ViewPager和数据库 [英] ViewPager and Database
问题描述
数据在数据库中,所以我通常使用CursorAdapter,并使用CursorLoader在ListView上,但现在我需要一个ViewPager而不是一个ListView,并且需要一个PagerAdapter,我只有它看到它的工作
The data is in a Database, so I would normally use CursorAdapter and have it work with CursorLoader on a ListView, however now I need a ViewPager instead of a ListView and that takes a PagerAdapter and I only have it have seen it work with lists.
是否有使用游标的原生传呼机适配器,或者不适合使用。
Is there a native pager adapter that uses a cursor or ill have to make it work?
感谢!
推荐答案
基于 CursorAdapter 我有一个实现扩展 FragmentPagerAdapter ,唯一的区别是您将使用来自光标实例化 Fragment 。
Based on the internals of the CursorAdapter I have an implementation that extends FragmentPagerAdapter with the only difference that you will use the information coming from a Cursor to instantiate a Fragment.
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 CursorFragmentPagerAdapter extends FragmentPagerAdapter {
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();
notifyDataSetChanged();
return oldCursor;
}
@Override
public long getItemId(int position) {
if (!mDataValid || !mCursor.moveToPosition(position)) {
return super.getItemId(position);
}
int rowId = mCursor.getInt(mRowIDColumn);
return rowId;
}
}
您可以轻松地根据需要修改代码。
If you need something else than Fragment's you can easily alter the code to your needs.
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