未優(yōu)化版本

    public class ExampleAdapter extends ArrayAdapter<Example> {
    
        int resourceId;
    
        public ExampleAdapter(Context context, int viewResource, ArrayList<Example> data) {
            super(context, viewResource, data);
            resourceId = viewResource;
        }
    
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View view;
            view = LayoutInflater.from(getContext()).inflate(resourceId, parent);
            TextView mTextVIew = (TextView)view.findViewById(R.id.text_view);
            Button mButton = (Button)view.findViewById(R.id.button);
            return view;
        }
    }

1.重用convertView

    @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View view;
            if(convertView == null) {
                view = LayoutInflater.from(getContext()).inflate(resourceId,parent);
            }else{
                view = convertView;
            }
           

            TextView mTextVIew = (TextView)view.findViewById(R.id.text_view);
            Button mButton = (Button)view.findViewById(R.id.button);            
            return view;
        }

convertView會(huì)將之前加載好的布局進(jìn)行緩存，假如convert不為null，可以直接獲取view。從而減少LayoutInflater加載布局的次數(shù)。

2.使用ViewHolder

定義一個(gè)ViewHolder類，存儲(chǔ)子View,使用SparseArray存儲(chǔ)子View的id和其對(duì)應(yīng)的View（此處使用了優(yōu)化過的int-object的hashmap, 可以減少內(nèi)存損耗）。使用時(shí)若不存在此子View，便創(chuàng)建，并存入SparseArray中。

    //此處不是內(nèi)部類
    public class ViewHolder {
            private ViewHolder(){};
            public static <T extends View> T get(View view, int id) {
                SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
                if (viewHolder == null) {
                    viewHolder = new SparseArray<View>();
                    view.setTag(viewHolder);
                }
                View childView = viewHolder.get(id);
                if (childView == null) {
                    childView = view.findViewById(id);
                    viewHolder.put(id, childView);
                }
                return (T) childView;
            }
        }

getView中的寫法

     @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            Thing thing = getItem(position);
            View view;
            if(convertView == null) {
                view = LayoutInflater.from(getContext()).inflate(resourceId,parent);
    
            }else{
                view = convertView;
            }
            TextView mText = ViewHolder.get(View,R.id.text_view);
            Button button = ViewHolder.get(View,R.id.button)
            return view;
        }

此寫法來自

3.使用RecyclerView，是ListView的升級(jí)版。