Fragment在FrameLayout

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原创最新推荐文章于 2026-05-13 10:17:33 发布 1.9k 阅读 AI 写同款· GEO 优化 ›

FrameLayout在添加Fragment时的应用之前在用郭霖的《Android第一行代码》学习布局的时候，觉得FrameLayout是一个神奇的布局：“这种布局没有任何的定位方式，所有控件都会摆放在布局的左上角”。当时实在无法想象这种布局是有什么用。直到今天，打算在同一个活动里通过点击按键添加碎片，实现整个屏幕背景的切换——后一个占据整屏的碎片添加进来替换前一个整屏的碎片。于是在activity_main中编写如下代码： <?xml vers 阅读详情

Fragment

API11(Android3.0)中引入了Fragment，由FragmentManager来管理。
Fragment extends object 。
Fragment也是Activity中的一个普通控件而已，只不过它可以像Activity一样用于显示的同时还能用来盛装其它控件，并且有类似Activity的lifecycle。
可被多个Acitivity重用, 在Acitivity运行中动态地移除、加入、交换等。
兼容API11(Android3.0)以前版本使用 v4.app.Fragment，Acitivity需要继承AppCompatActivity，通过getSupportFragmentManager() 获得v4.app.FragmentManager 。
API11(Android3.0)以后可使用 app.Fragment，通过getFragmentManager()获得app.FragmentManager 。

生命周期lifecycle

类似Acitivty，但是由Activity管理，由许多不同点。

简单添加到Activity方法

 private void add() {
        OneFragment oneFragment = OneFragment.newInstance("");
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.add(R.id.fl_container, oneFragment, "one");
        transaction.commit();
    }

将Fragment添加到Activity中，并生效。
重要的类有FragmentManager 和FragmentTransaction，在下面详细分析。

Fragment相关的类及其方法

FragmentManager

FragmentManager是一个抽象类, getFragmentManager()获取的是FragmentManagerImpl ,是一个实现类

//调用层级 最后是FragmentManagerImpl 
getFragmentManager()  
  -->FragmentController(Fragment's lifecycle)
  -->getFragmentManagerImpl()
  -->FragmentHostCallback 
  -->final FragmentManagerImpl mFragmentManager = new FragmentManagerImpl();

FragmentManager.java中定义FragmentManager /FragmentManagerImpl / FragmentManagerState三个类/接口
beginTransaction() 获得FragmentTransaction,FragmentManagerImpl 中的Override的beginTransaction()

 @Override
    public FragmentTransaction beginTransaction() {
        return new BackStackRecord(this);
    }

findFragmentById(@IdRes int id) 相同id ,取第一个找到的,一般就是最上面的。
findFragmentByTag（String tag）相同tag,取第一个找到的,一般就是最上面的。
getFragments() 返回ArrayList< Fragment > mActive; 可能存在null
持有一个BackStackRecord的列表 ArrayList< BackStackRecord > mBackStackIndices

FragmentTransaction

add 和 replace 影响的只是界面，而控制回退的，是事务
FragmentTransaction 是一个抽象类, beginTransaction()获取的是BackStackRecord,是一个实现类
BackStackRecord extends FragmentTransaction
add 和 replace 影响的只是界面，而控制回退的是事务,add 和 replace最后调用addOp(Op op)

addOp(Op op) 添加到队列mOps中,通过commit才会提交

void addOp(Op op) {
      mOps.add(op);
      op.enterAnim = mEnterAnim;
      op.exitAnim = mExitAnim;
      op.popEnterAnim = mPopEnterAnim;
      op.popExitAnim = mPopExitAnim;
  }

addToBackStack(将事务添加到回退栈里)

@Override
  public FragmentTransaction addToBackStack(String name) {
      if (!mAllowAddToBackStack) {
          throw new IllegalStateException(
                  "This FragmentTransaction is not allowed to be added to the back stack.");
      }
      mAddToBackStack = true;
      mName = name;
      return this;
  }

commit (提交到处理队列里,默认不会添加到回退栈,默认等待执行),调用commitInternal(false)

int commitInternal(boolean allowStateLoss) {
      if (mCommitted) throw new IllegalStateException("commit already called");
      if (FragmentManagerImpl.DEBUG) {
          Log.v(TAG, "Commit: " + this);
          LogWriter logw = new LogWriter(TAG);
          PrintWriter pw = new PrintWriter(logw);
          dump("  ", null, pw, null);
          pw.close();
      }
      mCommitted = true;
      if (mAddToBackStack) {
          mIndex = mManager.allocBackStackIndex(this);
      } else {
          mIndex = -1;
      }
      mManager.enqueueAction(this, allowStateLoss);
      return mIndex;
  }

add

add(@IdRes int containerViewId, Fragment fragment)
可能出现 Fragment already added 错误,原因:add 已经add的fragment(hashcode一样)
lifecycle方法调用情况

10-23 17:01:58.737 13673-13673/com.wega.android E/Frag+Frame: OneFragment==null==OneFragment
10-23 17:01:58.743 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onAttach
10-23 17:01:58.744 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onCreate
10-23 17:01:58.744 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onCreateView
10-23 17:01:58.753 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onActivityCreated
10-23 17:01:58.753 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onStart
10-23 17:01:58.753 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onResume

在add 前需要new Fragment() ,但是new不会调起Framgent生命周期动作如:oncreate ,而 Acitivty不需要我们new的,是由系统创建的.

remove

remove(Fragment fragment)
Remove an existing fragment
先获得已存在fragment才能remove 不能传空值
通过findFragmentById() findFragmentByTag()获得已存在fragment
lifecycle方法调用情况

10-23 17:02:55.873 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onPause
10-23 17:02:55.874 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onStop
10-23 17:02:55.874 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onDestroyView
10-23 17:02:55.874 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onDestroy
10-23 17:02:55.874 13673-13673/com.wega.android E/Frag+Frame: OneFragment==0==onDetach

replace

replace(@IdRes int containerViewId, Fragment fragment)
不能传空值
先remove掉相同id的所有fragment，然后在add当前的这个fragment
add 和 remove 结合
lifecycle方法调用情况

10-23 17:07:11.092 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==OneFragment
10-23 17:07:11.098 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onAttach
10-23 17:07:11.098 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onCreate
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==0==onPause
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==0==onStop
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==0==onDestroyView
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==0==onDestroy
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==0==onDetach
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onCreateView
10-23 17:07:11.099 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onActivityCreated
10-23 17:07:11.100 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onStart
10-23 17:07:11.100 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onResume

hide

hide(Fragment fragment)
与show一起作用
hide 已经添加的fragment 不能传空值
hide fragment 不会调用生命周期

show

show(Fragment fragment)
与hide一起作用
This is only relevant for fragments whose views have been added to a container
show已经hide的fragment
show fragment 不会调用生命周期

detach

detach(Fragment fragment)
与attach一起作用
不能传空值
lifecycle方法调用情况

10-23 17:07:41.687 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onPause
10-23 17:07:41.687 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onStop
10-23 17:07:41.687 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onDestroyView

attach

-attach(Fragment fragment)
- 与detach一起作用
- 不能传空值
- lifecycle方法调用情况

10-23 17:07:56.420 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onCreateView
10-23 17:07:56.420 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onActivityCreated
10-23 17:07:56.421 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onStart
10-23 17:07:56.421 24280-24280/com.wega.android E/Frag+Frame: OneFragment==null==onResume

重建切屏

Fragment也有onSaveInstanceState的方法，在此方法中进行保存数据，然后在onCreate或者onCreateView或者onActivityCreated进行恢复都可以。

 @Override
    public void onSaveInstanceState(Bundle outState) {
        outState.putString("name", "save");
        super.onSaveInstanceState(outState);

        Log.e("Activity", TAG +"=="+mTag1+"=="+"onSaveInstanceState"+"=="+outState.getString("name"));
    }
 @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(savedInstanceState!=null)
        {
            Log.e("Activity", TAG +"=="+mTag1+"=="+"onCreate"+"=="+savedInstanceState.getString("name"));
        }
        Bundle arguments = getArguments();
        if(arguments!=null)
        {
            mTag1 = arguments.getString("tag");
        }
        Log.e("Activity", TAG +"=="+mTag1+"=="+"onCreate");
    }

demo源码

FragmentActivity

package com.wega.android.fragment;

import android.content.DialogInterface;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

import com.wega.android.R;

import java.util.List;

public class FragmentActivity extends AppCompatActivity implements View.OnClickListener {

    private String LOG_TAG="Frag+Frame";

    private FragmentManager mManager;
    private OneFragment mOneFragment;
    private String TAG;
    private int num;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment);
        mManager = getSupportFragmentManager();
        TAG = this.getClass().getSimpleName();
        if (savedInstanceState == null) {
            Log.e(LOG_TAG, TAG + "==onCreate");
        } else {

            String name = savedInstanceState.getString("name");
            Log.e(LOG_TAG, TAG + "==onCreate==name==" + name);
        }
        findViewById(R.id.add).setOnClickListener(this);
        findViewById(R.id.remove).setOnClickListener(this);
        findViewById(R.id.replace).setOnClickListener(this);
        findViewById(R.id.log).setOnClickListener(this);
        findViewById(R.id.show).setOnClickListener(this);
        findViewById(R.id.hide).setOnClickListener(this);
        findViewById(R.id.attach).setOnClickListener(this);
        findViewById(R.id.detach).setOnClickListener(this);
    }


    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.add:
                add();
                break;
            case R.id.remove:
                remove();
                break;
            case R.id.replace:
                replace();
                break;
            case R.id.show:
                show();
                break;
            case R.id.hide:
                hide();
                break;
            case R.id.log:
                getFragmentList();
                break;
            case R.id.attach:
                attach();
                break;
            case R.id.detach:
                detach();
                break;
        }
    }



    private void add() {

        OneFragment oneFragment = OneFragment.newInstance("" + num++);
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.add(R.id.fl_container, oneFragment, "one");
        transaction.commit();
    }


    private void remove(){
        Fragment fragmentById = mManager.findFragmentById(R.id.fl_container);
        FragmentTransaction transaction = mManager.beginTransaction();
        if(fragmentById!=null)
        {
            transaction.remove(fragmentById);
        }
        transaction.commit();
    }


    private void replace() {

        if (mOneFragment == null) {
            mOneFragment = new OneFragment();
        }
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.replace(R.id.fl_container, mOneFragment);
        transaction.commit();

    }


    private void show() {
        Fragment fragmentById = mManager.findFragmentById(R.id.fl_container);
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.show(fragmentById);
        transaction.commit();
    }


    private void hide() {
        Fragment fragmentById = mManager.findFragmentById(R.id.fl_container);
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.hide(fragmentById);
        transaction.commit();
    }

    private void attach() {
        Fragment fragmentById = mManager.findFragmentById(R.id.fl_container);
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.attach(fragmentById);
        transaction.commit();
    }

    private void detach() {
        Fragment fragmentById = mManager.findFragmentById(R.id.fl_container);
        FragmentTransaction transaction = mManager.beginTransaction();
        transaction.detach(fragmentById);
        transaction.commit();
    }

    private void getFragmentList() {
        Fragment fragment = mManager.findFragmentById(R.id.fl_container);
        Fragment fragment1 = mManager.findFragmentByTag("one");
        if (fragment != null) {
            Log.e("fragment", "findFragmentById=" + fragment.toString());
        }

        if (fragment1 != null) {
            Log.e("fragments1", "findFragmentByTag=" + fragment1.toString());
        }

        List<Fragment> fragments = mManager.getFragments();
        if (fragments == null) {
            return;
        }

        for (int i = 0; i < fragments.size(); i++) {

            if (fragments.get(i) == null) {
                Log.e("fragments", "null");
            } else {
                Log.e("fragments", fragments.get(i).toString());
            }

        }
        Log.e("fragments", "==========");

    }

}

OneFragment

package com.wega.android.fragment;


import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.wega.android.R;


/**
 * A simple {@link Fragment} subclass.
 */
public class OneFragment extends Fragment {


    private String TAG;
    private String LOG_TAG="Frag+Frame";
    private String mTag1;

    public OneFragment() {
        TAG =this.getClass().getSimpleName();
        Bundle arguments = getArguments();
        if(arguments!=null)
        {
            mTag1 = arguments.getString("tag");
        }
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"OneFragment");
    }

    public static OneFragment newInstance(String tag) {

        Bundle args = new Bundle();
        args.putString("tag",tag);
        OneFragment fragment = new OneFragment();
        fragment.setArguments(args);
        return fragment;
    }




    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Bundle arguments = getArguments();
        if(arguments!=null)
        {
            mTag1 = arguments.getString("tag");
        }
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onAttach");
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if(savedInstanceState!=null)
        {
            Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onCreate"+"=="+savedInstanceState.getString("name"));
        }
        Bundle arguments = getArguments();
        if(arguments!=null)
        {
            mTag1 = arguments.getString("tag");
        }
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onCreate");

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        TAG =this.getClass().getSimpleName();
        Bundle arguments = getArguments();
        if(arguments!=null)
        {
            mTag1 = arguments.getString("tag");
        }
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onCreateView");
        View inflate = inflater.inflate(R.layout.fragment_one, container, false);
        TextView viewById = (TextView) inflate.findViewById(R.id.tv_hashcode);
        viewById.setText(this.toString()+"tag=="+mTag1);
        return inflate;
    }


    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onActivityCreated");
    }

    @Override
    public void onStart() {
        super.onStart();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onStart");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onResume");
    }


    @Override
    public void onPause() {
        super.onPause();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onPause");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onStop");
    }


    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onDestroyView");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onDestroy");
    }


    @Override
    public void onDetach() {
        super.onDetach();
        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onDetach");
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        outState.putString("name", "save");
        super.onSaveInstanceState(outState);

        Log.e(LOG_TAG, TAG +"=="+mTag1+"=="+"onSaveInstanceState"+"=="+outState.getString("name"));
    }



}