编辑文本字段未检测。抛出空指针异常

Question

我尝试了很多方法，但我的应用程序一直崩溃。

我尝试调试运行应用程序时返回此错误。

java.lang.NullPointerException: 尝试在空对象引用

上调用虚拟方法'android.text.Editable android.widget.EditText.getText()'

package com.zybooks.pigdice;


import androidx.appcompat.app.AppCompatActivity;

import android.app.Dialog;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    final Context context = this;
    //private EditText playerName;
    private String name;
    private int target_score_display;
    //public TextView player_name;
    private  EditText targetScore;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //player_name = findViewById(R.id.player_name);
        targetScore = dialog.findViewById(R.id.enter_target_score);
        //playerName = findViewById(R.id.enter_player_name);



        Button start_game = findViewById(R.id.start_game);
        start_game.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // custom dialog
                final Dialog dialog = new Dialog(context);
                dialog.setContentView(R.layout.dialogbox);
                dialog.setTitle("Title...");
                Button dialogButton = dialog.findViewById(R.id.start_game_dialog);
                // if button is clicked, close the custom dialog
                dialogButton.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        try{
                            String value = targetScore.getText().toString();
                            target_score_display = Integer.parseInt(targetScore.getText().toString());
                            Intent intent = new Intent(getApplicationContext(),Gameplay.class);
                            intent.putExtra("TARGET_SCORE",target_score_display);
                            Bundle bundle = new Bundle();
                            bundle.putString("TARGET_SCORE",value);
                            intent.putExtras(bundle);
                            startActivity(intent);
                        } catch(NumberFormatException nfe) {
                            System.out.println("Could not parse " + nfe);
                        }
                    }
                });
                dialog.show();
            }
        });
    }
}

正在尝试将对话框中的输入传递给下一个 Activity。已经为此苦苦挣扎了 3 个多小时。

Answer 1

您只能在创建对话框后调用 dialog.findViewById（在 onClick 内）。创建 Activity 时它没有内容，因此您找不到它的视图。例如，正确获取 dialogButton

所以当你试图从不存在的视图中获取文本时，它会抛出异常

编辑文本字段未检测。抛出空指针异常

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编辑文本字段未检测。抛出空指针异常