Android 按钮音量变化？

嘿，伙计们，当我运行我的应用程序时，它会进入主屏幕。从那里，我按下两个图像按钮中的一个，一个声音开始播放。我遇到的问题是，当我第一次按下按钮时，声音正常且响亮，按钮活动将我带到下一个布局。如果我从布局回到主屏幕并再次尝试按下按钮，我仍然可以听到声音，但几乎听不到。有时几乎听不见。如何使声音始终保持一致？谢谢

DragonFutureActivity.java

package com.Dragon_Fruit;

import java.io.IOException;

import android.app.Activity;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ImageButton;

public class DragonFruitActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // ***BUTTON SOUND***//
        final MediaPlayer buttonSound = MediaPlayer.create(
                DragonFruitActivity.this, R.raw.button_click);

        ImageButton playbutton = (ImageButton) findViewById(R.id.playbutton);
        playbutton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                arg0.setBackgroundResource(R.drawable.playbuttonselected);
                // TODO Auto-generated method stub
                if(buttonSound.isPlaying()) {
                    buttonSound.stop();
                }

                try {
                    buttonSound.prepare();
                } catch (IllegalStateException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                buttonSound.start();

                startActivity(new Intent(DragonFruitActivity.this,
                        playbutton.class));
            }

        });
        ImageButton settingsbutton = (ImageButton) findViewById(R.id.settingsbutton);
        settingsbutton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                if(buttonSound.isPlaying()) {
                    buttonSound.stop();
                }

                try {
                    buttonSound.prepare();
                } catch (IllegalStateException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                buttonSound.start();

                startActivity(new Intent(DragonFruitActivity.this,
                        settingsbutton.class));
            }

        });
    }
}

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声音有多长？如果是真的很短（好的，这很有意义。我该怎么做呢？我使用Adobe Audition编辑声音文件。我想你可以在这里免费试用：等等，我该如何使用声音池？