FragmentTabHost+Fragment+Viewpage遇到的Fragment重複載入問題
阿新 • • 發佈:2019-02-18
一、在開發App需到底部Tab切換頁面,並能通過手勢左右滑動切換的功能時(類似於微細Android版本的效果),在開發過程首頁展示的fragment頁面需要嵌入地圖,也就是說把地圖放到一個Fragment裡面,還要支援切換,遇到地圖上的Marker總是無法打上,所有的地圖設定都不起作用,當切換地圖時,地圖資料不儲存等一系列問題,通過在網上搜索和摸索現在把所有的問題總結一下。
導致這種情況的元凶就fragment多次建立例項的問題,在使用FragmentTabHost+Fragment+Viewpage時一其有兩個地方法需要引用到Framgent這個類:
1、在FragmentTabHost中增加選項卡時:
public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
}
第二個引數是Class型別,即傳入Fragment.class(),在呼叫.class()方法時,fragment被實便化了一次,其生命週期方法被呼叫一次
2、在Viewpage中新增Fragment項時:
在些使用的FragmentStatePagerAdapter實現類
public class FragmentAdapter extends FragmentStatePagerAdapter { List<Fragment> fragments; private String[] titles = new String[]{}; public FragmentAdapter(FragmentManager fm, List<Fragment> fragments) { super(fm); this.fragments = fragments; } @Override public Fragment getItem(int position) { return fragments.get(position); } @Overridepublic int getCount() { return fragments == null ? 0 : fragments.size(); } @Override public CharSequence getPageTitle(int position) { return titles[position]; } }
1、在其建構函式中有List<Fragment> fragments引數,在這裡面需要傳入new Fragment(),之前在呼叫.class已經建立一個fragment例項,但是我無法在其它容器中找到它,
所以只能new一個,這裡又建立一次,導致其中元素和引數及控制元件都是不唯一的,所有出現了地圖的設定和資料是無效的
2、在切換fragment時總是在重新走oncreateView()方法和其它生命周其方法,導致很多業務受到影響。
二、解決些問題的方向是如何做到只建立一個Fragment並切換時不走其生命週期方法:
1、修改FragmentTabHost類,保留其Tab建立和切換功能
將之前要傳入的Class只接改成Fragment例,我們是能做到Fragment只new一次的,哈哈;
在切換時是通過tag去尋找的,在原碼中寫的是這樣,如果沒有就通過反射來建立一個,這就是fragment第一次例項化的原因
所有我修改其中的TabInfo類
if (newTab.fragment == null) {
newTab.fragment = Fragment.instantiate(mContext,
newTab.clss.getName(), newTab.args);
ft.add(mContainerId, newTab.fragment, newTab.tag);
2、在doTabChanged中使用的是,改成show或hide就不會重新走生命週期方法了
ft.detach(mLastTab.fragment);
//需要改成ft.hide(mLastTab.fragment);
ft.attach(mLastTab.fragment)
//需要改成ft.show(mLastTab.fragment);
最後的改造程式碼如下:import java.util.ArrayList;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.TabHost;
import android.widget.TabWidget;
/**
* Special TabHost that allows the use of {@link Fragment} objects for
* its tab content. When placing this in a view hierarchy, after inflating
* the hierarchy you must call {@link #setup(Context, FragmentManager, int)}
* to complete the initialization of the tab host.
*
* <p>Here is a simple example of using a FragmentTabHost in an Activity:
*
* {@sample development/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentTabs.java
* complete}
*
* <p>This can also be used inside of a fragment through fragment nesting:
*
* {@sample development/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentTabsFragmentSupport.java
* complete}
*/
public class FragmentTabHost extends TabHost
implements TabHost.OnTabChangeListener {
private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>();
private FrameLayout mRealTabContent;
private Context mContext;
private FragmentManager mFragmentManager;
private int mContainerId;
private TabHost.OnTabChangeListener mOnTabChangeListener;
private TabInfo mLastTab;
private boolean mAttached;
static final class TabInfo {
private final String tag;
private final Bundle args;
private final Fragment fragment;
TabInfo(String _tag,Fragment _fragment, Bundle _args) {
tag = _tag;
args = _args;
fragment = _fragment;
}
}
static class DummyTabFactory implements TabHost.TabContentFactory {
private final Context mContext;
public DummyTabFactory(Context context) {
mContext = context;
}
@Override
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
static class SavedState extends BaseSavedState {
String curTab;
SavedState(Parcelable superState) {
super(superState);
}
private SavedState(Parcel in) {
super(in);
curTab = in.readString();
}
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeString(curTab);
}
@Override
public String toString() {
return "FragmentTabHost.SavedState{"
+ Integer.toHexString(System.identityHashCode(this))
+ " curTab=" + curTab + "}";
}
public static final Parcelable.Creator<SavedState> CREATOR
= new Parcelable.Creator<SavedState>() {
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
public FragmentTabHost(Context context) {
// Note that we call through to the version that takes an AttributeSet,
// because the simple Context construct can result in a broken object!
super(context, null);
initFragmentTabHost(context, null);
}
public FragmentTabHost(Context context, AttributeSet attrs) {
super(context, attrs);
initFragmentTabHost(context, attrs);
}
private void initFragmentTabHost(Context context, AttributeSet attrs) {
TypedArray a = context.obtainStyledAttributes(attrs,
new int[] { android.R.attr.inflatedId }, 0, 0);
mContainerId = a.getResourceId(0, 0);
a.recycle();
super.setOnTabChangedListener(this);
}
private void ensureHierarchy(Context context) {
// If owner hasn't made its own view hierarchy, then as a convenience
// we will construct a standard one here.
if (findViewById(android.R.id.tabs) == null) {
LinearLayout ll = new LinearLayout(context);
ll.setOrientation(LinearLayout.VERTICAL);
addView(ll, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.FILL_PARENT));
TabWidget tw = new TabWidget(context);
tw.setId(android.R.id.tabs);
tw.setOrientation(TabWidget.HORIZONTAL);
ll.addView(tw, new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT, 0));
FrameLayout fl = new FrameLayout(context);
fl.setId(android.R.id.tabcontent);
ll.addView(fl, new LinearLayout.LayoutParams(0, 0, 0));
mRealTabContent = fl = new FrameLayout(context);
mRealTabContent.setId(mContainerId);
ll.addView(fl, new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.FILL_PARENT, 0, 1));
}
}
/**
* @deprecated Don't call the original TabHost setup, you must instead
* call {@link #setup(Context, FragmentManager)} or
* {@link #setup(Context, FragmentManager, int)}.
*/
@Override @Deprecated
public void setup() {
throw new IllegalStateException(
"Must call setup() that takes a Context and FragmentManager");
}
public void setup(Context context, FragmentManager manager) {
ensureHierarchy(context); // Ensure views required by super.setup()
super.setup();
mContext = context;
mFragmentManager = manager;
ensureContent();
}
public void setup(Context context, FragmentManager manager, int containerId) {
ensureHierarchy(context); // Ensure views required by super.setup()
super.setup();
mContext = context;
mFragmentManager = manager;
mContainerId = containerId;
ensureContent();
mRealTabContent.setId(containerId);
// We must have an ID to be able to save/restore our state. If
// the owner hasn't set one at this point, we will set it ourself.
if (getId() == View.NO_ID) {
setId(android.R.id.tabhost);
}
}
private void ensureContent() {
if (mRealTabContent == null) {
mRealTabContent = (FrameLayout)findViewById(mContainerId);
if (mRealTabContent == null) {
throw new IllegalStateException(
"No tab content FrameLayout found for id " + mContainerId);
}
}
}
@Override
public void setOnTabChangedListener(OnTabChangeListener l) {
mOnTabChangeListener = l;
}
public void addTab(TabHost.TabSpec tabSpec, Fragment fragment, Bundle args) {
tabSpec.setContent(new DummyTabFactory(mContext));
String tag = tabSpec.getTag();
TabInfo info = new TabInfo(tag, fragment, args);
mTabs.add(info);
addTab(tabSpec);
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
mAttached = false;
}
@Override
protected Parcelable onSaveInstanceState() {
Parcelable superState = super.onSaveInstanceState();
SavedState ss = new SavedState(superState);
ss.curTab = getCurrentTabTag();
return ss;
}
@Override
protected void onRestoreInstanceState(Parcelable state) {
if (!(state instanceof SavedState)) {
super.onRestoreInstanceState(state);
return;
}
SavedState ss = (SavedState) state;
super.onRestoreInstanceState(ss.getSuperState());
setCurrentTabByTag(ss.curTab);
}
@Override
public void onTabChanged(String tabId) {
if (mAttached) {
FragmentTransaction ft = doTabChanged(tabId, null);
if (ft != null) {
ft.commit();
}
}
if (mOnTabChangeListener != null) {
mOnTabChangeListener.onTabChanged(tabId);
}
}
private FragmentTransaction doTabChanged(String tabId, FragmentTransaction ft) {
TabInfo newTab = null;
for (int i=0; i<mTabs.size(); i++) {
TabInfo tab = mTabs.get(i);
if (tab.tag.equals(tabId)) {
newTab = tab;
}
}
if (newTab == null) {
throw new IllegalStateException("No tab known for tag " + tabId);
}
if (mLastTab != newTab) {
if (ft == null) {
ft = mFragmentManager.beginTransaction();
}
if (mLastTab != null) {
if (mLastTab.fragment != null) {
ft.hide(mLastTab.fragment);
}
}
if (newTab != null) {
if (null == mFragmentManager.getFragments() || !mFragmentManager.getFragments().contains(newTab.fragment)) {
ft.add(mContainerId, newTab.fragment, newTab.tag);
} else {
ft.show(newTab.fragment);
}
}
mLastTab = newTab;
}
return ft;
}
}
三、最後是使用高德地圖在切換時黑屏問題
1、使用com.amap.api.maps.TextureSupportMapFragment即可解決
2、由於地圖是可滑動的,這樣就和viewpage產生了衝突,重寫ViewPage即可,尋找到可滾動的View,然後將事件攔截就可完美運行了。
public class ViewPagerCompat extends ViewPager {
public ViewPagerCompat(Context context) {
super(context);
}
public ViewPagerCompat(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
if(v.getClass().getName().contains("com.amap.api")) {
return true;
}
return super.canScroll(v, checkV, dx, x, y);
}
}