Java 如何访问以前的活动

我从OnCreate方法中的“firstplayer=player1.getText（）.toString（）；”中获取“java.lang.NullPointerException”。我的代码中的player1是上一个活动中的编辑文本之一

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.EditText;


public class startwith2player extends ActionBarActivity {
private boolean playerone = true , playertwo = false ;
private Integer score1 = 0 , score2 = 0;
private Integer flag4 = 0 , flag5 = 0 , flag6 = 0 , flag7 = 0, flag8 = 0, flag9 = 0 , flag10 = 0, flag11 = 0, flag12 = 0;
private Integer counter1 = 0 , counter2 = 0;
TextView tex1 ;
TextView tex2 ;
String firstplayer = "";
String secondplayer = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_startwith2player);
     tex1 = (TextView) findViewById(R.id.textView3);
     tex2 = (TextView) findViewById(R.id.textView4);
    EditText player1 = (EditText)findViewById(R.id.editText);
    EditText player2 = (EditText)findViewById(R.id.editText2);
    firstplayer = player1.getText().toString();
    secondplayer = player2.getText().toString();
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_startwith2player, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
public void refresh(){
    BlueAllBoxes();
    if(playerone){
        playerone = false;
        playertwo = true;
    }
    else{
    playerone = true;
    playertwo = false;
    }
    flag4 = 0 ; flag5 = 0 ; flag6 = 0 ; flag7 = 0; flag8 = 0; flag9 = 0 ; flag10 = 0; flag11 = 0; flag12 = 0;
    counter1 = 0 ; counter2 = 0;
}

public void BlueAllBoxes(){
    Button button4 = (Button) findViewById(R.id.button4);
    button4.setBackgroundColor(0xFF4B4BFF);
    Button button5 = (Button) findViewById(R.id.button5);
    button5.setBackgroundColor(0xFF4B4BFF);
    Button button6 = (Button) findViewById(R.id.button6);
    button6.setBackgroundColor(0xFF4B4BFF);
    Button button7 = (Button) findViewById(R.id.button7);
    button7.setBackgroundColor(0xFF4B4BFF);
    Button button8 = (Button) findViewById(R.id.button8);
    button8.setBackgroundColor(0xFF4B4BFF);
    Button button9 = (Button) findViewById(R.id.button9);
    button9.setBackgroundColor(0xFF4B4BFF);
    Button button10 = (Button) findViewById(R.id.button10);
    button10.setBackgroundColor(0xFF4B4BFF);
    Button button11 = (Button) findViewById(R.id.button11);
    button11.setBackgroundColor(0xFF4B4BFF);
    Button button12 = (Button) findViewById(R.id.button12);
    button12.setBackgroundColor(0xFF4B4BFF);
}
public void button4(View view) {
    if(counter1 == 3){
        if(flag4 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
               // tex1.setText(String.valueOf(score1));
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
            refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
 else {
        if (flag4 == 0) {
            flag4 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
              BlueAllBoxes();
        }
    }
}
public void button5(View view) {
    if(counter1 == 3){
        if(flag5 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

               if(playerone) {
                    score1 = score1 + 30;
                   tex1.setText(firstplayer + " : " + score1 );
                }
               else {
                   score2 = score2 + 30;
                   tex2.setText(secondplayer + " : " + score2 );
                }
                if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        if (flag5 == 0) {
            flag5 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
                BlueAllBoxes();
        }
    }
}
public void button6(View view) {
    if(counter1 == 3){
        if(flag6 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
                if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        if (flag6 == 0) {
            flag6 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
                BlueAllBoxes();
        }
    }
}
public void button7(View view) {
    if(counter1 == 3){
        if(flag7 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1);
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag7 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button8(View view) {
    if(counter1 == 3){
        if(flag8 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag8 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button9(View view) {
    if(counter1 == 3){
        if(flag9 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag9 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button10(View view) {
    if(counter1 == 3){
        if(flag10 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag10 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button11(View view) {
    if(counter1 == 3){
        if(flag11 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2);
            }
        }
    }
    else {
        flag11 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button12(View view) {
    if(counter1 == 3){
        if(flag12 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2);
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2);
            }
        }
    }
    else {
        flag12 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
 }

我认为findviewbyd（R.id.editText）；返回NULL，但它不应返回NULL，因为我在以前的活动中有EditText id为的EditText这里是我以前的XML活动

我想从上一个活动中的EditText中获取文本，然后在当前活动中使用该字符串。我该怎么做

我的代码中的player1是上一个活动中的编辑文本之一

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.EditText;


public class startwith2player extends ActionBarActivity {
private boolean playerone = true , playertwo = false ;
private Integer score1 = 0 , score2 = 0;
private Integer flag4 = 0 , flag5 = 0 , flag6 = 0 , flag7 = 0, flag8 = 0, flag9 = 0 , flag10 = 0, flag11 = 0, flag12 = 0;
private Integer counter1 = 0 , counter2 = 0;
TextView tex1 ;
TextView tex2 ;
String firstplayer = "";
String secondplayer = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_startwith2player);
     tex1 = (TextView) findViewById(R.id.textView3);
     tex2 = (TextView) findViewById(R.id.textView4);
    EditText player1 = (EditText)findViewById(R.id.editText);
    EditText player2 = (EditText)findViewById(R.id.editText2);
    firstplayer = player1.getText().toString();
    secondplayer = player2.getText().toString();
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_startwith2player, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
public void refresh(){
    BlueAllBoxes();
    if(playerone){
        playerone = false;
        playertwo = true;
    }
    else{
    playerone = true;
    playertwo = false;
    }
    flag4 = 0 ; flag5 = 0 ; flag6 = 0 ; flag7 = 0; flag8 = 0; flag9 = 0 ; flag10 = 0; flag11 = 0; flag12 = 0;
    counter1 = 0 ; counter2 = 0;
}

public void BlueAllBoxes(){
    Button button4 = (Button) findViewById(R.id.button4);
    button4.setBackgroundColor(0xFF4B4BFF);
    Button button5 = (Button) findViewById(R.id.button5);
    button5.setBackgroundColor(0xFF4B4BFF);
    Button button6 = (Button) findViewById(R.id.button6);
    button6.setBackgroundColor(0xFF4B4BFF);
    Button button7 = (Button) findViewById(R.id.button7);
    button7.setBackgroundColor(0xFF4B4BFF);
    Button button8 = (Button) findViewById(R.id.button8);
    button8.setBackgroundColor(0xFF4B4BFF);
    Button button9 = (Button) findViewById(R.id.button9);
    button9.setBackgroundColor(0xFF4B4BFF);
    Button button10 = (Button) findViewById(R.id.button10);
    button10.setBackgroundColor(0xFF4B4BFF);
    Button button11 = (Button) findViewById(R.id.button11);
    button11.setBackgroundColor(0xFF4B4BFF);
    Button button12 = (Button) findViewById(R.id.button12);
    button12.setBackgroundColor(0xFF4B4BFF);
}
public void button4(View view) {
    if(counter1 == 3){
        if(flag4 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
               // tex1.setText(String.valueOf(score1));
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
            refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
 else {
        if (flag4 == 0) {
            flag4 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
              BlueAllBoxes();
        }
    }
}
public void button5(View view) {
    if(counter1 == 3){
        if(flag5 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

               if(playerone) {
                    score1 = score1 + 30;
                   tex1.setText(firstplayer + " : " + score1 );
                }
               else {
                   score2 = score2 + 30;
                   tex2.setText(secondplayer + " : " + score2 );
                }
                if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        if (flag5 == 0) {
            flag5 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
                BlueAllBoxes();
        }
    }
}
public void button6(View view) {
    if(counter1 == 3){
        if(flag6 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
                if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        if (flag6 == 0) {
            flag6 = 1;
            view.setBackgroundColor(0xFF67FF5A);
            counter1++;
            if(counter1 == 3)
                BlueAllBoxes();
        }
    }
}
public void button7(View view) {
    if(counter1 == 3){
        if(flag7 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1);
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag7 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button8(View view) {
    if(counter1 == 3){
        if(flag8 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag8 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button9(View view) {
    if(counter1 == 3){
        if(flag9 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag9 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button10(View view) {
    if(counter1 == 3){
        if(flag10 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2 );
            }
        }
    }
    else {
        flag10 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button11(View view) {
    if(counter1 == 3){
        if(flag11 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2 );
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2);
            }
        }
    }
    else {
        flag11 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
public void button12(View view) {
    if(counter1 == 3){
        if(flag12 == 1) {
            view.setBackgroundColor(0xFF67FF5A);
            counter2++;

            if(playerone) {
                score1 = score1 + 30;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 + 30;
                tex2.setText(secondplayer + " : " + score2);
            }
            if(counter2 == 3)
                refresh();
        }
        else{
            view.setBackgroundColor(0xFFFF231E);
            if(playerone) {
                score1 = score1 - 10;
                tex1.setText(firstplayer + " : " + score1 );
            }
            else {
                score2 = score2 - 10;
                tex2.setText(secondplayer + " : " + score2);
            }
        }
    }
    else {
        flag12 = 1;
        view.setBackgroundColor(0xFF67FF5A);
        counter1++;
        if(counter1 == 3)
            BlueAllBoxes();
    }
}
 }

这是一种糟糕的设计实践，如果没有实质性的欺骗，这是行不通的

我认为findviewbyd（R.id.editText）；返回NULL，但它不应返回NULL，因为我在以前的活动中有EditText id为的EditText这里是我以前的XML活动

您无法通过这种方式获得对另一个活动视图的引用，即使可以，您也不应该假设，一旦该活动离开屏幕并且您当前的活动已替换它，这些视图仍然有效

相反，让第一个活动将此信息转发给第二个活动作为额外的意图。如果信息是相当持久的，你也可以考虑把它放在共享的首选项中。在某些情况下，将其存储为应用程序对象的字段可能是合适的，在一些特殊情况下，不可能使用全局变量

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始终仔细检查前一项活动可能未获得该值的可能性；事实上，取决于清单的设置方式，如果Android需要终止并重新创建您的进程，那么之前的活动可能从未运行过，或者在当前进程中可能没有运行过，因为在此期间运行了其他资源匮乏的程序。

答案很简单。文本为空。看它上面的那条线

EditText player1 = (EditText)findViewById(R.id.editText);
    EditText player2 = (EditText)findViewById(R.id.editText2);
    firstplayer = player1.getText().toString();
    secondplayer = player2.getText().toString();

您已经初始化了为空的player1和player2，然后可以使用firstplayer=player1.getText（）.toString（）；从空的player1获取文本

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我的建议是添加按钮，然后使用gettext（）获取其值。

我对本机Android开发一无所知，但很明显，

findViewById（R.id.editText）

正在返回

null

。我在这里看到了一大堆关于Android资源的问题，所以我猜在资源定义上有一些问题，你在寻找什么。在Android中，当它发生时，你认为它不应该清理项目。如何调用取决于哪个IDE，但通常在“构建”菜单中。之所以会出现错误，是因为调用的edittext不在活动的xml范围内，即R.layout.activity\u startwith2player。这不是从其他活动中获取文本的正确方法。使用意图将数据从一个活动传递到另一个活动。从上一个活动中，将意图传递给第二个活动。Intent Intent=新Intent（这个，startwith2player.class）；intent.putExtra（“firstplayer”，player1.getText（）.toString（））；意向性；在startwith2player活动中，删除player1的编辑文本，因为这将导致错误。您可以通过字符串firstplayer=intent.getStringExtra（“firstplayer”）获取从上一个活动传递的数据；这不是问题所在