FragmentManager分析(个人笔记)

最新推荐文章于 2024-04-27 13:50:26 发布

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最新推荐文章于 2024-04-27 13:50:26 发布

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本文链接：https://blog.youkuaiyun.com/u012198036/article/details/51295735

本文详细分析了在Android中如何使用FragmentManager动态添加Fragment，包括getFragmentManager、事务操作如add和commit，以及从父Fragment添加子Fragment的特殊之处。

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在Activity中动态添加Fragment:

FragmentTransaction transaction = getFragmentManager().beginTransaction();
        transaction.add(R.id.content, fragment);
        transaction.commit();

1.getFragmentManager():

final FragmentController mFragments = FragmentController.createController(new HostCallbacks());//Activity通过FragmentController来控制Fragment

public FragmentManager getFragmentManager() {
        return mFragments.getFragmentManager();
    }

HostCallbacks():

public HostCallbacks() {
            super(Activity.this /*activity*/);
        }

FragmentHostCallback(Activity activity) {
        this(activity, activity /*context*/, activity.mHandler, 0 /*windowAnimations*/);
    }

    FragmentHostCallback(Activity activity, Context context, Handler handler,
            int windowAnimations) {
        mActivity = activity;//持有当前Activity
        mContext = context;
        mHandler = handler;
        mWindowAnimations = windowAnimations;
    }

createController():

 public static final FragmentController createController(FragmentHostCallback<?> callbacks) {
        return new FragmentController(callbacks);
    }

private FragmentController(FragmentHostCallback<?> callbacks) {
        mHost = callbacks;//持有HostCallbacks,HostCallbacks持有Activity
    }

final FragmentManagerImpl mFragmentManager = new FragmentManagerImpl();

FragmentManagerImpl getFragmentManagerImpl() {
        return mFragmentManager;//这就是Activity中getFragmentManager()最后得到的
    }

2.beginTransaction()

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

public BackStackRecord(FragmentManagerImpl manager) {
        mManager = manager;//BackStackRecord是FragmentTransaction的实现类,持有FragmentManager
    }

3.add()

public FragmentTransaction add(Fragment fragment, String tag) {
        doAddOp(0, fragment, tag, OP_ADD);
        return this;
    }

  private void doAddOp(int containerViewId, Fragment fragment, String tag, int opcmd) {
        fragment.mFragmentManager = mManager;

        if (tag != null) {
            if (fragment.mTag != null && !tag.equals(fragment.mTag)) {
                throw new IllegalStateException("Can't change tag of fragment "
                        + fragment + ": was " + fragment.mTag
                        + " now " + tag);
            }
            fragment.mTag = tag;
        }

        if (containerViewId != 0) {
            if (fragment.mFragmentId != 0 && fragment.mFragmentId != containerViewId) {
                throw new IllegalStateException("Can't change container ID of fragment "
                        + fragment + ": was " + fragment.mFragmentId
                        + " now " + containerViewId);
            }
            fragment.mContainerId = fragment.mFragmentId = containerViewId;
        }

        Op op = new Op();//系列操作的子节点
        op.cmd = opcmd;
        op.fragment = fragment;
        addOp(op);
    }

void addOp(Op op) {//双向链表结构
        if (mHead == null) {
            mHead = mTail = op;
        } else {
            op.prev = mTail;
            mTail.next = op;
            mTail = op;
        }
        op.enterAnim = mEnterAnim;
        op.exitAnim = mExitAnim;
        op.popEnterAnim = mPopEnterAnim;
        op.popExitAnim = mPopExitAnim;
        mNumOp++;
    }

4.commit()

public int commit() {
        return 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(Log.VERBOSE, TAG);
            PrintWriter pw = new FastPrintWriter(logw, false, 1024);
            dump("  ", null, pw, null);
            pw.flush();
        }
        mCommitted = true;
        if (mAddToBackStack) {
            mIndex = mManager.allocBackStackIndex(this);
        } else {
            mIndex = -1;
        }
        mManager.enqueueAction(this, allowStateLoss);
        return mIndex;
    }

public void enqueueAction(Runnable action, boolean allowStateLoss) {
        if (!allowStateLoss) {
            checkStateLoss();
        }
        synchronized (this) {
            if (mDestroyed || mHost == null) {
                throw new IllegalStateException("Activity has been destroyed");
            }
            if (mPendingActions == null) {
                mPendingActions = new ArrayList<Runnable>();
            }
            mPendingActions.add(action);
            if (mPendingActions.size() == 1) {
                mHost.getHandler().removeCallbacks(mExecCommit);
                mHost.getHandler().post(mExecCommit);//将Runnable对象入队到mHost.getHandler()的消息队列中
            }
        }
    }

//mHost的由来

 public void attachController(FragmentHostCallback<?> host, FragmentContainer container,
            Fragment parent) {
        if (mHost != null) throw new IllegalStateException("Already attached");
        mHost = host; //FragmentManagerImpl中对mHost的赋值
        mContainer = container;
        mParent = parent;
    }

public void attachHost(Fragment parent) {
        mHost.mFragmentManager.attachController(
                mHost, mHost /*container*/, parent);//FragmentController中对attachController的调用,由上面可知,mHost是在Activity中创建FragmentController对象的时候传入的HostCallbacks对象
    }

//什么时候赋值mHost
final void attach(Context context, ActivityThread aThread,
            Instrumentation instr, IBinder token, int ident,
            Application application, Intent intent, ActivityInfo info,
            CharSequence title, Activity parent, String id,
            NonConfigurationInstances lastNonConfigurationInstances,
            Configuration config, String referrer, IVoiceInteractor voiceInteractor) {
        attachBaseContext(context);

        mFragments.attachHost(null /*parent*/);//Activity中通过attach()去调用FragmentController中的attachHost(),传入null,最后会赋值给FragmentManager的mParent
        ...
    }

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
                    ...
        // System.out.println("##### [" + System.currentTimeMillis() + "] 
                activity.attach(appContext, this, getInstrumentation(), r.token,
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstances, config,
                        r.referrer, r.voiceInteractor);//ActivityThread中调用Activity的attach(),而这里的performLaunchActivity()是应用启动的时候调用
                        ...          
                return activity;
    }

/** 真正操作Fragment的地方 */
void moveToState(Fragment f, int newState, int transit, int transitionStyle,
            boolean keepActive) {
            ...
            switch (f.mState) {
                case Fragment.INITIALIZING: /* Fragment初始化,还没创建 */
                    if (DEBUG) Log.v(TAG, "moveto CREATED: " + f);
                    if (f.mSavedFragmentState != null) {
                        f.mSavedViewState = f.mSavedFragmentState.getSparseParcelableArray(
                                FragmentManagerImpl.VIEW_STATE_TAG);
                        f.mTarget = getFragment(f.mSavedFragmentState,
                                FragmentManagerImpl.TARGET_STATE_TAG);
                        if (f.mTarget != null) {
                            f.mTargetRequestCode = f.mSavedFragmentState.getInt(
                                    FragmentManagerImpl.TARGET_REQUEST_CODE_STATE_TAG, 0);
                        }
                        f.mUserVisibleHint = f.mSavedFragmentState.getBoolean(
                                FragmentManagerImpl.USER_VISIBLE_HINT_TAG, true);
                        if (!f.mUserVisibleHint) {
                            f.mDeferStart = true;
                            if (newState > Fragment.STOPPED) {
                                newState = Fragment.STOPPED;
                            }
                        }
                    }
                    f.mHost = mHost;//持有Activity的Fragment回调类
                    f.mParentFragment = mParent;//Activity添加,值为null,由Fragment添加,值为父Fragment
                    f.mFragmentManager = mParent != null
                            ? mParent.mChildFragmentManager : mHost.getFragmentManagerImpl();//由此可知,Fragment.getFragmentManager()返回的父类的FragmentManager()
                    f.mCalled = false;
                    f.onAttach(mHost.getContext());//绑定Fragment和Activity
                    if (!f.mCalled) {
                        throw new SuperNotCalledException("Fragment " + f
                                + " did not call through to super.onAttach()");
                    }
                    if (f.mParentFragment == null) { /*没有父Fragment,回调Activity的onAttachFragment()*/
                        mHost.onAttachFragment(f);
                    }

                    if (!f.mRetaining) {
                        f.performCreate(f.mSavedFragmentState);
                    }
                    f.mRetaining = false;
                    if (f.mFromLayout) {
                        // For fragments that are part of the content view
                        // layout, we need to instantiate the view immediately
                        // and the inflater will take care of adding it.
                        f.mView = f.performCreateView(f.getLayoutInflater(
                                f.mSavedFragmentState), null, f.mSavedFragmentState);
                        if (f.mView != null) {
                            f.mView.setSaveFromParentEnabled(false);
                            if (f.mHidden) f.mView.setVisibility(View.GONE);
                            f.onViewCreated(f.mView, f.mSavedFragmentState);
                        }
                    }
                case Fragment.CREATED://Fragment创建
                    if (newState > Fragment.CREATED) {
                        if (DEBUG) Log.v(TAG, "moveto ACTIVITY_CREATED: " + f);
                        if (!f.mFromLayout) {
                            ViewGroup container = null;
                            if (f.mContainerId != 0) {
                                container = (ViewGroup)mContainer.onFindViewById(f.mContainerId);
                                if (container == null && !f.mRestored) {
                                    throwException(new IllegalArgumentException(
                                            "No view found for id 0x"
                                            + Integer.toHexString(f.mContainerId) + " ("
                                            + f.getResources().getResourceName(f.mContainerId)
                                            + ") for fragment " + f));
                                }
                            }
                            f.mContainer = container;
                            f.mView = f.performCreateView(f.getLayoutInflater(
                                    f.mSavedFragmentState), container, f.mSavedFragmentState);//回调Fragment的onCreateView()
                            if (f.mView != null) {
                                f.mView.setSaveFromParentEnabled(false);
                                if (container != null) {
                                    Animator anim = loadAnimator(f, transit, true,
                                            transitionStyle);
                                    if (anim != null) {
                                        anim.setTarget(f.mView);
                                        setHWLayerAnimListenerIfAlpha(f.mView, anim);
                                        anim.start();
                                    }
                                    container.addView(f.mView);//将Fragment的View添加到父类的布局中
                                }
                                if (f.mHidden) f.mView.setVisibility(View.GONE);
                                f.onViewCreated(f.mView, f.mSavedFragmentState);//回调Fragment的onViewCreated()
                            }
                        }

                        f.performActivityCreated(f.mSavedFragmentState);//回调Fragment的onActivityCreated()
                        if (f.mView != null) {
                            f.restoreViewState(f.mSavedFragmentState);
                        }
                        f.mSavedFragmentState = null;
                    }
               ...

               /*其他Fragment的生命周期函数回调类似*/
    }