How to access variables in separate functions - Android

问题

I have written this small app and it works perfectly. But I am new to java and assume there must be a better way to write this so that the variables can be read in both functions. Is there?

package max.multiplebuttons.com;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.view.View.OnClickListener;

public class multibuttons extends Activity implements OnClickListener {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        TextView question = (TextView)findViewById(R.id.question);
        TextView textView = (TextView)findViewById(R.id.textView);
        Button answer1 = (Button)findViewById(R.id.answer1);
        Button answer2 = (Button)findViewById(R.id.answer2);
        answer1.setText("button1");
        answer2.setText("button2");
        question.setText("click a button");
        textView.setText("Some Text");
        answer1.setOnClickListener(this);
        answer2.setOnClickListener(this);
    }
    public void onClick(View v){
        TextView textView = (TextView)findViewById(R.id.textView);
        Button answer1 = (Button)findViewById(R.id.answer1);
        Button answer2 = (Button)findViewById(R.id.answer2);
        if(v==answer1){
            textView.setText("1");
        }
        if(v==answer2){
            textView.setText("2");
        }
    }
}

回答1:

Make them variables that belong to the class by declaring them outside of any method but inside the class:

public class multibuttons extends Activity implements OnClickListener {
TextView question;
TextView textview;
//etc.

}

Then you just need to initialise them inside the onCreate method:

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    question = (TextView)findViewById(R.id.question);
    textView = (TextView)findViewById(R.id.textView);
    //...

You don't need to initialise them again at all in the onClick method:

public void onClick(View v){
    if(v==answer1){
        textView.setText("1");
    }
    if(v==answer2){
        textView.setText("2");
    }
}

Variables declared inside a method (or any block of statements enclosed by braces like {} ) only have scope (i.e. they are only visible) inside that method/block. Variables declared as class variables can be given public, private, protected or default/package scope. Declare them as public to be able to access them in any other class.

来源：https://stackoverflow.com/questions/4979975/how-to-access-variables-in-separate-functions-android

标签

java

android

function

variables

shared