Android：ActionBar，TabListener和support.v4.Fragment
我使用MainActivity构建了一个应用程序，该应用程序扩展了FragmentActivity并具有带三个选项卡的ActionBar。 在每个标签上，我想附上一个ParentFragment ，它应该控制内部页面之间的滑动。 结果应该是按下用户应该从ParentFragment的不同实例更改的选项卡，然后在每个ParentFragment内的TextViewFragments之间ParentFragment 。
现在我可以在三个选项卡之间完全切换，但问题是ParentFragment没有正确显示，它似乎甚至没有创建，因为我甚至无法看到onCreate() ， onCreateView()和onViewCreated()函数LogCat视图。
我认为问题出现在自定义TabListener类及其函数中，但我无法真正理解问题所在。 我试图在很多网站上进行搜索，并且已经查看了很多示例，但没有一个与相同的情况有关。
我在想什么或者我在这里做错了什么？
这是我的MainActivity：
import java.util.Random;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.graphics.drawable.Drawable;
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.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import com.viewpagerindicator.PageIndicator;
public class MainActivity extends FragmentActivity {
MyAdapter mAdapter;
ViewPager mPager;
PageIndicator mIndicator;
private View mCustomView;
private static final Random RANDOM = new Random();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
ActionBar.LayoutParams params = new ActionBar.LayoutParams(
ActionBar.LayoutParams.MATCH_PARENT,
ActionBar.LayoutParams.MATCH_PARENT, Gravity.CENTER);
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setDisplayUseLogoEnabled(false);
actionBar.setDisplayShowHomeEnabled(false);
actionBar.addTab(actionBar
.newTab()
.setIcon(getIcon(0, true))
.setTabListener(
new TabListener<ParentFragment>(this, "home",
ParentFragment.class)));
actionBar.addTab(actionBar
.newTab()
.setIcon(getIcon(1, false))
.setTabListener(
new TabListener<ParentFragment>(this, "apps",
ParentFragment.class)));
actionBar.addTab(actionBar
.newTab()
.setIcon(getIcon(2, false))
.setTabListener(
new TabListener<ParentFragment>(this, "settings",
ParentFragment.class)));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
}
public static class TabListener<T extends Fragment> implements
ActionBar.TabListener {
private Fragment mFragment;
private final FragmentActivity mActivity;
private final String mTag;
private final Class<T> mClass;
private final Bundle mArgs;
private FragmentTransaction fft;
public static final String TAG = TabListener.class.getSimpleName();
public TabListener(FragmentActivity activity, String tag, Class<T> clz) {
this(activity, tag, clz, null);
}
public TabListener(FragmentActivity activity, String tag, Class<T> clz,
Bundle args) {
mActivity = activity;
mTag = tag;
mClass = clz;
mArgs = args;
mFragment = mActivity.getSupportFragmentManager()
.findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached()) {
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
}
}
public void onTabSelected(Tab tab, android.app.FragmentTransaction ft) {
System.out.println(TAG + (" - ") + " -> mTag "
+ mTag + " selected!");
fft = mActivity.getSupportFragmentManager().beginTransaction();
if (mFragment == null) {
mFragment = Fragment.instantiate(mActivity, mClass.getName());
fft.add(android.R.id.content, mFragment, mTag);
} else {
System.out.println(TAG + (" - ") + " -> Fragment con mTag = " + mTag
+ " trovato con tag!");
fft.attach(mFragment);
fft.commit();
}
}
@Override
public void onTabReselected(Tab tab, android.app.FragmentTransaction ft) {
}
@Override
public void onTabUnselected(Tab tab, android.app.FragmentTransaction ft) {
mFragment = mActivity.getSupportFragmentManager()
.findFragmentByTag(mTag);
System.out.println(TAG + (" - ") + " -> mTag "
+ mTag + " unselected!");
if (mFragment != null && !mFragment.isDetached()) {
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
}
}
}
public Drawable getIcon(int tabPosition, boolean selected) {
switch (tabPosition) {
case 0:
return getResources().getDrawable(R.drawable.actionbar_home);
case 1:
return getResources().getDrawable(R.drawable.actionbar_apps);
case 2:
return getResources().getDrawable(R.drawable.actionbar_settings);
}
return null;
}
}
这是我的ParentFragment，它现在已经扩展了android.support.v4.app.Fragment类：
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.viewpagerindicator.IconPageIndicator;
import com.viewpagerindicator.PageIndicator;
public class ParentFragment extends Fragment {
public static final String TAG = ParentFragment.class.getSimpleName();
MyAdapter fragmentAdapter;
ViewPager mPager;
PageIndicator mIndicator;
public static ParentFragment newInstance() {
System.out.println(TAG + " - newInstance()");
System.out.println(TAG + " - " + methodName());
ParentFragment fragment = new ParentFragment();
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
System.out.println(TAG + " - onCreate()");
System.out.println(TAG + " - " + methodName());
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
System.out.println(TAG + " - onCreateView()");
System.out.println(TAG + " - " + methodName());
fragmentAdapter = new MyAdapter(getFragmentManager());
View view = inflater.inflate(R.layout.simple_icons, container, false);
mPager = (ViewPager) view.findViewById(R.id.pager);
mPager.setAdapter(fragmentAdapter);
return view;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
System.out.println(TAG + " - onViewCreated()" );
System.out.println(TAG + " - " + methodName());
super.onViewCreated(view, savedInstanceState);
mIndicator = (IconPageIndicator) getActivity().findViewById(R.id.indicator);
mIndicator.setViewPager(mPager);
}
}
这是MyAdapter类：
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import com.viewpagerindicator.IconPagerAdapter;
public class MyAdapter extends PagerAdapter {
FragmentManager myFragmentMgr;
private FragmentTransaction mCurTransaction;
protected static final String[] CONTENT = new String[] { "This", "Is", "A", "Test", };
protected static final int[] ICONS = new int[] {
R.drawable.icon_page_indicator,
R.drawable.icon_page_indicator,
R.drawable.icon_page_indicator,
R.drawable.perm_group_calendar,
R.drawable.perm_group_camera,
R.drawable.perm_group_device_alarms,
R.drawable.perm_group_location
};
private int mCount = CONTENT.length;
public MyAdapter(FragmentManager fm) {
super();
myFragmentMgr = fm;
}
@Override
public int getCount() {
return 3;
}
@Override
public Object instantiateItem(ViewGroup viewGroup, int position) {
ParentFragment fragment = ParentFragment.newInstance();
return fragment;
}
@Override
public void destroyItem(ViewGroup viewGroup, int position, Object obj) {
if (mCurTransaction == null) {
mCurTransaction = myFragmentMgr.beginTransaction();
}
mCurTransaction.detach((Fragment)obj);
}
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
return false;
}
public Fragment getItem(int position) {
Bundle args = new Bundle();
args.putInt(TextViewFragment.POSITION_KEY, position);
return TextViewFragment.newInstance(args);
}
@Override
public CharSequence getPageTitle(int position) {
return "Fragment # " + position;
}
public int getIconResId(int index) {
return ICONS[index % ICONS.length];
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
}
和最后一个TextViewFragment类：
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
public class TextViewFragment extends Fragment {
public static final String POSITION_KEY = "POSITION";
public static final String TITLE_KEY = "TITLE";
public static TextViewFragment newInstance(Bundle args) {
TextViewFragment fragment = new TextViewFragment();
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_test, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
TextView textview = (TextView) view.findViewById(R.id.textViewPosition);
final int position;
if (getArguments() != null) {
position = getArguments().getInt(POSITION_KEY);
textview.setText(Integer.toString(position));
} else {
position = 0;
textview.setText("Child Fragment");
}
textview.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(v.getContext(), "Clicked Position: " + position,
Toast.LENGTH_LONG).show();
}
});
}
}
-----编辑：解决方案-----
由于“低声誉”我无法回答自己的问题，但无论如何我都会分享这个解决方案，以帮助其他人并希望恢复一些投票。
我终于找到了让事情为我工作的方式，我希望这可以对遇到同样问题的其他人有所帮助。 正如我怀疑的，问题出在TabListener中。 我的问题是用这段代码改变了那部分：
public static class TabListener<T extends Fragment> implements
ActionBar.TabListener {
private Fragment mFragment;
private final FragmentActivity mActivity;
private final String mTag;
private final Class<T> mClass;
private final Bundle mArgs;
private FragmentTransaction fft;
public TabListener(FragmentActivity activity, String tag, Class<T> clz) {
this(activity, tag, clz, null);
}
public TabListener(FragmentActivity activity, String tag, Class<T> clz,
Bundle args) {
mActivity = activity;
mTag = tag;
mClass = clz;
mArgs = args;
System.out.println(TAG + " - " + methodName() + " - Constructor of TabListener -> mTag = "
+ mTag);
// Check to see if we already have a fragment for this tab, probably
// from a previously saved state. If so, deactivate it, because our
// initial state is that a tab isn't shown.
mFragment = mActivity.getSupportFragmentManager()
.findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached()) {
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager()
.executePendingTransactions();
}
}
public void onTabSelected(Tab tab, android.app.FragmentTransaction ft) {
Fragment tmp = mActivity.getSupportFragmentManager()
.findFragmentByTag(mTag);
fft = mActivity.getSupportFragmentManager().beginTransaction();
if (mFragment == null) {
System.out.println(TAG + " - " + methodName() + " - add mFragment " + mTag);
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
fft.add(android.R.id.content, mFragment, mTag);
fft.commit();
mActivity.getSupportFragmentManager()
.executePendingTransactions();
} else {
System.out.println(TAG + " - " + methodName() + " - attach mFragment " + mTag);
// If it exists, simply attach it in order to show it
fft.attach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager()
.executePendingTransactions();
}
}
@Override
public void onTabReselected(Tab tab, android.app.FragmentTransaction ft) {
System.out.println(TAG + " - " + methodName() + " - mFragment " + mTag);
}
@Override
public void onTabUnselected(Tab tab, android.app.FragmentTransaction ft) {
mFragment = mActivity.getSupportFragmentManager()
.findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached()) {
System.out.println(TAG + " - " + methodName() + " - detach mFragment " + mTag);
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager()
.executePendingTransactions();
}
}
public static final String TAG = TabListener.class.getSimpleName();
private static final int CLIENT_CODE_STACK_INDEX;
static {
// Finds out the index of "this code" in the returned stack trace -
// funny but it differs in JDK 1.5 and 1.6
int i = 0;
for (StackTraceElement ste : Thread.currentThread().getStackTrace()) {
i++;
if (ste.getClassName().equals(TabListener.class.getName())) {
break;
}
}
CLIENT_CODE_STACK_INDEX = i;
}
public static String methodName() {
if (Thread.currentThread().getStackTrace().length < CLIENT_CODE_STACK_INDEX)
return Thread.currentThread().getStackTrace()[CLIENT_CODE_STACK_INDEX]
.getMethodName() + "()";
else
return new String(
"methodName() - stackTrace index is out of bound");
}
}
基本的区别在于在每行commit()之后添加以下行：
mActivity.getSupportFragmentManager().executePendingTransactions();
这个问题实际上很少记录，可能只在特定的条件下才会发生，但我希望这个解决方案可以为有相同问题的其他人节省一些时间！
谢谢你的回答，我对支持库有着完全相同的问题，当我试图在标签之间切换时，片段将被叠加在彼此的顶部。 在解决方案中有一些未使用的变量，所以我把它清理了一下：
public static class TabListener<T extends Fragment> implements ActionBar.TabListener {
private Fragment mFragment;
private final FragmentActivity mActivity;
private final String mTag;
private final Class<T> mClass;
private FragmentTransaction fft;
public TabListener(FragmentActivity activity, String tag, Class<T> clz) {
mActivity = activity;
mTag = tag;
mClass = clz;
// Check to see if we already have a fragment for this tab, probably
// from a previously saved state. If so, deactivate it, because our
// initial state is that a tab isn't shown.
mFragment = mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached()) {
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager()
.executePendingTransactions();
}
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
mFragment = mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
fft = mActivity.getSupportFragmentManager().beginTransaction();
if (mFragment == null) {
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
ft.add(R.id.content_view, mFragment, mTag);
//fft.add(android.R.id.content, mFragment, mTag);
fft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
} else {
// If it exists, simply attach it in order to show it
fft.attach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
}
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
mFragment = mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
if (mFragment != null && !mFragment.isDetached()) {
fft = mActivity.getSupportFragmentManager().beginTransaction();
fft.detach(mFragment);
fft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
}
}
}
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