在listview 优化其中,会使用到setTag()以及getTag()方法

代码例如以下：

@Override			public View getView(int position, View convertView, ViewGroup parent) {				ViewHolder viewHolder;			    if(convertView==null){			    	viewHolder = new ViewHolder();			    	convertView = inflater.inflate(R.layout.item, null);			    	viewHolder.tvAge = (TextView) convertView.findViewById(R.id.tvAge);			    	viewHolder.tvName = (TextView) convertView.findViewById(R.id.tvName);			    	convertView.setTag(viewHolder);			    }else{			    	viewHolder = (ViewHolder) convertView.getTag();			    }			    viewHolder.tvAge.setText("年龄:  "+persons.get(position).age);			    viewHolder.tvName.setText("年龄:  "+persons.get(position).name);			    				return convertView;			}		}		class ViewHolder{			TextView tvAge;			TextView tvName;		}

setTag()方法是在View类中,所以全部的类都能够使用setTag()方法,我们看下View源代码中代码：

/**     * Returns this view's tag.     *     * @return the Object stored in this view as a tag     *     * @see #setTag(Object)     * @see #getTag(int)     */    @ViewDebug.ExportedProperty    public Object getTag() {        return mTag;    }    /**     * Sets the tag associated with this view. A tag can be used to mark     * a view in its hierarchy and does not have to be unique within the     * hierarchy. Tags can also be used to store data within a view without     * resorting to another data structure.     *     * @param tag an Object to tag the view with     *     * @see #getTag()     * @see #setTag(int, Object)     */    public void setTag(final Object tag) {        mTag = tag;    }    /**     * Returns the tag associated with this view and the specified key.     *     * @param key The key identifying the tag     *     * @return the Object stored in this view as a tag     *     * @see #setTag(int, Object)     * @see #getTag()     */    public Object getTag(int key) {        if (mKeyedTags != null) return mKeyedTags.get(key);        return null;    }

意思是说给view设置标签,setTag()中设置的Object类,所以getTag()方法要强转,通常是View对象携带什么參数,就能够使用setTag方法把參数传递过去就能够