Android GC内存泄露问题(2)

　　由此可以看出，如果我们不去使用convertView，而是每次都在getView()中重新实例化一个View对象的话，即浪费时间，也造成内存垃圾，给垃圾回收增加压力，如果垃圾回收来不及的话，虚拟机将不得不给该应用进程分配更多的内存，造成不必要的内存开支。

layout.xml

<?xml version="1.0" encoding="utf-8" ?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="60dip">
  <ImageView android:id="@+id/icon" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:paddingLeft="9px" />
  <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_toRightOf="@id/icon" android:textAppearance="?android:attr/textAppearanceMedium" android:paddingLeft="9px" />
  </RelativeLayout>

能引起内存泄露的代码: BadAdapter.java

public class BadAdapter extends BaseAdapter {
    ......

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d("MyAdapter", "Position:" + position + "---"
                + String.valueOf(System.currentTimeMillis()));
        final LayoutInflater inflater = (LayoutInflater) mContext
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflater.inflate(R.layout.list_item_icon_text, null);
        ((ImageView) v.findViewById(R.id.icon)).setImageResource(R.drawable.icon);
        ((TextView) v.findViewById(R.id.text)).setText(mData[position]);
        return v;
    }
}

修正优化示例代码示例代码：GoodAdapter.java

public class GoodAdapter extends BaseAdapter {

......

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d("MyAdapter", "Position:" + position + "---"
                + String.valueOf(System.currentTimeMillis()));
        ViewHolder holder;
        if (convertView == null) {
            final LayoutInflater inflater = (LayoutInflater) mContext
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item_icon_text, null);
            holder = new ViewHolder();
            holder.icon = (ImageView) convertView.findViewById(R.id.icon);
            holder.text = (TextView) convertView.findViewById(R.id.text);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.icon.setImageResource(R.drawable.icon);
        holder.text.setText(mData[position]);
        return convertView;
    }

static class ViewHolder {
        ImageView icon;
        TextView text;
    }
}

MainActivity.java

public class MainActivity extends ListActivity {
    private BadAdapter/GoodAdapter mAdapter;

private String[] mArrData;

/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mArrData = new String[1000];
        for (int i = 0; i < 1000; i++) {
            mArrData[i] = "Google IO Adapter";
        }
        mAdapter = new BadAdapter/GoodAdapter(this, mArrData);
        setListAdapter(mAdapter);
    }
}

3）ThreadLocal使用不当

　　如果我们粗暴的把ThreadLocal设置null,而不调用remove()方法或set(null),那么就可能造成ThreadLocal绑定的对象长期也能被回收，因而产出内存泄露。