Question

我最近一直在2.1 SDK（版本7）中工作，并创建了一些图像，这些图像将通过ImageSwitcher显示，并通过库中的一个示例应用程序进行更改。我的图像都在200Kb左右，我注意到当我切换它们时，Android崩溃时出现Out-Of-Memory错误。我知道堆大小通常是16Mb，所以我不明白为什么200Kb图像会崩溃应用程序。我在drawables目录中有21个图像，但一次只显示一个。

这是我的标记：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    android:background="#FFFFFF">


         <ScrollView android:id="@+id/scroll"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"
         android:layout_marginBottom="17dp">
             <ImageSwitcher android:id="@+id/switcher"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/adView"
            android:background="#FFFFFF"/>
        </ScrollView>

    <Gallery android:id="@+id/gallery"
        android:background="#66000000"
        android:layout_width="fill_parent"
        android:layout_height="60dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"        
        android:gravity="center_vertical"
        android:spacing="13dp"/>
</RelativeLayout>

我的代码主要来自ImageSwitcher / Gallery的Google Sample：

public class HomeActivity extends Activity implements 
AdapterView.OnItemSelectedListener, ViewSwitcher.ViewFactory{

    private Integer[] mThumbIds = {
            R.drawable.a3035, R.drawable.a40,
            R.drawable.a45, R.drawable.a50,
            R.drawable.a55, R.drawable.a60,
            R.drawable.a70, R.drawable.a80,
            R.drawable.a90,R.drawable.a100,
            R.drawable.a110,R.drawable.a120,
            R.drawable.a130,R.drawable.a140,
            R.drawable.a150,R.drawable.a160,
            R.drawable.a170,R.drawable.a180,
            R.drawable.a190,R.drawable.a200210,
            R.drawable.a220300};

    private Integer[] mImageIds = {
            R.drawable.aird3035, R.drawable.aird40, R.drawable.aird45,
            R.drawable.aird50, R.drawable.aird55, R.drawable.aird60,
            R.drawable.aird70, R.drawable.aird80,R.drawable.aird90,
            R.drawable.aird100, R.drawable.aird110, R.drawable.aird120,
            R.drawable.aird130, R.drawable.aird140,R.drawable.aird150,
            R.drawable.aird160, R.drawable.aird170,R.drawable.aird180,
            R.drawable.aird190, R.drawable.aird200210,R.drawable.aird220300};

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.main);

        mSwitcher = (ImageSwitcher) findViewById(R.id.switcher);
        mSwitcher.setFactory(this);
        mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));
        mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_out));

        scroll = (ScrollView)findViewById(R.id.scroll);

        Gallery g = (Gallery) findViewById(R.id.gallery);
        g.setAdapter(new ImageAdapter(this));
        g.setOnItemSelectedListener(this);    
    }

    @Override
    public void onPause()
    {
        super.onPause();
        System.gc();
    }
    @Override
    public void onDestroy()
    {
        super.onDestroy();
    }
    public void onItemSelected(AdapterView parent, View v, int position, long id) {
        mSwitcher.setImageResource(mImageIds[position]);
        scroll.scrollTo(0,0);
            System.gc();
    }

    public void onNothingSelected(AdapterView parent) {
    }

    public View makeView() {
        ImageView i = new ImageView(this);
        i.setBackgroundColor(0xFFFFFF);
        i.setScaleType(ImageView.ScaleType.FIT_CENTER);
        i.setLayoutParams(new ImageSwitcher.LayoutParams(LayoutParams.WRAP_CONTENT,
                LayoutParams.WRAP_CONTENT));
        return i;
    }

    private ImageSwitcher mSwitcher;
    private ScrollView scroll;

    public class ImageAdapter extends BaseAdapter {
        public ImageAdapter(Context c) {
            mContext = c;
        }

        public int getCount() {
            return mThumbIds.length;
        }

        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {

            if(convertView == null) { // create new view
                convertView = new ImageView(mContext);

                convertView.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

            }
            ImageView iv = (ImageView) convertView;
            iv.setImageResource(mThumbIds[position]);
            return convertView;
        }

        private Context mContext;

    }     

}

如果您注意到OnItemSelected方法，我甚至强制调用垃圾收集器，但我仍然崩溃。如果我将图像缩小到每个93Kb左右（这意味着我的分辨率会因较大的屏幕而丢失），我的应用程序不会崩溃。

任何人都可以提供一些有关为什么会发生这种情况的更多信息，并且更好，一种有效的解决方法吗？

Answer 1

试试这段代码：

  public View getView(int position, View convertView, ViewGroup parent)
  {
      if(convertView == null)
      { // create new view
          convertView = new ImageView(mContext);
          convertView.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
      }
      ImageView iv = (ImageView) convertView;
      BitmapFactory.Options options=new BitmapFactory.Options();
      options.inPurgeable=true; //bitmap can be purged to disk
      Bitmap bm=BitmapFactory.decodeResource(mContext.getResources(), mThumbIds[position], options);
      iv.setImageBitmap(bm);
      return iv;
  }

这里的关键点是BitmapFactory.Options.inPurgeable = true;（这是自我解释） - 你也可以与其他选项一起玩 - 有时它有帮助

Answer 2

不要致电System.gc（）。显着降低性能。请勿在UI线程中执行此操作。 NEVER！

带有小图像的ImageSwitcher出现内存不足错误

2 个答案: