我有以下代码显示一个图像与字母,

public class MainActivity extends Activity 
{
    private String[] capital_letters,small_letters;
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        this.requestwindowFeature(Window.FEATURE_NO_TITLE);
        this.getwindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onStart()
    {
        super.onStart();

        try
        {
            capital_letters = getApplicationContext().getResources().getStringArray( R.array.capital_letters );
            small_letters = getApplicationContext().getResources().getStringArray( R.array.small_letters );

            MyAdapter adapter = new MyAdapter ( MainActivity.this,capital_letters,small_letters );
            ListView list = ( ListView ) findViewById( R.id.list );
            list.setAdapter( adapter );

            list.setonItemClickListener( new AdapterView.OnItemClickListener() 
            {
                @Override
                public void onItemClick(AdapterView<?> arg0,View arg1,int position,long id ) 
                {
                    Intent intent = new Intent ( MainActivity.this,Letteractivity.class );
                    intent.putExtra( "position",position );
                    intent.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
                    startActivity(intent);
                    overridePendingTransition( 0,0 );
                }
            });
        }
        catch ( Exception e ){e.printstacktrace();}
    }
}

我如何使我的代码如此轻巧的工作非常顺利.平滑的表现意义,适当声明变量,循环,垃圾收集使用等？

看看 this question and all its answers,谈到Android上的性能优化很多.

我在我的应用程序中使用谷歌地方自动填充建议.它工作正常,但我想改善其性能.当用户键入某个地点时,它会在长时间延迟后或有时在删除最后一个字符后给出建议.我如何提高它的性能？
请帮我.
提前致谢

这是我的代码

public class invoice extends Activity
{

AutoCompleteTextView edit_destination;
DownloadTask placesDownloadTask;
DownloadTask placeDetailsDownloadTask;
ParserTask placesParserTask;
ParserTask placeDetailsParserTask;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    // Todo Auto-generated method stub    
    super.onCreate(savedInstanceState);
    requestwindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.create_invoice_activity);

edit_destination=(AutoCompleteTextView) findViewById(R.id.destination);
    edit_destination.setThreshold(1);       

    edit_destination.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s,int start,int before,int count) {   
            // Creating a DownloadTask to download Google Places matching "s"
            placesDownloadTask = new DownloadTask(PLACES);

            // Getting url to the Google Places Autocomplete api
            String url = getAutoCompleteUrl(s.toString());

            // Start downloading Google Places
            // This causes to execute doInBackground() of DownloadTask class
            placesDownloadTask.execute(url);
        }

        @Override
        public void beforeTextChanged(CharSequence s,int count,int after) {
            // Todo Auto-generated method stub
        }

        @Override
        public void afterTextChanged(Editable s) {
            // Todo Auto-generated method stub              
        }
    }); 

    edit_destination.setonItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0,View arg1,int index,long id) {

                ListView lv = (ListView) arg0;
                SimpleAdapter adapter = (SimpleAdapter) arg0.getAdapter();

                HashMap<String,String> hm = (HashMap<String,String>) adapter.getItem(index);


                selected_place=hm.get("description");


                // Creating a DownloadTask to download Places details of the selected place
                placeDetailsDownloadTask = new DownloadTask(PLACES_DETAILS);

                // Getting url to the Google Places details api
                String url = getPlaceDetailsUrl(hm.get("reference"));                   

                // Start downloading Google Place Details
                // This causes to execute doInBackground() of DownloadTask class
                placeDetailsDownloadTask.execute(url);

        }
    });     

}


private String getAutoCompleteUrl(String place){

        // Obtain browser key from https://code.google.com/apis/console
        String key = "YOUR KEY";

        // place to be be searched
        String input = "input="+place;

        // place type to be searched
        String types = "types=geocode";

        // Sensor enabled
        String sensor = "sensor=false";         

        // Building the parameters to the web service
        String parameters = input+"&"+types+"&"+sensor+"&"+key;

        // Output format
        String output = "json";

        // Building the url to the web service
        String url = "https://maps.googleapis.com/maps/api/place/autocomplete/"+output+"?"+parameters;

        return url;
    }


    private String getPlaceDetailsUrl(String ref){

        // Obtain browser key from https://code.google.com/apis/console
        String key = "YOUR KEY";

        // reference of place
        String reference = "reference="+ref;                    

        // Sensor enabled
        String sensor = "sensor=false";         

        // Building the parameters to the web service
        String parameters = reference+"&"+sensor+"&"+key;

        // Output format
        String output = "json";

        // Building the url to the web service
        String url = "https://maps.googleapis.com/maps/api/place/details/"+output+"?"+parameters;

        return url;
    }

    /** A method to download json data from url */
    private String downloadUrl(String strUrl) throws IOException{
        String data = "";
        InputStream iStream = null;
        HttpURLConnection urlConnection = null;
        try{
                URL url = new URL(strUrl);

                // Creating an http connection to communicate with url 
                urlConnection = (HttpURLConnection) url.openConnection();

                // Connecting to url 
                urlConnection.connect();

                // Reading data from url 
                iStream = urlConnection.getInputStream();

                BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

                StringBuffer sb  = new StringBuffer();

                String line = "";
                while( ( line = br.readLine())  != null){
                        sb.append(line);
                }

                data = sb.toString();

                br.close();

        }catch(Exception e){
                Log.d("Exception while downloading url",e.toString());
        }finally{
                iStream.close();
                urlConnection.disconnect();
        }
        return data;
     }


    // Fetches data from url passed
    private class DownloadTask extends AsyncTask<String,Void,String>{

        private int downloadType=0;

        // Constructor
        public DownloadTask(int type){
        this.downloadType = type;

        }

        @Override
        protected String doInBackground(String... url) {

            // For storing data from web service
            String data = "";

            try{
                // Fetching the data from web service
                data = downloadUrl(url[0]);
            }catch(Exception e){
                Log.d("Background Task",e.toString());
            }
            return data;        
        }

        @Override
        protected void onPostExecute(String result) {           
            super.onPostExecute(result);        

            switch(downloadType){
            case PLACES:
                // Creating ParserTask for parsing Google Places
                placesParserTask = new ParserTask(PLACES);

                // Start parsing google places json data
                // This causes to execute doInBackground() of ParserTask class
                System.out.println(result);
                placesParserTask.execute(result);

                break;

            case PLACES_DETAILS : 
                // Creating ParserTask for parsing Google Places
                placeDetailsParserTask = new ParserTask(PLACES_DETAILS);

                // Starting Parsing the JSON string
                // This causes to execute doInBackground() of ParserTask class
                placeDetailsParserTask.execute(result);                             
            }           
        }       
    }     


    /** A class to parse the Google Places in JSON format */
    private class ParserTask extends AsyncTask<String,Integer,List<HashMap<String,String>>>{

        int parserType = 0;

        public ParserTask(int type){
            this.parserType = type;
        }

        @Override
        protected List<HashMap<String,String>> doInBackground(String... jsonData) {

            JSONObject jObject;         
            List<HashMap<String,String>> list = null;           

            try{
                jObject = new JSONObject(jsonData[0]);

                switch(parserType){
                case PLACES :
                    PlaceJSONParser placeJsonParser = new PlaceJSONParser();
                    // Getting the parsed data as a List construct
                    list = placeJsonParser.parse(jObject);
                    break;
                case PLACES_DETAILS :                       
                    PlaceDetailsJSONParser placeDetailsJsonParser = new PlaceDetailsJSONParser();
                    // Getting the parsed data as a List construct
                    list = placeDetailsJsonParser.parse(jObject);
                }

            }catch(Exception e){
                Log.d("Exception",e.toString());
            }
            return list;
        }

        @Override
        protected void onPostExecute(List<HashMap<String,String>> result) {

                switch(parserType){
                case PLACES :
                    String[] from = new String[] { "description"};
                    int[] to = new int[] { android.R.id.text1 };

                    // Creating a SimpleAdapter for the AutoCompleteTextView
                    SimpleAdapter adapter = new SimpleAdapter(getBaseContext(),result,android.R.layout.simple_list_item_1,from,to);             

                    // Setting the adapter
                    edit_destination.setAdapter(adapter);                       
                    break;
                case PLACES_DETAILS :                       
                    HashMap<String,String> hm = result.get(0);

                    // Getting latitude from the parsed data 
                     latitude = Double.parseDouble(hm.get("lat"));

                    System.out.println(latitude);

                    // Getting longitude from the parsed data
                     longitude = Double.parseDouble(hm.get("lng"));     
                    System.out.println(longitude);


                    Toast.makeText(invoice.this,latitude+","+longitude,Toast.LENGTH_LONG).show();



                    SharedPreferences pref=getSharedPreferences("LOC",0);


                    String S_lat,S_long;
                   S_lat=pref.getString("LAT","");
                   S_long= pref.getString("LONG",""); 

                    source_lat=Double.parseDouble(S_lat);
                    source_long=Double.parseDouble(S_long);








                    break;                      
                }           
        }           
    }

用以下代码替换autocompleteTextView的“addTextChangedListener”方法…

edit_destination.setonKeyListener(new OnKeyListener() {
    public boolean onKey(View arg0,int arg1,KeyEvent arg2) {
        return false;
    }

});
edit_destination.addTextChangedListener(new TextWatcher() {

    @Override
    public void onTextChanged(CharSequence s,int count) {   
        // Creating a DownloadTask to download Google Places matching "s"

        if(placesDownloadTask!=null)
        {                        
              Log.i("--placesDownloadTask--","progress_status : "+placesDownloadTask.getStatus());
              placesDownloadTask.cancel(true);      
        }


    }

    @Override
    public void beforeTextChanged(CharSequence s,int after) {
        // Todo Auto-generated method stub

    }

    @Override
    public void afterTextChanged(Editable s) {
        // Todo Auto-generated method stub      
        String chterm; 
        chterm=edit_destination.getText().toString();
        Log.i("---final selected text---",""+chterm);
        placesDownloadTask = new DownloadTask(PLACES);

        // Getting url to the Google Places Autocomplete api
        String url = getAutoCompleteUrl(s.toString());

        // Start downloading Google Places
        // This causes to execute doInBackground() of DownloadTask class
        placesDownloadTask.execute(url);
    }
});

不是从onTextChanged发出调用,而是从afterTextChanged调用它,它减少了每个字符后的调用次数,从而减少了延迟.

尝试一下,它可能对你有所帮助.

我是代表们的新概念.我已经知道它类似于C中的指针.在其优势中,它提到了代表的有效使用提高了性能.

考虑到它是一个指针.它如何改善应用程序的性能？

如果有人能用一个简单的例子解释这一点,那将会有所帮助.

代表们并不直接关注提高性能 – 它们是关于抽象调用的.用C语言来说,它确实就像一个方法指针.

代表的大多数使用与性能无关.让我们从一开始就明确这一点.

但是,这可以用来帮助提高性能的一个主要时间是,它允许像元编程这样的场景.代码(通常是库代码)可以在运行时基于配置信息构建复杂的行为链,然后通过Expression,TypeBuilder或Dynamicmethod(或基本上任何允许您构造IL的API)将该信息编译到方法中.但是要调用这样一个动态生成的方法,您需要一个委托 – 因为从C#编译的静态IL不能引用当时不存在的方法.

请注意,执行此操作的另一种方法是使用TypeBuilder创建(在运行时)从子类继承的新类型或实现已知接口,然后创建动态生成类型的实例,该实例可以强制转换为预期API以通常的方式正常调用.

我有一个文本文件与100000对：字和频率.

test.in文件与文字：

> 1行 – 所有字频对的总计数
> 2行〜〜100 001 – 字频对
> 100 002行 – 用户输入字的总数
>从100 003到最终用户输入字

我解析这个文件并把这些单词放进去

Dictionary<string,double> dictionary;

我想在以下代码中执行一些搜索顺序逻辑：

for(int i=0;i<15000;i++)
{
    tempInputWord = //take data from file(or other sources)

    var adviceWords = dictionary
                .Where(p => p.Key.StartsWith(searchWord,StringComparison.Ordinal))
                .OrderByDescending(ks => ks.Value)
                .ThenBy(ks => ks.Key,StringComparer.Ordinal)
                .Take(10)
                .ToList();

    //some output
}

问题：该代码必须在不到10秒的时间内运行.

在我的电脑(核心i5 2400,8gb RAM)与Parallel.For() – 约91秒.

你能给我一些如何提高性能的建议吗？

更新：

万岁！我们做到了！
谢谢@CodesInChaos,@usr,@T_D和所有参与解决问题的人.

最后的代码：

var kvList = dictionary.OrderBy(ks => ks.Key,StringComparer.Ordinal).ToList();

var strComparer = new MyStringComparer();
var intComparer = new MyIntComparer();
var kvListSize = kvList.Count;
var allUserWords = new List<string>();
for (int i = 0; i < userWordQuantity; i++)
{
    var searchWord = Console.ReadLine();
    allUserWords.Add(searchWord);
}
var result =  allUserWords
    .AsParallel()
    .AsOrdered()
    .Select(searchWord =>
    {
        int startIndex = kvList.BinarySearch(new keyvaluePair<string,int>(searchWord,0),strComparer);
        if (startIndex < 0)
            startIndex = ~startIndex;

        var matches = new List<keyvaluePair<string,int>>();

        bool isNotEnd = true;
        for (int j = startIndex; j < kvListSize ; j++)
        {
            isNotEnd = kvList[j].Key.StartsWith(searchWord,StringComparison.Ordinal);
            if (isNotEnd) matches.Add(kvList[j]);
            else break;
        }
        matches.sort(intComparer);

        var res = matches.Select(s => s.Key).Take(10).ToList();

        return res;
    });
foreach (var adviceWords in result)
{
   foreach (var adviceWord in adviceWords)
   {
       Console.WriteLine(adviceWord);
   }
   Console.WriteLine();
}

6 sec (9 sec without manual loop (with linq)))

>按键排序列表< keyvaluePair< string,decimal>>替换字典.

对于搜索,我使用一个子字符串直接在其前缀之前进行序数比较.所以我可以用二进制搜索找到第一个候选人.由于候选人是连续的,我可以用TakeWhile代替Where.

int startIndex = dictionary.BinarySearch(searchWord,comparer);
if(startIndex < 0)
    startIndex = ~startIndex;

var adviceWords = dictionary
            .Skip(startIndex)
            .TakeWhile(p => p.Key.StartsWith(searchWord,StringComparison.Ordinal))
            .OrderByDescending(ks => ks.Value)
            .ThenBy(ks => ks.Key)
            .Select(s => s.Key)
            .Take(10).ToList();

>确保对所有操作使用顺序比较,包括初始排序,二进制搜索和StartsWith检查.>我会在并行循环之外调用Console.ReadLine.可能使用AsParallel().在搜索单词的集合上选择(…)而不是Parallel.For.