对编程非常陌生，试图理解为什么我在R.raw文件夹中的文件中遇到了空指针异常。 Android Studio可以识别文件，并且在编译器中没有任何错误。谢谢！
公共类MainActivity扩展了AppCompatActivity {
private SoundPool mSoundPool;
private int cID;
private int dID;
private int eID;
private int fID;
private int gID;
private int aID;
private int bID;
我只是尝试在新项目中重做编程，因为我不确定自己做错了什么。
public void playC（视图）{
mSoundPool.play(cID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playD(View view) {
mSoundPool.play(dID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playE(View view) {
mSoundPool.play(eID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playF(View view) {
mSoundPool.play(fID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playG(View view) {
mSoundPool.play(gID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playA(View view) {
mSoundPool.play(aID, 1.0f, 1.0f, 0, 0, 1 );
}
public void playB(View view) {
mSoundPool.play(bID, 1.0f, 1.0f, 0, 0, 1 );
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cID = mSoundPool.load(getApplicationContext(), R.raw.note1_c, 1);
dID = mSoundPool.load(getApplicationContext(), R.raw.note2_d, 1);
eID = mSoundPool.load(getApplicationContext(), R.raw.note3_e, 1);
fID = mSoundPool.load(getApplicationContext(), R.raw.note4_f, 1);
gID = mSoundPool.load(getApplicationContext(), R.raw.note5_g, 1);
aID = mSoundPool.load(getApplicationContext(), R.raw.note6_a, 1);
bID = mSoundPool.load(getApplicationContext(), R.raw.note7_b, 1);
}
}