我正在尝试实现片段之间的通信，但无法理解如何实现一件事。我有选项卡+滑动（viewpager），我可以在选项卡之间滑动并查看片段content which are binded by default but I cannot call another fragment, for instance, by button click in one of the tab的内容，新片段将出现在当前选项卡中，并且如果您尝试在此之后滑动不会出现空指针异常。现在我有一半的工作片段调用。我的意思是调用了新片段，我在日志文件中看到了它，但没有显示任何内容，当我尝试在它之后滑动时，我遇到了崩溃 - 空指针异常。
我的标签活动：
package com.example.tabstest;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.util.Log;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.ActionBar.Tab;
import com.actionbarsherlock.app.ActionBar.TabListener;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuItem;
public class TabsActivity extends SherlockFragmentActivity implements TabListener {
private static final String TAG = "TabsActivity";
AppSectionsPagerAdapter mAppSectionsPagerAdapter;
private ViewPager mViewPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mViewPager = (ViewPager) findViewById(R.id.pager);
mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager(), mViewPager);
final ActionBar actionBar = getSupportActionBar();
actionBar.setHomeButtonEnabled(false);
actionBar.setDisplayUseLogoEnabled(true);
actionBar.setDisplayShowTitleEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mViewPager.setAdapter(mAppSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
actionBar.addTab(actionBar.newTab().setTag("home").setText("Home").setTabListener(this));
actionBar.addTab(actionBar.newTab().setTag("calculator").setText("Calculator").setTabListener(this));
actionBar.addTab(actionBar.newTab().setTag("login").setText("Log in").setTabListener(this));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
getSupportMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
return super.onOptionsItemSelected(item);
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the primary sections of the app.
*/
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {
private FragmentManager mFm;
private ViewPager mVp;
public AppSectionsPagerAdapter(FragmentManager fm, ViewPager viewPager) {
super(fm);
mFm = fm;
mVp = viewPager;
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 1:
return new CalculatorFragment();
case 2:
Fragment LogInFragment = new LogInFragment();
Bundle userProfile = new Bundle();
userProfile.putString("USER", "Test");
LogInFragment.setArguments(userProfile);
return LogInFragment;
default:
return new HomeFragment();
}
}
@Override
public int getCount() {
return 3;
}
public void selectPage(int page) {
mVp.setCurrentItem(page);
}
public void replaceFragment(int FragmentContatiner, Fragment newFragment) {
Log.w(TAG, "Replace Fragment!");
FragmentTransaction transaction = mFm.beginTransaction();
transaction.replace(FragmentContatiner, newFragment).addToBackStack(null).commit();
notifyDataSetChanged();
}
}
}
编辑：我尝试用新片段替换当前片段的片段之一：
package com.example.tabstest;
import com.actionbarsherlock.app.SherlockFragment;
import com.example.tabstest.TabsActivity.AppSectionsPagerAdapter;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class HomeFragment extends SherlockFragment {
private static final String TAG = "HomeFragment";
private View rootView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.fragment_home, container, false);
rootView.findViewById(R.id.bCalculate).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
AppSectionsPagerAdapter aspa = new AppSectionsPagerAdapter(getFragmentManager(), (ViewPager) getActivity().findViewById(R.id.pager));
// aspa.selectPage(1);
Fragment LogInFragment = new LogInFragment();
Bundle userProfile = new Bundle();
userProfile.putString("USER", "Test");
LogInFragment.setArguments(userProfile);
aspa.replaceFragment(rootView.findViewById(R.id.HomePage).getId(), LogInFragment);
}
});
return rootView;
}
}
那是我的 fragment_home 布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/HomePage"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="@+id/ivGetLoan"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight=".1"
android:src="@android:color/darker_gray" />
<Button
android:id="@+id/bCalculate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Calculate your loan" />
</LinearLayout>
它被替换了，我看到了 LogInFragment 的内容，但是当它被替换时，我不仅看到了所有 LogInFragment 内容，还看到了用于从旧片段内容中替换片段的按钮。
如果您使用 ViewPager 作为容器，则会出现 NullPointer 异常：
12-09 20:37:52.416: E/AndroidRuntime(24660): FATAL EXCEPTION: main
12-09 20:37:52.416: E/AndroidRuntime(24660): java.lang.NullPointerException
12-09 20:37:52.416: E/AndroidRuntime(24660): at com.example.tabstest.HomeFragment$1.onClick(HomeFragment.java:30)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.view.View.performClick(View.java:2461)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.view.View$PerformClick.run(View.java:8890)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.os.Handler.handleCallback(Handler.java:587)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.os.Handler.dispatchMessage(Handler.java:92)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.os.Looper.loop(Looper.java:123)
12-09 20:37:52.416: E/AndroidRuntime(24660): at android.app.ActivityThread.main(ActivityThread.java:4627)
12-09 20:37:52.416: E/AndroidRuntime(24660): at java.lang.reflect.Method.invokeNative(Native Method)
12-09 20:37:52.416: E/AndroidRuntime(24660): at java.lang.reflect.Method.invoke(Method.java:521)
12-09 20:37:52.416: E/AndroidRuntime(24660): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
12-09 20:37:52.416: E/AndroidRuntime(24660): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
12-09 20:37:52.416: E/AndroidRuntime(24660): at dalvik.system.NativeStart.main(Native Method)
新思想
不幸的是，它不t help me. Than more I deal with fragments than a bit more I understand about them. I mark that I cannot replace fragment which is used to jump on another fragment. That is to say if I use fragment with container android.R.id.container where is a button which I will press to replace current fragment on another one then you will receive NUllpointer exception.I didn理解这样的动作顺序。首先，您单击然后替换，但 nullpointer 异常反之亦然 - 没有 onclick，没有替换。当你有 ActionBar 和容器 android.R.id.contenT 的另一种情况。当您单击操作栏中的一个 hte 操作菜单按钮以将 android.r.id.content 中的片段替换为另一个片段时，一切都会好起来的，它将被正确替换。如何替换具有一些要替换的操作的片段另一个片段上的当前片段？