导航回后台活动 Android

Question

我有 3 个活动：1. 类别列表； 2、本分类新闻； 3. 新闻详情

看下面的图片！

我通过在android清单文件中将第二个活动设置为第三个活动的父活动来实现从第三个活动到第二个活动的后退按钮，但它看不到在第一个活动中选择的类别，因此它不显示列表和崩溃，有人能帮我实现后退按钮吗？

这是我想要实现后退按钮的活动代码

public class Categorii_LIst_Item_Clicked extends ActionBarActivity {

static Context context;
static Bundle extras;

SectionsPagerAdapter mSectionsPagerAdapter;
static ImageLoader imageLoader;
static DisplayImageOptions options;

ViewPager mViewPager;

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

        context = this;
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        extras = getIntent().getExtras();

        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        //Setup the ImageLoader, we'll use this to display our images
        ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(this).build();
        imageLoader = ImageLoader.getInstance();
        imageLoader.init(config);

        //Setup options for ImageLoader so it will handle caching for us.
        options = new DisplayImageOptions.Builder()
                .cacheInMemory()
                .cacheOnDisc()
                .build();


    }



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

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}


public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

@Override
public Fragment getItem(int position) {
    if (position == 0) {
        return PlaceholderFragment.newInstance(position);
    } else if (position == 1) {
        return VideoFragment.newInstance1(position);
    }
    return PlaceholderFragment.newInstance(position);
}

@Override
public int getCount() {
    return 2;
}

@Override
public CharSequence getPageTitle(int position) {
    Locale l = Locale.getDefault();
    switch (position) {
        case 0:
            return getString(R.string.title_section4).toUpperCase(l);
        case 1:
            return getString(R.string.title_section5).toUpperCase(l);
    }
    return null;
}
}


public static class PlaceholderFragment extends Fragment {


private static final String ARG_SECTION_NUMBER = "section_number";


public static PlaceholderFragment newInstance(int sectionNumber) {
    PlaceholderFragment fragment = new PlaceholderFragment();
    Bundle args = new Bundle();
    args.putInt(ARG_SECTION_NUMBER, sectionNumber);
    fragment.setArguments(args);
    return fragment;
}

public PlaceholderFragment() {
}

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

    View rootView = inflater.inflate(R.layout.fragment_list_item_clicked, container, false);


    TextView pDate = (TextView) rootView.findViewById(R.id.textView);
    pDate.setText(extras.getString("pdate"));


    TextView ptitle = (TextView) rootView.findViewById(R.id.section_label);
    ptitle.setText(extras.getString("pname"));


    TextView pnText = (TextView) rootView.findViewById(R.id.textView2);
    pnText.setText(extras.getString("pText"));


    //Setup a listener we can use to swtich from the loading indicator to the Image once it's ready
    ImageLoadingListener listener = new ImageLoadingListener() {


        @Override
        public void onLoadingStarted(String arg0, View arg1) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onLoadingCancelled(String arg0, View arg1) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onLoadingComplete(String arg0, View arg1, Bitmap arg2) {
            // i/ndicator.setVisibility(View.INVISIBLE);
            // iconImg.setVisibility(View.VISIBLE);
        }

        @Override
        public void onLoadingFailed(String arg0, View arg1, FailReason arg2) {
            // TODO Auto-generated method stub

        }

    };

    //Load the image and use our options so caching is handled.
    final ImageView iconImg = (ImageView) rootView.findViewById(R.id.imageView);
    imageLoader.displayImage(extras.getString("pImage"), iconImg, options, listener);


    return rootView;
}
}


public static class VideoFragment extends Fragment {


private static final String ARG_SECTION_NUMBER = "section_number";


public static VideoFragment newInstance1(int sectionNumber) {
    VideoFragment fragment = new VideoFragment();
    Bundle args = new Bundle();
    args.putInt(ARG_SECTION_NUMBER, sectionNumber);
    fragment.setArguments(args);
    return fragment;
}

public VideoFragment() {
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.video_fragment, container, false);
    VideoView myVideoView = (VideoView) rootView.findViewById(R.id.videoView);
    Uri video = Uri.parse(extras.getString("pVideo"));
    myVideoView.setMediaController(new MediaController(context));
    myVideoView.setVideoURI(video);
    myVideoView.requestFocus();
    //myVideoView.start();

    return rootView;
}
}
}

Answer 1

当您在清单中为向上导航指定父活动时：

    android:parentActivityName

并且当您单击操作栏中的向上按钮时，父活动将重新启动（在您的情况下它是类别活动），而不是避免活动重新启动。 只需将此代码放在您的第 3 个活动中即可完成最上面的活动（即有关新闻的详细信息）。

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    // Respond to the action bar's Up/Home button
    case android.R.id.home:
        finish();
        return true;
    }
    return super.onOptionsItemSelected(item);
}

并从清单中删除 parentActivityName。