IntentExtras 和选项卡式活动

Question

我使用 Android Studio new -> 选项卡式活动向导来创建选项卡式活动。我通过另一个活动片段的意图打开该活动。我通过 Intent Extras 向这个选项卡式活动发送额外的数据。

我知道我应该在活动中捕获额外的意图，然后将这些数据放入片段参数中。我在我的应用程序中多次使用片段进行常规空白活动。但是我似乎迷失了在选项卡式活动代码中的确切位置，我应该额外捕获意图并声明片段的参数。任何人都可以提供任何方向吗？到目前为止，无论我将标准意图 extra-> 片段参数代码放在哪里，我都只会遇到错误。

这是我来自 Android Studio 模板的选项卡式活动代码：

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;

import java.util.Locale;


public class therapy_screen extends ActionBarActivity implements ActionBar.TabListener {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link 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_therapy_screen);

        // Set up the action bar.
        final ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        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) {
                actionBar.setSelectedNavigationItem(position);
            }
        });

        // For each of the sections in the app, add a tab to the action bar.
        for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
            // Create a tab with text corresponding to the page title defined by
            // the adapter. Also specify this Activity object, which implements
            // the TabListener interface, as the callback (listener) for when
            // this tab is selected.
            actionBar.addTab(
                    actionBar.newTab()
                            .setText(mSectionsPagerAdapter.getPageTitle(i))
                            .setTabListener(this));
        }
    }


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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

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

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
        // When the given tab is selected, switch to the corresponding page in
        // the ViewPager.
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            return therapy_screen_fragment.newInstance(position + 1);
        }

        @Override
        public int getCount() {
            // Show 2 total pages.
            return 2;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
                case 0:
                    return getString(R.string.title_section1).toUpperCase(l);
                case 1:
                    return getString(R.string.title_section2).toUpperCase(l);
            }
            return null;
        }
    }
}

我试图捕捉和解析意图，例如：

@Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        return therapy_screen_fragment.newInstance(position + 1, getIntent().getExtras().getString("btnId"));
    }

但是我得到一个错误。我还尝试将 getExtras() 定位在“onCreate(Bundle savedInstanceState)”下，就像在其他空白活动中一样。但我也得到一个错误。

那么，什么是正确的方法来捕获选项卡式活动中的额外意图，然后将这些参数解析为在活动选项卡下显示内容的片段？

Answer 1

哦，看在他妈的份上！非常抱歉耽误您的时间！问题是对于这个特定的活动，我的 putExtra() 中有错字。而且我认为问题出在我获取这些额外内容的方法中......当然，错误是 NullPointException （或类似的东西），原因是我正在寻找的额外内容没有设置。感谢 NSimon 用有问题的评论引导我朝着正确的方向前进！

因此，在 onCreate 方法中获取 extra 是正确的。只是为了澄清是否有人陷入同样的​​困境。

最后我使用了我已经在答案中发布的解决方案（但由于 putExtra 中的拼写错误而出错）：

@Override
public Fragment getItem(int position) {
    // getItem is called to instantiate the fragment for the given page.
    return therapy_screen_fragment.newInstance(position + 1, getIntent().getExtras().getString("btnId"));
}