，继续把动态加载也写完。
下图的绿色部分就是一个Fragment：

核心代码：

        ShowNameFragment mFragment = ShowNameFragment.newInstance("zj", "hubei");
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction =manager.beginTransaction();
        fragmentTransaction.replace(R.id.framelayout,mFragment);
        fragmentTransaction.commit();
        
		//简写
        ShowNameFragment mFragment = ShowNameFragment.newInstance("zj", "hubei");
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.framelayout, mFragment)
                .commit();
   
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具体实现：

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ShowNameFragment mFragment = ShowNameFragment.newInstance("zj", "hubei");
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction =manager.beginTransaction();
        fragmentTransaction.replace(R.id.framelayout,mFragment);
        fragmentTransaction.commit();
    }
}
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activity_main.xml

注意添加id

<FrameLayout 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:id="@+id/framelayout"
    tools:context=".MainActivity">
FrameLayout>
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ShowNameFragment.java

注意：newInstance()是Android studio默认添加的

import android.os.Bundle;

import androidx.fragment.app.Fragment;

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

public class ShowNameFragment extends Fragment {

    private static final String NAME = "name";
    private static final String PROVINCE = "province";


    private String mName;
    private String mProvince;

    public ShowNameFragment() {
    }


    public static ShowNameFragment newInstance(String param1, String param2) {
        ShowNameFragment fragment = new ShowNameFragment();
        Bundle args = new Bundle();
        args.putString(NAME, param1);
        args.putString(PROVINCE, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mName = getArguments().getString(NAME);
            mProvince = getArguments().getString(PROVINCE);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_show_name, container, false);
    }

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fragment_show_name.xml

<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"
    android:background="#00ff00"
    tools:context=".ShowNameFragment">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_blank_fragment"
        android:layout_gravity="center"
        android:textColor="#ffffff"
        android:background="#ff0000"/>

FrameLayout>
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2. 一定要用FrameLayout来装Fragment吗？用LinearLayout行不行？

试下：

//activity 布局修改





//fragment布局宽高改为200dp



    



//加载id修改为linearlayout
  getSupportFragmentManager().beginTransaction()
                .replace(R.id.linearlayout, mFragment)
                .commit();

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正常运行：

3. 一个布局里面只能加载一个Fragment吗？

当然不是。尝试在LinearLayout布局里面再加一个Fragment，这次不用replace()，这次用add()

		//activity修改
        ShowNameFragment mFragment = ShowNameFragment.newInstance("zj", "hubei");
        ShowNameFragment mFragment2 = ShowNameFragment.newInstance("zj", "guangdong");
        getSupportFragmentManager().beginTransaction()
                .replace(R.id.linearlayout, mFragment)
                .commit();
        getSupportFragmentManager().beginTransaction()
                .add(R.id.linearlayout, mFragment2)
                .commit();
		
	//fragment修改
	@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view= inflater.inflate(R.layout.fragment_show_name, container, false);
        TextView tv=view.findViewById(R.id.tv_name);
        tv.setText(mProvince);
        return view;
    }


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效果如下图：

所以一个布局里面是可以加载多个Fragment的。

4. 为什么多数情况下采用FrameLayout加载Fragment？

因为多数情况下，一个布局里面只需要显示一个Fragment。这种情况下比起LinearLayout和RelativeLayout，使用FrameLayout更好。