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Use FragmentStatePagerAdapter with cursor rather than Collection/Array data structure
package com.example;
import android.content.Context;
import android.database.Cursor;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.util.SparseIntArray;
import android.view.ViewGroup;
import java.util.HashMap;
public abstract class CursorFragmentStatePagerAdapter extends FragmentStatePagerAdapter {
protected boolean mDataValid;
protected Cursor mCursor;
protected Context mContext;
protected SparseIntArray mItemPositions;
protected HashMap<Object, Integer> mObjectMap;
protected int mRowIDColumn;
public CursorFragmentPagerAdapter(Context context, FragmentManager fm, Cursor cursor) {
super(fm);
init(context, cursor);
}
void init(Context context, Cursor c) {
mObjectMap = new HashMap<Object, Integer>();
boolean cursorPresent = c != null;
mCursor = c;
mDataValid = cursorPresent;
mContext = context;
mRowIDColumn = cursorPresent ? c.getColumnIndexOrThrow("_id") : -1;
}
public Cursor getCursor() {
return mCursor;
}
@Override
public int getItemPosition(Object object) {
Integer rowId = mObjectMap.get(object);
if (rowId != null && mItemPositions != null) {
return mItemPositions.get(rowId, POSITION_NONE);
}
return POSITION_NONE;
}
public void setItemPositions() {
mItemPositions = null;
if (mDataValid) {
int count = mCursor.getCount();
mItemPositions = new SparseIntArray(count);
mCursor.moveToPosition(-1);
while (mCursor.moveToNext()) {
int rowId = mCursor.getInt(mRowIDColumn);
int cursorPos = mCursor.getPosition();
mItemPositions.append(rowId, cursorPos);
}
}
}
@Override
public Fragment getItem(int position) {
if (mDataValid) {
mCursor.moveToPosition(position);
return getItem(mContext, mCursor);
} else {
return null;
}
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
mObjectMap.remove(object);
super.destroyItem(container, position, object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
if (!mDataValid) {
throw new IllegalStateException("this should only be called when the cursor is valid");
}
if (!mCursor.moveToPosition(position)) {
throw new IllegalStateException("couldn't move cursor to position " + position);
}
int rowId = mCursor.getInt(mRowIDColumn);
Object obj = super.instantiateItem(container, position);
mObjectMap.put(obj, Integer.valueOf(rowId));
return obj;
}
public abstract Fragment getItem(Context context, Cursor cursor);
@Override
public int getCount() {
if (mDataValid) {
return mCursor.getCount();
} else {
return 0;
}
}
public void changeCursor(Cursor cursor) {
Cursor old = swapCursor(cursor);
if (old != null) {
old.close();
}
}
public Cursor swapCursor(Cursor newCursor) {
if (newCursor == mCursor) {
return null;
}
Cursor oldCursor = mCursor;
mCursor = newCursor;
if (newCursor != null) {
mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
mDataValid = true;
} else {
mRowIDColumn = -1;
mDataValid = false;
}
setItemPositions();
if (mDataValid){
notifyDataSetChanged();
}
return oldCursor;
}
}
@zaur
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zaur commented Apr 30, 2015

Thank you, guys. Saved my release.

@IEnoobong
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Thanks a lot, for help... Please how can it be used?

@efung
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efung commented Jun 22, 2016

Thanks for this. Minor typo in L22 in name of constructor.

@efung
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efung commented Jun 23, 2016

If the adapter is instantiated with a non-null Cursor, and swapCursor or changeCursor is never called, the item positions map is never initialized. I believe a call to setItemPositions() is missing after L34.

@justsanjit
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Thank you very much. Perfect and quick solution for my problem.

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