java - oncreate(bundle)将在 Activity 中调用

Question

我创建了一个 Activity (MainActivity.java)扩展到Activity.java 我再次创建另一个 Activity (products.java)，现在我将这个 Activity (products.java)扩展到MainActivity.java
所以我的问题是 onCreate(bundle) 将在我的 products.java 类中调用其父类(super class) onCreate(bundle) 或其自己的 onCreate(bundle) ，我的代码如下:

MainActivity.java

import java.util.Locale;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.SearchManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;


public class MainActivity extends Activity {
    protected DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    public ActionBarDrawerToggle mDrawerToggle;

    private CharSequence mDrawerTitle;
    private CharSequence mTitle;
    private String[] mPlanetTitles;

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

        mTitle = mDrawerTitle = getTitle();
        mPlanetTitles = getResources().getStringArray(R.array.List_Content);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        // set a custom shadow that overlays the main content when the drawer opens
        mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
        // set up the drawer's list view with items and click listener
        mDrawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, mPlanetTitles));
        mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

        // enable ActionBar app icon to behave as action to toggle nav drawer
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        // ActionBarDrawerToggle ties together the the proper interactions
        // between the sliding drawer and the action bar app icon
        mDrawerToggle = new ActionBarDrawerToggle(
                this,                  /* host Activity */
                mDrawerLayout,         /* DrawerLayout object */
                R.drawable.ic_drawer,  /* nav drawer image to replace 'Up' caret */
                R.string.drawer_open,  /* "open drawer" description for accessibility */
                R.string.drawer_close  /* "close drawer" description for accessibility */
                ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            //displayView(0);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.main, menu);
        return super.onCreateOptionsMenu(menu);
    }

    /* Called whenever we call invalidateOptionsMenu() */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // If the nav drawer is open, hide action items related to the content view
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
         // The action bar home/up action should open or close the drawer.
         // ActionBarDrawerToggle will take care of this.
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action buttons
        switch(item.getItemId()) {
        case R.id.action_websearch:
            // create intent to perform web search for this planet
            Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
            intent.putExtra(SearchManager.QUERY, getActionBar().getTitle());
            // catch event that there's no activity to handle intent
            if (intent.resolveActivity(getPackageManager()) != null) {
                startActivity(intent);
            } else {
                Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
            }
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    /* The click listner for ListView in the navigation drawer */
    private class DrawerItemClickListener implements ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            displayView(position);
        }
    }

    @SuppressWarnings("unused")
    private void displayView(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        switch (position) {
        case 0: Intent product = new Intent(MainActivity.this,Products.class);
                startActivity(product);

            break;
        case 1: Intent notes = new Intent (MainActivity.this,Notes.class);
                startActivity(notes);

            break;
        case 2: Intent Contacts = new Intent (MainActivity.this,Contacts.class);
                startActivity(Contacts);

            break;
        case 3:
            Intent viewPdf = new Intent (MainActivity.this,pdfView.class);
            startActivity(viewPdf);
            break;
        case 4:
            Intent search = new Intent (MainActivity.this,search.class);
            startActivity(search);
            break;
        /*case 5:
            fragment = new WhatsHotFragment();
            break;*/

        default:
            break;
        }

        mDrawerList.setItemChecked(position, true);
        mDrawerList.setSelection(position);
        //setTitle(mDrawerList[position]);
        mDrawerLayout.closeDrawer(mDrawerList);
    }


    @Override
    public void setTitle(CharSequence title) {
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    /**
     * When using the ActionBarDrawerToggle, you must call it during
     * onPostCreate() and onConfigurationChanged()...
     */

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggls
        mDrawerToggle.onConfigurationChanged(newConfig);
    }

    /**
     * Fragment that appears in the "content_frame", shows a planet
     */
    public static class PlanetFragment extends Fragment {
        public static final String ARG_PLANET_NUMBER = "planet_number";

        public PlanetFragment() {
            // Empty constructor required for fragment subclasses
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_planet, container, false);
            int i = getArguments().getInt(ARG_PLANET_NUMBER);
            String planet = getResources().getStringArray(R.array.List_Content)[i];

            int imageId = getResources().getIdentifier(planet.toLowerCase(Locale.getDefault()),
                            "drawable", getActivity().getPackageName());
            ((ImageView) rootView.findViewById(R.id.image)).setImageResource(imageId);
            getActivity().setTitle(planet);
            return rootView;
        }
    }
}

和products.java

import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.Toast;

public class Products extends MainActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        LayoutInflater inflater = (LayoutInflater) this
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View contentView = inflater.inflate(R.layout.products, null, false);
        mDrawerLayout.addView(contentView, 0);

        GridView gridview = (GridView)findViewById(R.id.productgridview);
        gridview.setAdapter(new ImageAdapter(this));

        gridview.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // TODO Auto-generated method stub
                Toast.makeText(Products.this, " "+position, Toast.LENGTH_SHORT).show();

            }
        });
    }

}

所以请告诉我这个 Activity 会发生什么，我对此感到困惑。 当我调用 products.java 类的 onCreate(bundle) 时，它将调用 MainActivity.java 的 onCreate(bundle) 或 products.java 的 onCreate(bundle)。

Answer 1

将会调用Product类的

onCreate()，然后调用MainActivity类的onCreate()，最后调用Activity类的onCreate()被召唤。