Android开发：使用DialogFragment获取EditText值并展示的实现方案

1. 主Activity布局文件 (activity_main.xml) #

这个布局包含两个用于展示结果的TextView，以及触发弹窗的按钮：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.example.eugene.myapplication.MainActivity">

    <TextView 
        android:id="@+id/textview_GoalName" 
        android:layout_width="match_parent" 
        android:layout_height="wrap_content" 
        android:layout_centerVertical="true" 
        android:gravity="center_horizontal" 
        android:text="Here will be your Goal Name" 
        android:textSize="30sp" />

    <TextView 
        android:id="@+id/textview_GoalAmount" 
        android:layout_width="match_parent" 
        android:layout_height="wrap_content" 
        android:layout_below="@+id/textview_GoalName" 
        android:gravity="center_horizontal" 
        android:text="Here will be your Goal Amount" 
        android:textSize="30sp" />

    <Button 
        android:id="@+id/button" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_below="@+id/textview_GoalAmount" 
        android:layout_centerHorizontal="true" 
        android:text="Create a Goal!" />
</RelativeLayout>

2. DialogFragment布局文件 (layout_dialog.xml) #

注意补充上闭合的</RelativeLayout>标签，原代码里漏了：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:padding="16dp">

    <EditText 
        android:id="@+id/edit_goalName" 
        android:layout_width="match_parent" 
        android:layout_height="wrap_content" 
        android:hint="Goal Name"/>

    <EditText 
        android:id="@+id/edit_goalAmt" 
        android:layout_width="match_parent" 
        android:layout_height="wrap_content" 
        android:layout_below="@+id/edit_goalName" 
        android:hint="Goal Amount" 
        android:inputType="number" />
</RelativeLayout>

3. 主Activity代码 (MainActivity.java) #

通过实现DialogFragment定义的接口，接收弹窗传递回来的输入值并更新UI：

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements ExampleDialog.ExampleDialogListener {
    private TextView textViewGoalName;
    private TextView textViewGoalAmt;
    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        textViewGoalName = findViewById(R.id.textview_GoalName);
        textViewGoalAmt = findViewById(R.id.textview_GoalAmount);
        button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                openDialog();
            }
        });
    }

    public void openDialog(){
        ExampleDialog exampleDialog = new ExampleDialog();
        exampleDialog.show(getSupportFragmentManager(), "example dialog");
    }

    @Override
    public void applyTexts(String goalName, String goalAmount) {
        textViewGoalName.setText(goalName);
        textViewGoalAmt.setText(goalAmount);
    }
}

4. DialogFragment代码 (ExampleDialog.java) #

修复了原代码里字符串比较错误（Java里不能用==判断字符串为空，改用TextUtils.isEmpty()更可靠），同时完善了非空校验逻辑：

import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatDialogFragment;

public class ExampleDialog extends AppCompatDialogFragment {
    private EditText editTextGoalName;
    private EditText editTextGoalAmt;
    private ExampleDialogListener listener;

    @Override
    public AlertDialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        LayoutInflater inflater = getActivity().getLayoutInflater();
        View view = inflater.inflate(R.layout.layout_dialog,null);

        builder.setView(view)
                .setTitle("Create Goal")
                .setNegativeButton("Maybe next time..", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i){
                        // 点击取消直接关闭弹窗，无需额外操作
                    }
                })
                .setPositiveButton("Start!", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i){
                        String goalName = editTextGoalName.getText().toString().trim();
                        String goalAmt = editTextGoalAmt.getText().toString().trim();
                        String message = "Fields Required";

                        // 修复字符串为空的判断逻辑
                        if (TextUtils.isEmpty(goalName) && TextUtils.isEmpty(goalAmt)){
                            Toast.makeText(getActivity(), message, Toast.LENGTH_SHORT).show();
                            return; // 校验不通过时不执行后续传值操作
                        }
                        // 把输入值传递给主Activity
                        listener.applyTexts(goalName, goalAmt);
                    }
                });

        editTextGoalName = view.findViewById(R.id.edit_goalName);
        editTextGoalAmt = view.findViewById(R.id.edit_goalAmt);
        return builder.create();
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        try {
            listener = (ExampleDialogListener) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString() + " Must implement ExampleDialogListener");
        }
    }

    // 定义回调接口，用于Fragment向Activity传递数据
    public interface ExampleDialogListener{
        void applyTexts(String goalName, String goalAmount);
    }
}

关键说明 #

1. 接口回调机制：这是Android中Fragment与Activity通信的标准方式，通过ExampleDialogListener接口，DialogFragment可以把输入值传递给实现了该接口的MainActivity。
2. 非空校验优化：用TextUtils.isEmpty()判断字符串为空，同时给输入内容做了trim()处理，避免用户输入空格导致的无效内容。
3. 代码健壮性：在非空校验不通过时，用return终止后续操作，避免空值传递到主Activity。

内容的提问来源于stack exchange，提问作者Waffles