在OnCreate中定义按钮-无法解析方法中的符号

Question

I'm a beginner as you'll see. I can't see where I can legally put the Button statements and the setText statements so this will compile. If I move one the other doesn't work and vice versa. I understand that the OnCreate is protected and so the "buttonOne" won't be passed to the playPhrases method but I've been changing thing around for a while now and nothing works. Simple explanations please.

    package com.example.android.languageapp;

import android.media.MediaPlayer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

import static android.R.attr.button;

public class MainActivity extends AppCompatActivity {

    MediaPlayer myMediaPlayer;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myMediaPlayer = MediaPlayer.create(this, R.raw.hello);

        String[] phrases = getResources().getStringArray(R.array.phrase);



        Button buttonOne = (Button) findViewById(R.id.button1);
        Button buttonTwo = (Button) findViewById(R.id.button2);
        Button buttonThree = (Button) findViewById(R.id.button3);
        Button buttonFour = (Button) findViewById(R.id.button4);
        Button buttonFive = (Button) findViewById(R.id.button5);
        Button buttonSix = (Button) findViewById(R.id.button6);
        Button buttonSeven = (Button) findViewById(R.id.button7);
        Button buttonEight = (Button) findViewById(R.id.button8);

        buttonOne.setText(phrases[0]);
        buttonTwo.setText(phrases[1]);
        buttonThree.setText(phrases[2]);
        buttonFour.setText(phrases[3]);
        buttonFive.setText(phrases[4]);
        buttonSix.setText(phrases[5]);
        buttonSeven.setText(phrases[6]);
        buttonEight.setText(phrases[7]);
    }


    public void playPhrases(View clickedButton) {

        int id = clickedButton.getId();

        Log.i("Button id", "" + id);

        if (id == buttonOne.getId()) {

            myMediaPlayer = MediaPlayer.create(this, R.raw.doyouspeakenglish);

            myMediaPlayer.start();
        }


    }



}

Thanks for your help

Answer 1

You use just use id in playPhrases click listener like this,

public void playPhrases(View clickedButton) {

    int id = clickedButton.getId();

    Log.i("Button id", "" + id);

    switch (id) {
        case R.id.R.id.button1:
            // Button 1 operation
            myMediaPlayer = MediaPlayer.create(this, R.raw.doyouspeakenglish);

            myMediaPlayer.start();
            break;
        case R.id.R.id.button2:
            // Button 2 operation
            break;
        case R.id.R.id.button3:
            // Button 3 operation
            break;
    }
    // We dont need button object
    //if (id == buttonOne.getId()) {
    //
    //    myMediaPlayer = MediaPlayer.create(this, R.raw.doyouspeakenglish);
    //
    //    myMediaPlayer.start();
    //}


}

Answer 2

Declare your Buttons outside the onCreate method and then attach them to views in your onCreate . That way you can access them later anywhere in your class. I have shown it with 3 buttons as example but you can do it the same way for all.

These button becomes Data members of the class or Global variables rather than Local Variables of onCreate method. To understand more about Global Vairables visit Here

public class MainActivity extends AppCompatActivity {
MediaPlayer myMediaPlayer;
Button buttonOne ,buttonTwo,buttonThree ; // Do it this way first for buttons to create reference

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myMediaPlayer = MediaPlayer.create(this, R.raw.hello);

    String[] phrases = getResources().getStringArray(R.array.phrase);


    // Access like this 
    buttonOne = (Button) findViewById(R.id.button1);
    buttonTwo = (Button) findViewById(R.id.button2);
    buttonThree = (Button) findViewById(R.id.button3);
    Button buttonFour = (Button) findViewById(R.id.button4);
    Button buttonFive = (Button) findViewById(R.id.button5);
    Button buttonSix = (Button) findViewById(R.id.button6);
    Button buttonSeven = (Button) findViewById(R.id.button7);
    Button buttonEight = (Button) findViewById(R.id.button8);

    buttonOne.setText(phrases[0]);
    buttonTwo.setText(phrases[1]);
    buttonThree.setText(phrases[2]);
    buttonFour.setText(phrases[3]);
    buttonFive.setText(phrases[4]);
    buttonSix.setText(phrases[5]);
    buttonSeven.setText(phrases[6]);
    buttonEight.setText(phrases[7]);
}


public void playPhrases(View clickedButton) {

    int id = clickedButton.getId();

    Log.i("Button id", "" + id);

    if (id == buttonOne.getId()) {

        myMediaPlayer = MediaPlayer.create(this, R.raw.doyouspeakenglish);

        myMediaPlayer.start();
    }


}



}

Answer 3

define Button Variables globally try this

public class MainActivity extends AppCompatActivity {

MediaPlayer myMediaPlayer;
Button buttonOne;
Button buttonTwo ;
Button buttonThree ;
Button buttonFour;
Button buttonFive;
Button buttonSix ;
Button buttonSeven ;
Button buttonEight;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myMediaPlayer = MediaPlayer.create(this, R.raw.hello);

    String[] phrases = getResources().getStringArray(R.array.phrase);



     buttonOne = (Button) findViewById(R.id.button1);
     buttonTwo = (Button) findViewById(R.id.button2);
     buttonThree = (Button) findViewById(R.id.button3);
     buttonFour = (Button) findViewById(R.id.button4);
     buttonFive = (Button) findViewById(R.id.button5);
     buttonSix = (Button) findViewById(R.id.button6);
     buttonSeven = (Button) findViewById(R.id.button7);
     buttonEight = (Button) findViewById(R.id.button8);

    buttonOne.setText(phrases[0]);
    buttonTwo.setText(phrases[1]);
    buttonThree.setText(phrases[2]);
    buttonFour.setText(phrases[3]);
    buttonFive.setText(phrases[4]);
    buttonSix.setText(phrases[5]);
    buttonSeven.setText(phrases[6]);
    buttonEight.setText(phrases[7]);
}


public void playPhrases(View clickedButton) {

    int id = clickedButton.getId();

    Log.i("Button id", "" + id);

    if (id == buttonOne.getId()) {

        myMediaPlayer = MediaPlayer.create(this, R.raw.doyouspeakenglish);

        myMediaPlayer.start();
    }


}

}

Answer 4

You have to move the declaration of your buttons variables out of the OnCreate method to declare it globally. Button buttonOne; Must be in the MainActivity class if you declare it in the method it can't be used in another one; Then you can still do : buttonOne = (Button) findViewById(R.id.button1); in OnCreate