Question

我到处寻找，但在每个帖子中问题似乎都存在。我使用FragmentStatePageAdapter实现了一个viewpager。当片段在UI上正确显示时，当我尝试将值传递给片段时，应用程序崩溃，因为片段未初始化。要检查我在每个部分中放置一个日志，只显示第一个和第三个日志。这是我的代码。

代码

resultsList[[1]]$coefficients
resultsList[[1]]$r.squared

这是我的日志：

public class MainActivity extends FragmentActivity implements      OnDataReceivedListener, OnStateChangedListener {

    ViewPager viewPager;
    PagerAdapter pagerAdapter;
    private ImageView logo;

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

        logo = (ImageView)findViewById(R.id.logo);

        viewPager = (ViewPager)findViewById(R.id.viewpager_first);
        pagerAdapter= new PagerAdapter(getSupportFragmentManager(),3);
        CircleIndicator indicator (CircleIndicator)findViewById(R.id.indicator);
        viewPager.setAdapter(pagerAdapter);
        indicator.setEnabled(true);
        indicator.setViewPager(viewPager);

        logo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                flipApi.startScan();
            }
        });

    }


    class PagerAdapter extends FragmentStatePagerAdapter {

        int num;
        public PagerAdapter(FragmentManager fm, int x) {
            super(fm);
            this.num=x;
        }

        public Fragment currentFragment;

        @Override
        public Fragment getItem(int position) {
            //add new fragment here for homepage viewpager

            switch (position) {

                case 0:
                    currentFragment = new Calorie_Fragment();
                    Log.d("flip",1+"");
                    return currentFragment;


                case 1:
                    currentFragment = new HeartRate_Fragment();
                    Log.d("flip",2+"");
                    return currentFragment;


                case 2:
                    currentFragment = new Steps_Fragment();
                    Log.d("flip",3+"");
                    return currentFragment;


                default:
                    return null;

            }

        }

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

        public Fragment getCurrentFragment() {
            return  this.currentFragment;
        }
    }
}

Answer 1

试试这个。：）

 class PagerAdapter extends FragmentStatePagerAdapter {

 HeartRate_Fragment heartRate_fragment;
Calorie_Fragment calorie_fragment;
 Steps_Fragment steps_fragment;

int num;
public PagerAdapter(FragmentManager fm, int x) {
    super(fm);
    this.num=x;
}
@Override
public Fragment getItem(int position) {
    //add new fragment here for homepage viewpager

    switch (position) {

        case 0:
            if(heartRate_fragment == null)
            heartRate_fragment = new HeartRate_Fragment();
            Log.d("flip",1+"");
            return heartRate_fragment;


        case 1:
            if(calorie_fragment == null)
            calorie_fragment = new Calorie_Fragment();
            Log.d("flip",2+"");
            return calorie_fragment;


        case 2:
            if(steps_fragment == null)
            steps_fragment = new Steps_Fragment();
            Log.d("flip",3+"");
            return steps_fragment;


        default:
            return null;

    }

}

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

public HeartRate_Fragment getHRFragment()
{
    return heartRate_fragment;
}
public Calorie_Fragment getCalorie_fragment()
{
    return calorie_fragment;
}
public  Steps_Fragment getSteps_fragment()
{
    return steps_fragment;
}

Viewpager显示正确的片段但不初始化它

1 个答案: