简单的Tictactoe游戏

Question

我创建了一个简单的tic-tac-toe游戏。gradle构建没有错误，并且生成了apk。

但是在我的手机中安装后，它显示了这样的...

java.lang.RuntimeException:无法启动活动

componentInfo {com.codec.dnv.tictactoe/com.codec.dnv.tictactoe.mainactivity}：java.lang.nullpointerexception： 尝试调用虚拟方法'void android.widget.button.setonClickListener(android.view.view.view $ onclicklistener('on null对象参考at android.app.Appivity.AcpivityThread.performlainchread.performlainchachactivity(activityThread.java：2814(。Handler.java:106(at Android.os.looper.loop(looper.java：173(at android.app.App.activityThread.main(activitythread.java:6634(java.lang.lang.reflect.reflect.reflect.method.method.method.invoke.invoke(本机方法(在com.android.internal.os.os.os.runtimeinit $ methodAndargScaller.run(runtimeinit.java:547 at com.android.internal.os.zygoteinit.main(zygoteinit.java：822( 引起的：(mainActivity.java：42(at android.app.activity.performcreate(activity.java：7074(at android.app.App.activity.performcreate(activity.java：7065(at android.app.app.instrumentation.callactimentation.callactivity.callactivityoncreate.java(Instrumation.java：Java：Java：Java：Java：Java：Java：Java：Java：Java：Java：Java：Java：1215(at android.app.activitythread.performlaunchactivity(activityThread.java:2767(>

如何克服这一点？

Answer 1

您正在为您的onclicklistener设置零值

android.widget.Button.setOnClickListener(android.view.View$OnClickListener)

我会尝试确定为什么它是零的，也许从未初始化。我们需要查看完整的代码块，以进一步帮助您。

Answer 2

公共类MainActivity扩展了AppCompatactivity bunplent.nclicklistener {

private Button[][] buttons = new Button[3][3];
private boolean player1Turn = true;
private int roundCount;
private int player1Points;
private int player2Points;
private TextView player1;
private TextView player2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    player1 = findViewById(R.id.player1);
    player2 = findViewById(R.id.player2);

    for (int x = 0; x < 3; x++) {
        for (int y = 0; y < 3; y++) {
            String buttonID = "button_" + x + y;
            int resID = getResources().getIdentifier(buttonID, "id", getPackageName());
            buttons[x][y] = findViewById(resID);
            buttons[x][y].setOnClickListener(this);
        }
    }
    Button buttonReset = findViewById(R.id.button_reset);
    buttonReset.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            resetGame();
        }
    });
}
@Override
public void onClick(View v) {
    if (!((Button) v).getText().toString().equals("")) {
        return;
    }
    if (player1Turn) {
        ((Button) v).setText("X");
    } else {
        ((Button) v).setText("Y");
    }
    roundCount++;
    if (checkWin()) {
        if (player1Turn) {
            player1Wins();
        } else {
            player2Wins();
        }
    } else if (roundCount == 9) {
        draw();
    } else {
        player1Turn = !player1Turn;
    }
}
private boolean checkWin() {
    String[][] field = new String[3][3];
    for (int x = 0; x < 3; x++) {
        for (int y = 0; y < 3; y++) {
            field[x][y] = buttons[x][y].getText().toString();
        }
    }
    for (int x = 0; x < 3; x++) {
        if (field[x][0].equals(field[x][1])
                && field[x][0].equals(field[x][2])
                && !field[x][0].equals("")) {
            return true;
        }
    }
    for (int x = 0; x < 3; x++) {
        if (field[0][x].equals(field[1][x])
                && field[0][x].equals(field[2][x])
                && !field[0][x].equals("")) {
            return true;
        }
    }

    if (field[0][0].equals(field[1][1])
            && field[0][0].equals(field[2][2])
            && !field[0][0].equals("")) {
        return true;
    }
    return field[0][2].equals(field[1][1])
            && field[0][2].equals(field[2][0])
            && !field[0][2].equals("");
}

private void player1Wins() {
    player1Points++;
    Toast.makeText(this, "Player 1 wins!", Toast.LENGTH_SHORT).show();
    updatePointsText();
    resetBoard();
}
private void player2Wins() {
    player2Points++;
    Toast.makeText(this, "Player 2 wins!", Toast.LENGTH_SHORT).show();
    updatePointsText();
    resetBoard();
}
private void draw() {
    Toast.makeText(this, "Draw!", Toast.LENGTH_SHORT).show();
    resetBoard();
}

private void updatePointsText() {
    player1.setText(getString(R.string.player_1_0, player1Points));
    player2.setText(getString(R.string.player_2_0, player2Points));
}
private void resetBoard() {
    for (int x = 0; x < 3; x++) {
        for (int y = 0; y < 3; y++) {
            buttons[x][y].setText("");
        }
    }
    roundCount = 0;
    player1Turn = true;
}
private void resetGame() {
    player1Points = 0;
    player2Points = 0;
    updatePointsText();
    resetBoard();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("roundCount", roundCount);
    outState.putInt("player1Points", player1Points);
    outState.putInt("player2Points", player2Points);
    outState.putBoolean("player1Turn", player1Turn);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    roundCount = savedInstanceState.getInt("roundCount");
    player1Points = savedInstanceState.getInt("player1Points");
    player2Points = savedInstanceState.getInt("player2Points");
    player1Turn = savedInstanceState.getBoolean("player1Turn");
}

}

代码在这里...