Question

我对Android编程很陌生，但我会尽力提供所需的所有信息。我正在使用新的android.support.v7.app.ActionBarActivity和android.support.v4.app.Fragment来显示Android API的标签布局，范围从8到17。我正面临一个问题，在我的活动中正确显示我的两个片段，因为它们在我选择其中一个片段后相互叠加。所以，这是我的主要活动代码：

package it.koopa.scank;

import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBar.Tab;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;

public class MainActivity extends ActionBarActivity {

    private final static String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //have to use getSupportActionBar from android.support.v7.app
        ActionBar actionBar = getSupportActionBar();

        //hello tab
        Tab tab = actionBar.newTab()
                .setText(R.string.tab_hello)
                .setTabListener(new TabListener<HelloFragment>(this, "hello", HelloFragment.class));
        actionBar.addTab(tab);

        //handle content tab
        tab = actionBar.newTab()
                .setText(R.string.tab_send)
                .setTabListener(new TabListener<HandleContentFragment>(this, "handle", HandleContentFragment.class));
        actionBar.addTab(tab);

        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    }

    @Override
    protected void onStart() {
        super.onStart();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.scank, menu);
        return true;
    }

    public static class TabListener<T extends Fragment> implements ActionBar.TabListener {
        private Fragment mFragment;
        private final ActionBarActivity mActivity;
        private final String mTag;
        private final Class<T> mClass;

        /**
         * Constructor used each time a new tab is created.
         * @param activity The host Activity, used to instantiate the fragment
         * @param tag The identifier tag for the fragment
         * @param clz The fragment's Class, used to instantiate the fragment
         */
        public TabListener(ActionBarActivity activity, String tag, Class<T> clz) {
            mActivity = activity;
            mTag = tag;
            mClass = clz;
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) {
            mFragment = mActivity.getSupportFragmentManager().findFragmentByTag(mTag);

            // Check if the fragment is already initialized
            if (mFragment == null) {
                // If not, instantiate and add it to the activity
                mFragment = Fragment.instantiate(mActivity, mClass.getName());
                ft.add(getCorrectActionBarId(), mFragment, mTag);
                Log.i(TAG, "FragID " + mFragment.getId() + ", FragTAG=" + mFragment.getTag() + " ADDED!!!");
            } else {
                // If it exists, simply attach it in order to show it
                ft.attach(mFragment);
                Log.i(TAG, "FragID " + mFragment.getId() + ", FragTAG=" + mFragment.getTag() + " attached.");
            }
        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) {
            if (mFragment != null) {
                // Detach the fragment, because another one is being attached
                ft.detach(mFragment);
                Log.i(TAG, "FragID " + mFragment.getId() + ", FragTAG=" + mFragment.getTag() + " detached.");
            }
        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
            // User selected the already selected tab. Usually do nothing.
        }
    }

    /**
     * Returns the correct id of the action bar
     * @return
     */
    public static int getCorrectActionBarId () {
        int androidVersion = Build.VERSION.SDK_INT;
        if (androidVersion >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
            return android.R.id.content;
        } else {
            return R.id.action_bar_activity_content;
        }
    }

}

这些是我的两个片段（都使用自己的xml布局）。第一个：

package it.koopa.scank;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class HelloFragment extends Fragment {
    private int index;

    public void onCreate(Bundle savedInstanceState) {        
        super.onCreate(savedInstanceState);
    }

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

        View v = inflater.inflate(R.layout.hello, container, false);
        Log.i("HelloFragment","I'm " + HelloFragment.class);

        return v;

    }
}

和第二个：

package it.koopa.scank;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class HandleContentFragment extends Fragment {
    private int index;

    public void onCreate(Bundle savedInstanceState) {        
        super.onCreate(savedInstanceState);
    }

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

        View v = inflater.inflate(R.layout.handle_content, container, false);
        Log.i("HandleContentFragment","I'm " + HandleContentFragment.class);

        return v;

    }
}

并且因此，如果我选择第二个选项卡，则视图将被放置在另一个选项卡上！我在Tabs using android.support.v7.app.ActionBar找到了一个类似的问题，但是接受的解决方案对我来说似乎不起作用。事实上，在我的主要活动中，您可以看到我使用

获取内容ID

    int androidVersion = Build.VERSION.SDK_INT;
    if (androidVersion >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        return android.R.id.content;
    } else {
        return R.id.action_bar_activity_content;
    }

但片段内容仍然被覆盖（因为我的声誉几乎为零，我无法上传图片）。我哪里错了？

更新：我的活动使用android:theme="@style/Theme.AppCompat.Light"。我正在使用Android 4.2.1测试Nexus i9250

Answer 1

这是一个已知的错误。您可以在此处找到解决方法：

https://code.google.com/p/android/issues/detail?id=58602

Answer 2

让每个Fragment都实现ActionBar.TabListener。将以下这些方法与片段中的其他代码一起添加

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
     mFragment = new MyFragment();
     ft.add(android.R.id.content, mFragment);
     ft.attach(mFragment);      
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    ft.remove(mFragment);
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub

}

您可以从主要活动中删除标签监听器。这可以解决所有问题。

Answer 3

只需在ft.show(mfragment)中调用onTabSelected方法，在ft.hide(mfragment)调用onTabUnselected方法。

看下面

public void onTabReselected(Tab tab, FragmentTransaction ft) {
  // TODO Auto-generated method stub
}

public void onTabSelected(Tab tab, FragmentTransaction ft) {
  ft.show(mfragment);
}

public void onTabUnselected(Tab tab, FragmentTransaction ft) {
  ft.hide(mfragment);       
}

Android TabLayout使用android.support.v7.app.ActionBar和android.support.v4.app.Fragment片段叠加

3 个答案: