利用Fragment实现Tab选项卡效果：
将RadioGroup与Fragment集合，实现tab选项卡效果，这里面最关键的几个文件：
1.FragmentTabAdapter类：
public class FragmentTabAdapter implements RadioGroup.onCheckedChangeListener
{
private List fragments; // 一个tab页面对应一个Fragment
private RadioGroup rgs; // 用于切换tab
private Activity activity; // Fragment所属的Activity
private int fragmentContentId; // Activity中所要被替换的区域的id
private int currentTab; // 当前Tab页面索引
private onRgsExtraCheckedChangedListener onRgsExtraCheckedChangedListener; // 用于让调用者在切换tab时候增加新的功能
public FragmentTabAdapter(Activity activity, List fragments, int fragmentContentId, RadioGroup rgs)
{
this.fragments = fragments;
this.rgs = rgs;
this.activity = activity;
this.fragmentContentId = fragmentContentId;
// 默认显示第一页
android.app.FragmentTransaction ft = activity.getFragmentManager().beginTransaction();
ft.add(fragmentContentId, fragments.get(0));
ft.commit();
rgs.setonCheckedChangeListener(this);
}
@Override
public void onCheckedChanged(RadioGroup radioGroup, int checkedId)
{
for(int i = 0; i < rgs.getChildCount(); i++)
{
if(rgs.getChildAt(i).getId() == (checkedId))
{
Fragment fragment = fragments.get(i);
FragmentTransaction ft = activity.getFragmentManager().beginTransaction();
getCurrentFragment().onPause(); // 暂停当前tab
// getCurrentFragment().onStop(); // 暂停当前tab
if(fragment.isAdded())
{
// fragment.onStart(); // 启动目标tab的onStart()
fragment.onResume(); // 启动目标tab的onResume()
}
else
{
ft.add(fragmentContentId, fragment);
}
showTab(i); // 显示目标tab
ft.commit();
// 如果设置了切换tab额外功能功能接口
if(null != onRgsExtraCheckedChangedListener)
{
onRgsExtraCheckedChangedListener.onRgsExtraCheckedChanged(radioGroup, checkedId, i);
}
}
}
}
private void showTab(int idx)
{
for(int i = 0; i < fragments.size(); i++)
{
Fragment fragment = fragments.get(i);
FragmentTransaction ft = activity.getFragmentManager().beginTransaction();
if(idx == i)
{
ft.show(fragment);
}
else
{
ft.hide(fragment);
}
ft.commit();
}
currentTab = idx; // 更新目标tab为当前tab
}
public int getCurrentTab()
{
return currentTab;
}
public Fragment getCurrentFragment()
{
return fragments.get(currentTab);
}
public onRgsExtraCheckedChangedListener getonRgsExtraCheckedChangedListener()
{
return onRgsExtraCheckedChangedListener;
}
public void setonRgsExtraCheckedChangedListener(onRgsExtraCheckedChangedListener onRgsExtraCheckedChangedListener)
{
this.onRgsExtraCheckedChangedListener = onRgsExtraCheckedChangedListener;
}
public interface onRgsExtraCheckedChangedListener
{
void onRgsExtraCheckedChanged(RadioGroup radioGroup, int checkedId, int index);
}
}
2.activity_main.xml布局文件：
3.MainActivity类：
public class MainActivity extends Activity
{
private RadioGroup rgs;
private List fragments = new ArrayList();
private int index;
private static Boolean isExit = false;
private static Boolean hasTask = false;
private RadioButton button;
private Timer tExit = new Timer();
private TimerTask task = new TimerTask()
{
@Override
public void run()
{
isExit = false;
hasTask = true;
}
};
private FragmentTabAdapter tabAdapter;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragments.add(new FragmentOne());
fragments.add(new FragmentTwo());
fragments.add(new FragmentThree());
rgs = (RadioGroup) findViewById(R.id.tabs_rg);
button = (RadioButton) findViewById(R.id.tab_rb_a);
tabAdapter = new FragmentTabAdapter(this, fragments, R.id.tab_content, rgs);
tabAdapter.setonRgsExtraCheckedChangedListener(new FragmentTabAdapter.onRgsExtraCheckedChangedListener()
{
@Override
public void onRgsExtraCheckedChanged(RadioGroup radioGroup, int checkedId, int index)
{
// 利用这个index可以实现，如果不是在主页，按第一遍让它先跳转到第一个Fragment
System.out.println("Extra---- " + index + " checked!!! ");
MainActivity.this.index = index;
}
});
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if(keyCode == KeyEvent.KEYCODE_BACK)
{
if(index == 0)
{
if(isExit == false)
{
isExit = true;
Toast.makeText(MainActivity.this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
if(!hasTask)
{
tExit.schedule(task, 1000);
}
}
else
{
finish();
System.exit(0);
}
}
else
{
// 如果不是在主页，按第一遍让它先跳转到第一个Fragment
// 利用上面的check方法会导致onCheckedChanged方法被执行多次
// rgs.check(button.getId());
button.setChecked(true);
}
}
return false;
}
}
为了能同时学习Fragment生命周期，我在Fragment每个生命周期方法中加入了log打印，一个有三个这样的Fragment，我只贴出其中一个代码，其余和这个一样：
public class FragmentOne extends baseFragment
{
private View view;
@Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
Log.d(TAG, "1==>FragmentOne=>onAttach");
}
@Override
public void onCreate(Bundle savedInstanceState)
{
Log.d(TAG, "2==>FragmentOne==>onCreate");
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
Log.d(TAG, "3==>FragmentOne==>onCreateView");
view = inflater.inflate(R.layout.fragment1, container, false);
TextView tv = (TextView) view.findViewById(R.id.tv);
tv.setText("FragmentOne");
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
Log.d(TAG, "4==>FragmentOne==>onActivityCreated");
super.onActivityCreated(savedInstanceState);
}
@Override
public void onStart()
{
Log.d(TAG, "5==>FragmentOne==>onStart");
super.onStart();
}
@Override
public void onResume()
{
Log.d(TAG, "6==>FragmentOne==>onResume");
super.onResume();
}
@Override
public void onPause()
{
Log.d(TAG, "7==>FragmentOne==>onPause");
super.onPause();
}
@Override
public void onStop()
{
Log.d(TAG, "8==>FragmentOne==>onStop");
super.onStop();
}
@Override
public void onDestroyView()
{
Log.d(TAG, "9==>FragmentOne==>onDestroyView");
super.onDestroyView();
}
@Override
public void onDestroy()
{
Log.d(TAG, "10==>FragmentOne==>onDestroy");
super.onDestroy();
}
@Override
public void onDetach()
{
Log.d(TAG, "11==>FragmentOne==>onDetach");
super.onDetach();
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState)
{
Log.d(TAG, "FragmentOne==>onViewCreated");
super.onViewCreated(view, savedInstanceState);
}
}
在编写过程中，我为了实现如果不是在主页，按第一遍让它先跳转到第一个Fragment这个效果，一开始使用了rgs.check(button.getId());这个方法，结果发现，这样的话onCheckedChanged监听事件会执行两次，后来改为button.setChecked(true);这个方法之后，成功解决了这个问题。
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