Question

这个项目有一些类似的帖子，但我仍然有以下错误：类型不匹配：无法从ScreenSlidePageFragment转换为Fragment。我正在尝试使用屏幕幻灯片运行项目。我能做什么？请帮我。谢谢。

import android.app.Fragment;
import android.app.FragmentManager;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.NavUtils;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;

/**
 * Demonstrates a "screen-slide" animation using a {@link ViewPager}. Because {@link ViewPager}
 * automatically plays such an animation when calling {@link ViewPager#setCurrentItem(int)},there
 * isn't any animation-specific code in this sample.
 *
 * <p>This sample shows a "next" button that advances the user to the next step in a wizard,
 * animating the current screen out (to the left) and the next screen in (from the right). The
 * reverse animation is played when the user presses the "previous" button.</p>
 *
 * @see ScreenSlidePageFragment
 */
public class ScreenSlideActivity extends FragmentActivity {
    /**
     * The number of pages (wizard steps) to show in this demo.
     */
    private static final int NUM_PAGES = 5;

    /**
     * The pager widget, which handles animation and allows swiping horizontally to access previous
     * and next wizard steps.
     */
    private ViewPager mPager;

    /**
     * The pager adapter, which provides the pages to the view pager widget.
     */
    private PagerAdapter mPagerAdapter;

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

        // Instantiate a ViewPager and a PagerAdapter.
        mPager = (ViewPager) findViewById(R.id.pager);
        mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);
        mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                // When changing pages, reset the action bar actions since they are dependent
                // on which page is currently active. An alternative approach is to have each
                // fragment expose actions itself (rather than the activity exposing actions),
                // but for simplicity, the activity provides the actions in this sample.
                invalidateOptionsMenu();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        getMenuInflater().inflate(R.menu.activity_screen_slide, menu);

        menu.findItem(R.id.action_previous).setEnabled(mPager.getCurrentItem() > 0);

        // Add either a "next" or "finish" button to the action bar, depending on which page
        // is currently selected.
        MenuItem item = menu.add(Menu.NONE, R.id.action_next, Menu.NONE,
                (mPager.getCurrentItem() == mPagerAdapter.getCount() - 1)
                        ? R.string.action_finish
                        : R.string.action_next);
        item.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM | MenuItem.SHOW_AS_ACTION_WITH_TEXT);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                // Navigate "up" the demo structure to the launchpad activity.
                // See http://developer.android.com/design/patterns/navigation.html for more.
                NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
                return true;

            case R.id.action_previous:
                // Go to the previous step in the wizard. If there is no previous step,
                // setCurrentItem will do nothing.
                mPager.setCurrentItem(mPager.getCurrentItem() - 1);
                return true;

            case R.id.action_next:
                // Advance to the next step in the wizard. If there is no next step, setCurrentItem
                // will do nothing.
                mPager.setCurrentItem(mPager.getCurrentItem() + 1);
                return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * A simple pager adapter that represents 5 {@link ScreenSlidePageFragment} objects, in
     * sequence.
     */
    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(android.support.v4.app.FragmentManager fm) {
            super(fm);
        }

        @Override
        public android.support.v4.app.Fragment getItem(int position) {
            return ScreenSlidePageFragment.create(position);
        }

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

Answer 1

在适配器中，尝试更改此内容：

@Override
        public android.support.v4.app.Fragment getItem(int position) {
            return ScreenSlidePageFragment.create(position);
        }

到此：

@Override
        public ScreenSlidePageFragment getItem(int position) {
            return ScreenSlidePageFragment.create(position);
        }

因为你告诉那个方法你要返回一个片段，但是你要返回一个ScreenSlidePageFragment。如果它给你一个类型不匹配错误消息，那么这可能是源。

类型不匹配：无法从ScreenSlidePageFragment转换为Fragment

1 个答案: