ViewPager代码:
public class CrimePagerActivity extends AppCompatActivity {
private static final String EXTRA_CRIME_ID =
"com.bignerdranch.android.criminalintent.crime_id";
private static ViewPager mViewPager;
public static List<Crime> mCrimes;
public static int indexPager;
private Button startButton;
private Button finishButton;
public static Intent newIntent(Context packageContext, UUID crimeId) {
Intent intent = new Intent(packageContext, CrimePagerActivity.class);
intent.putExtra(EXTRA_CRIME_ID, crimeId);
return intent;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_crime_pager);
UUID crimeId = (UUID) getIntent()
.getSerializableExtra(EXTRA_CRIME_ID);
mViewPager = (ViewPager) findViewById(R.id.crime_view_pager);
mViewPager.setClipToPadding(false);
mViewPager.setPadding(20, 0, 20, 0);
mViewPager.setPageMargin(20);
mCrimes = CrimeLab.get(this).getCrimes();
FragmentManager fragmentManager = getSupportFragmentManager();
mViewPager.setAdapter(new FragmentStatePagerAdapter(fragmentManager) {
@Override
public Fragment getItem(int position) { // !!!
Crime crime = mCrimes.get(position);
indexPager = position;
return CrimeFragment.newInstance(crime.getId());
}
@Override
public int getCount() {
return mCrimes.size(); //!!!!!!!!
}
});
for (int i = 0; i < mCrimes.size(); i++) {
if (mCrimes.get(i).getId().equals(crimeId)) {
mViewPager.setCurrentItem(i);
indexPager = i;
break;
}
}
}
public static void razmeshcheniyePager(int a){
mViewPager.setCurrentItem(a);
}
}
和片段代码:
public class CrimeFragment extends Fragment {
private static final String ARG_CRIME_ID = "crime_id";
private Crime mCrime;
private EditText mTitleField;
private Button mDateButton;
private CheckBox mSolvedCheckBox;
private Button startButton;
private Button finishButton;
private CrimePagerActivity mPagerActivity;
public static CrimeFragment newInstance(UUID crimeId) {
Bundle args = new Bundle();
args.putSerializable(ARG_CRIME_ID, crimeId);
CrimeFragment fragment = new CrimeFragment();
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
UUID crimeId = (UUID) getArguments().getSerializable(ARG_CRIME_ID);
mCrime = CrimeLab.get(getActivity()).getCrime(crimeId);
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_crime, container, false); // уточнить, что происходит здесь
mTitleField = (EditText) v.findViewById(R.id.crime_title);
startButton = (Button) v.findViewById(R.id.start_button);
if(CrimePagerActivity.indexPager == 2) startButton.setEnabled(false);
startButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mPagerActivity.razmeshcheniyePager(0);
}
});
finishButton = (Button) v.findViewById(R.id.fifsh_button);
if (CrimePagerActivity.indexPager == CrimePagerActivity.mCrimes.size()-3) finishButton.setEnabled(false);
finishButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mPagerActivity.razmeshcheniyePager(CrimePagerActivity.mCrimes.size()-1);
}
});
mTitleField.setText(mCrime.getTitle());
mTitleField.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
mCrime.setTitle(s.toString()); // возвращает строку, которая используется для задания заголовка Crime
}
@Override
public void afterTextChanged(Editable s) {
}
});
mDateButton = (Button) v.findViewById(R.id.crime_date); // кнопка во фрагменте создаётся немного не так, как в активности
mDateButton.setText(mCrime.getDate().toString()); // вывод даты на кнопке
mDateButton.setEnabled(false); // блокироание возможности нажатия кнопки
mSolvedCheckBox = (CheckBox)v.findViewById(R.id.crime_solved);
mSolvedCheckBox.setChecked(mCrime.isSolved()); // метод setChecked меняет булеву значение булевой переменной на противоположное
mSolvedCheckBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
mCrime.setSolved(isChecked);
}
});
return v;
}
}
我需要阻止按钮移动到列表的开头或结尾,以防用户已经在列表的开头或结尾。为此,我试图通过静态变量传递元素的位置。问题在于该元素的位置未正确传输(即,当应传输数字0时传输2,当应传输数字99时传输97)。并且即使您在片段代码中考虑了这一点,按钮锁仍然无法正常工作(按钮甚至可能在附近的几个元素上被阻塞)。我尝试使用调试查找问题,然后遇到了另一个晦涩的功能。锁定按钮之前,该代码可以依次调用多次(可能根本无法调用)。匿名类new FragmentStatePagerAdapter(在CrimePagerActivity活动中)中某些方法的代码可以被调用很多次。请说明正在发生的事情以及如何处理。
P.S。示例代码摘自《 Android编程:大书呆子牧场指南》(第3版)(大书呆子牧场指南)一书。比尔·菲利普斯,克里斯·斯图尔特,克里斯汀·马西卡诺。第11章
您正在indexPager
中设置getItem()
。这是不对的。 getItem()
可以由于任何原因随时调用,不一定反映当前查看或选择的项目。您需要找到另一种设置当前“选定”项目的方法。