背景粘性并发标记扫描GC释放

Question

I have an application that checks the database every 10 seconds if there is any new data, if there is any data it will get it and stop checking the database.

I have implemented a text watcher to check if the textbox is empty. If it is, it will check the database, if it contains any text it will stop.

This is my code:

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    txtBoxUser.addTextChangedListener(checkUserRent);

    getData();
}


//TEXTWATCHER FOR GETTING PERSON WHO RENTED BOX
private final TextWatcher checkUserRent = new TextWatcher() {
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }
    public void afterTextChanged(Editable s) {
        if (s.length() == 0) {
            check();
        } else {
            Toast.makeText(MainActivity.this, "STOP",
                    Toast.LENGTH_LONG).show();
        }
    }
};


public void start(View view)
{
    getData();
}

public void cancel(View view)
{
    txtBoxUser.setText("");
    txtBoxPasscode.setText("");
}

private void getData(){

  final String id = txtBoxName.getText().toString().trim();

    class GetEmployee extends AsyncTask<Void,Void,String>{
        ProgressDialog loading;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
       //     loading = ProgressDialog.show(MainActivity.this,"Fetching...","Wait...",false,false);
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
      //      loading.dismiss();
            showEmployee(s);
        }

        @Override
        protected String doInBackground(Void... params) {
            RequestHandler rh = new RequestHandler();
            String s = rh.sendGetRequestParam(DATA_URL,id);
            return s;
        }
    }
    GetEmployee ge = new GetEmployee();
    ge.execute();
}

private void showEmployee(String json){
    try {
        JSONObject jsonObject = new JSONObject(json);
        JSONArray result = jsonObject.getJSONArray(JSON_ARRAY);
        JSONObject c = result.getJSONObject(0);
        String name = c.getString(GET_BOXUSER);
        String desg = c.getString(GET_PASSCODE);

        txtBoxUser.setText(name);
        txtBoxPasscode.setText(desg);

    } catch (JSONException e) {
        e.printStackTrace();
    }
}


private void check()
{
    getData();

}

But I get this in the logcat while it is waiting for the data. I am just wondering is it okay or safe?

I/art: Background sticky concurrent mark sweep GC freed 5614(449KB) AllocSpace objects, 18(288KB) LOS objects, 33% free, 1691KB/2MB, paused 5.354ms total 10.731ms
I/art: Background sticky concurrent mark sweep GC freed 7039(557KB) AllocSpace objects, 22(352KB) LOS objects, 39% free, 1561KB/2MB, paused 10.554ms total 15.931ms 
I/art: Background partial concurrent mark sweep GC freed 7279(564KB) AllocSpace objects, 21(336KB) LOS objects, 40% free, 1504KB/2MB, paused 5.721ms total 15.823ms
I/art: WaitForGcToComplete blocked for 5.375ms for cause HeapTrim
I/art: Background partial concurrent mark sweep GC freed 7650(591KB) AllocSpace objects, 22(352KB) LOS objects, 40% free, 1505KB/2MB, paused 5.511ms total 21.465ms

Answer 1

This is perfectly fine. It means that you're using memory, then its being freed by the GC. Its only a problem is either you go out of memory, or you see performance hiccups due to garbage collection. But its not anything you need to race to fix.

Answer 2

I have had the same issue. Your code will work, but if this hangs for too long, the app can get a App Not Responding error and close. It also defeats the purpose of using an AsyncTask.

The issue is that your AsyncTask contains a text view so it will block any other actions while executing. To fix this, make your AsyncTask static and pass it a reference to the Text view. Then store it in a WeakReference.

static class GetEmployee extends AsyncTask<Void,Void,String>{

    WeakReference<TextView> textUserWeakReference;
    WeakReference<TextView> textPassWeakReference;
    GetEmployee(TextView textUser, TextView textPass) {
        textUserWeakReference = new WeakReference<>(textUser);
        textPassWeakReference = new WeakReference<>(textPass);
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
   //     loading = ProgressDialog.show(MainActivity.this,"Fetching...","Wait...",false,false);
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
  //      loading.dismiss();
        TextView textUser = textUserWeakReference.get();
        TextView textPass = textPassWeakReference.get();
        if(textView != null && textPass != null)
            showEmployee(s, textUser, textPass);
    }

    @Override
    protected String doInBackground(Void... params) {
        RequestHandler rh = new RequestHandler();
        String s = rh.sendGetRequestParam(DATA_URL,id);
        return s;
    }
}
private static void showEmployee(String json, TextView txtBoxUser, TextView txtBoxPassCode){
try {
    JSONObject jsonObject = new JSONObject(json);
    JSONArray result = jsonObject.getJSONArray(JSON_ARRAY);
    JSONObject c = result.getJSONObject(0);
    String name = c.getString(GET_BOXUSER);
    String desg = c.getString(GET_PASSCODE);

    txtBoxUser.setText(name);
    txtBoxPasscode.setText(desg);

} catch (JSONException e) {
    e.printStackTrace();
}
}