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我現在編寫了一個測驗,我在FOR-query下設置了一個媒體播放器,每當用戶點擊正確答案時,就會播放聲音。現在在同一個活動中,我希望bttOFF將靜音活動的聲音,我該怎麼做?我用mp.setVolume(0,0)設置了一個onClickListener;但是應用程序在重新啓動時崩潰。感謝您的期待! :d執行靜音按鈕時,應用程序崩潰

  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的:

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) 
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添加您的logcat請 –

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logcat的加先生! – Alan

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什麼是96? –

回答

2

您獲取到findViewById來回您closeButtoncloseButton2

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我已經在代碼的最後幾行做到了這一點,錯誤是從mpsetvolume .. – Alan

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你的問題是在空視圖上添加一個'clickListener'而不是mp,重讀拋出的異常 –

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我是新來的,你能幫我先生嗎? – Alan

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如文檔中示出了用於在MediaPlayer類[這裏](https://developer.android.com/reference/android/media/MediaPlayer.html#setVolume(float,浮動))所需的參數是浮動。你可以嘗試這樣做:

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

然後看看是否解決了你的問題。

setVolume

API等級加1

void setVolume (float leftVolume, float rightVolume)

設置本播放器的音量。建議使用此API來平衡應用程序中音頻流的輸出。除非您正在編寫用於控制用戶設置的應用程序,否則應優先使用此API,而不是用於設置特定類型的所有流的音量的setStreamVolume(int, int, int)。請注意,傳遞的音量值是0.0到1.0範圍內的原始標量。 UI控件應該以對數形式進行縮放。

參數

leftVolume float: left volume scalar 

rightVolume float: right volume scalar 
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它是'NullPointerException'而不是'IllegalArgumentexception' –

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@OussemaAroua該評論當我創建答案時不可見,但你是對的 –

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不起作用.. – Alan

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