实施静音按钮时应用程序崩溃

Question

我编写了一个测验程序，现在我在 FOR 查询下设置了一个媒体播放器，每次用户回答正确时都会播放声音。现在在同一个 Activity 中，我希望 bttOFF 将 Activity 的声音静音，我该怎么做？我用 mp.setVolume(0,0) 设置了一个 onClickListener；但是应用程序在重启时崩溃。感谢您的观看！ :D

         public class QuizActivity extends AppCompatActivity {

private ActionBarDrawerToggle mToggle;

private QuestionLibrary mQuestionLibrary = new QuestionLibrary();

private TextView mScoreView;
private TextView mQuestionView;
private Button mButtonChoice1;
private Button mButtonChoice2;
private Button mButtonChoice3;
private String mAnswer;
private int mScore = 0;
private int mQuestionNumber = 0;
Dialog dialog;
Dialog dialog2;
TextView closeButton;
TextView closeButton2;


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

    final MediaPlayer mp = new MediaPlayer();

    //Dialog 1
    createDialog();
    Button dialogButton = (Button) findViewById(R.id.dialogbtn);
    dialogButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dialog.show();

        }
    });

    closeButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dialog.dismiss();
        }
    });
    //end Dialog 1

    //Dialog 2
    createDialog2();
    Button dialogButton2 = (Button) findViewById(R.id.dialogbtn2);
    dialogButton2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dialog2.show();

        }
    });


    closeButton2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dialog2.dismiss();
        }
    });
    //end Dialog 2

    Button bttON = (Button)findViewById(R.id.bttON);

    bttON.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mp.setVolume(0,0);


        }


    });




    TextView shareTextView = (TextView) findViewById(R.id.share);
    shareTextView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent myIntent = new Intent(Intent.ACTION_SEND);
            myIntent.setType("text/plain");
            myIntent.putExtra(Intent.EXTRA_SUBJECT, "Hello!");
            myIntent.putExtra(Intent.EXTRA_TEXT, "My highscore in Quizzi is very high! I bet you can't beat me except you are cleverer than me. Download the app now! https://play.google.com/store/apps/details?id=amapps.impossiblequiz");
            startActivity(Intent.createChooser(myIntent, "Share with:"));
        }
    });

    mQuestionLibrary.shuffle();


    setSupportActionBar((Toolbar) findViewById(R.id.nav_action));
    DrawerLayout mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
    mToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
    mDrawerLayout.addDrawerListener(mToggle);
    mToggle.syncState();
    getSupportActionBar().setDisplayHomeAsUpEnabled(true); // Able to see the Navigation Burger "Button"

    ((NavigationView) findViewById(R.id.nv1)).setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {
            switch (menuItem.getItemId()) {
                case R.id.nav_stats:
                    startActivity(new Intent(QuizActivity.this, Menu2.class));
                    break;
                case R.id.nav_about:
                    startActivity(new Intent(QuizActivity.this, Menu3.class));
                    break;
            }

            return true;
        }
    });

    mScoreView = (TextView) findViewById(R.id.score_score);
    mQuestionView = (TextView) findViewById(R.id.question);
    mButtonChoice1 = (Button) findViewById(R.id.choice1);
    mButtonChoice2 = (Button) findViewById(R.id.choice2);
    mButtonChoice3 = (Button) findViewById(R.id.choice3);

    final List<Button> choices = new ArrayList<>();
    choices.add(mButtonChoice1);
    choices.add(mButtonChoice2);
    choices.add(mButtonChoice3);

    updateQuestion();



    for (final Button choice : choices) {
        choice.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                if (choice.getText().equals(mAnswer)) {


                    try {
                        mp.reset();
                        AssetFileDescriptor afd;
                        afd = getAssets().openFd("sample.mp3");
                        mp.setDataSource(afd.getFileDescriptor(),afd.getStartOffset(),afd.getLength());
                        mp.prepare();
                        mp.start();
                    } catch (IllegalStateException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    updateScore();
                    updateQuestion();
                    Toast.makeText(QuizActivity.this, "Correct", Toast.LENGTH_SHORT).show();



                } else {
                    Toast.makeText(QuizActivity.this, "Wrong... Try again!", Toast.LENGTH_SHORT).show();

                    Intent intent = new Intent(QuizActivity.this, Menu2.class);
                    intent.putExtra("score", mScore); // pass score to Menu2
                    startActivity(intent);
                }
            }
        });
    }

}

private void updateQuestion() {
    if (mQuestionNumber < mQuestionLibrary.getLength()) {
        mQuestionView.setText(mQuestionLibrary.getQuestion(mQuestionNumber));
        mButtonChoice1.setText(mQuestionLibrary.getChoice1(mQuestionNumber));
        mButtonChoice2.setText(mQuestionLibrary.getChoice2(mQuestionNumber));
        mButtonChoice3.setText(mQuestionLibrary.getChoice3(mQuestionNumber));
        mAnswer = mQuestionLibrary.getCorrectAnswer(mQuestionNumber++);
    } else {
        Toast.makeText(QuizActivity.this, "Last Question! You are very intelligent!", Toast.LENGTH_SHORT).show();
        Intent intent = new Intent(QuizActivity.this, Menu2.class);
        intent.putExtra("score", mScore);
        startActivity(intent);
    }
}

private void updateScore() {
    mScoreView.setText(String.valueOf(++mScore));

    SharedPreferences mypref = getPreferences(MODE_PRIVATE);
    int highScore = mypref.getInt("highScore", 0);

    if (mScore > highScore) {
        SharedPreferences.Editor editor = mypref.edit();
        editor.putInt("highScore", mScore);
        editor.apply();
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    return mToggle.onOptionsItemSelected(item) || super.onOptionsItemSelected(item);
}

private void createDialog() {
    dialog = new Dialog(this);
    dialog.setTitle("Tutorial");
    dialog.setContentView(R.layout.popup_menu1_1);
    closeButton = (TextView) dialog.findViewById(R.id.closeTXT);
}


private void createDialog2() {
    dialog2 = new Dialog(this);
    dialog2.setTitle("Settings");
    dialog2.setContentView(R.layout.popup_menu1_2);
   closeButton2 = (TextView) dialog2.findViewById(R.id.closeTXT2);

}

Logcat:

    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
                                                                     at shapy.appz.QuizActivity.onCreate(QuizActivity.java:96)

Answer 1

如 MediaPlayer class [此处]( https://developer.android.com/reference/android/media/MediaPlayer.html#setVolume(float, float) 的文档中所示，所需的参数是浮点数。您可以尝试这样做：

public void onClick(View v) {
    mp.setVolume( 0.0, 0.0 );
}

看看是否能解决您的问题。

setVolume

added in API level 1

void setVolume (float leftVolume, float rightVolume)

Sets the volume on this player. This API is recommended for balancing the output of audio streams within an application. Unless you are writing an application to control user settings, this API should be used in preference to setStreamVolume(int, int, int) which sets the volume of ALL streams of a particular type. Note that the passed volume values are raw scalars in range 0.0 to 1.0. UI controls should be scaled logarithmically.

参数

leftVolume  float: left volume scalar

rightVolume float: right volume scalar

Answer 2

年从您的 closeButton 和 closeButton2

达到 findViewById

实施静音按钮时应用程序崩溃

App crashes when implementing mute button

java

audio

android

nullpointerexception

android-mediaplayer