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Android中的ViewPager滯後問題

2015-06-26 65 views
2

我在ViewPager中順利滑動時遇到了問題。我的目標是使用Volley Library從URL下載圖像，並且在從左向右或從右向左滑動的過程中必須在ViewPager中顯示下載的圖像，沒有任何滯後問題。我附加了在刷圖像時滯後的代碼。Android中的ViewPager滯後問題

這是我的活動類，其中包含視圖尋呼機：

ViewPagerActivity.java

public class ViewPagerActivity extends Activity { 
ViewPager pager; 
String[] URL; 
PagerAdapter objPagerAdapter; 
ArrayList<String> _arrayImagePath=new ArrayList<String>(); 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_view_pager); 
    pager=(ViewPager)findViewById(R.id.pagerView); 

    // Setting the 70 images URL 
    URL= new String[] { "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg", 
      "http://vignette3.wikia.nocookie.net/dragonball/images/7/71/PollutionAura2.png/revision/latest?cb=20101211235024", 
      "http://vignette2.wikia.nocookie.net/aread/images/6/6f/V02_Back.jpg/revision/latest?cb=20140501154842", 
      "http://vignette1.wikia.nocookie.net/tmnt/images/d/d5/Tnmt-disneyscreencaps_com-5817.jpg/revision/latest?cb=20130428155629", 
      "https://upload.wikimedia.org/wikipedia/commons/2/27/Sunset_at_Selsey_beach_4.jpg", 
      "http://img1.wikia.nocookie.net/__cb20140806200752/disney/images/d/d8/Little-mermaid-1080p-disneyscreencaps.com-782.jpg", 
      "http://img3.wikia.nocookie.net/__cb20141022183927/howtotrainyourdragon/images/c/c5/When_gothi_drops_that_flag_we_race.jpg", 
      "http://img.gawkerassets.com/img/17jy4w1lonvyijpg/original.jpg" 
      }; 

    objPagerAdapter=new ViewPagerAdapter(ViewPagerActivity.this, _arrayImagePath); 
    pager.setAdapter(objPagerAdapter); 

    // Calling Volley Library to Download the Image for each URLi 

    for(int i=0;i<URL.length;i++) 
    { 
     DownloadImages(URL[i], i); 
    } 


} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.view_pager, 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(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 
void DownloadImages(String imageURL_in,final int counter_in) 
{ 
    final String counter=String.valueOf(counter_in); 
    ImageRequest imageRequest = new ImageRequest(imageURL_in, 
      new Response.Listener<Bitmap>() { 

     @Override 
     public void onResponse(final Bitmap response) { 
      try{ 
       Log.v("Response Received =",""+counter_in); 
       // Saved in SD Card and getting the Path 
       String imagePath = SavedInSDCard(response, counter + "_hires"); 
       //Added ImagePath 
       _arrayImagePath.add(imagePath); 
       // Notifying the Adapter 
       objPagerAdapter.notifyDataSetChanged(); 


      } catch (Exception e) {e.printStackTrace();} 
     } 
    }, 0, 0, null, null); 
    ApplicationController.getInstance().addToRequestQueue(imageRequest); 



} 
public String SavedInSDCard(Bitmap bitmap2, String dishId) { 

    File dir = new File(ApplicationController.getAppContext() 
      .getExternalFilesDir("ViewPager_POC") + "/Cache"); 
    // Create the storage directory if it does not exist 
    if (!dir.exists()) { 
     dir.mkdirs(); 
    } 
    String stDishID = dishId; 
    String formatedDsihID = stDishID.replace(":", "R"); 
    File file = new File(dir, formatedDsihID); 
    try { 
     FileOutputStream out = new FileOutputStream(file); 
     bitmap2.compress(Bitmap.CompressFormat.JPEG, 100, out); 
     out.flush(); 
     out.close(); 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
    String imgPath = dir + "/" + formatedDsihID; 
    return imgPath; 
}

這是我的xml文件：

activity_view_pager.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:paddingBottom="@dimen/activity_vertical_margin" 
android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
tools:context="com.example.poc_viewpager.ViewPagerActivity" > 

<android.support.v4.view.ViewPager 
    android:id="@+id/pagerView" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" /></RelativeLayout>

這是我的ViewPager項目xml文件：

view_pager_item.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:orientation="vertical" > 

<ImageView 
    android:id="@+id/images" 
    android:layout_width="match_parent" 
    android:layout_height="300dp" 
    android:layout_alignParentLeft="true" 
    android:src="@drawable/ic_launcher" /> 

<TextView 
    android:id="@+id/counter" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignParentBottom="true" 
    android:layout_centerHorizontal="true" 
    android:layout_marginBottom="44dp" 
    android:text="Large Text" 
    android:textAppearance="?android:attr/textAppearanceLarge" /> 

</RelativeLayout>

這是適配器類查看傳呼機的：

ViewPagerAdapter.class

public class ViewPagerAdapter extends PagerAdapter{ 
Context _context; 
LayoutInflater inflater; 

ArrayList<String> _arrayImagePath; 

public ViewPagerAdapter(Context context_in, ArrayList<String> imagePath_in) { 
    _arrayImagePath=imagePath_in; 
    _context = context_in; 
} 

@Override 
public int getCount() { 
    return _arrayImagePath.size(); 
} 

@Override 
public void destroyItem(View container, int position, Object object) { 
    // TODO Auto-generated method stub 
    ((ViewPager) container).removeView((View) object); 
} 

@Override 
public Object instantiateItem(ViewGroup container, int position) { 

    // Declare Variables 
    TextView txtCounter; 
    ImageView imgView; 

    inflater = (LayoutInflater) _context 
      .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    View itemView = inflater.inflate(R.layout.view_pager_item, container, 
      false); 

    txtCounter = (TextView) itemView.findViewById(R.id.counter); 
    imgView= (ImageView) itemView.findViewById(R.id.images); 

    //Setting the values for Image and textview 
    txtCounter.setText(""+(position+1));   
    Bitmap bitmap = BitmapFactory.decodeFile(_arrayImagePath.get(position)); 
    imgView.setImageBitmap(bitmap); 


    // Add viewpager_item.xml to ViewPager 
    ((ViewPager) container).addView(itemView); 

    return itemView; 
} 
@Override 
public boolean isViewFromObject(View view, Object object) { 
    return view == ((RelativeLayout) object); 
} 

}

提出任何想法來解決這個滯後？

來源

2015-06-26 Ashok

回答

0

在UI線程上使用decodeFile不是一個好主意，因爲它可能需要一段時間。例如，您可以使用AsyncTask。

看看Android開發者方面，有一個很好的指南： http://developer.android.com/training/displaying-bitmaps/process-bitmap.html

而變化增加一些像這樣的代碼：

class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> { 
    private final WeakReference<ImageView> imageViewReference; 

    public BitmapWorkerTask(ImageView imageView) { 
     imageViewReference = new WeakReference<ImageView>(imageView); 
    } 
    @Override 
    protected Bitmap doInBackground(String... params) { 
     String path = params[0]; 
     return BitmapFactory.decodeFile(path); 
    } 

    @Override 
    protected void onPostExecute(Bitmap bitmap) { 
     if (imageViewReference != null && bitmap != null) { 
      final ImageView imageView = imageViewReference.get(); 
      if (imageView != null) { 
       imageView.setImageBitmap(bitmap); 
     } 
    } 
} 
}

而在你instantiateItem可以使用：

BitmapWorkerTask task = new BitmapWorkerTask(imgView); 
task.execute(_arrayImagePath.get(position));

還沒有測試過，但它應該有助於理解問題。 如果您發現錯誤，請編輯代碼。

來源

2015-06-26 20:23:10 FlanschiFox

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