Question

我有MainActivity，它有FragmentTabHost和几个标签。选项卡中的每个片段都可以替换为另一个片段，因此如果我们向后导航，我们将看到此选项卡的第一个显示片段（每个选项卡的自有堆栈）。我有一个非常有效的解决方案。

以下示例演示了TabHost，其中包含第一个选项卡的2个选项卡和片段类。

有没有更简单，更好或更优雅的方法来实现这一结果？

AbstractPrimaryFragment.java。此类是一个根片段类，用于替换其中的片段。其他选项卡片段类可以扩展此超类。

public abstract class AbstractPrimaryFragment extends Fragment {

// Simple framelayout.
private static final int RES_ID = R.layout.primary_fragment_layout;

protected static final int CONTENT_LAYOUT_ID = R.id.primary_fragment_layout;

protected Fragment mActiveFragment;

public AbstractPrimaryFragment()
{
    setRetainInstance(true);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
    return inflater.inflate(RES_ID, container, false);
}

@Override
public void onActivityCreated(Bundle savedInstanceState)
{
    super.onActivityCreated(savedInstanceState);

    // Check if active fragment is in layout, if not, make default fragment for this tab.
    mActiveFragment = getChildFragmentManager().findFragmentById(CONTENT_LAYOUT_ID);
    if (mActiveFragment == null)
    {
        mActiveFragment = makeDefaultActiveFragment();
        String tag = getDefaultFragmentTag();
        getChildFragmentManager().beginTransaction().add(CONTENT_LAYOUT_ID, mActiveFragment, tag).commit();
    }
}

public boolean onBackPressed()
{
    boolean backPressed = false;
    final FragmentManager fragmentManager = getChildFragmentManager();
    if (fragmentManager.getBackStackEntryCount() > 0)
    {
        fragmentManager.addOnBackStackChangedListener(new OnBackStackChangedListener()
        {
            @Override
            public void onBackStackChanged()
            {
                mActiveFragment = fragmentManager.findFragmentById(CONTENT_LAYOUT_ID);
                fragmentManager.removeOnBackStackChangedListener(this);
            }
        });
        fragmentManager.popBackStack();
        backPressed = true;
    }

    return backPressed;
}

protected abstract Fragment makeDefaultActiveFragment();

protected abstract String getDefaultFragmentTag(); }

Tab1PrimaryFragment.java

public class Tab1PrimaryFragment extends AbstractPrimaryFragment implements OnTab1Fragment1Listener {

private static final String FRAGMENT1_TAG = "tab1_fragment1";
private static final String FRAGMENT2_TAG = "tab2_fragment2";

@Override
protected Fragment makeDefaultActiveFragment()
{
    return new Tab1Fragment1();
}

@Override
protected String getDefaultFragmentTag()
{
    return FRAGMENT1_TAG;
}

@Override
public void onTab1Fragment1ButtonClick(Tab1Fragment1 tab1Fragment1)
{
    Tab1Fragment2 tab1Fragment2 = new Tab1Fragment2();
    getChildFragmentManager().beginTransaction().replace(CONTENT_LAYOUT_ID, tab1Fragment2, FRAGMENT2_TAG).addToBackStack(tab1Fragment1.getTag()).commit();
    mActiveFragment = tab1Fragment2;
}}

Tab1Fragment1.class（默认活动片段）

public class Tab1Fragment1 extends Fragment {

public interface OnTab1Fragment1Listener
{
    public void onTab1Fragment1ButtonClick(Tab1Fragment1 tab1Fragment1);
}

private OnTab1Fragment1Listener mOnTab1Fragment1Listener;

public void setOnTab1Fragment1Listener(OnTab1Fragment1Listener onTab1Fragment1Listener)
{
    mOnTab1Fragment1Listener = onTab1Fragment1Listener;
}


@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    Fragment parentFragment = getParentFragment();
    if (parentFragment != null && parentFragment instanceof OnTab1Fragment1Listener)
    {
        mOnTab1Fragment1Listener = (OnTab1Fragment1Listener) parentFragment;
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
    Button button = new Button(getActivity());
    button.setOnClickListener(new OnClickListener()
        {

            @Override
            public void onClick(View v)
            {   
                if(mOnTab1Fragment1Listener != null)
                {
                   mOnTab1Fragment1Listener.onTab1Fragment1ButtonClick(Tab1Fragment1.this);
                }
            }
        });
    return button; }}

Tab1Fragment2.java。虚拟片段。调用onTab1Fragment1ButtonClick时会显示此片段。

public class Tab1Fragment2 extends Fragment {}

和MainActivity.java

public class MainActivity extends FragmentActivity {
private static final int RES_ID = R.layout.main_activity;
private static final int TAB_CONTENT_ID = android.R.id.tabcontent;
private static final int TABHOST_ID = android.R.id.tabhost;

private static final String TAB1_PRIMARY_FRAGMENT_TAG = "tab1_primary_fragment";
private static final String TAB2_PRIMARY_FRAGMENT_TAG = "tab2_primary_fragment"

private FragmentTabHost mTabHost;

@Override
protected void onCreate(Bundle bundle)
{
    super.onCreate(bundle);

    setContentView(RES_ID);
    initializeTabHost();
}

private void initializeTabHost()
{
    mTabHost = (FragmentTabHost) findViewById(TABHOST_ID);
    mTabHost.setup(this, getSupportFragmentManager(), TAB_CONTENT_ID);
    LayoutInflater inflater = LayoutInflater.from(this);
    mTabHost.addTab(mTabHost.newTabSpec(TAB1_PRIMARY_FRAGMENT_TAG).setIndicator(inflater.inflate(R.layout.smth1, null)), Tab1PrimaryFragment.class, null);
    mTabHost.addTab(mTabHost.newTabSpec(TAB2_PRIMARY_FRAGMENT_TAG).setIndicator(inflater.inflate(R.layout.smth2, null)), Tab2PrimaryFragment.class, null); 
}

@Override
public void onBackPressed()
{
    Fragment fragment = getSupportFragmentManager().findFragmentById(TAB_CONTENT_ID);
    if (fragment != null && fragment instanceof AbstractPrimaryFragment)
    {
        if (((AbstractPrimaryFragment) fragment).onBackPressed())
        {
            return;
        }
    }

    super.onBackPressed();
}}

FragmentTabHost为每个选项卡提供自己的片段堆栈

0 个答案: