Fragment动态实现及解决Fragment重叠问题

其他 2018-06-12 05:17:20 阅读次数: 0

一、知识回顾

（1）onSaveInstanceState()和onRestoreInstanceState()调用机制

  地址：https://blog.csdn.net/qq_34490018/article/details/80069365

（2）Fragment基础详解

  地址：https://blog.csdn.net/qq_34490018/article/details/80100941

二、实现原理

  因为replace()方法是先将存在的Fragment删除再添加新的Fragment，所以内存波动大，网络请求消耗大。

  因此我们常用add()方法、hide()和show()方法配合使用，达到Fragment切换效果。如选中想显示的Fragment，先利用hide()方法隐藏所有的Fragment，当Fragment不存在时，利用add()方法添加Fragment；当Fragment存在时，利用show()方法显示选中的Fragment。

三、Fragment重叠问题

  因为使用add()的原因，当Activity被系统回收时，内存中还保存着Fragment相关信息，所有导致再次启动应用时，会出现Fragment重叠现象。

（1）模拟情景再现

      打开手机设置，再打开开发者模式选项，将不保留活动打开。

（2）解决方法

     在之前，我们先来回顾下两个知识点，一个是onSaveInstanceState()和onRestoreInstanceState()调用机制，另一个是add()方法的参数add(int containerViewId, Fragment fragment, String tag)。tag为Fragment的标识，用于恢复数据时，findFragmentByTag()寻找相关tag标识。

      add()方法增加tag标识：

transaction.add(R.id.content, homeFragment, FRAGMENT_TAG[index]);
transaction.add(R.id.title,homeTitleFragment,FRAGMENT_TITLE_TAG[index]);
transaction.add(R.id.content, demandFragment, FRAGMENT_TAG[index]);
transaction.add(R.id.title,demandTitleFragment,FRAGMENT_TITLE_TAG[index]);
transaction.add(R.id.content, newsFragment, FRAGMENT_TAG[index]);
transaction.add(R.id.title,newsTitleFragment,FRAGMENT_TITLE_TAG[index]);
transaction.add(R.id.content, personalFragment, FRAGMENT_TAG[index]);
transaction.add(R.id.title,personalTitleFragment,FRAGMENT_TITLE_TAG[index]);

      onSaveInstanceState(Bundle outState)保存关闭前选中的Fragment：

    /*
    * 保存TAB选中状态
    * */
    @Override
    protected void onSaveInstanceState(Bundle outState) {
         //如果用以下这种做法则不保存状态，再次进来的话会显示默认tab
        //总是执行这句代码来调用父类去保存视图层的状态
        //保存tab选中的状态;
        super.onSaveInstanceState(outState);
        outState.putInt("TAG",TAG);
    }

      在onCreate()中恢复数据：

        //savedInstanceState不为空
        if(savedInstanceState!=null){
            homeFragment=(HomeFragment)fragmentManager.findFragmentByTag("homeFragment");
            demandFragment=(DemandFragment) fragmentManager.findFragmentByTag("demandFragment");
            newsFragment=(NewsFragment)fragmentManager.findFragmentByTag("newsFragment");
            personalFragment=(PersonalFragment)fragmentManager.findFragmentByTag("personalFragment");
            homeTitleFragment=(HomeTitleFragment)fragmentManager.findFragmentByTag("homeTitleFragment");
            demandTitleFragment=(DemandTitleFragment)fragmentManager.findFragmentByTag("demandTitleFragment");
            newsTitleFragment=(NewsTitleFragment)fragmentManager.findFragmentByTag("newsTitleFragment");
            personalTitleFragment=(PersonalTitleFragment)fragmentManager.findFragmentByTag("personalTitleFragment");
            //打开关闭前的Fragment
            setTabSelection(savedInstanceState.getInt("TAG"));
        }else{
            //打开第一个Fragment
            setTabSelection(selindex);
        }

四、 部分核心代码

MainActivity.java

package agrpro.com.agrpro;

import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.graphics.Color;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.TextView;
import com.baidu.mapapi.SDKInitializer;


public class MainActivity extends Activity implements View.OnClickListener {
    //TAG标识
    private int TAG;
    private int selindex=0;
    private static final  String[] FRAGMENT_TAG = {"homeFragment","demandFragment","newsFragment","personalFragment"};
    private static final  String[] FRAGMENT_TITLE_TAG={"homeTitleFragment","demandTitleFragment","newsTitleFragment","personalTitleFragment"};
    //Fragment控件
    private HomeFragment homeFragment;
    private DemandFragment demandFragment;
    private NewsFragment newsFragment;
    private PersonalFragment personalFragment;
    private HomeTitleFragment homeTitleFragment;
    private DemandTitleFragment demandTitleFragment;
    private NewsTitleFragment newsTitleFragment;
    private PersonalTitleFragment personalTitleFragment;
    private View homeLayout;
    private View demandLayout;
    private View newsLayout;
    private View personalLayout;
    private ImageView homeImage;
    private ImageView demandImage;
    private ImageView newsImage;
    private ImageView personalImage;
    private TextView homeText;
    private TextView demandText;
    private TextView newsText;
    private TextView personalText;
    //Fragmnet管理
    private FragmentManager fragmentManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //状态栏
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Window window = getWindow();
            window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
            window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                    | View.SYSTEM_UI_FLAG_LAYOUT_STABLE);
            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
            window.setStatusBarColor(Color.TRANSPARENT);
        }
        super.onCreate(savedInstanceState);
        //百度地图
        //在使用SDK各组件之前初始化context信息，传入ApplicationContext
        //注意该方法要再setContentView方法之前实现
        SDKInitializer.initialize(getApplicationContext());
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        // 状态栏初始化布局元素
        View statusBar = findViewById(R.id.statusBarView);
        statusBar.setBackgroundColor(getResources().getColor(R.color.limegreen));
        ViewGroup.LayoutParams layoutParams = statusBar.getLayoutParams();
        layoutParams.height = getStatusBarHeight();

        initViews();
        fragmentManager = getFragmentManager();
        //savedInstanceState不为空
        if(savedInstanceState!=null){
            homeFragment=(HomeFragment)fragmentManager.findFragmentByTag("homeFragment");
            demandFragment=(DemandFragment) fragmentManager.findFragmentByTag("demandFragment");
            newsFragment=(NewsFragment)fragmentManager.findFragmentByTag("newsFragment");
            personalFragment=(PersonalFragment)fragmentManager.findFragmentByTag("personalFragment");
            homeTitleFragment=(HomeTitleFragment)fragmentManager.findFragmentByTag("homeTitleFragment");
            demandTitleFragment=(DemandTitleFragment)fragmentManager.findFragmentByTag("demandTitleFragment");
            newsTitleFragment=(NewsTitleFragment)fragmentManager.findFragmentByTag("newsTitleFragment");
            personalTitleFragment=(PersonalTitleFragment)fragmentManager.findFragmentByTag("personalTitleFragment");
            //打开关闭前的Fragment
            setTabSelection(savedInstanceState.getInt("TAG"));
        }else{
            //打开第一个Fragment
            setTabSelection(selindex);
        }
    }
    //动态获取状态栏高度
    private int getStatusBarHeight() {
        int result = 0;
        //获取状态栏高度的资源id
        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
        if (resourceId > 0) {
            result = getResources().getDimensionPixelSize(resourceId);
        }
        return result;
    }
    //初始化布局控件
    private void initViews() {
        homeLayout = findViewById(R.id.home_layout);
        demandLayout = findViewById(R.id.demand_layout);
        newsLayout = findViewById(R.id.news_layout);
        personalLayout = findViewById(R.id.personal_layout);
        homeImage = (ImageView) findViewById(R.id.home_image);
        demandImage = (ImageView) findViewById(R.id.demand_image);
        newsImage = (ImageView) findViewById(R.id.news_image);
        personalImage = (ImageView) findViewById(R.id.personal_image);
        homeText = (TextView) findViewById(R.id.home_text);
        demandText = (TextView) findViewById(R.id.demand_text);
        newsText = (TextView) findViewById(R.id.news_text);
        personalText = (TextView) findViewById(R.id.personal_text);
        //点击监听
        homeLayout.setOnClickListener(this);
        demandLayout.setOnClickListener(this);
        newsLayout.setOnClickListener(this);
        personalLayout.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.home_layout:
                // 当点击了首页tab时，选中第1个tab
                setTabSelection(0);
                break;
            case R.id.demand_layout:
                // 当点击了供求tab时，选中第2个tab
                setTabSelection(1);
                break;
            case R.id.news_layout:
                // 当点击了发现tab时，选中第3个tab
                setTabSelection(2);
                break;
            case R.id.personal_layout:
                // 当点击了我的tab时，选中第4个tab
                setTabSelection(3);
                break;
            default:
                break;
        }
    }

    /**
     * 根据传入的index参数来设置选中的tab页。
     */
    private void setTabSelection(int index) {
        // 每次选中之前先清楚掉上次的选中状态
        clearSelection();
        // 开启一个Fragment事务
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        // 先隐藏掉所有的Fragment，以防止有多个Fragment显示在界面上的情况
        hideFragments(transaction);
        switch (index) {
            case 0:
                //     messageImage.setImageResource(R.drawable.message_selected);
                TAG=0;
                homeText.setTextColor(homeText.getResources().getColor(R.color.limegreen));
                if (homeFragment == null) {
                    // 如果MessageFragment为空，则创建一个并添加到界面上
                    homeFragment = new HomeFragment();
                    homeTitleFragment=new HomeTitleFragment();
                    transaction.add(R.id.content, homeFragment, FRAGMENT_TAG[index]);
                    transaction.add(R.id.title,homeTitleFragment,FRAGMENT_TITLE_TAG[index]);
                } else {
                    // 如果MessageFragment不为空，则直接将它显示出来
                    transaction.show(homeFragment);
                    transaction.show(homeTitleFragment);
                }
                break;
            case 1:
                //  contactsImage.setImageResource(R.drawable.contacts_selected);
                TAG=1;
                demandText.setTextColor(demandText.getResources().getColor(R.color.limegreen));
                if (demandFragment == null) {
                    // 如果ContactsFragment为空，则创建一个并添加到界面上
                    demandFragment = new DemandFragment();
                    demandTitleFragment=new DemandTitleFragment();
                    transaction.add(R.id.content, demandFragment, FRAGMENT_TAG[index]);
                    transaction.add(R.id.title,demandTitleFragment,FRAGMENT_TITLE_TAG[index]);
                } else {
                    // 如果ContactsFragment不为空，则直接将它显示出来
                    transaction.show(demandFragment);
                    transaction.show(demandTitleFragment);
                }
                break;
            case 2:
                //     newsImage.setImageResource(R.drawable.news_selected);
                TAG=2;
                newsText.setTextColor(newsText.getResources().getColor(R.color.limegreen));
                if (newsFragment == null) {
                    // 如果NewsFragment为空，则创建一个并添加到界面上
                    newsFragment = new NewsFragment();
                    newsTitleFragment=new NewsTitleFragment();
                    transaction.add(R.id.content, newsFragment, FRAGMENT_TAG[index]);
                    transaction.add(R.id.title,newsTitleFragment,FRAGMENT_TITLE_TAG[index]);
                } else {
                    // 如果NewsFragment不为空，则直接将它显示出来
                    transaction.show(newsFragment);
                    transaction.show(newsTitleFragment);
                }
                break;
            case 3:
            default:
                //    settingImage.setImageResource(R.drawable.setting_selected);
                TAG=3;
                personalText.setTextColor(personalText.getResources().getColor(R.color.limegreen));
                if (personalFragment == null) {
                    // 如果SettingFragment为空，则创建一个并添加到界面上
                    personalFragment = new PersonalFragment();
                    personalTitleFragment=new PersonalTitleFragment();
                    transaction.add(R.id.content, personalFragment, FRAGMENT_TAG[index]);
                    transaction.add(R.id.title,personalTitleFragment,FRAGMENT_TITLE_TAG[index]);
                } else {
                    // 如果SettingFragment不为空，则直接将它显示出来
                    transaction.show(personalFragment);
                    transaction.show(personalTitleFragment);
                }
                break;
        }
        transaction.commit();
    }

    /**
     * 清除掉所有的选中状态。
     */
    private void clearSelection() {
        homeImage.setImageResource(R.drawable.home);
        homeText.setTextColor(Color.parseColor("#82858b"));
        demandImage.setImageResource(R.drawable.demand);
        demandText.setTextColor(Color.parseColor("#82858b"));
        newsImage.setImageResource(R.drawable.news);
        newsText.setTextColor(Color.parseColor("#82858b"));
        personalImage.setImageResource(R.drawable.personal);
        personalText.setTextColor(Color.parseColor("#82858b"));
    }

    /**
     * 将所有的Fragment都置为隐藏状态。
     * 用于对Fragment执行操作的事务
     */
    private void hideFragments(FragmentTransaction transaction) {
        if (homeFragment != null) {
            transaction.hide(homeFragment);
            transaction.hide(homeTitleFragment);
        }
        if (demandFragment != null) {
            transaction.hide(demandFragment);
            transaction.hide(demandTitleFragment);
        }
        if (newsFragment != null) {
            transaction.hide(newsFragment);
            transaction.hide(newsTitleFragment);
        }
        if (personalFragment != null) {
            transaction.hide(personalFragment);
            transaction.hide(personalTitleFragment);
        }
    }
    /*
    * 保存TAB选中状态
    * */
    @Override
    protected void onSaveInstanceState(Bundle outState) {
         //如果用以下这种做法则不保存状态，再次进来的话会显示默认tab
        //总是执行这句代码来调用父类去保存视图层的状态
        //保存tab选中的状态;
        super.onSaveInstanceState(outState);
        outState.putInt("TAG",TAG);
    }
}

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:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="agrpro.com.agrpro.MainActivity">

    <FrameLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/title"
        android:layout_above="@+id/app_bottom">
    </FrameLayout>

    <View
        android:id="@+id/statusBarView"
        android:layout_alignParentTop="true"
        android:background="#00000000"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"></View>

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_below="@+id/statusBarView"
        android:id="@+id/title">
    </FrameLayout>



    <LinearLayout
        android:id="@+id/app_bottom"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:background="@drawable/solid">

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

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:orientation="vertical">

                <ImageView
                    android:id="@+id/home_image"
                    android:layout_width="60dp"
                    android:layout_height="20dp"
                    android:layout_gravity="center_horizontal"
                    android:src="@drawable/home" />

                <TextView
                    android:id="@+id/home_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:text="首页"
                    android:textColor="#82858b" />
            </LinearLayout>
        </RelativeLayout>

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

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:orientation="vertical">

                <ImageView
                    android:id="@+id/demand_image"
                    android:layout_width="60dp"
                    android:layout_height="20dp"
                    android:layout_gravity="center_horizontal"
                    android:src="@drawable/demand" />

                <TextView
                    android:id="@+id/demand_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:text="供求"
                    android:textColor="#82858b" />
            </LinearLayout>
        </RelativeLayout>

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

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:orientation="vertical">

                <ImageView
                    android:id="@+id/news_image"
                    android:layout_width="60dp"
                    android:layout_height="20dp"
                    android:layout_gravity="center_horizontal"
                    android:src="@drawable/news" />

                <TextView
                    android:id="@+id/news_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:text="发现"
                    android:textColor="#82858b" />
            </LinearLayout>
        </RelativeLayout>

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

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:orientation="vertical">

                <ImageView
                    android:id="@+id/personal_image"
                    android:layout_width="60dp"
                    android:layout_height="20dp"
                    android:layout_gravity="center_horizontal"
                    android:src="@drawable/personal" />

                <TextView
                    android:id="@+id/personal_text"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:text="我的"
                    android:textColor="#82858b" />
            </LinearLayout>
        </RelativeLayout>
    </LinearLayout>

</RelativeLayout>

HomeTitleFragment.java

package agrpro.com.agrpro;

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

/**
 * Created by Administrator on 2018/4/19.
 */

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

hometitle_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/limegreen"
    android:padding="5dp"
    android:focusable="true"
    android:focusableInTouchMode="true">

    <TextView
        android:id="@+id/imageView"
        android:layout_width="30dp"
        android:text="地图"
        android:textSize="15sp"
        android:textColor="@color/white"
        android:gravity="center"
        android:layout_height="50dp"
        android:layout_alignParentTop="true"
        android:layout_alignBottom="@+id/editText"
        android:layout_alignParentStart="true"
        android:layout_toStartOf="@+id/editText" />

    <EditText
        android:id="@+id/editText"
        android:background="@drawable/edittext_selector"
        android:layout_width="250dp"
        android:layout_height="35dp"
        android:hint="搜索"
        android:drawableLeft="@android:drawable/ic_menu_search"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />
    <TextView
        android:id="@+id/aimageView"
        android:layout_width="30dp"
        android:text="扫一扫"
        android:textSize="15sp"
        android:textColor="@color/white"
        android:gravity="center"
        android:layout_height="50dp"
        android:layout_alignParentTop="true"
        android:layout_alignParentEnd="true"
        android:layout_alignBottom="@+id/editText"
        android:layout_toEndOf="@+id/editText" />

</RelativeLayout>

HomeFragment.java

package agrpro.com.agrpro;

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

import com.baidu.mapapi.map.BaiduMap;
import com.baidu.mapapi.map.TextureMapView;

/**
 * Created by Administrator on 2018/4/19.
 */

public class HomeFragment extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View homeLayout = inflater.inflate(R.layout.home_layout, container, false);
        return homeLayout;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
    }


}

home_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:gravity="center"
        android:text="首页页面"/>

</RelativeLayout>

因为其他Fragment页面跟首页Fragment页面类似，所以只贴以上部分代码。。。


五、效果图



猜你喜欢

转载自blog.csdn.net/qq_34490018/article/details/80205967
今日推荐
火速冲上 GitHub 热榜 —— 开源编程语言、框架哪有这么可爱？
北京人形机器人创新中心发布全球首个纯电驱拟人奔跑的全尺寸人形机器人“天工”
LFOSSA 源来如此公开课 | 掌握云原生未来：CNCF 认证全面攻略与备考秘籍
国产云输入法——仅华为无云端数据上传安全问题
开源日报 | 工业开源项目OGG 1.0；姐姐，你要和我一起配置火狐吗；苹果AI遥遥落后？Fedora 40
开放签电子签章：停止新增，优化体验，前进更进（五一假期前工作）
周排行
Metasploit文件目录与入侵基本概念
跨域(CORS)请求问题[No 'Access-Control-Allow-Origin' header is present on the requested resource]常见解决方案
CodeIgniter 源码解读之 CodeIgniter.php（二）
SAS入门之（四）改变数据类型
初识元组
[数学建模]数学建模算法和模型（B站视频）（二）
Nginx 服务器源码安装配置流程
C#实现语音视频录制 【基于MCapture + MFile】
开发进度4
下载安装vue的方法网址
每日归档
更多
2024-04-28(0)
2024-04-27(56)
2024-04-26(39)
2024-04-25(22)
2024-04-24(36)
2024-04-23(26)
2024-04-22(39)
2024-04-21(0)
2024-04-20(6)
2024-04-19(5)

代码天地 © 2018 codetd.com

境外服务器   最新电视剧2022