Question

package hjroh0315.numbergame;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.util.Random;

public class MainActivity extends AppCompatActivity {
    int SelN=-1;
    Random Rand = new Random();
    TextView Hint = (TextView)findViewById(R.id.textView);
    EditText GuessInput = (EditText)findViewById(R.id.editText);
    Button NewNumber = (Button)findViewById(R.id.button);
    Button Guess = (Button)findViewById(R.id.button2);
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NewNumber.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                SelN = Rand.nextInt(100);
            }
        });
        Guess.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String Guessed = GuessInput.getText().toString();
                int Num = Integer.parseInt(Guessed);
                if(SelN == -1)Hint.setText("Error: Number not generated.");
                else if (Num < SelN)
                {
                    Hint.setText("Up");
                }
                else if(Num > SelN)
                {
                    Hint.setText("Down");
                }
                else
                {
                    Hint.setText("Good");
                    SelN=-1;
                }
            }
        });
    }
}

当我运行此代码时，该应用程序立即崩溃。它说第15行有一个错误。但我不明白为什么。有人可以向我解释一下吗？附：这是一个猜测游戏，这是我的一个项目。

Answer 1

你不应该在onCreate方法之外初始化textview：

TextView Hint = (TextView)findViewById(R.id.textView);

布局尚未膨胀，因此无法找到它

您应该在

之后复制onCreate方法中的所有findViewById

setContentView();

试试这样：

public class MainActivity extends AppCompatActivity {
    int SelN=-1;
    Random Rand = new Random();
    TextView Hint;
    EditText GuessInput; 
    Button NewNumber; 
    Button Guess; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Hint = (TextView)findViewById(R.id.textView);
       GuessInput = (EditText)findViewById(R.id.editText);
    NewNumber = (Button)findViewById(R.id.button);
    Guess = (Button)findViewById(R.id.button2);

        NewNumber.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                SelN = Rand.nextInt(100);
            }
        });
        Guess.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String Guessed = GuessInput.getText().toString();
                int Num = Integer.parseInt(Guessed);
                if(SelN == -1)Hint.setText("Error: Number not generated.");
                else if (Num < SelN)
                {
                    Hint.setText("Up");
                }
                else if(Num > SelN)
                {
                    Hint.setText("Down");
                }
                else
                {
                    Hint.setText("Good");
                    SelN=-1;
                }
            }
        });
    }
}

我的数字猜谜游戏代码出了什么问题？

1 个答案: