Android开发入门：代码示例解析

public class MyActivity extends Activity {
    static final int PICK_CONTACT_REQUEST = 0;

    protected boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {
            // 当用户按下中心键时，允许他们选择一个联系人
            startActivityForResult(
                    new Intent(Intent.ACTION_PICK,
                            new Uri("content://contacts")),
                    PICK_CONTACT_REQUEST);
            return true;
        }
        return false;
    }

    protected void onActivityResult(int requestCode, int resultCode,
                                    Intent data) {
        if (requestCode == PICK_CONTACT_REQUEST) {
            if (resultCode == RESULT_OK) {
                // 已选择联系人，此处仅将其显示给用户
                startActivity(new Intent(Intent.ACTION_VIEW, data));
            }
        }
    }
}