在swipeview片段的内部使用回收站视图
[英]Using a recycler view inside a fragment of a swipeview
问题描述
我试图在片段的回收器视图中显示mySQLiteDB。 如果可以的话，我正在使用Fragment Activities类作为MainActivity。 我正在片段内设置回收站视图。 getAllFixedCosts方法未像我希望的那样显示所有数据。 这是整个片段活动：
public class FragmentActivity extends AppCompatActivity {
int MoneyAmount;
String FixedCostItem;
int FixedItemCostAmount;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment);
SharedPreferences sharedPrefs = getSharedPreferences("MyPrefs", 0);
String Money = (sharedPrefs.getString("AMOUNTMONEY", "WhatsUP"));
MoneyAmount = Integer.parseInt(Money);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
Cursor cursor = getAllFixedCosts();
mAdapter = new FixedCostsAdapter(this, cursor);
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
public Cursor getAllFixedCosts() {
return readDB.query(
FixedCostsContract.FixedCostsEntry.TABLE_NAME,
null,
null,
null,
null,
null,
null);
}
public void addFixedCost(String FixedItem, String FixedCostAmount){
if(FixedItem.length() == 0 ||
FixedCostAmount.length() == 0){
return;
}
FixedItemCostAmount = Integer.parseInt(FixedCostAmount);
addFixedCostDB(FixedCostItem, FixedItemCostAmount);
mAdapter.swapCursor(getAllFixedCosts());
}
private void addFixedCostDB(String FixedCostItem,int FixedCostItemAmount) {
ContentValues cv = new ContentValues();
cv.put(FixedCostsContract.FixedCostsEntry.COLUMN_COST_NAME, FixedCostItem);
cv.put(FixedCostsContract.FixedCostsEntry.COLUMN_COST_AMOUNT, FixedCostItemAmount);
mDB.insert(FixedCostsContract.FixedCostsEntry.TABLE_NAME, null, cv);
mDB.close();
}
@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_, 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);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position){
case 0:
FixedCosts fixedCosts = new FixedCosts();
return fixedCosts;
}
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "Fixed Costs";
case 1:
return "Long term investments";
case 2:
return "SECTION 3";
}
return null;
}
}
}
滑动视图的第一个片段应该具有一个回收站视图，该视图显示来自SQLiteDB的数据，但是在调用时崩溃。 这是片段：
public class FixedCosts extends Fragment {
SQLiteDatabase mDB;
SQLiteDatabase readDB;
FixedCostsAdapter mAdapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fixed_costs_fragment, container, false);
SharedPreferences sharedPrefs = this.getActivity().getSharedPreferences("MyPrefs", 0);
Button launchDialog = (Button) view.findViewById(R.id.AddNewFixedCostsButton);
launchDialog.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DialogFragment dialog = new InfoDialogFragment();
dialog.show(getFragmentManager(), "dialog");
}
});
FragmentActivity fragmentActivity = new FragmentActivity();
String amount = (sharedPrefs.getString("AMOUNTMONEY", "WhatsUP"));
String TextAmount = "$"+amount;
RecyclerView FCRecycler = (RecyclerView) view.findViewById(R.id.FixedCostsRV);
FixedCostsDbHelper dbHelper = new FixedCostsDbHelper(getActivity());
mDB = dbHelper.getWritableDatabase();
Cursor cursor = fragmentActivity.getAllFixedCosts();
mAdapter = new FixedCostsAdapter(getActivity(), cursor);
FCRecycler.setAdapter(mAdapter);
readDB = dbHelper.getReadableDatabase();
FCRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));
TextView TitletextView = (TextView) view.findViewById(R.id.amountTitle);
TitletextView.setText(TextAmount);
return view;
}
}
我试图通过发送将其作为参数来获取用户输入的数据。 这是获取SQLiteDB数据的对话框片段：
public class InfoDialogFragment extends DialogFragment {
public InfoDialogFragment() {
}
@NonNull
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
final AlertDialog.Builder adb = new AlertDialog.Builder(getActivity());
final LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.info_dialogfrag, null);
adb.setView(view);
final EditText itemET = (EditText)view.findViewById(R.id.getItem);
final EditText itemAmountET = (EditText)view.findViewById(R.id.getItemAmount);
adb
/*.setIcon()*/
.setTitle("Fixed Cost")
.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String FixedCostItem = itemET.getText().toString();
String FixedCostItemAmount = itemAmountET.getText().toString();
if(FixedCostItem.length() == 0 || FixedCostItemAmount.length() == 0){
Toast.makeText(getActivity(),"Enter Item and Amount", Toast.LENGTH_SHORT).show();
}else{
FragmentActivity fragmentActivity = new FragmentActivity();
fragmentActivity.addFixedCost(FixedCostItem, FixedCostItemAmount);
dialog.dismiss();
}
}
})
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
InfoDialogFragment.this.getDialog().cancel();
}
});
return adb.create();
}
}
最后，我有一个适配器，给出了NullPointerException。 我认为这堂课是对的，但是在此过程中，它会受到其他因素的影响。 这是适配器：
public class FixedCostsAdapter extends RecyclerView.Adapter<FixedCostsAdapter.FixedCostViewHolder> {
private Cursor mCursor;
private Context mContext;
public FixedCostsAdapter(Context context, Cursor cursor) {
this.mContext = context;
this.mCursor = cursor;
}
public void swapCursor(Cursor newCursor) {
// Always close the previous mCursor first
if (mCursor != null) mCursor.close();
mCursor = newCursor;
if (newCursor != null) {
// Force the RecyclerView to refresh
this.notifyDataSetChanged();
}
}
@Override
public FixedCostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(mContext);
View view = inflater.inflate(R.layout.recyclerviewlayout, parent, false);
return new FixedCostViewHolder(view);
}
@Override
public void onBindViewHolder(FixedCostViewHolder holder, int position) {
if (!mCursor.moveToPosition(position))
return; // bail if returned null
// Update the view holder with the information needed to display
String name = mCursor.getString(mCursor.getColumnIndex(FixedCostsContract.FixedCostsEntry.COLUMN_COST_NAME));
int costAmount = mCursor.getInt(mCursor.getColumnIndex(FixedCostsContract.FixedCostsEntry.COLUMN_COST_AMOUNT));
// COMPLETED (6) Retrieve the id from the cursor and
long id = mCursor.getLong(mCursor.getColumnIndex(FixedCostsContract.FixedCostsEntry._ID));
// Display the guest name
holder.item.setText(name);
// Display the party count
holder.amount.setText(String.valueOf(costAmount));
// COMPLETED (7) Set the tag of the itemview in the holder to the id
holder.itemView.setTag(id);
}
@Override
public int getItemCount() {
return mCursor.getCount();
}
class FixedCostViewHolder extends RecyclerView.ViewHolder {
TextView item;
TextView amount;
public FixedCostViewHolder(View itemView) {
super(itemView);
item = (TextView)itemView.findViewById(R.id.textItem);
amount = (TextView)itemView.findViewById(R.id.textAmount);
}
}
}
错误日志：
07-12 18:54:13.289 12915-12915/com.example.android.budgetcrunch
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.budgetcrunch, PID: 12915
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.budgetcrunch/com.example.android.budgetcrunch.FragmentActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.query(java.lang.String, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String, java.lang.String, java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1631)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6682)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.query(java.lang.String, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String, java.lang.String, java.lang.String)' on a null object reference
at com.example.android.budgetcrunch.FragmentActivity.getAllFixedCosts(FragmentActivity.java:79)
at com.example.android.budgetcrunch.FragmentActivity.onCreate(FragmentActivity.java:66)
at android.app.Activity.performCreate(Activity.java:6942)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2880)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1631)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6682)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
感谢您的任何帮助。
1 个解决方案
解决方案1
0 2017-07-12 22:47:11
您正在初始化readDB之前调用它。
这是您的错误：
java.lang.NullPointerException: com.example.android.budgetcrunch.FragmentActivity.getAllFixedCosts(FragmentActivity.java:79)
在初始化之前，您正在调用方法getAllFixedCosts() 。
这是您的顺序：
Cursor cursor = fragmentActivity.getAllFixedCosts(); // THIS CRASHES
mAdapter = new FixedCostsAdapter(getActivity(), cursor);
FCRecycler.setAdapter(mAdapter);
readDB = dbHelper.getReadableDatabase(); // THIS INITIALIZES THE DB
因此， getAllFixedCosts()正在执行：
return readDB.query(…
但是readDB在您调用时为null。
解决方案：将行readDB = dbHelper.get…移动到崩溃的行的正上方（ Cursor cursor = fragmentActivity.get… ）
定位在片段内的回收器视图项内的按钮侦听器
[英]Target a button listener that is inside a recycler view item that is inside a fragment
我想使用回收者视图将数据从Firebase获取到内部片段
[英]I want to get data from firebase to inside fragment with recycler view
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.