Android碎片的使用

一、动态添加碎片

1》

新建三个布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/b1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="按钮"/>
</LinearLayout>

======================================================================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#00ff00">
    <TextView
        android:layout_gravity="center_horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:text="这是右部碎片"/>
</LinearLayout>
===========================================================================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffff00">
<TextView
    android:layout_gravity="center_horizontal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="20sp"
    android:text="这是另一个右部碎片"/>
</LinearLayout>
====================================================================================

2》新建三个类与三个布局对应

三个类的内容几乎相同重写Fragment类中的onCreateView方法使用inflater将布局引入到view中

package com.example.fragmenttest;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by lenovo on 2019/1/27.
 */

public class LeftFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.feft_fragment,container,false);
        return view;
    }
}
======================================================================================

public class RightFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.rightfragment,container,false);
        return view;
    }
}

======================================================================================

public class AnotherRightFragment extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.another_right_fragment,container,false);
        return view;
    }
}

3》编写主界面

将第二个fragment换成了FrameLayout布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <fragment
        android:name="com.example.fragmenttest.LeftFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:id="@+id/left_fragment"/>
    <FrameLayout
        android:name="com.example.fragmenttest.RightFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:id="@+id/right_fragment"/>

</LinearLayout>

======================================================================================
下面代码中有repaceFragment函数用于往FramLayout中添加布局
（1）创建待添加布局的实例
（2）获取FragmentManager实例可用getSupportFragmentManager();获取
（3）开启一个事务FragmentTransaction transaction=fragmentManager.beginTransaction()
（4）向容器中添加或替换布局replace（）需要传入容器id和待添加的碎片实例
（5）提交事务，commit

package com.example.fragmenttest;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
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=(Button)findViewById(R.id.b1);
        button.setOnClickListener(this);
        repaceFragment(new RightFragment());
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.b1:
                repaceFragment(new AnotherRightFragment());
                break;
            default:
                break;
        }
    }
    public void repaceFragment(Fragment fragment){
        FragmentManager fragmentManager=getSupportFragmentManager();
        FragmentTransaction transaction=fragmentManager.beginTransaction();
        transaction.replace(R.id.right_fragment,fragment);
        transaction.commit();
    }
}

二、在碎片中模拟返回栈

transaction.addToBackStack(null);可以将事物添加到返回栈中，参数传入null即可

public void repaceFragment(Fragment fragment){
    FragmentManager fragmentManager=getSupportFragmentManager();
    FragmentTransaction transaction=fragmentManager.beginTransaction();
    transaction.replace(R.id.right_fragment,fragment);
    transaction.addToBackStack(null);
    transaction.commit();
}

三、碎片之间的通信

四、限定符的使用

在res目录下新建layout—large文件夹，在该文件夹下新建activity_main.xml，

large为限定符，当分辨率较大时会调用layout—large/activity_main.xml,否则会调用activity_main.xml

4》