android UI：底部菜单栏的学习与制作——Fragment碎片一

碎片（Fragment） 嵌入与活动中的UI片段，为了合理的分配布局而存在，这是我的简单理解。多用于兼顾手机与平板的UI，也适用于灵活高级的UI制作。

Demo 简单的按键切换两片不同的Demo

新建left_fragment.xml

<?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/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Button"
        />

</LinearLayout>

新建right_fragment.xml

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

新建another_right_fragment.xml

<?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_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:textSize="20sp"
        android:text="This is right fragment"/>

</LinearLayout>

main_Activity.xml

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

</LinearLayout>

分别新建对应的类

package test.example.com.fragmenttest;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by hs769 on 2017/4/4.
 */

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

package test.example.com.fragmenttest;

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

/**
 * Created by hs769 on 2017/4/4.
 */

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

package test.example.com.fragmenttest;

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

/**
 * Created by hs769 on 2017/4/4.
 */

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

package test.example.com.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.button);
        button.setOnClickListener(this);
        replaceFragment(new RightFragment());
    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id.button:
                replaceFragment(new AnotherRightFragment());
                break;
            default:
                break;
        }
    }
    private void replaceFragment(Fragment fragment){
        FragmentManager fragmentManager=getSupportFragmentManager();
        FragmentTransaction transaction=fragmentManager.beginTransaction();
        transaction.replace(R.id.right_layout,fragment);
        transaction.commit();
    }
}

LeftFragment，RightFragment和another_Right_Fragment这三个类分别extends（继承）Fragment类，这是一个关键，因为有两个包中含有Fragment，建议选择android.support.v4.app.Fragment

  如果包选择不一样会出现如下错误（MainAcitvity.java），如图更改即可：找到出问题的类，更换包，完毕

  最终效果实现点击button切换碎片（下图为点击前后的变化，分别为两个Fragment）