activity的onCreateView与Fragment关联的生命周期事件

一时失言乱红尘 2022-11-10 10:58 146阅读 0赞

# Activity #

onCreateView实现：

public View onCreateView(View parent, String name, Context context, AttributeSet attrs) { 
            if (!"fragment".equals(name)) { 
                return onCreateView(name, context, attrs);
            }
    
            return mFragments.onCreateView(parent, name, context, attrs);
        }

# FragmentManager #

mFragments.onCreateView实现：

public View onCreateView(View parent, String name, Context context, AttributeSet attrs) { 
            return mHost.mFragmentManager.onCreateView(parent, name, context, attrs);
        }

mHost.mFragmentManager.onCreateView的实现：

@Override
        public View onCreateView(View parent, String name, Context context, AttributeSet attrs) { 
            if (!"fragment".equals(name)) { 
                return null;
            }
    
            String fname = attrs.getAttributeValue(null, "class");
            TypedArray a =
                    context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.Fragment);
            if (fname == null) { 
                fname = a.getString(com.android.internal.R.styleable.Fragment_name);
            }
            int id = a.getResourceId(com.android.internal.R.styleable.Fragment_id, View.NO_ID);
            String tag = a.getString(com.android.internal.R.styleable.Fragment_tag);
            a.recycle();
    
            int containerId = parent != null ? parent.getId() : 0;
            if (containerId == View.NO_ID && id == View.NO_ID && tag == null) { 
                throw new IllegalArgumentException(attrs.getPositionDescription()
                        + ": Must specify unique android:id, android:tag, or have a parent with"
                        + " an id for " + fname);
            }
    
            // If we restored from a previous state, we may already have
            // instantiated this fragment from the state and should use
            // that instance instead of making a new one.
            Fragment fragment = id != View.NO_ID ? findFragmentById(id) : null;
            if (fragment == null && tag != null) { 
                fragment = findFragmentByTag(tag);
            }
            if (fragment == null && containerId != View.NO_ID) { 
                fragment = findFragmentById(containerId);
            }
    
            if (FragmentManagerImpl.DEBUG) Log.v(TAG, "onCreateView: id=0x"
                    + Integer.toHexString(id) + " fname=" + fname
                    + " existing=" + fragment);
            if (fragment == null) { 
                fragment = mContainer.instantiate(context, fname, null);
                fragment.mFromLayout = true;
                fragment.mFragmentId = id != 0 ? id : containerId;
                fragment.mContainerId = containerId;
                fragment.mTag = tag;
                fragment.mInLayout = true;
                fragment.mFragmentManager = this;
                fragment.mHost = mHost;
                fragment.onInflate(mHost.getContext(), attrs, fragment.mSavedFragmentState);
                addFragment(fragment, true);
            } else if (fragment.mInLayout) { 
                // A fragment already exists and it is not one we restored from
                // previous state.
                throw new IllegalArgumentException(attrs.getPositionDescription()
                        + ": Duplicate id 0x" + Integer.toHexString(id)
                        + ", tag " + tag + ", or parent id 0x" + Integer.toHexString(containerId)
                        + " with another fragment for " + fname);
            } else { 
                // This fragment was retained from a previous instance; get it
                // going now.
                fragment.mInLayout = true;
                fragment.mHost = mHost;
                // If this fragment is newly instantiated (either right now, or
                // from last saved state), then give it the attributes to
                // initialize itself.
                if (!fragment.mRetaining) { 
                    fragment.onInflate(mHost.getContext(), attrs, fragment.mSavedFragmentState);
                }
            }
    
            // If we haven't finished entering the CREATED state ourselves yet,
            // push the inflated child fragment along. This will ensureInflatedFragmentView
            // at the right phase of the lifecycle so that we will have mView populated
            // for compliant fragments below.
            if (mCurState < Fragment.CREATED && fragment.mFromLayout) { 
                moveToState(fragment, Fragment.CREATED, 0, 0, false);
            } else { 
                moveToState(fragment);
            }
    
            if (fragment.mView == null) { 
                throw new IllegalStateException("Fragment " + fname
                        + " did not create a view.");
            }
            if (id != 0) { 
                fragment.mView.setId(id);
            }
            if (fragment.mView.getTag() == null) { 
                fragment.mView.setTag(tag);
            }
            return fragment.mView;
        }

## moveToState ##

moveToState调用了fragment众多的生命周期函数：

Fragment.mState == Fragment.CREATE时
    // 内部会调用Fragment的onCreateView函数， 我们重载的onCreateView函数此时就会被调用
    f.performCreateView(...)
    // 在performCreateView成功之后，立刻就会调用onViewCreated函数
    f.onViewCreated()

此外，Fragment.mState == Fragment.INITIALIZING时，moveToState 内部还会调用onAttach等生命周期函数

# 总结 #

没什么好总结的，了解了一下activity的onCreateView和fragment之间生命周期调用关系