我在Android中遇到ViewPager和ViewPagerAdapter的問題。 我使用一個viewpager與2靜態片段(一個使用textEdit和第二個使用列表視圖)。他們工作得很好。 但我有一個動態的第三個片段的問題。 它使用相機,必須立即執行,銷燬,重新實施。所以,ViewPagerAdapter可以包含2或3個分檔。 當我重新初始化第三個片段時,出現問題,我在OnCreateView()後得到了一個NPE(主佈局視圖在此方法後爲空,但在方法內不爲null)。ViewPager和動態碎片:再次instaciation給NPE
沒有爲主要活動代碼:)
mViewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager();
mTabLayout = (TabLayout) findViewById(R.id.tabs);
mTabLayout.setupWithViewPager(mViewPager);
的setupViewPager(:
private void setupViewPager() {
mViewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
mTabFragmentDocument = new TabFragmentDocument();
mTabFragmentDocument.setApp(this);
mTabFragmentText = new TabFragmentText();
mTabFragmentText.setApp(this);
mViewPagerAdapter.addFragment(mTabFragmentText, AbstractDefiner.TEXT);
mViewPagerAdapter.addFragment(mTabFragmentDocument, AbstractDefiner.DOCUMENT);
mViewPager.setAdapter(mViewPagerAdapter);
}
要創建第三個片段:
mTabFragment = new TabFragment();
mTabFragment .setApp(this);
mViewPagerAdapter.addFragment(mTabFragment, "THIRD");
mViewPagerAdapter.notifyDataSetChanged();
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
mViewPager.setCurrentItem(2);
mViewPagerAdapter.notifyDataSetChanged();
mTabFragment .setParams(tmp[1], tmp[2], tmp[3], tmp[4]);
mTabFragment .setupView();
mTabFragment .startWork();
}
}, 1000);
並摧毀它:
mViewPager.setCurrentItem(0);
mViewPager.removeViewAt(2);
mTabFragment .onDestroy();
mViewPagerAdapter.remove(2);
mViewPagerAdapter.notifyDataSetChanged();
mTabFragment = null;
然後,適配器代碼:
static class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
public void remove(int index) {
mFragmentList.remove(index);
mFragmentTitleList.remove(index);
}
@Override
public int getItemPosition(Object object) {
return PagerAdapter.POSITION_NONE;
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
最後,第三個片段的代碼:
public class TabFragment extends Fragment implements SurfaceHolder.Callback,
GLSurfaceView.Renderer {
private static final String LOGCAT = "WEB_RTC_VISIO";
private HomeActivity mApp;
private String p1;
private String p2;
private String p3;
private String p4;
private VideoSource mLocalVideoSource;
private VideoRenderer.Callbacks mLocalRenderer;
private VideoRenderer.Callbacks mRemoteRenderer;
private GLSurfaceView mVideoView;
private SurfaceView mDrawView;
private SurfaceHolder mDrawHolder;
private ImageView mCursor;
private String mBgBytesString;
private ImageView mImgView;
private View mV;
public TabFragment() {
// Required empty public constructor
}
public void setApp(HomeActivity app) {
mApp = app;
}
public void setParams(String p1, String p2, String p3,
String p4) {
this.p1= p1;
this.p2= p2;
this.p4= p4;
this.p3= p3;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
mV = inflater.inflate(R.layout.third_layout, container, false);
return mV;
}
@Override
public void onDetach() {
super.onDetach();
}
public void setupView() {
RequestUserPermission requestUserPermission = new RequestUserPermission(mApp);
requestUserPermission.verifyStoragePermissions();
mImgView = (ImageView) mV.findViewById(R.id.img_display); // NPE HERE
TextView mTest1= (TextView) mV.findViewById(R.id.test1);
mRequestLabelTextView.setText("test 1");
TextView mTest2= (TextView) mV.findViewById(R.id.test2);
mEquipmentSerialTextView.setText("test 2");
// View that displays the view from the camera
mVideoView = (GLSurfaceView) mV.findViewById(R.id.gl_surface);
// View that displays the cursor and drawing associated
mDrawView = (SurfaceView) mV.findViewById(R.id.draw_surface);
mDrawHolder = mDrawView.getHolder();
mDrawHolder.setFormat(PixelFormat.TRANSPARENT);
mDrawHolder.addCallback(this);
// Image of the cursor
mCursor = (ImageView) mV.findViewById(R.id.mouseCursor);
// Some more inits
}
public void startWork() {
//SOME WORK
}
}
所以,第一個instanciation是好的,但在第二次,我得到了NPE在獲取ImageView ... 有人可以幫助我理解這個問題嗎?
在此先感謝!
你爲什麼要摧毀它? –
因爲我需要禁止用戶在不需要的時候使用3片段,並且釋放相機資源。 然後,爲了將來,我需要使用相機創建2個不同的片段,取決於情況取得第三個片段的地方... – Aeldred