UIPopoverController做了个例子，在做时碰到一个郁闷的问题。例子代码检查没有问题，也不报错，可popover就是不显示，纠结哈。参考了些博文也没找到答案，最后无意中发现popover显示的位置我设的是向下UIPopoverArrowDirectionDown导致没能显示出来。

以下为实例：

//
//  SearchPopoverViewController.h
//  Ipad004
//  搜索框-显示popover
//  Created by Dwen on 12-11-2.
//  Copyright (c) 2012年 __MyCompanyName__. All rights reserved.
//
#import <UIKit/UIKit.h>
@interface SearchPopoverViewController : UITableViewController
@end

#import "SearchPopoverViewController.h"

@interface SearchPopoverViewController ()

@end

@implementation SearchPopoverViewController

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
	return YES;
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return 4;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
    }
    cell.textLabel.text = @"商品";
    cell.detailTextLabel.text = @"约800条";
    return cell;
}

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
 
}

@end

SearchPopoverViewController *spVC = [[SearchPopoverViewController alloc] initWithNibName:@"SearchPopoverViewController" bundle:nil];

//    SearchPopoverViewController *spVC = [[SearchPopoverViewController alloc] initWithStyle:UITableViewStylePlain];
    spVC.contentSizeForViewInPopover = CGSizeMake(200, 300);
    popover = [[UIPopoverController alloc] initWithContentViewController:spVC];
    [popover presentPopoverFromRect:[self.searchBar bounds] inView:self.searchBar permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];

问题：

The problem: poor texture quality in android app written with Andengine(wraps opengl), especially on gradients which appear as steps in few colours. Problem occurs on real and virtual device

Settings: default texture, fullscreen, native resolution, android 2.2. I have tried to enforce PixelFromat with:

public void onAttachedToWindow() {
    super.onAttachedToWindow();
    Window window = getWindow();
    window.setFormat(PixelFormat.RGBA_8888);
}

Haven't made any difference.

Commenting line: GLHelper.disableDither(pGL); helped a little with textures, but made particles look bad, so a guess it is not the source of problem.

Example loading code:

public static void loadResources(StreamgameActivity game) {
    magnetTexture = new BitmapTextureAtlas(512, 512, TextureOptions.BILINEAR);
    magnetTextureRegion = BitmapTextureAtlasTextureRegionFactory
       .createFromAsset(magnetTexture, game,"bateria128CMatte_none.png", 0, 0);
    game.getEngine().getTextureManager().loadTexture(magnetTexture);
}

解决方法：

方法一：

Andengine seems to use be default 16bit rendering mode. To change that I have done:
this.mRenderSurfaceView = new RenderSurfaceView(this);
mRenderSurfaceView.setEGLConfigChooser(8,8,8,8,0,0);//!!
mRenderSurfaceView.setRenderer(mEngine);
mRenderSurfaceView.getHolder().setFormat(PixelFormat.RGBA_8888);//!!
in onSetContentView method.

方法二：

if someone is experiencing poor texture quality and banding for GLES2 here is the solution: just overridepreDraw() of your Sprite and enable dithering like this:
Sprite electricityOff = new Sprite(0, 0, mElectricityOffTextureRegion, getVertexBufferObjectManager()) {
    @Override
    protected void preDraw(GLState pGLState, Camera pCamera) {
        super.preDraw(pGLState, pCamera);
        pGLState.enableDither();
    }
};
Key element is pGLState.enableDither();. You will not need anything else but in case you want to ensure 32bit rendering for the surface and activity you can add:
@Override
protected void onSetContentView() {
    mRenderSurfaceView = new RenderSurfaceView(this);
    mRenderSurfaceView.setEGLConfigChooser(8, 8, 8, 8, 24, 0);
    mRenderSurfaceView.setRenderer(mEngine, this);
    mRenderSurfaceView.getHolder().setFormat(PixelFormat.RGBA_8888);

    this.setContentView(mRenderSurfaceView, BaseGameActivity.createSurfaceViewLayoutParams());
}


@Override
public void onAttachedToWindow() {
    super.onAttachedToWindow();
    Window window = getWindow();
    window.setFormat(PixelFormat.RGBA_8888);
}