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n1ce2cv

园龄：5年2个月粉丝：4关注：1

Fragment

Fragment

  • Fragment表示应用界面中可重复使用的一部分。Fragment 定义和管理自己的布局，具有自己的生命周期，并且可以处理自己的输入事件。Fragment 不能独立存在，而是必须由 Activity 或另一个 Fragment 托管。Fragment 的视图层次结构会成为宿主的视图层次结构的一部分，或附加到宿主的视图层次结构。
  • activity_main.xml中的fragment必须有id
  • 当 Activity 处于 STARTED 生命周期状态或更高的状态时，可以添加、替换或移除 Fragment。
  • 可以在同一 Activity 或多个 Activity 中使用同一 Fragment 类的多个实例。

多个fragment

  • fragment1.xml
<?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:orientation="vertical"
    tools:context=".BlankFragment1">
 
    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:text="@string/hello_blank_fragment" />
 
    <Button
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:id="@+id/btn"
        android:text="按钮"/>
 
</LinearLayout>
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    tools:context=".MainActivity"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <fragment
        android:id="@+id/fragment1"
        android:name="com.example.myfragment1.BlankFragment1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"/>
 
    <fragment
        android:id="@+id/fragment2"
        android:name="com.example.myfragment1.BlankFragment2"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="2"/>
 
</LinearLayout>
  • BlankFragment1.java
package com.example.myfragment1;
 
import android.os.Build;
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;
import android.widget.TextView;
 
public class BlankFragment1 extends Fragment {
 
    private View root;
    private TextView textView;
    private Button button;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        if(root == null){
            root = inflater.inflate(R.layout.fragment_blank1, null);
        }
        textView = root.findViewById(R.id.tv);
        button = root.findViewById(R.id.btn);
 
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                textView.setText("被点击了");
            }
        });
 
        return root;
    }
}

动态添加fragment

  1. 创建一个待处理的fragment

  2. 获取FragmentManager，通常用getSupportFragmentManager()

  3. 开启一个事务transaction，一般调用fragmentManager的beginTransaction()

  4. 使用transaction进行fragment替换

  5. 提交事务

  		6. Transaction
    		#将一个fragment实例添加到Activity里面指定id的容器中
    		add(Fragment fragment, String tag)
    		add(int containerViewId, Fragment fragment)
    		add(int containerViewId, Fragment fragment, String tag);
    		 #将一个fragment实例从FragmentManager的FragmentList中移除
    		remove(Fragment fragment);
    		#只控制Fragment的隐藏
    		hide(Fragment fragment)
    		#只控制Fragment的显示
    		show(Fragment fragment)
    		#清除视图，从containerid指定的Added列表移除，FragmentList依然保留
    		detach(Fragment fragment)
    		#创建视图，添加到containerid指定的Added列表，FragmentList依然保留
    		attach(Fragment fragment)
    		#替换containerViewId中的fragment，它会把containerViewId中所有fragment删除，然后添加当前的fragment
    		replace(int containerViewId, Fragment fragment)
    		replace(int containerViewId, Fragment fragment, String tag)
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">
 
    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="change"/>
 
    <Button
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="replace"/>
 
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#ffff00"
        android:id="@+id/fl"/>
 
 
</LinearLayout>
  • MainActivity.java
package com.example.myfragment2;
 
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.Button;
import android.widget.Toast;
 
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        Button button1 = findViewById(R.id.btn1);
        Button button2 = findViewById(R.id.btn2);
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
    }
 
    @Override
    public void onClick(View view) {
        switch (view.getId()){
            case R.id.btn1:
 
                // activity 与 fragment通信
                // 原生方法：Bundle
                Bundle bundle = new Bundle();
                bundle.putString("haha", "xixi");
                BlankFragment1 blankFragment1 = new BlankFragment1();
                blankFragment1.setArguments(bundle);
 
                // 使用接口通信
                blankFragment1.setFragmentCallback(new IFragmentCallback() {
                    @Override
                    public void sendMsgToActivity(String str) {
                        Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();
                    }
 
                    @Override
                    public String getMsgFromActivity() {
                        return "发送给Fragment的";
                    }
                });
 
                replaceFragment(blankFragment1);
                break;
            case R.id.btn2:
                replaceFragment(new ItemFragment());
                break;
            default:
                break;
        }
    }
 
    // 动态切换fragment
    private void replaceFragment(Fragment fragment) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        // 开启一个事务
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        // 替换containerViewId中的fragment，它会把containerViewId中所有fragment删除，然后添加当前的fragment
        fragmentTransaction.replace(R.id.fl, fragment);
 
        // 放到同一个栈里，点返回时显示上一个fragment
        fragmentTransaction.addToBackStack(null);
 
        fragmentTransaction.commit();
    }
}

activity与fragment通信

原生方法：Bundle

case R.id.btn1:
 
    // activity 与 fragment通信
    // 原生方法：Bundle
    Bundle bundle = new Bundle();
    bundle.putString("haha", "xixi");
    BlankFragment1 blankFragment1 = new BlankFragment1();
    blankFragment1.setArguments(bundle);
 
    replaceFragment(blankFragment1);
    break;
// 在fragment中获取当前fragment的arguments
Bundle bundle = this.getArguments();
String str = bundle.getString("haha");
Log.e("wmj", "value=" + str);

接口方案

  • IFragmentCallback.java
package com.example.myfragment2;
 
public interface IFragmentCallback {
    void sendMsgToActivity(String str);
    String getMsgFromActivity();
}
  • MainActivity.java
case R.id.btn1:
 
    // activity 与 fragment通信
    // 原生方法：Bundle
    Bundle bundle = new Bundle();
    bundle.putString("haha", "xixi");
    BlankFragment1 blankFragment1 = new BlankFragment1();
    blankFragment1.setArguments(bundle);
 
    // 使用接口通信
    blankFragment1.setFragmentCallback(new IFragmentCallback() {
        @Override
        public void sendMsgToActivity(String str) {
            Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show();
        }
 
        @Override
        public String getMsgFromActivity() {
            return "发送给Fragment的";
        }
    });
 
    replaceFragment(blankFragment1);
    break;
  • BlankFragment1.java
package com.example.myfragment2;
 
import android.os.Bundle;
 
import androidx.fragment.app.Fragment;
 
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
 
 
public class BlankFragment1 extends Fragment {
 
    private View rootview;
 
    private IFragmentCallback fragmentCallback;// 用来接收activity中的接口型对象
 
    public void setFragmentCallback(IFragmentCallback fragmentCallback) {
        this.fragmentCallback = fragmentCallback;
    }
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        // 在fragment中获取当前fragment的arguments
        Bundle bundle = this.getArguments();
        String str = bundle.getString("haha");
        Log.e("wmj", "value=" + str);
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        if(rootview == null){
            rootview = inflater.inflate(R.layout.fragment_blank1, container, false);
        }
        Button button = rootview.findViewById(R.id.btn3);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
//                fragmentCallback.sendMsgToActivity("发送给Activity");
                String str = fragmentCallback.getMsgFromActivity();
                Toast.makeText(BlankFragment1.this.getContext(), str, Toast.LENGTH_SHORT).show();
            }
        });
        return rootview;
    }
 
    @Override
    public void onResume() {
 
        super.onResume();
    }
}

其他方案：eventBus，LiveData

  • 使用了观察者模式

Fragment生命周期

  1. 创建：onAttach() -> onCreate() -> onCreateView() -> onActivityCreated() -> onStart() -> onResume()
  2. 按下主屏键：onPause() -> onStop()
  3. 重新打开：onStart() -> onResume()
  4. 按下后退键：onPause() -> onStop() -> onDestroyView() -> onDestroy() -> onDetach()

Fragment和ViewPager滑动效果

  • buttom_layout.xml
<?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="55dp"
    android:background="#B0C4DE">
 
    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:gravity="center"
        android:orientation="vertical"
        android:id="@+id/tab_weixin">
 
        <ImageView
            android:layout_width="32dp"
            android:layout_height="32dp"
            android:background="@drawable/tab_weixin"
            android:id="@+id/iv_weixin"/>
        <TextView
            android:layout_width="32dp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="微信"
            android:id="@+id/tv_weixin"/>
 
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:gravity="center"
        android:orientation="vertical"
        android:id="@+id/tab_pay">
 
        <ImageView
            android:layout_width="32dp"
            android:layout_height="32dp"
            android:background="@drawable/tab_pay"
            android:id="@+id/iv_pay"/>
        <TextView
            android:layout_width="32dp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="支付"
            android:id="@+id/tv_pay"/>
 
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:gravity="center"
        android:orientation="vertical"
        android:id="@+id/tab_weixin1">
 
        <ImageView
            android:layout_width="32dp"
            android:layout_height="32dp"
            android:background="@drawable/tab_weixin1"
            android:id="@+id/iv_weixin1"/>
        <TextView
            android:layout_width="32dp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="微"
            android:id="@+id/tv_weixin1"/>
 
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:layout_gravity="center"
        android:gravity="center"
        android:orientation="vertical"
        android:id="@+id/tab_weixin2">
 
        <ImageView
            android:layout_width="32dp"
            android:layout_height="32dp"
            android:background="@drawable/tab_weixin2"
            android:id="@+id/iv_weixin2"/>
        <TextView
            android:layout_width="32dp"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="信"
            android:id="@+id/tv_weixin2"/>
 
    </LinearLayout>
 
</LinearLayout>
  • fragment_blank.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".BlankFragment">
 
    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:textSize="36sp"
        android:id="@+id/tv"
        android:text="@string/hello_blank_fragment" />
 
</FrameLayout>
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <androidx.viewpager2.widget.ViewPager2
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:id="@+id/vp"/>
 
    <include layout="@layout/bottom_layout"></include>
 
</LinearLayout>
  • tab_weixin.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/weixin2" android:state_selected="true"/>
    <item android:drawable="@drawable/weixin1"/>
</selector>
  • BlankFragment.java
package com.example.mywechat;
 
import android.os.Bundle;
 
import androidx.fragment.app.Fragment;
 
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
 
import java.util.ArrayList;
import java.util.List;
 
public class BlankFragment extends Fragment {
 
    private static final String ARG_TEXT = "param1";
    private View rootView;
    private String mTextString;
 
    public BlankFragment() {
        // Required empty public constructor
    }
 
    public static BlankFragment newInstance(String param1) {
        BlankFragment fragment = new BlankFragment();
        Bundle args = new Bundle();
        args.putString(ARG_TEXT, param1);
        fragment.setArguments(args);
        return fragment;
    }
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mTextString = getArguments().getString(ARG_TEXT);
        }
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        if(rootView == null){
            rootView = inflater.inflate(R.layout.fragment_blank, container, false);
        }
        initView();
        return rootView;
    }
 
    private void initView() {
        TextView textView = rootView.findViewById(R.id.tv);
        textView.setText(mTextString);
    }
}
  • MainActivity.java
package com.example.mywechat;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.widget.ViewPager2;
 
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
 
    private ViewPager2 viewPager;
    private LinearLayout llweixin, llweixin1, llweixin2, llpay;
    private ImageView ivweixin, ivweixin1, ivweixin2, ivpay, ivCurrent;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        initPager();
        initTabView();
    }
 
    private void initPager() {
        List<Fragment> fragments = new ArrayList<>();
        fragments.add(BlankFragment.newInstance("微信"));
        fragments.add(BlankFragment.newInstance("通讯录"));
        fragments.add(BlankFragment.newInstance("发现"));
        fragments.add(BlankFragment.newInstance("我"));
 
        viewPager = findViewById(R.id.vp);
        MyFragmentPagerAdapter myFragmentPagerAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager(), getLifecycle(), fragments);
        viewPager.setAdapter(myFragmentPagerAdapter);
        viewPager.registerOnPageChangeCallback(new ViewPager2.OnPageChangeCallback() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                super.onPageScrolled(position, positionOffset, positionOffsetPixels);
            }
 
            @Override
            public void onPageSelected(int position) {
                super.onPageSelected(position);
                changeTab(position);
            }
 
            @Override
            public void onPageScrollStateChanged(int state) {
                super.onPageScrollStateChanged(state);
            }
        });
    }
 
    private void changeTab(int position) {
        ivCurrent.setSelected(false); // 当前的按钮先复位
        switch (position){
            case R.id.tab_weixin:
                viewPager.setCurrentItem(0);
            case 0:
                ivweixin.setSelected(true);
                ivCurrent = ivweixin;
                break;
            case R.id.tab_pay:
                viewPager.setCurrentItem(1);
            case 1:
                ivpay.setSelected(true);
                ivCurrent = ivpay;
                break;
            case R.id.tab_weixin1:
                viewPager.setCurrentItem(2);
            case 2:
                ivweixin1.setSelected(true);
                ivCurrent = ivweixin1;
                break;
            case R.id.tab_weixin2:
                viewPager.setCurrentItem(3);
            case 3:
                ivweixin2.setSelected(true);
                ivCurrent = ivweixin2;
                break;
        }
    }
 
    private void initTabView(){
        llweixin = findViewById(R.id.tab_weixin);
        llweixin.setOnClickListener(this);
        llweixin1 = findViewById(R.id.tab_weixin1);
        llweixin1.setOnClickListener(this);
        llweixin2 = findViewById(R.id.tab_weixin2);
        llweixin2.setOnClickListener(this);
        llpay = findViewById(R.id.tab_pay);
        llpay.setOnClickListener(this);
        ivweixin = findViewById(R.id.iv_weixin);
        ivweixin1 = findViewById(R.id.iv_weixin1);
        ivweixin2 = findViewById(R.id.iv_weixin2);
        ivpay = findViewById(R.id.iv_pay);
 
        llweixin.setSelected(true);
        ivCurrent = ivweixin;
    }
 
    @Override
    public void onClick(View view) {
        changeTab(view.getId());
    }
}
  • MyFragmentPagerAdapter.java
package com.example.mywechat;
 
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;
 
import java.util.ArrayList;
import java.util.List;
 
public class MyFragmentPagerAdapter extends FragmentStateAdapter {
 
    private List<Fragment> fragmentList = new ArrayList<>();
 
    public MyFragmentPagerAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle, List<Fragment> fragments) {
        super(fragmentManager, lifecycle);
        fragmentList = fragments;
    }
 
    @NonNull
    @Override
    public Fragment createFragment(int position) {
        return fragmentList.get(position);
    }
 
    @Override
    public int getItemCount() {
        return fragmentList.size();
    }
}

与fragment通信

使用ViewModel

fragment和activity

  • Activity中
viewModel = new ViewModelProvider(this).get(CityViewModel.class);
  • Fragment中
/**
 * MainActivity用作MainActivity和WeatherDetailFragment中的范围，因此为它们提供了相同的 ViewModel。
 * 如果WeatherDetailFragment将自身用作范围，即viewModel = new ViewModelProvider(this).get(CityViewModel.class);
 * 会为其提供与MainActivity不同的ViewModel。
 */
// viewModel = new ViewModelProvider(this).get(CityViewModel.class); // 不同的viewmodel
viewModel = new ViewModelProvider(requireActivity()).get(CityViewModel.class);

本文作者：n1ce2cv

本文链接：https://www.cnblogs.com/sprinining/p/14955032.html

版权声明：本作品采用知识共享署名-非商业性使用-禁止演绎 2.5 中国大陆许可协议进行许可。

posted @   n1ce2cv  阅读(148)  评论(0)  编辑  收藏  举报
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