android 内存溢出

参考：http://1002878825-qq-com.iteye.com/blog/1735356

出现情况：

1.使用大图片，没有及时recycle。
　　4.0后bitmap.option 中有 inPurgeable 内存不足可以回收,之前版本必须自己回收

解决：1.option 减小图片加载 2.使用软引用，及时recycle

2.listview的convertView 以及未用holder机制的运用

　　原因：contentView 系统已经缓存

解决：1.holder 判断 contentView是会否为空

　　   2.提高顺滑度listview lazy loading data ----- 参考资料：api demo list 13 滑动时不赋值

public class List13 extends ListActivity implements ListView.OnScrollListener {

    private TextView mStatus;
    
    private boolean mBusy = false;
    
    /**
     * Will not bind views while the list is scrolling
     * 
     */
    private class SlowAdapter extends BaseAdapter {
        private LayoutInflater mInflater;
        
        public SlowAdapter(Context context) {
            mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        /**
         * The number of items in the list is determined by the number of speeches
         * in our array.
         * 
         * @see android.widget.ListAdapter#getCount()
         */
        public int getCount() {
            return mStrings.length;
        }

        /**
         * Since the data comes from an array, just returning the index is
         * sufficent to get at the data. If we were using a more complex data
         * structure, we would return whatever object represents one row in the
         * list.
         * 
         * @see android.widget.ListAdapter#getItem(int)
         */
        public Object getItem(int position) {
            return position;
        }

        /**
         * Use the array index as a unique id.
         * 
         * @see android.widget.ListAdapter#getItemId(int)
         */
        public long getItemId(int position) {
            return position;
        }

        /**
         * Make a view to hold each row.
         * 
         * @see android.widget.ListAdapter#getView(int, android.view.View,
         *      android.view.ViewGroup)
         */
        public View getView(int position, View convertView, ViewGroup parent) {
            TextView text;
            
            if (convertView == null) {
                text = (TextView)mInflater.inflate(android.R.layout.simple_list_item_1, parent, false);
            } else {
                text = (TextView)convertView;
            }

            if (!mBusy) {
                text.setText(mStrings[position]);
                // Null tag means the view has the correct data
                text.setTag(null);
            } else {
                text.setText("Loading...");
                // Non-null tag means the view still needs to load it's data
                text.setTag(this);
            }

            return text;
        }
    }
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_13);
        mStatus = (TextView) findViewById(R.id.status);
        mStatus.setText("Idle");
        
        // Use an existing ListAdapter that will map an array
        // of strings to TextViews
        setListAdapter(new SlowAdapter(this));
        
        getListView().setOnScrollListener(this);
    }
    
    
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
            int totalItemCount) {
    }
    

    public void onScrollStateChanged(AbsListView view, int scrollState) {
        switch (scrollState) {
        case OnScrollListener.SCROLL_STATE_IDLE:
            mBusy = false;
            
            int first = view.getFirstVisiblePosition();
            int count = view.getChildCount();
            for (int i=0; i<count; i++) {
                TextView t = (TextView)view.getChildAt(i);
                if (t.getTag() != null) {
                    t.setText(mStrings[first + i]);
                    t.setTag(null);
                }
            }
            
            mStatus.setText("Idle");
            break;
        case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
            mBusy = true;
            mStatus.setText("Touch scroll");
            break;
        case OnScrollListener.SCROLL_STATE_FLING:
            mBusy = true;
            mStatus.setText("Fling");
            break;
        }
    }

3.单个页面，横竖屏切换N次后

　　解决：1.去除xml中相关设置，改在程序中设置背景图（放在onCreate()方法中）：
　　　　　2. 跟上面方法相似，直接把xml配置文件加载成view 再放到一个容器里，然后直接调用 this.setContentView(View view)方法，避免xml的重复加载

　　　　　3.Activity中添加了 android:configChanges属性，目的是当所指定属性(Configuration Changes)发生改变时，通知程序调用 onConfigurationChanged()函数

解决通用方法：

1.SoftReference 和 WeakReference的使用

2.压缩图片参考解决bitmap章节

3.修改虚拟机参数 VMRuntime.getRuntime().setTargetHeapUtilization(0.75); 

4.不要为Context长期保存引用(生命周期结束处理掉)

5.尽量用ApplicationContext

6.垃圾回收器并不保证能准确回收内存，这样在使用自己需要的内容时，主要生命周期和及时释放掉不需要的对象。尽量在Activity的生命周期结束时，在onDestroy中把我们做引用的其他对象做释放，比如：cursor.close()。