Android开发Fragment的使用学习

基本概念

Fragment是Android3.0(API11)提出的概念，support-v4库中也开发了一套Fragment API，最低兼容Android 1.6。所以在开发中要注意不要导错包

导入support-v4 compile 'com.android.support:support-v4:24.2.1

导入support-fragment com.android.support:support-fragment:24.2.1

• 一个Activity可以有多个Fragment
• Frament可以被多个Activity重用
• 它有自己的生命周期，可以接收监听事件
• 在运行Activity时可以被删除、替代。

生命周期

底部导航Demo

1、编写activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

    tools:context=".MainActivity">

    <fragment

        android:id="@+id/fragment"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:name="com."></fragment>

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="50dp"

        android:orientation="horizontal"

        android:layout_alignParentBottom="true">

        <ImageView

            android:id="@+id/btn1"

            android:layout_width="50dp"

            android:layout_height="50dp"

            android:src="@mipmap/icon1"

            android:layout_weight="1"

            />

        <ImageView

            android:id="@+id/btn2"

            android:layout_width="50dp"

            android:layout_height="50dp"

            android:src="@mipmap/icon2"

            android:layout_weight="1"

            />

        <ImageView

            android:id="@+id/btn3"

            android:layout_width="50dp"

            android:layout_height="50dp"

            android:src="@mipmap/icon3"

            android:layout_weight="1"

            />

        <ImageView

            android:id="@+id/btn4"

            android:layout_width="50dp"

            android:layout_height="50dp"

            android:src="@mipmap/icon4"

            android:layout_weight="1"

            />

    </LinearLayout>

</RelativeLayout>

2、一式4份准备fragment1_activity.xml的布局文件(背景和文件名改下)

<?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="@drawable/f1">

</LinearLayout>

3、Fragment_one.java文件一式4份，对于上一步的fragment布局

package com.example.fragmenttest;

import androidx.fragment.app.Fragment;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import androidx.annotation.Nullable;

public class Fragment_one extends Fragment {

    @Nullable

    @Override

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

        return inflater.inflate(R.layout.fragment1_activty,container,false);

    }

}

4、编写MainActivty.java

package com.example.fragmenttest;

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.ImageView;

public class MainActivity extends AppCompatActivity {

    ImageView btn1;

    ImageView btn2;

    ImageView btn3;

    ImageView btn4;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initView();

    }

    private void initView() {

        btn1 = findViewById(R.id.btn1);

        btn2 = findViewById(R.id.btn2);

        btn3 = findViewById(R.id.btn3);

        btn4 = findViewById(R.id.btn4);

        btn1.setOnClickListener(l);

        btn2.setOnClickListener(l);

        btn3.setOnClickListener(l);

        btn4.setOnClickListener(l);

    }

    View.OnClickListener l =  new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            FragmentManager fm = getSupportFragmentManager();

            FragmentTransaction ft = fm.beginTransaction();

            Fragment f = null;

            switch (v.getId()){

                case R.id.btn1:

                    f =  new Fragment_one();

                    break;

                case R.id.btn2:

                    f =  new Fragment_two();

                    break;

                case R.id.btn3:

                    f =  new Fragment_three();

                    break;

                case R.id.btn4:

                    f =  new Fragment_four();

                    break;

                default:

                    break;

            }

            ft.replace(R.id.fragment,f);

            ft.commit();

        }

    };

}

效果: