从异步任务获取结果到列表视图

Question

我正在开发一款将英语单词翻译成波斯语的应用程序当我放置小型数据库时，一切顺利。但是当我使用长数据库时 UI 冻结。然后我使用异步在后台加载数据库，但我无法将 executioner 方法的结果发送到 Activity?

中的列表视图

public class MainActivity extends ListActivity {

private database db;
private EditText ed_txt;
private TextView tv;
private RadioButton rb_en;
private RadioButton rb_fa;

private String[] searched_word;
private String[] en;
private String[] fa;



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

    db=new database(this, "dictionary", null, 1);
    db.useable();

    ed_txt=(EditText)findViewById(R.id.ed_txt);
    tv=(TextView)findViewById(R.id.tv);
    rb_en=(RadioButton)findViewById(R.id.rb_en);
    rb_fa=(RadioButton)findViewById(R.id.rb_fa);

    //refresher(ed_txt.getText().toString(), "en");

    ed_txt.addTextChangedListener(new TextWatcher() {


        @Override
        public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
            if(rb_en.isChecked()){
            refresher(ed_txt.getText().toString(), "en");

        }
        else if (rb_fa.isChecked()) {
            refresher(ed_txt.getText().toString(), "per");

        }
        }

        @Override
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
                int arg3) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable arg0) {
            // TODO Auto-generated method stub
             new AsynctaskClass(handler).execute();
        }
    });



}

public class AsynctaskClass extends AsyncTask<Void, Void, Void> {

    private Handler handler;
    public AsynctaskClass(Handler handler ){
     this.handler = handler;
   }
    @Override
    protected Void doInBackground(Void... params) {
       Message message = handler.obtainMessage();
       //response you wish to send to the listview as String object
       message.obj =new String();
       message.what = 1 ;//You can use any value which will help you to distinguish the Handler response received at the activity.
       handler.sendMessage(message);
    return null;

    }

}

Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
    }
};


class AA extends ArrayAdapter<String>{

    public AA(){
        super(MainActivity.this,R.layout.row_search,en);
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        LayoutInflater in=getLayoutInflater();
        View row=in.inflate(R.layout.row_search, parent, false);


        TextView tv_searched_word=(TextView)row.findViewById(R.id.tv_searched_word);

        tv_searched_word.setText(en[position]);

        return (row);
    }

}


private void refresher(String text, String field){
    db.open();
    int s = db.shmaresh_jostojoo(text, field);
    if (ed_txt.getText().toString().equals("")) {
        s = 0;
        tv.setText(" لطفا کلمه مورد نطرتان را وارد کنید");
    }else {
        tv.setText(" تعداد "+s+" یافت شد ");

    }
    //searched_word[s];
    en=new String[s];
    fa=new String[s];

    for (int i = 0; i < s; i++) {
        //searched_word[i]=db.jostojoo(i, col, word, field);
        if(field.equals("en")){
            en[i]=db.jostojoo(i, 1, text, field);
        }else{
            en[i]=db.jostojoo(i, 2, text, field);
        }
        //en[i]=db.jostojoo(i, 1, text, field);
        //fa[i]=db.jostojoo(i, 2, text, field);
    }



    setListAdapter(new AA());
    db.close();
}

https://github.com/mohammadi66/Dictionary-En-2-Fa.git

Answer 1

在你的代码中我看不到任何异步任务，但使用 Handler 可能会解决你的问题。

在您的 Activity 中定义处理程序如下：

Handler handler = new Handler() {
                    @Override
                    public void handleMessage(Message msg) {
                        super.handleMessage(msg);
                    }
 }

然后使用此处理程序对象并将其传递给异步任务，如下所示：

  new AsynctaskClass(handler, other params as you need).execute();

现在您的异步任务将如下所示：

public class AsynctaskClass extends AsyncTask<Void, Void, Void> {

    private Handler handler;
    public AsynctaskClass(Handler handler, other params ){
     this.handler = handler;
   }
   ...
   ...
}

现在在你的 Asynctask 的 doInBackground() 中，执行任何你喜欢的操作，然后当你得到你想要发送到列表视图的结果时添加以下代码：

@Override
protected Void doInBackground(Void... params) {
   Message message = handler.obtainMessage();
   message.obj = response you wish to send to the listview as String object;
   message.what = 1 //You can use any value which will help you to distinguish the Handler response received at the activity.
   handler.sendMessage(message);

}

就是这样。现在当 sendMessage() 将在 asynctask 中调用时...在您的 Acitivity handleMessage() 中将获得触发器...，因为您可以获取从 asynctask 发送的数据作为 msg.obj.toString().. 现在使用此数据执行 UI 修改。

希望对您有所帮助。

从异步任务获取结果到列表视图

get result from asynctask to list view

android

android-asynctask