管理片段

Question

我现在正在创建一个简单的页面浏览器支持的应用程序，您可以在其中水平切换到片段。对于我的应用程序，我想对所有片段使用相同的背景，片段之间的唯一区别是文本。我目前已经制作了一些片段，应用程序已经过度征集，它占用了大量空间并使用了大量内存。我想以某种方式优化应用程序，以便最小化运行它所需的空间和内存。这是我的MainActivity的代码:(我正在为每个片段创建一个类和不同的布局，因为我目前还没有熟悉其他任何方式） - 编辑：我忘了说，此刻我只有7个片段，但对于我的应用程序，我需要400-500个片段，因此必须进行优化。

public class MainActivity extends FragmentActivity  {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide
 * fragments for each of the sections. We use a
 * {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
 * will keep every loaded fragment in memory. If this becomes too memory
 * intensive, it may be best to switch to a
 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
ViewPager mViewPager;

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

    // Set up the action bar.


    // Create the adapter that will return a fragment for each of the three
    // primary sections of the app.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    // When swiping between different sections, select the corresponding
    // tab. We can also use ActionBar.Tab#select() to do this if we have
    // a reference to the Tab.
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
        }        
    });

}


public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {Fragment f = null;
    switch(position){
    case 0:
    {
    f = new DummySectionFragment();//YourFragment
    // set arguments here, if required
    Bundle args = new Bundle();
    f.setArguments(args);
    break;
    }
    case 1:
    {
        f = new Fragment2();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }
    case 2:
    {
        f = new Fragment3();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }
    case 3:
    {
        f = new Fragment4();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }
    case 4:
    {
        f = new Fragment5();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }
    case 5:
    {
        f = new Fragment6();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }
    case 6:
    {
        f = new Fragment7();//YourFragment
        // set arguments here, if required
        Bundle args = new Bundle();
        f.setArguments(args);
        break;
    }

    default:
      throw new IllegalArgumentException("not this many fragments: " + position);
    }


    return f;
    }



    @Override
    public int getCount() {
        // Show 3 total pages.
        return 7;
    }


}

/**
 * A dummy fragment representing a section of the app, but that simply
 * displays dummy text.
 */
public static class DummySectionFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public DummySectionFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main_dummy, container, false);
        TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }


}  public static class Fragment2 extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public Fragment2() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment2, container, false);
        TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}  public static class Fragment3 extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public Fragment3() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment3, container, false);
        TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}  public static class Fragment4 extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public Fragment4() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment4, container, false);
        TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}  public static class Fragment5 extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    public static final String ARG_SECTION_NUMBER = "section_number";

    public Fragment5() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment5, container, false);
        TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
        dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    } }  
    public static class Fragment6 extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        public static final String ARG_SECTION_NUMBER = "section_number";

        public Fragment6() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment6, container, false);
            TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
            dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }   } 
        public static class Fragment7 extends Fragment {
            /**
             * The fragment argument representing the section number for this
             * fragment.
             */
            public static final String ARG_SECTION_NUMBER = "section_number";

            public Fragment7() {
            }

            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                    Bundle savedInstanceState) {
                View rootView = inflater.inflate(R.layout.fragment7, container, false);
                TextView dummyTextView = (TextView) rootView.findViewById(R.id.section_label);
                dummyTextView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
                return rootView;    }


}
}

Answer 1

  

要管理活动中的片段，您需要使用   FragmentManager。要获得它，请从您的调用getFragmentManager（）   活性。

     

您可以使用FragmentManager执行的一些操作包括：

public class MainActivity extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {

    private static final String APP_ID = "80e4eede56844462ef3cdc721208c31f";

    private static final int PERMISSION_ACCESS_COARSE_LOCATION = 1;
    private GoogleApiClient googleApiClient;

    private TextView textView;


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

        textView = (TextView) findViewById(R.id.textView);

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
                    PERMISSION_ACCESS_COARSE_LOCATION);
        }

        googleApiClient = new GoogleApiClient.Builder(this, this, this).addApi(LocationServices.API).build();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_ACCESS_COARSE_LOCATION:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    // All good!
                } else {
                    Toast.makeText(this, "Need your location", Toast.LENGTH_SHORT).show();
                }

                break;
        }
    }

    @Override
    protected void onStart() {
        super.onStart();
        if (googleApiClient != null) {
            googleApiClient.connect();
        }
    }

    @Override
    protected void onStop() {
        googleApiClient.disconnect();
        super.onStop();
    }

    @Override
    public void onConnected(Bundle bundle) {
        Log.i(MainActivity.class.getSimpleName(), "Connected to Google Play Services");

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            Location lastLocation = LocationServices.FusedLocationApi.getLastLocation(googleApiClient);

            double lat = lastLocation.getLatitude(), lon = lastLocation.getLongitude();
            String units = "imperial";
            String url = String.format("http://api.openweathermap.org/data/2.5/weather?lat=%f&lon=%f&units=%s&appid=%s",
                    lat, lon, units, APP_ID);
            new GetWeatherTask(textView).execute(url);
        }
    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Log.i(MainActivity.class.getSimpleName(), "Can't connect to Google Play Services!");
    }

    private class GetWeatherTask extends AsyncTask<Object, Object, Double> {
        private TextView textView;


        public GetWeatherTask(TextView textView) {
            this.textView = textView;
        }

        @Override
        protected Double doInBackground(Object... strings) {

            double weather = 0;

            try {
                URL url = new URL((String) strings[0]);
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                InputStream stream = new BufferedInputStream(urlConnection.getInputStream());
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stream));
                StringBuilder builder = new StringBuilder();

                String inputString;
                while ((inputString = bufferedReader.readLine()) != null) {
                    builder.append(inputString);
                }

                JSONObject topLevel = new JSONObject(builder.toString());
                JSONObject main = topLevel.getJSONObject("main");
                weather = main.getDouble("temp");


                urlConnection.disconnect();
            } catch (IOException | JSONException e) {
                e.printStackTrace();
            }
            return weather;
        }

        @Override
        public void onPostExecute(Double temp) {
                textView.setText("Weather temperature is " + temp);

        }

    }
}

     

findFragmentByTag（）（用于提供或不提供UI的片段）。       使用popBackStack（）（用户模拟Back命令）从后端堆栈弹出片段。       使用addOnBackStackChangedListener（）为后备栈注册一个监听器。