如何解决按下按键时的铃声/警报错误？

Question

我在此行收到此错误 按钮button1 =（按钮）findViewById（R.id.alarm）;

java.lang.RuntimeException：无法实例化活动ComponentInfo {com.example.user.appidea / com.example.user.appidea.MainActivity}：java.lang.NullPointerException：尝试调用虚拟方法'android.view。空对象引用上的Window $ Callback android.view.Window.getCallback（）'

   public class MainActivity extends AppCompatActivity {
    private Button button;
    **Button button1 = (Button) findViewById(R.id.alarm);**


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

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                INSERT CODE HERE

            }
        });
    }
}

Answer 1

尝试这个工作示例

final MediaPlayer mpRingtone = MediaPlayer.create(this, R.raw.musicfile);
mpRingtone.start();