Java 如何在Android中将用户输入从一个活动传递到另一个活动

我正在创建一个基本的转换应用程序，它可以转换用户输入的公里结数，反之亦然。目前，它显示结果的位置与用户最初输入图形的位置相同。我想知道如何在新活动中显示结果？目前，正如我所说，我只是设法让它出现在用户最初输入他们的图形的同一位置，然后第二个活动弹出。我错过了什么？请查看我的代码，谢谢：

MainActivity.java

package winfield.joe.wind.v1;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.Toast;

public class MainActivity extends Activity {

    // public var
    private EditText text;

    // default func
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Toast.makeText(this, "onCreate!", Toast.LENGTH_LONG).show();
        setContentView(R.layout.activity_main);
        // findViewById = Finds a view that was identified by the id attribute
        // from the XML that was processed in onCreate(Bundle).
        // (EditText) = typecast
        text = (EditText) findViewById(R.id.userInput);
    }

    //Will be executed by clicking on the calculate button because we assigned "calc" to the "onClick" Property

    public void calc(View view) {

        RadioButton toKilometers = (RadioButton) findViewById(R.id.toKilometers);
        RadioButton toKnots = (RadioButton) findViewById(R.id.toKnots);

        if (text.getText().length() == 0) {
            // if the text field is empty show the message "enter a valid number" via toast message
            Toast.makeText(this, "enter a valid number", Toast.LENGTH_LONG).show();
        } else {

            int result = R.string.userInput;
            Intent i = new Intent(MainActivity.this, SecondActivity.class);
            putExtra("userInput", result); 
            startActivity(i);

            // parse input Value from Text Field
            double inputValue = Double.parseDouble(text.getText().toString());
            // convert to...
            if (toKilometers.isChecked()) {
                text.setText(String.valueOf(convertToKM(inputValue)));
                // uncheck "to km" Button
                toKilometers.setChecked(false);
                // check "to knots" Button
                toKnots.setChecked(true);
            } else { /* if toKnots button isChecked() */
                text.setText(String.valueOf(convertToKnots(inputValue)));
                // uncheck "to knots" Button
                toKnots.setChecked(false);
                // check "to km" Button
                toKilometers.setChecked(true);
            }
        }

    }


    private void putExtra(String string, int result) {
        // TODO Auto-generated method stub
    }

    private double convertToKM(double inputValue) {
        // convert knots to km
        return (inputValue * 1.8);
    }

    private double convertToKnots(double inputValue) {
        // convert km to knots
        return (inputValue * 0.539956803);
    }

}

package winfield.joe.wind.v1;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class SecondActivity extends Activity {

    Bundle extras = getIntent().getExtras();
    int result = extras.getInt("results"); 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
    }

    //onClick GoBack method assigned to the Go Back? button which returns the user to main activity from the second activity
    public void GoBack(View view) {

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Are you sure?");

            // set dialog message
            builder .setCancelable(false)

                    .setPositiveButton("Convert Again",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            //You return to Main Activity  
                            Intent intent = new Intent(SecondActivity.this, MainActivity.class);
                            startActivity(intent);
                        }
                    })

                    .setNeutralButton("Back to Home",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            //You return to the home page
                            Intent intent = new Intent(Intent.ACTION_MAIN);
                            intent.addCategory(Intent.CATEGORY_HOME);
                            startActivity(intent);
                        }
                    })

                    .setNegativeButton("View Results",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            // if this button is clicked, just close the dialog box and do nothing
                            dialog.cancel();
                        }
                    });

        AlertDialog alert = builder.create();
        alert.show();

    }

}

SecondActivity.java

package winfield.joe.wind.v1;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.Toast;

public class MainActivity extends Activity {

    // public var
    private EditText text;

    // default func
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Toast.makeText(this, "onCreate!", Toast.LENGTH_LONG).show();
        setContentView(R.layout.activity_main);
        // findViewById = Finds a view that was identified by the id attribute
        // from the XML that was processed in onCreate(Bundle).
        // (EditText) = typecast
        text = (EditText) findViewById(R.id.userInput);
    }

    //Will be executed by clicking on the calculate button because we assigned "calc" to the "onClick" Property

    public void calc(View view) {

        RadioButton toKilometers = (RadioButton) findViewById(R.id.toKilometers);
        RadioButton toKnots = (RadioButton) findViewById(R.id.toKnots);

        if (text.getText().length() == 0) {
            // if the text field is empty show the message "enter a valid number" via toast message
            Toast.makeText(this, "enter a valid number", Toast.LENGTH_LONG).show();
        } else {

            int result = R.string.userInput;
            Intent i = new Intent(MainActivity.this, SecondActivity.class);
            putExtra("userInput", result); 
            startActivity(i);

            // parse input Value from Text Field
            double inputValue = Double.parseDouble(text.getText().toString());
            // convert to...
            if (toKilometers.isChecked()) {
                text.setText(String.valueOf(convertToKM(inputValue)));
                // uncheck "to km" Button
                toKilometers.setChecked(false);
                // check "to knots" Button
                toKnots.setChecked(true);
            } else { /* if toKnots button isChecked() */
                text.setText(String.valueOf(convertToKnots(inputValue)));
                // uncheck "to knots" Button
                toKnots.setChecked(false);
                // check "to km" Button
                toKilometers.setChecked(true);
            }
        }

    }


    private void putExtra(String string, int result) {
        // TODO Auto-generated method stub
    }

    private double convertToKM(double inputValue) {
        // convert knots to km
        return (inputValue * 1.8);
    }

    private double convertToKnots(double inputValue) {
        // convert km to knots
        return (inputValue * 0.539956803);
    }

}

package winfield.joe.wind.v1;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;

public class SecondActivity extends Activity {

    Bundle extras = getIntent().getExtras();
    int result = extras.getInt("results"); 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
    }

    //onClick GoBack method assigned to the Go Back? button which returns the user to main activity from the second activity
    public void GoBack(View view) {

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Are you sure?");

            // set dialog message
            builder .setCancelable(false)

                    .setPositiveButton("Convert Again",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            //You return to Main Activity  
                            Intent intent = new Intent(SecondActivity.this, MainActivity.class);
                            startActivity(intent);
                        }
                    })

                    .setNeutralButton("Back to Home",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            //You return to the home page
                            Intent intent = new Intent(Intent.ACTION_MAIN);
                            intent.addCategory(Intent.CATEGORY_HOME);
                            startActivity(intent);
                        }
                    })

                    .setNegativeButton("View Results",new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog,int id) {
                            // if this button is clicked, just close the dialog box and do nothing
                            dialog.cancel();
                        }
                    });

        AlertDialog alert = builder.create();
        alert.show();

    }

}

活动\u main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true"
    android:background="@color/bgColor"
    android:orientation="vertical">

    <!--TITLE-->

    <TextView
        android:id="@+id/titleMain"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="22dp"
        android:gravity="center"
        android:text="@string/titleMain"
        android:textColor="@color/textColor"
        android:textColorHint="@color/textColor"
        android:textColorLink="#ffffff"
        android:textSize="30sp" />

    <!--USER-INPUT-->

    <EditText
        android:id="@+id/userInput"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:ems="10"
        android:hint="@+string/userInput"
        android:inputType="numberDecimal"
        android:paddingEnd="40dp"
        android:paddingStart="20dp"
        android:paddingTop="30dp" >

        <requestFocus />
    </EditText>

      <!--TWO RADIO BUTTONS-->
      <LinearLayout

          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:paddingLeft="10dp"
          android:paddingRight="10dp">

          <!--toKNOTS-->

          <RadioButton
              android:id="@+id/toKnots"
              android:layout_width="0dp"
              android:layout_height="wrap_content"
              android:layout_gravity="center"
              android:layout_marginStart="10dp"
              android:layout_marginTop="10dp"
              android:layout_weight="0.04"
              android:checked="true"
              android:text="@string/toKnots" />

          <!--toKM-->

          <RadioButton
              android:id="@+id/toKilometers"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_gravity="center"
              android:layout_marginEnd="20dp"
              android:layout_marginTop="10dp"
              android:text="@string/toKilometers" />

      </LinearLayout>

      <!--CALCULATE-->

      <Button
          android:id="@+id/valueCalc"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center"
          android:layout_marginEnd="10dp"
          android:layout_marginStart="10dp"
          android:layout_marginTop="30dp"
          android:onClick="calc"
          android:text="@string/valueCalc" />

</LinearLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_alignParentBottom="true"
    android:layout_alignParentEnd="true"
    android:background="@color/bgColor"
    android:orientation="vertical"
    tools:context="${relativePackage}.${activityClass}" >

    <!-- TITLE -->

    <TextView
        android:id="@+id/titleResults"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="24dp"
        android:gravity="center"
        android:text="@string/titleResults"
        android:textColor="@color/textColor"
        android:textColorHint="@color/textColor"
        android:textColorLink="#ffffff"
        android:textSize="25sp" />

    <EditText
        android:id="@+id/results"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="20dp"
        android:layout_marginTop="30dp"
        android:ems="10"
        android:hint="@string/results"
        android:inputType="numberDecimal"
        android:textColorHint="@color/textColor" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/GoBack"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="40dp"
        android:text="@string/GoBack"
        android:onClick="GoBack" />

</LinearLayout>

---

如果您想将任何内容从一个活动传递到另一个活动，可以使用

putExtra

进行传递，它会将数据从一个活动发送到另一个活动，并在另一个活动中使用

getExtras

获取该数据

要发送数据

String str = "value";
Intent launchResult = new Intent(MainActivity.this, SecondActivity.class);
putExtra("key", str);
startActivity(launchResult);

要在另一个活动中接收数据

Bundle extras = getIntent().getExtras();
String str = extras.getStr("key");

编辑：

在我的回答中，

键

是在

发送方活动

和

接收方活动

中必须保持相同的任何唯一值

之所以出现错误，是因为您传递了一个字符串值，其中必须传递键，并且接收器中的键活动也不匹配

请参见下面的更改，它应该可以工作

MainActivity.class

int result = R.string.userInput;
Intent i = new Intent(MainActivity.this, SecondActivity.class);
putExtra("userInput", result); 
startActivity(i);

Bundle extras = getIntent().getExtras();
int result = extras.getInt("userInput"); 

SecondActivity.class

int result = R.string.userInput;
Intent i = new Intent(MainActivity.this, SecondActivity.class);
putExtra("userInput", result); 
startActivity(i);

Bundle extras = getIntent().getExtras();
int result = extras.getInt("userInput"); 

---

使用下面的代码将值从一个活动传递到另一个活动

Intent launchResult = new Intent(MainActivity.this, SecondActivity.class);
launchResult.putExtra("output",result);

---

您无法编辑我的答案来解释您遇到的错误，请在我的答案上写下评论，以便我能够理解您仍然存在的问题。很抱歉，单击了错误的按钮。。我在你的回答下提交了更多的进展。谢谢，J。很抱歉，请点击编辑而不是回复。在我的主要活动中，我输入了：

code

intresult=R.string.userInput；意图i=新意图（MainActivity.this，SecondActivity.class）；putExtra（getString（R.string.userInput），result）；星触觉（i）

code

在我的第二个活动中，我输入了：

code

Bundle extras=getIntent（）.getExtra（）；int result=extras.getInt（“用户输入”）<代码>代码以适合我的数据类型和id，但我仍然会遇到错误。。有什么想法吗？哦，好吧，我明白为什么了。现在只有一个错误在

code

Bundle extras=getIntent（）.getExtra（）上<代码>代码，内容为：“类型意图的getExtra（）方法未定义”。不过，有大约20-30个建议的修复程序。这修复了Eclipse中的错误，但现在当我单击按钮更改活动时，它崩溃了。我不太清楚为什么，没有任何错误。我不太确定我还能给你看些什么？@joewinfield91编辑你的问题并添加你的

logcat

错误，这样我就能理解你的应用程序崩溃的原因。我可以编辑我的问题是的，但我有大约100多个logcat错误，所以在这个评论部分可能很难阅读所有这些错误，你不这样认为吗？