Question

您好我正在使用应用程序，其中：

查看寻呼机是否有活动。
在该视图寻呼机上，我显示了2个片段（frag1和frag2）。
按钮点击frag1我们又添加了一个片段（比如说frag3）。
然后按下frag3，我回到了frag1。

问题：

问题是当我从背面按下frag3回到frag1时，有时frag1没有附加到活动。

我无法弄清楚这是怎么回事。

如果发生这种情况，那么解决方案是什么，这样我就可以停止活动来分离frag1或重新初始化frag1。

请帮忙。

Answer 1

此代码可以帮助您

public class PageAdapter extends FragmentPagerAdapter  implements IconPagerAdapter {
    protected static final int[] PAGER = new int[] {
            R.drawable.image1,
            R.drawable.image2,
            R.drawable.image3,
            R.drawable.image4
    };

    private int mCount = PAGER.length;

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

    @Override
    public Fragment getItem(int position) {
        return new PagerFragment(PAGER[position]);
    }

    @Override
    public int getIconResId(int index) {
        return ICONS[index % PAGER.length];
    }

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

    public void setCount(int count) {
        if (count > 0 && count <= 10) {
            mCount = count;
            notifyDataSetChanged();
        }
    }
}

定义碎片

public final class PagerFragment extends Fragment {
    private static final String KEY_CONTENT = "PagerFragment:Content";
    int imageSource;

    public PagerFragment(int imageSource) {
        this.imageSource = imageSource;

    }

    public PagerFragment() {

    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if ((savedInstanceState != null) && savedInstanceState.containsKey(KEY_CONTENT)) {
            imageSource = savedInstanceState.getInt(KEY_CONTENT);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ViewGroup root = (ViewGroup) inflater.inflate(R.layout.indicatorpage, null);
        ImageView image = (ImageView) root.findViewById(R.id.pagerImage);
        image.setImageResource(imageSource);
        setRetainInstance(true);
        return root;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt(KEY_CONTENT, imageSource);
    }
}

MainActivity Class

public class MainActivity extends FragmentActivity {
    PagerFragmentAdapter mAdapter;
    ViewPager mPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAdapter = new PagerFragmentAdapter(getSupportFragmentManager());
        mPager = (ViewPager) findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);
        mPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                System.out.println("selected page is :" + position);

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

        CirclePageIndicator mIndicator = (CirclePageIndicator) findViewById(R.id.indicator);
        mIndicator.setViewPager(mPager);

        final float density = getResources().getDisplayMetrics().density;
        mIndicator.setRadius(7 * density);
        mIndicator.setPageColor(0x00000000);
        mIndicator.setFillColor(0xFFFFFFFF);
        mIndicator.setStrokeColor(0xFFFFFFFF);
        mIndicator.setStrokeWidth(1 * density);
    }

    @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, 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);
    }
}

片段显示但未附加到活动

1 个答案: