java - 按钮点击监听器

Question

我有这个代码:

public class MainActivity extends Activity {

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

    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    MediaPlayer sound1, sound2;
    sound1 = MediaPlayer.create(this, R.raw.cows);
    sound2 = MediaPlayer.create(this, R.raw.sheep);

    final Button button1 = (Button) findViewById(R.id.Button01);
    button1.setOnClickListener(this);

    final Button button2 = (Button) findViewById(R.id.Button02);
    button1.setOnClickListener(this);

    public void onClick(View v) {
        switch(v.getId()) {
            case R.id.Button01:
                sound1.start();
                break;
            case R.id.Button02:
                sound2.start();
                break;
        }
    }

    protected void onDestroy() {
        sound1.release();
        sound2.release();
        super.onDestroy();
    }
}

我收到一条警告，指出按钮和 View 不正确。
但是，我不明白上面的代码有什么问题。
看来我需要实例化按钮类和 View 类。
但我不知道该怎么做。

Answer 1

这应该在方法内部

sound1 = MediaPlayer.create(this, R.raw.cows);
sound2 = MediaPlayer.create(this, R.raw.sheep);


final Button button1 = (Button) findViewById(R.id.Button01);
button1.setOnClickListener(this);

final Button button2 = (Button) findViewById(R.id.Button02);
button1.setOnClickListener(this); // should be button2

您可以在onCreate中初始化 View

Button button1,button2;
MediaPlayer sound1,sound2;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sound1 = MediaPlayer.create(this, R.raw.cows);
sound2 = MediaPlayer.create(this, R.raw.sheep);

button1 = (Button) findViewById(R.id.Button01);
button1.setOnClickListener(this);
button2 = (Button) findViewById(R.id.Button02);
button2.setOnClickListener(this);
}

然后

public class MainActivity extends Activity implements onClickListener {