安卓Fragment实现碎片切换

朱雀 2024-03-30 10:52 71阅读 0赞

**目录**

Fragment理论：

Fragment生命周期

具体例子：切换碎片

创建安卓应用SwitchFragment

创建碎片

打开主界面：

碎片界面类实现功能

优化：

--------------------

### Fragment理论： ###

Fragment是Android3.0引入的新API，它代表Activity的子模板，所以可以把fragment理解为Activity片段。Fragment必须被“嵌入”Avtivity中使用，因此Fragment也拥有自己的生命周期，不过Fragment的生命周期受Activity所控制，也就是说Activity停止的时候，Activity中所有的Fragment都会被停止，其它状态也是一样。

#### Fragment生命周期 ####

附加与分离：onAttach() + onDetach()  
创建和销毁：onCreate() + onDestroy()  
创建视图和销毁视图：onCreateView() + onDestroyView()  
可见和不可见：onStart() + onStop()  
可交互和不可交互：onResume() + onPause()  
原文链接：https://blog.csdn.net/howard2005/article/details/127853054

### 具体例子：切换碎片 ###

#### 创建安卓应用`SwitchFragment` ####

![e0e6a0822422443e98601e3b18c09f3f.png][]

创建成功：

![a328989cc6d44cf1be91ea8b24ae9843.png][]

插入图片素材

将三张背景图片拷贝到`drawable`目录

![9802c57365b6434e944b5795150deaa7.png][]

在字符资源字符串资源文件`strings.xml里面输入代码：`

![63d67079573b4c43adde77de897fa46b.png][]

具体代码：

<resources>
        <string name="app_name">切换碎片</string>
        <string name="first_fragment">第一个碎片</string>
        <string name="second_fragment">第二个碎片</string>
        <string name="third_fragment">第三个碎片</string>
        <string name="next_fragment">下一个碎片</string>
    </resources>

打开主布局资源文件`activity_main.xml输入 代码：`

![440328067d784963bfa73e928ba6ab47.png][]

具体代码：

<?xml version="1.0" encoding="utf-8"?>
    <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/container"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    
    </FrameLayout>

#### 创建碎片 ####

（1）创建第一个碎片

![6c0dc834afaf4bd182850df79f88bd13.png][]

设置碎片名称 - `FirstFragment`

![3374c174cfb442c9848059b04d4d9aae.png][]

创建成功：

![b20fd45c3a13488c974e423054e10362.png][]

修改第一个碎片的布局资源文件 `fragment_first.xml`

![1974acf8662a45748813e2be2e06825b.png][]

具体代码：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 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="@drawable/img1"
        android:gravity="center"
        android:orientation="vertical"
        tools:context=".FirstFragment">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="30dp"
            android:text="@string/first_fragment"
            android:textSize="50sp"
            android:textColor="#ff0000"/>
        <Button
            android:id="@+id/btn_next_fragment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="doNextFragment"
            android:text="@string/next_fragment"
            android:textSize="30sp"/>
    
    
    </LinearLayout>

创建第二个碎片`SecondFragment`

![dd2fc0b3dbed4f6f959bb35b022b5ebf.png][]

创建成功：

![a5aee320ba1e472084c6a38890bb34b0.png][]

修改第二个碎片的布局资源文件 fragment\_second.xml

![9dbf852982fb4ba1875a57eada4bc5f6.png][]

具体代码：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 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="@drawable/img2"
        android:gravity="center"
        android:orientation="vertical"
        tools:context=".SecondFragment">
    
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="30dp"
            android:text="@string/second_fragment"
            android:textSize="50sp"
            android:textColor="#00ff00"/>
        <Button
            android:id="@+id/btn_next_fragment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="doNextFragment"
            android:text="@string/second_fragment"
            android:textSize="30sp"/>
    </LinearLayout>

创建第三个碎片`ThirdFragment`

![abb8b39b36d940ec883510ad8ab4d194.png][]

创建成功：

![031e3d7c3df24958afc9e168e2e8e2f8.png][]

修改第三个碎片的布局资源文件 `fragment_third.xml`

![9170e5ca38f54cda8bf236015fa9c5fb.png][]

具体代码：

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 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="@drawable/img3"
        android:gravity="center"
        android:orientation="vertical"
        tools:context=".ThirdFragment">
    
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="30dp"
            android:text="@string/third_fragment"
            android:textSize="50sp"
            android:textColor="#0000ff"/>
        <Button
            android:id="@+id/btn_next_fragment"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="doNextFragment"
            android:text="@string/third_fragment"
            android:textSize="30sp"/>
    </LinearLayout>

#### 打开主界面： ####

![a1febc8cfe0441aca730ffcd63f27972.png][]

![83d44aa77656471fb5af9568c6475384.png][]

具体代码：

package net.zyt.switch_fragment;
    
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.fragment.app.Fragment;
    import androidx.fragment.app.FragmentManager;
    
    import android.os.Bundle;
    
    public class MainActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            //利用布局资源文件设置用户界面
            setContentView(R.layout.activity_main);
    
    
            //获取碎片管理器
            FragmentManager fm=getSupportFragmentManager();
    
            //在主容器里面添加第一个碎片
            fm.beginTransaction().add(R.id.container,new FirstFragment()).commit();
    
        }
    }

#### 碎片界面类实现功能 ####

（1）第一个碎片界面类实现功能,`打开FirstFragment`

![5c4625143f884b4598140ceb5ae95564.png][]

![702062ddca4c429788540b1d1de0f81d.png][]

具体代码：

package net.zyt.switch_fragment;
    
    import android.os.Bundle;
    
    import androidx.fragment.app.Fragment;
    
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    
    public class FirstFragment extends Fragment {
    
    
        private Button btnNextFragment;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }
        
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            //获取碎片视图
            View view=inflater.inflate(R.layout.fragment_first,container,false);
            //通过资源标识符获取控件实例
            btnNextFragment=view.findViewById(R.id.btn_next_fragment);
            //给按钮注册单击事件监听器
            btnNextFragment.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //切换到第二个碎片
                    getFragmentManager().
                            beginTransaction().addToBackStack("next")
                            .replace(R.id.container,new SecondFragment())
                            .commit();
    
                }
            });
            //返回碎片视图
            return view;
        }
    }

第二个碎片界面类实现功能,打开第二个碎片界面类 `SecondFragment`

![ca665ac4a3754b60a8caea5e62609d64.png][]

具体代码：

package net.zyt.switch_fragment;
    
    import android.os.Bundle;
    
    import androidx.fragment.app.Fragment;
    
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    
    public class SecondFragment extends Fragment {
    
    
        private Button btnNextFragment;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            //获取碎片视图
            View view = inflater.inflate(R.layout.fragment_second, container, false);
            //通过资源标识符获取控件实例
            btnNextFragment = view.findViewById(R.id.btn_next_fragment);
            //给按钮注册单击事件监听器
            btnNextFragment.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //切换到第二个碎片
                    getFragmentManager().
                            beginTransaction().addToBackStack("next")
                            .replace(R.id.container, new ThirdFragment())
                            .commit();
    
                }
            });
            //返回碎片视图
            return view;
        }}

第三个碎片界面类实现功能,打开三个碎片界面类`ThirdFragment`

![8823dbe017274d02b2a0ec86a9602351.png][]

具体代码：

package net.zyt.switch_fragment;
    
    import android.os.Bundle;
    
    import androidx.fragment.app.Fragment;
    
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    
    public class ThirdFragment extends Fragment {
    
    
        private Button btnNextFragment;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            //获取碎片视图
            View view = inflater.inflate(R.layout.fragment_third, container, false);
            //通过资源标识符获取控件实例
            btnNextFragment = view.findViewById(R.id.btn_next_fragment);
            //给按钮注册单击事件监听器
            btnNextFragment.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //切换到第二个碎片
                    getFragmentManager().
                            beginTransaction().addToBackStack("next")
                            .replace(R.id.container, new FirstFragment())
                            .commit();
    
                }
            });
            //返回碎片视图
            return view;
        }}

启动应用查看效果：

![c90290d0b15040c5816faaa441a2545a.gif][]

#### 优化： ####

每次切换碎片时，都是利用new来创建新的碎片，这样在不断切换碎片的过程中，就导致资源的浪费

创建碎片列表类

碎片列表类 `FragmentList`用于保存程序要用到的碎片对象

![bbc03038ed9f4a30b810a5294eb5e909.png][]

![2d3c20eab60c42bfa842bcd1eab011ba.png][]

![fee4c156b4f14e16ac6425cf13aebe09.png][]

具体代码：

package net.zyt.switch_fragment;
    import androidx.fragment.app.Fragment;
    import java.util.ArrayList;
    import java.util.List;
    
    public class FragmentList{
        public static List<Fragment> fragments = new ArrayList<>();
    }

修改主界面类

在碎片列表类里保存程序所需要的碎片对象

![6ab258d3be4e4c5fbdaa4830e04481f1.png][]

具体代码：

package net.zyt.switch_fragment;
    
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.fragment.app.Fragment;
    import androidx.fragment.app.FragmentManager;
    
    import android.os.Bundle;
    
    public class MainActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            //利用布局资源文件设置用户界面
            setContentView(R.layout.activity_main);
    
    
            //获取碎片管理器
            FragmentManager fm=getSupportFragmentManager();
            //创建三个碎片，添加到碎片列表
            FragmentList.fragments.add(new FirstFragment());
            FragmentList.fragments.add(new SecondFragment());
            FragmentList.fragments.add(new ThirdFragment());
    
            //在主容器里面添加第一个碎片
            fm.beginTransaction().add(R.id.container,FragmentList.fragments.get(0)).commit();
    
        }
    }

修改第一个碎片界面类

将`new SecondFragment()`改成`FragmentList.fragments.get(1)`

![37f02878081e4222b0e6e83e615ccd48.png][]

修改第二个碎片界面类

将`new ThirdFragment()`改成`FragmentList.fragments.get(2)`

![9c0342cdb32a46e7b41ae205264f487f.png][]

修改第三个碎片界面类

将`new FirstFragment()`改成`FragmentList.fragments.get(0)`

![0cafba00d24d447d89ff35a253a059fe.png][]

运行程序查看效果：

![3b88e205be15414a976ca90f349459b4.gif][]

[e0e6a0822422443e98601e3b18c09f3f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/56f7cc3eac3e40409e1da0e8435ad968.png
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[031e3d7c3df24958afc9e168e2e8e2f8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/58846839a2b6436fb7c2920eb2417bb4.png
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[5c4625143f884b4598140ceb5ae95564.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/f220b4aef1d945a7a8e2de9070d1d6ee.png
[702062ddca4c429788540b1d1de0f81d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/a1d76d4a7f7b48ff917734b7206ece48.png
[ca665ac4a3754b60a8caea5e62609d64.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/b01c301618ff4b79afb4bab8fe5aeb38.png
[8823dbe017274d02b2a0ec86a9602351.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/30/439b218476164ab3b09f4107eb628fba.png
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