Question

以下是我的代码 - 我有一个简单的微调器来显示数组数据。我通过调用WebService获取数组。数组填充正确，但调用微调器时应用程序崩溃。

我试图在我的主要活动中调用AsyncTask并在onCreate活动之外声明我的数组，但是数组会自动初始化。

请帮忙 -

import android.support.v7.app.ActionBarActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class MainActivity extends ActionBarActivity {



    private String[] loan_type = new String[5];
    String[] curr_arr = new String[5];


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

        //Call Web-Service to fill the drop down list

        loan_type = getResources().getStringArray(R.array.loan_type);
        AsyncCallWS task = new AsyncCallWS();
        task.execute();

        //*******************************************



    }


    //Create Async Task
    private class AsyncCallWS extends AsyncTask<String[], Void, Void> {
        @Override
        protected Void doInBackground(String[]... params) {
                        //Invoke webservice
             String[] temp_arr = new String[5];
             Spinner spinner = (Spinner)findViewById(R.id.spinner1);
             temp_arr = CallWebService.invokeHelloWorldWS("Hello","getCurrency");

             if (temp_arr[0] != null){
                ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(MainActivity.this,
                        android.R.layout.simple_spinner_item, temp_arr);
                dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                spinner.setAdapter(dataAdapter);
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            //Set response
            //tv.setText(displayText);
                        //Make ProgressBar invisible
            //pg.setVisibility(View.INVISIBLE);


        }

        @Override
        protected void onPreExecute() {
                        //Make ProgressBar invisible
            //pg.setVisibility(View.VISIBLE);

        }

        @Override
        protected void onProgressUpdate(Void... values) {
        }

    }
    //**************************************************************************
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

下面＆＃39;工作代码 -

import android.support.v7.app.ActionBarActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class MainActivity extends ActionBarActivity {



    private String[] loan_type = new String[5];
    String[] curr_arr = new String[5];
    String[] temp_arr = new String[5];


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

        //Call Web-Service to fill the drop down list

        loan_type = getResources().getStringArray(R.array.loan_type);
        AsyncCallWS task = new AsyncCallWS();
        task.execute();

        //*******************************************



    }


    //Create Async Task
    private class AsyncCallWS extends AsyncTask<String[], Void, Void> {
        @Override
        protected Void doInBackground(String[]... params) {
                        //Invoke webservice


             temp_arr = CallWebService.invokeHelloWorldWS("Hello","getCurrency");


            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            //Set response
            //tv.setText(displayText);
                        //Make ProgressBar invisible
            //pg.setVisibility(View.INVISIBLE);
            if (temp_arr[0] != null){
                Spinner spinner = (Spinner)findViewById(R.id.spinner1);
                ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(MainActivity.this,
                        android.R.layout.simple_spinner_item, temp_arr);
                dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                spinner.setAdapter(dataAdapter);
            }

        }

        @Override
        protected void onPreExecute() {
                        //Make ProgressBar invisible
            //pg.setVisibility(View.VISIBLE);

        }

        @Override
        protected void onProgressUpdate(Void... values) {
        }

    }
    //**************************************************************************
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

doInBackground

是一种异步方法，您可以从中更改UI。你可以通过设置Spinner来规则化。将您在doInBackground中检索到的任何数据传递给在UI线程上运行的onPostExecute，并在那里创建您的微调器。如果您的应用程序崩溃了，请查看堆栈跟踪，其中大部分时间都会告诉您哪些错误。如果你问一个问题，也可以发布堆栈跟踪：）

Answer 2

您必须在任务中的onPostExecute上执行查看操作。

private class AsyncCallWS extends AsyncTask<String[], Void, String[]> {
    @Override
    protected String[] doInBackground(String[]... params) {
        //Invoke webservice
        String[] temp_arr = new String[5];
        Spinner spinner = (Spinner)findViewById(R.id.spinner1);
        temp_arr = CallWebService.invokeHelloWorldWS("Hello","getCurrency");
        return temp_arr ;
    }

    @Override
    protected void onPostExecute(String[] temp_arr) {
        if (temp_arr[0] != null){
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(MainActivity.this,
                    android.R.layout.simple_spinner_item, temp_arr);
            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            spinner.setAdapter(dataAdapter);
        }
    }

    @Override
    protected void onPreExecute() {
                    //Make ProgressBar invisible
        //pg.setVisibility(View.VISIBLE);

    }

    @Override
    protected void onProgressUpdate(Void... values) {
    }

}

如何使用Webservice在Spinner中填充数据？

2 个答案: