Fragment - Android

本篇文章记录的是Android应用中的Fragment.Fragment必须委托在activity中才能运行.

基本使用

1.新建类(MeFragment),继承自Fragment.

package com.example.myapplication.fragment;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import com.example.myapplication.R;
public class MeFragment extends Fragment {
    private String startupArgument;
    private View view;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        if (view == null) {
            view = inflater.inflate(R.layout.me, null);
        }
        return view;
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getArguments();
        if (bundle != null) {
            startupArgument = bundle.getString("startup");
            Log.e("ysd", "onCreate: me 当前传递的参数是  => " + startupArgument);
        }

    }
}

2.创建布局xml.在布局的xml中,添加fragment组件(必须指定ID).使用name与Java类进行绑定(MyFragment).

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/pink"
    android:orientation="vertical">

    <fragment
        android:id="@+id/fragment"
        android:name="com.example.myapplication.fragment.MeFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
 </LinearLayout>

消息通信

1.Activity传递消息给Fragment

参数传递:

Boundle,在实例化Fragement时,通过putArguments设置.在Fragment内,通过this.getArguments.

 Fragment frag = new MeFragment();
            Bundle bundle = new Bundle();
            bundle.putString("startup", "这是me参数");
            frag.setArguments(bundle);

参数获取:

每次切换,会触发onCreate生命周期,在onCreate函数中,获取参数.

package com.example.myapplication.fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import com.example.myapplication.R;
public class MeFragment extends Fragment {
    private String startupArgument;
    private View view;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        if (view == null) {
            view = inflater.inflate(R.layout.me, null);
        }
        return view;
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getArguments();
        if (bundle != null) {
            startupArgument = bundle.getString("startup");
            Log.e("ysd", "onCreate: me 当前传递的参数是  => " + startupArgument);
        }

    }
}

动态切换

FragmentManager fragmentManager =  getSupportFragmentManager();
FragmentTransition transition = fragmentManager.beginTransition();
// 此处指定fragment显示的区域
transition.replace(R.id.frameLayout,fragment);
transition.addToBackStack(null); // 增加到回退栈.
transtion.commit();

生命周期

onCreate

事件点击.

onCreateView

创建view,点击事件

root =  inflater.inflate(R.layout.fragment1,container,false)
return root

完整代码

主布局:

布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/pink"
    android:orientation="vertical">

 
    <FrameLayout
        android:id="@+id/framelayout"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="120dp"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_recommand"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="推荐" />

        <Button
            android:id="@+id/btn_me"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"

            android:text="我的" />
    </LinearLayout>

</LinearLayout>

MainActivity:

package com.example.myapplication;

import static com.example.myapplication.R.id.btn_me;
import static com.example.myapplication.R.id.btn_recommand;

import android.os.Bundle;
import android.view.View;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;

import com.example.myapplication.fragment.MeFragment;
import com.example.myapplication.fragment.RecommandFragment;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private final String TAG = "ysd";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(btn_me).setOnClickListener(this);
        findViewById(btn_recommand).setOnClickListener(this);
    }

    @Override
    protected void onRestart() {
        super.onRestart();
    }

    @Override
    protected void onPostResume() {
        super.onPostResume();
    }


    @Override
    public void onClick(View v) {
        int id = v.getId();
        if (id == btn_me) {
            Fragment frag = new MeFragment();
            Bundle bundle = new Bundle();
            bundle.putString("startup", "这是me参数");
            frag.setArguments(bundle);
            replaceFragment(frag);
            return;
        }

        if (id == btn_recommand) {
            Fragment frag = new RecommandFragment();
            Bundle bundle = new Bundle();
            bundle.putString("startup", "这是recommand参数");
            frag.setArguments(bundle);
            replaceFragment(frag);
        }
    }

    private void replaceFragment(Fragment frag) {
        final FragmentManager supportFragmentManager = getSupportFragmentManager();
        final FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();
        // 该参数指定视图.
        fragmentTransaction.replace(R.id.framelayout, frag);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }
}

个人页

布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="个人页面"
        android:textSize="36sp" />
</LinearLayout>

fragment:

package com.example.myapplication.fragment;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.example.myapplication.R;

public class MeFragment extends Fragment {
    private String startupArgument;
    private View view;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        if (view == null) {
            view = inflater.inflate(R.layout.me, null);
        }
        return view;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getArguments();
        if (bundle != null) {
            startupArgument = bundle.getString("startup");
            Log.e("ysd", "onCreate: me 当前传递的参数是  => " + startupArgument);
        }

    }
}

推荐页

布局:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="推荐页面"
        android:textSize="36sp" />
</androidx.constraintlayout.widget.ConstraintLayout>

fragment:

package com.example.myapplication.fragment;

import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.example.myapplication.R;

public class RecommandFragment extends Fragment {
    private String startupArgument;
    private View view;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle bundle = getArguments();
        if (bundle != null) {
            startupArgument = bundle.getString("startup");
        }
        Log.e("ysd", "onCreate: 当前获得的参数是 " + startupArgument);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        if (view == null) {
            view = inflater.inflate(R.layout.recommand, null);
        }
        return view;
    }
}

结果