Android 从对象调用findViewById（）
我正在练习android应用程序开发，并编写台球记分板Android 从对象调用findViewById（）,android,Android,我正在练习android应用程序开发，并编写台球记分板 public class Board extends AppCompatActivity { private Rack rack; private int currentPlayer; public Board() { rack = new Rack(); currentPlayer = 0; } public void setCurrentPlayer(int n
public class Board extends AppCompatActivity {
private Rack rack;
private int currentPlayer;
public Board() {
rack = new Rack();
currentPlayer = 0;
}
public void setCurrentPlayer(int n) {
currentPlayer = n;
}
public void pocket(int ballNumber) {
TextView scoreView = (TextView) findViewById(R.id.pocketed0);
scoreView.setText("FOO");
}
}
public class MainActivity extends AppCompatActivity {
Board board;
String pocketedHistory = "";
String pointString = "";
int points = 0;
String selectedPocket = "S";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
board = new Board();
}
public void pocket5(View v) {
board.pocket(5);
}
pocket5（）public class Board extends AppCompatActivity
...
onCreatesetContentView你也不应该创建这样一个活动的新实例，你必须使用意图启动一个活动我猜你是android新手，事情不正确，你需要了解更多 对于此问题，您可以这样尝试：-
public class Board{
private Rack rack;
private int currentPlayer;
public Board() {
rack = new Rack();
currentPlayer = 0;
}
public void setCurrentPlayer(int n) {
currentPlayer = n;
}
public String pocket(int ballNumber) {
return "FOO";
}
}
public class MainActivity extends AppCompatActivity {
Board board;
String pocketedHistory = "";
String pointString = "";
int points = 0;
String selectedPocket = "S";
TextView scoreView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
scoreView = scoreView.findViewById(R.id.pocketed0);
board = new Board();
}
public void pocket5(View v) {
scoreView.setText(board.pocket(5));
}
}
public class Board{
private Rack rack;
private int currentPlayer;
public Board() {
rack = new Rack();
currentPlayer = 0;
}
public void setCurrentPlayer(int n) {
currentPlayer = n;
}
public String pocket(int ballNumber) {
return "FOO";
}
}
public class MainActivity extends AppCompatActivity {
Board board;
String pocketedHistory = "";
String pointString = "";
int points = 0;
String selectedPocket = "S";
TextView scoreView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
scoreView = scoreView.findViewById(R.id.pocketed0);
board = new Board();
}
public void pocket5(View v) {
scoreView.setText(board.pocket(5));
}
}
这里的问题是如何使用和理解
活动类BoardfindViewByIdmain活动的context
作为constructor
参数传递给Board
类
将Board
类修改为：
public class Board {
private Rack rack;
private int currentPlayer;
private Activity mActivity;
public Board(Activity activity) {
mActivity = activity;
rack = new Rack();
currentPlayer = 0;
}
public void setCurrentPlayer(int n) {
currentPlayer = n;
}
public void pocket(int ballNumber) {
TextView scoreView = (TextView)
mActivity.findViewById(R.id.pocketed0);
scoreView.setText("FOO");
}
}
并修改您的main活动
：
public class MainActivity extends AppCompatActivity {
Board board;
String pocketedHistory = "";
String pointString = "";
int points = 0;
String selectedPocket = "S";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
board = new Board(this);
}
public void pocket5(View v) {
board.pocket(5);
}
}
谢谢大家的回答。我是如此的不耐烦以至于停止了Udacity的视频并开始写作。我认为findViewById（）提供Board对象访问视图对我来说是直观而直接的。这就是为什么我愚蠢地让董事会扩展活动。谢谢你的洞察力，@Kidus！当我更改代码时，medthod无法解决如下问题。你能帮我解释一下吗？>C:\Users\mitsu\AndroidStudioProjects\Japan9ballScorer\app\src\main\java\com\example\android\japan9\u ballscorer\Board.java:22：错误：找不到symbol>TextView scoreView=（TextView）mContext.findViewById（R.id.pocketed0）；>symbol:method findviewbyd（int）>位置：Context`@uemurm类型的变量mContext您没有在Board类中导入上下文库/类吗