Question

我很难创建合适的Intent。 Intent在Context下显示一条红线。这是我的代码，任何人都可以帮助我摆脱这个问题。

这是MainCategory.java（选项卡式活动）

public class MainCategory extends AppCompatActivity {

/**
 * 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}.
 */
private SectionsPagerAdapter mSectionsPagerAdapter;

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

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // 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.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);


    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

}


@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_main_category, 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);
}

/**
 * A placeholder fragment containing a simple view.
 */


/**
 * 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 a PlaceholderFragment (defined as a static inner class below).
        switch(position){
            case 0: return Mc1_Activity.newInstance();
            case 1 : return Mc2_Activity.newInstance() ;
            // default: return MyFragment.newInstance();

        }
        return null;

    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 2;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "SECTION 1";
            case 1:
                return "SECTION 2";
            case 2:
                return "SECTION 3";
        }
        return null;
    }
}
}

这是PlaceholderFragment.java

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

public PlaceholderFragment() {
}

/**
 * Returns a new instance of this fragment for the given 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;
}
}

这是由Mc1_Activity.java命名的选项卡式活动的片段活动

public class Mc1_Activity extends Fragment {

public static Mc1_Activity newInstance() {
    Mc1_Activity fragment = new Mc1_Activity();
    return fragment;
}

public Mc1_Activity() {
}

ImageView iv;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.mc1_fragment, container, false);
    iv = (ImageView) rootView.findViewById(R.id.iv_mc1);
    iv.setBackgroundResource(R.drawable.mc1);

    iv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent go = new Intent(this,next_activity.class);
            startActivity(go);
        }
    });
    return rootView;
}
}

这是mc1_fragment.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.user.evacookingrecipes.MainCategory">

<ImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/iv_mc1"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />
</RelativeLayout>

这是Activity_Main_Category.xml

<?xml version="1.0" encoding="utf-8"?>

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/appbar_padding_top"
    android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/AppTheme.PopupOverlay">

    </android.support.v7.widget.Toolbar>

</android.support.design.widget.AppBarLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="end|bottom"
    android:layout_margin="@dimen/fab_margin"
    android:src="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

我在上下文中遇到问题。

iv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent go = new Intent(this,SoupDesertsCooking.class);
            startActivity(go);
        }
    });

Answer 1

 iv.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent go = new Intent(getActivity(),next_activity.class);
        startActivity(go);
    }
});

Answer 2

像这样使用，因为this正在片段中传递onClick个上下文：

iv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent go = new Intent(getActivity(),SoupDesertsCooking.class);
            startActivity(go);
        }
    });

Answer 3

getActivity()

iv.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent go = new Intent(getActivity(), SoupDesertsCooking.class);
            startActivity(go);
        }
    });

Answer 4

使用两个选项中的一个：

或

Intent go = new Intent(getActivity(), SoupDesertsCooking.class);
startActivity(go);

在这种情况下如何获得活动背景？

4 个答案: