在這個getView，編程視圖生成中初始化RelativeLayout

Question

我在一個適配器中使用了一個getView，我正在創建一個imageview並使之等於convertView，其中視圖已經被初始化了。它包含圖像縮略圖，其中一些代表視頻。

@Override 
    public View getView(int position, View convertView, ViewGroup container) { 
     // First check if this is the top row 

     if (position < mNumColumns) { 
      if (convertView == null) { 
       convertView = new View(mContext); 
      } 
      // Set empty view with height of ActionBar 
      //convertView.setLayoutParams(new AbsListView.LayoutParams(
      //  LayoutParams.MATCH_PARENT, mActionBarHeight)); 
      return convertView; 
     } 

     // Now handle the main ImageView thumbnails 
     ImageView imageView; 
     if (convertView == null) { // if it's not recycled, instantiate and initialize 
      imageView = new RecyclingImageView(mContext); 
      imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
      imageView.setLayoutParams(mImageViewLayoutParams); 
     } else { // Otherwise re-use the converted view 
      imageView = (ImageView) convertView; 
     } 

     // Check the height matches our calculated column width 
     if (imageView.getLayoutParams().height != mItemHeight) { 
      imageView.setLayoutParams(mImageViewLayoutParams); 
     } 

     imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 

     if(images.get(position - mNumColumns).getUriString().contains("video")){ 
      //display video icon 
     } 
     else 
     { 
      //don't display video icon 
     } 

     // Finally load the image asynchronously into the ImageView, this also takes care of 
     // setting a placeholder image while the background thread runs 
     if (images != null && !images.isEmpty()) 
      mImageFetcher.loadImage(images.get(position - mNumColumns).getUriString()/*.imageUrls[position - mNumColumns]*/, imageView); 
     return imageView; 
    } 

縮略圖沒有一個「播放」按鈕，對他們來指定，他們是視頻，所以在這種情況下，我需要添加一個播放按鈕，編程。

通常情況下，我使用了一個帶有膨脹佈局的視圖模式，在這種情況下我沒有這樣做，因爲我實際上不想在內存中使用某些東西。

所以不是我想以編程方式做出RelativeLayout的每個單元（mRelativeLayout = (RelativeLayout)convertView）的根視圖，並添加ImageView的和PLAYBUTTON ImageView的成convertview

我該怎麼辦呢？它要求本聲明的修改，但我不知道如何初始化全部重新使用的視圖

} else { // Otherwise re-use the converted view 
      imageView = (ImageView) convertView; 
     } 

Answer 1

的性能損失

我會讓你的getView()始終返回一個RelativeLayout對象（我將其稱爲containerView），您將其作爲子女添加到ImageView(s)。

這裏唯一的問題是您需要給這些孩子標識符，以便您可以稍後從回收的convertView中檢索它們。請注意，我爲此使用了內置靜態View.generateViewId()，這是API級別17.如果您需要它在API-level-17之前工作，則可以使用唯一整數（例如1，2等）創建自己的ID ） - 只要確保它們不大於0x0FFFFFF。 更新：我在下面添加了代碼。

查看我在以下幾點添加的評論。

@Override 
public View getView(int position, View convertView, ViewGroup container) { 
    // First check if this is the top row 
    if (position < mNumColumns) { 
     if (convertView == null) { 
      convertView = new View(mContext); 
     } 
     // Set empty view with height of ActionBar 
     //convertView.setLayoutParams(new AbsListView.LayoutParams(
     //  LayoutParams.MATCH_PARENT, mActionBarHeight)); 
     return convertView; 
    } 

    // Now handle the main ImageView thumbnails 
    RelativeLayout containerView; 
    ImageView imageView; 
    ImageView videoIconView; // TODO: or whatever type you want to use for this... 
    if (convertView == null) { // if it's not recycled, instantiate and initialize 
     containerView = new RelativeLayout(mContext); 
     // TODO: The layout params that you used for the image view you probably 
     // now want to use for the container view instead... 
     imageView.setLayoutParams(mImageViewLayoutParams); // If so, you can change their name... 

     imageView = new RecyclingImageView(mContext); 
     imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 
     //imageView.setLayoutParams(mImageViewLayoutParams); // This probably isn't needed any more. 

     // Generate an Id to use for later retrieval of the imageView... 
     // This assumes it was initialized to -1 in the constructor to mark it being unset. 
     // Note, this could be done elsewhere in this adapter class (such as in 
     // the constructor when mImageId is initialized, since it only 
     // needs to be done once (not once per view) -- I'm just doing it here 
     // to avoid having to show any other functions. 
     if (mImageId == -1) { 
      mImageId = View.generateViewId(); 
     } 
     imageView.setId(mImageId); 

     containerView.addView(imageView, RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT); 

     // NOTE: At this point, I would personally always just add the video icon 
     // as a child of containerView here no matter what (generating another unique 
     // view Id for it, mVideoIconId, similar to how was shown above for the imageView) 
     // and then set it to either VISIBLE or INVISIBLE/GONE below depending on whether 
     // the URL contains the word "video" or not. 
     // For example: 
     vidoIconView = new <whatever>; 
     // TODO: setup videoIconView with the proper drawable, scaling, etc. here... 
     if (mVideoIconId == -1) { 
      mVideoIconId = View.generateViewId(); 
     } 
     videoIconView.setId(mVideoIconId); 
     containerView.addView(videoIconView, RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT); 
     final RelativeLayout.LayoutParams layout = ((RelativeLayout.LayoutParams)containerView.getLayoutParams()); 
     layout.addRule(RelativeLayout.LayoutParams.CENTER_HORIZONTAL); // ... or whatever else you want 
     layout.addRule(RelativeLayout.LayoutParams.ALIGN_PARENT_BOTTOM); // ... or whatever else you want 
    } else { 
     // Otherwise re-use the converted view 
     containerView = (RelativeLayout) convertView; 
     imageView = containerView.findViewById(mImageId); 
     videoIconView = containerView.findViewById(mVideoIconId); // see comment above 
    } 


    // Check the height matches our calculated column width 
    if (containerView.getLayoutParams().height != mItemHeight) { 
     containerView.setLayoutParams(mImageViewLayoutParams); 
    } 

    if(images.get(position - mNumColumns).getUriString().contains("video")){ 
     //display video icon 
     // see comment above, here you can probably just do something like: 
     videoIconView.setVisibility(View.VISIBLE); 
    } 
    else 
    { 
     //don't display video icon 
     videoIconView.setVisibility(View.GONE); // could also use INVISIBLE here... up to you. 
    } 

    // Finally load the image asynchronously into the ImageView, this also takes care of 
    // setting a placeholder image while the background thread runs 
    if (images != null && !images.isEmpty()) 
     mImageFetcher.loadImage(images.get(position - mNumColumns).getUriString()/*.imageUrls[position - mNumColumns]*/, imageView); 
    return containerView; 
} 

---

更新：
針對在評論的問題，我用的是這樣的（在我的自定義 「的ViewController」 基類）：

private static int s_nextGeneratedId = 1; 

/** 
* Try to do the same thing as View.generateViewId() when using API level < 17. 
* @return Unique integer that can be used with setId() on a View. 
*/ 
protected static int generateViewId() { 
    // AAPT-generated IDs have the high byte nonzero; clamp to the range under that. 
    if (++s_nextGeneratedId > 0x00FFFFFF) 
     s_nextGeneratedId = 1; // Roll over to 1, not 0. 
    return s_nextGeneratedId; 
} 

請注意，您不需要網格中每個單元格的唯一視圖ID。相反，您只需要使用findViewById()就可以訪問的每種類型的子視圖。所以在你的情況下，你可能只需要兩個獨特的ID。由於從您的xml佈局文件自動生成的視圖ID通常非常大，因此我發現使用低數字手動生成的ID（如上所示）很方便。

Answer 2

我覺得這裏最好的辦法是使用返回不同類型的視圖的適配器（由優先於getViewTypeCount()和getItemViewType()），例如如this answer中所述。

這樣你就不需要以編程方式修改返回的視圖。只需定義兩個XML佈局，然後根據該位置的項目是否有視頻，對其中一個或另一個進行膨脹/重用。

這不僅是清晰的，你不會有「轉化」一種觀點認爲到時的視頻行作爲convertView提供用於其他項目其他沒有一個，或者反之亦然