从onItemSelctedListener内部传递变量

Question

我在setOnItemSelectedListeners中声明了不同的变量(temperature_var、size_var、yolk_var)，并希望将这些变量传递给按钮的另一个setOnClickListener。

问题是我不能访问setOnClickListener中的变量(例如temperature_var)，因此Eclipse告诉我在本地声明该变量。我不确定如何在onclick/OnItemSelectedListeners中传递这些变量。完整的代码如下所示：

package com.example.eggtimer;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnItemSelectedListener {

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

        // Call Spinners & Buttons
        Spinner temperature = (Spinner) findViewById(R.id.spinnerTemperature);
        Spinner size = (Spinner) findViewById(R.id.spinnerSize);
        Spinner yolk = (Spinner) findViewById(R.id.spinnerYolk);

        // Register Spinners & Buttons
       temperature.setOnItemSelectedListener(this);
       size.setOnItemSelectedListener(this);
       yolk.setOnItemSelectedListener(this);


        // Call Adapters
         ArrayAdapter<String> adapter_temperature = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.temperature));
            // Sets the list template
            adapter_temperature.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         ArrayAdapter<String> adapter_size = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.size));
            // Sets the list template
            adapter_size.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         ArrayAdapter<String> adapter_yolk = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.yolk));
            // Sets the list template
            adapter_yolk.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);        

        // Combine Adapters with Spinners   
        temperature.setAdapter(adapter_temperature);
        size.setAdapter(adapter_size);
        yolk.setAdapter(adapter_yolk);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    public void onItemSelected(AdapterView<?> arg0, View v, int arg2,
            long arg3) {
        Toast.makeText(getApplicationContext(), "It works", Toast.LENGTH_LONG).show();

        // Call Adapters again ==> I do not know why this is necessary but otherwise the array adapters can not be found within onItemSelected
         ArrayAdapter<String> adapter_temperature = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.temperature));
            // Sets the list template
            adapter_temperature.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         ArrayAdapter<String> adapter_size = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.size));
            // Sets the list template
            adapter_size.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
         ArrayAdapter<String> adapter_yolk = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, getResources().getStringArray(R.array.yolk));
            // Sets the list template
            adapter_yolk.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);   

        // Call next button
         Button next = (Button) findViewById(R.id.buttonNext);

        // Debug Variables
        TextView debug1 = (TextView) findViewById(R.id.textViewDebug1);
        TextView debug2 = (TextView) findViewById(R.id.textViewDebug2);
        TextView debug3 = (TextView) findViewById(R.id.textViewDebug3);

        switch(v.getId()) {
        case R.id.spinnerSize:

            Toast.makeText(getApplicationContext(), "Spinner selected", Toast.LENGTH_LONG).show();


            break;
        default:
            break;
        }


    }

    public void onNothingSelected(AdapterView<?> arg0) {
        // TODO Auto-generated method stub

    }
}

Answer 1

基本上，声明为final的字段在第一次设置后不能更改。

因此，为了能够从OnItemSelectedListeners (和其他侦听器)中访问字段，我建议您选择让Activity实现OnItemSelectedListener，而不是像在代码中那样使用匿名方法。

看一下这个例子：http://start-jandroid.blogspot.dk/2011/01/android-spinner-example.html

这家伙只使用了一个微调器，但正如您所看到的，微调器将其ItemSelectedListener设置为活动(this)。

现在在活动的: onItemSelected侦听器中，您应该创建一个开关，如下所示：

@Override
public void onItemSelected(AdapterView<?> parent, View v, int position,
    long id) {
    switch(v.getId) {
    case R.id.mySpinner1:
        // Do stuff when the mySpinner1 has been selected like changing some text on a button like so:
        someString = "myNewString";
        myButton1.setText(someString);
        break;
    case R.id.mySpinner2:
        // Do stuff when the mySpinner2 has been selected like changing some text on another button like so:
        someOtherString = "mybrandNewString";
        myButton2.setText(someOtherString);
        break;
    default:
        break;
    }
}

Answer 2

如果要在onclick侦听器外部使用这些变量，请在该侦听器外部声明这些变量。

只需将它们放在活动中，所有不同的监听器都可以访问它们。

另外，如果它们所做的只是在视图上设置文本，那么您可以让activity实现OnItemSelectedListener，并让它们都进入相同的onItemSelected方法。然后，您可以调用list.getItemAtPosition()并将其转换为字符串。它稍微简化了你的代码。