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嵌套Tab在Android應(yīng)用中用途廣泛，之前做過(guò)的一些東西都是運(yùn)用了TabActivity。但是由于在Android Developers中說(shuō)到了“TabActivity was deprecated in API level 13." ，并且建議大家使用Fragment。所以學(xué)習(xí)了嵌套Fragment的使用，參考了這個(gè)博客中的相關(guān)思路和代碼。

在Android Developers中對(duì)于Fragment（中文版看這里）的描述：A Fragment represents a behaviors or a portion of user interface in an Activity. You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities. You can think of a fragment as a modular section of an activity, which has its own lifecycle, receives its own input events, and which you can add or remove while the activity is running.

簡(jiǎn)單來(lái)說(shuō)，F(xiàn)ragment就是被嵌入在Activity中用來(lái)表現(xiàn)UI的一個(gè)可模塊化和可重用的組件。Fragment在大屏幕設(shè)備中應(yīng)用可以非常廣泛，開(kāi)發(fā)者可以通過(guò)自己巧妙的設(shè)計(jì)讓UI更加靈活和美觀。

創(chuàng)建Fragment

創(chuàng)建Fragment，必須創(chuàng)建一個(gè)Fragment的子類(lèi)。

創(chuàng)建一個(gè)自己的Fragment，需要?jiǎng)?chuàng)建一個(gè)Fragment的子類(lèi)。Fragment的生命周期和Activity的生命周期類(lèi)似，它包含了很多與Activity類(lèi)似的回調(diào)函數(shù)。

[java] view plaincopy

public void onCreate (Bundle savedInstanceState)

創(chuàng)建fragment的時(shí)候調(diào)用onCreate()方法

[java] view plaincopy

public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)

在第一次繪制UI的時(shí)候系統(tǒng)調(diào)用該方法，為了繪制UI，返回一個(gè)fragment布局的根View。

將Fragment添加到Activity的方法

1.在layout文件中聲明fragment

[plain] view plaincopy

<FrameLayout
android:id="@+id/fragment_container"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1.0"
android:background="#fffab3" >
</FrameLayout>

2.將一個(gè)fragment添加到viewgroup中，使用FragmentTransaction添加、替換或者刪除fragment。

[java] view plaincopy

private void addFragmentToStack(Fragment fragment) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.fragment_container, fragment);
ft.commit();
}

Fragment生命周期

異常分析

關(guān)于解決 java.lang.IllegalStateException The specified child already has a parent. You must call removeView()的方法

在運(yùn)行調(diào)試的時(shí)候會(huì)發(fā)現(xiàn)，在第二次點(diǎn)擊一個(gè)相同的tab的時(shí)候，會(huì)出現(xiàn)上述異常。

這個(gè)異常說(shuō)的是，這個(gè)特定的child view已經(jīng)存在一個(gè)parent view了，必須讓parent view調(diào)用removeView()方法。

經(jīng)過(guò)對(duì)fragment的生命周期的分析

運(yùn)行順序：點(diǎn)擊tab1，點(diǎn)擊tab2，再點(diǎn)擊tab1.

具體fragment的生命周期是：

對(duì)上圖進(jìn)行分析，可以發(fā)現(xiàn)，出問(wèn)題的是viewpager中的view。當(dāng)切換不同的viewpager（即fragment,每個(gè)fragment中裝載了一個(gè)viewpager）時(shí)，調(diào)用了startActivity()方法的時(shí)候，傳入了相同的id，會(huì)返回相同的對(duì)象。而當(dāng)我們?cè)诘诙握{(diào)用的時(shí)候，傳入了相同的id是復(fù)用了原來(lái)的view，這就導(dǎo)致了view被指定多個(gè)parent view。

所以解決辦法就是，在使用這個(gè)view之前首先判斷其是否存在parent view，這調(diào)用getParent()方法可以實(shí)現(xiàn)。如果存在parent view，那么就調(diào)用removeAllViewsInLayout()方法。代碼如下：

[java] view plaincopy

for (View view : viewList) {
ViewGroup p = (ViewGroup) view.getParent();
if (p != null) {
p.removeAllViewsInLayout();
}
}

結(jié)果展示

完成之后在模擬器中運(yùn)行的效果如圖：

主要代碼

PS：完整工程點(diǎn)這里下載

TestFragmentActivity.java

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package com.test;
import java.util.ArrayList;
import android.annotation.SuppressLint;
import android.app.LocalActivityManager;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.LinearLayout;
/**
* 嵌套Fragment的使用
*
* @author zouliping
*
*/
public class TestFragmentActivity extends FragmentActivity {
private LocalActivityManager manager;
private ArrayList<View> list1 = new ArrayList<View>();
private ArrayList<View> list2 = new ArrayList<View>();
private ArrayList<View> list3 = new ArrayList<View>();
private Fragment[] fragments;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.test_fragments);
manager = new LocalActivityManager(this, false);
manager.dispatchCreate(savedInstanceState);
initViews();
}
/**
* 初始化Views
*/
private void initViews() {
findViewById(R.id.tv1).setOnClickListener(listener);
findViewById(R.id.tv2).setOnClickListener(listener);
findViewById(R.id.tv3).setOnClickListener(listener);
fragments = new FragmentParent[3];
fragments[0] = FragmentParent.newInstance(list1, new String[] {
"page1_1", "page1_2", "page1_3" });
fragments[1] = FragmentParent.newInstance(list2, new String[] {
"page2_1", "page2_2", "page2_3" });
fragments[2] = FragmentParent.newInstance(list3, new String[] {
"page3_1", "page3_2", "page3_3" });
initPager();
findViewById(R.id.tv1).performClick();
}
/**
* 獲取view
*
* @param id
* @param intent
* @return
*/
private View getView(String id, Intent intent) {
return manager.startActivity(id, intent).getDecorView();
}
/**
* 根據(jù)parent position初始化viewPager
*/
private void initPager() {
Intent intent;
// tab1
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list1.add(getView("tab1_1", intent));
intent = new Intent(TestFragmentActivity.this, Test2Activity.class);
list1.add(getView("tab1_2", intent));
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list1.add(getView("tab1_3", intent));
// tab2
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list2.add(getView("tab2_1", intent));
intent = new Intent(TestFragmentActivity.this, Test2Activity.class);
list2.add(getView("tab2_2", intent));
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list2.add(getView("tab2_3", intent));
// tab3
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list3.add(getView("tab2_1", intent));
intent = new Intent(TestFragmentActivity.this, Test2Activity.class);
list3.add(getView("tab2_2", intent));
intent = new Intent(TestFragmentActivity.this, Test1Activity.class);
list3.add(getView("tab2_3", intent));
}
private OnClickListener listener = new OnClickListener() {
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.tv1:
addFragmentToStack(fragments[0]);
break;
case R.id.tv2:
addFragmentToStack(fragments[1]);
break;
case R.id.tv3:
addFragmentToStack(fragments[2]);
break;
}
}
};
private void addFragmentToStack(Fragment fragment) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.replace(R.id.fragment_container, fragment);
ft.commit();
}
/**
* 嵌套Fragment
*
*/
@SuppressLint("ValidFragment")
public final static class FragmentParent extends Fragment {
/**
* 工廠方法，返回一個(gè)新的FragmentParent的實(shí)例
*
* @param list
* @param str
* @return
*/
public static final FragmentParent newInstance(ArrayList<View> list,
String[] str) {
FragmentParent framentParent = new FragmentParent();
Bundle bundle = new Bundle();
bundle.putSerializable("pager_view_list", list);
bundle.putStringArray("pager_title_ary", str);
framentParent.setArguments(bundle);
return framentParent;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d("test fragment", "fragment create view");
LinearLayout convertView = (LinearLayout) inflater.inflate(
R.layout.viewpager_fragments, container, false);
ViewPager pager = (ViewPager) convertView.findViewById(R.id.pager);
@SuppressWarnings("unchecked")
final ArrayList<View> viewList = (ArrayList<View>) getArguments()
.getSerializable("pager_view_list");
final String[] titles = getArguments().getStringArray(
"pager_title_ary");
for (View view : viewList) {
ViewGroup p = (ViewGroup) view.getParent();
if (p != null) {
p.removeAllViewsInLayout();
}
}
pager.setAdapter(new PagerAdapter() {
@Override
public boolean isViewFromObject(View view, Object obj) {
return view == obj;
}
@Override
public int getCount() {
return viewList.size();
}
@Override
public void destroyItem(ViewGroup container, int position,
Object object) {
container.removeView(viewList.get(position));
}
@Override
public CharSequence getPageTitle(int position) {
return titles[position];
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
container.addView(viewList.get(position));
return viewList.get(position);
}
});
return convertView;
}
@Override
public void onStart() {
super.onStart();
Log.d("test fragment", "fregment start");
}
@Override
public void onStop() {
super.onStop();
Log.d("test fragment", "fregment stop");
}
@Override
public void onResume() {
super.onResume();
Log.d("test fragment", "fregment resume");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d("test fragment", "fregment destroy");
}
@Override
public void onDetach() {
super.onDetach();
Log.d("test fragment", "fregment detach");
}
}
}

布局文件 test_fragments.xml

[plain] view plaincopy

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<FrameLayout
android:id="@+id/fragment_container"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1.0"
android:background="#fffab3" >
</FrameLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="@android:color/black"
android:orientation="horizontal" >
<TextView
android:id="@+id/tv1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:text="tab1"
android:textColor="#ffffff"
android:textIsSelectable="true"
android:textSize="25sp" />
<TextView
android:id="@+id/tv2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="15dp"
android:layout_marginTop="10dp"
android:text="tab2"
android:textColor="#ffffff"
android:textIsSelectable="true"
android:textSize="25sp" />
<TextView
android:id="@+id/tv3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginLeft="15dp"
android:layout_marginTop="10dp"
android:text="tab3"
android:textColor="#ffffff"
android:textIsSelectable="true"
android:textSize="25sp" />
</LinearLayout>
</LinearLayout>

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創(chuàng)建Fragment

將Fragment添加到Activity的方法

Fragment生命周期

異常分析

結(jié)果展示

主要代碼