Android 从第一个活动到第二个活动的返回按钮会使应用程序崩溃

好的，这就是我的问题，我有两个活动，它们都是用来输入信息的。一个通向另一个。 当我在第二个活动中按下返回按钮时，应用程序崩溃，我不知道为什么

这是第一个活动的代码：

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.support.design.widget.Snackbar;

public class Add_Score extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add__score);
        final Button Next = (Button)findViewById(R.id.buttonNext);
        final Intent Add_Comment_Picture = new Intent(this, Add_Comment_Picture.class);

        Next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                String score = ((EditText) findViewById(R.id.editText)).getText().toString();
                String desc = ((EditText)findViewById(R.id.editTextDesc)).getText().toString();
                if(score.compareTo("") != 0 && desc.compareTo("") != 0){
                    startActivity(Add_Comment_Picture);
                    Add_Comment_Picture.putExtra("score", score);
                    Add_Comment_Picture.putExtra("desc" , desc );
                    startActivity(Add_Comment_Picture);
                }
                else{
                    Snackbar.make(v , "Please fill in the score and description" , Snackbar.LENGTH_LONG).show();
                }
            }
        });
    }
}

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Build;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

public class Add_Comment_Picture extends AppCompatActivity {
    static final int CAM_REQUEST = 1;
    static final int RESULT_LOAD_IMAGE = 2;
    ImageView imageView;
    ImageButton button;
    ImageButton buttonGallery;
    String mCurrentPhotoPath;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add__comment__picture);
        button = (ImageButton) findViewById(R.id.imageButtonCamera);
        imageView = (ImageView) findViewById(R.id.imageView);
        buttonGallery = (ImageButton) findViewById(R.id.imageButtonGallery_f);


        Calendar c = Calendar.getInstance();

        String hours = Globals.getTimePadding(c.get(Calendar.HOUR));
        String minutes = Globals.getTimePadding(c.get(Calendar.MINUTE));
        String time = hours + ":" + minutes;
        String value = getIntent().getExtras().getString("score");
        String value2 = getIntent().getExtras().getString("desc");
        TextView scoreText = (TextView) findViewById(R.id.textViewScore);
        scoreText.setText("Score: " + value);
        TextView t = (TextView) findViewById(R.id.textViewDatec);
        t.setText(time);
        TextView descText = (TextView) findViewById(R.id.textViewDesc);
        descText.setText(value2);


        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent camera_intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                File file = getFile();
                camera_intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
                startActivityForResult(camera_intent, CAM_REQUEST);
            }
        });

        buttonGallery.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent intent_gallery = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                startActivityForResult(intent_gallery , RESULT_LOAD_IMAGE);
            }
        });

    }



    private String createFileName(){
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        return "JPEG_" + timeStamp + "_.jpg";
    }

    @Override
    protected void onStart() {
        super.onStart();

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

            int hasWritePermission = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE);
            int hasReadPermission = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
            int hasCameraPermission = checkSelfPermission(Manifest.permission.CAMERA);

            List<String> permissions = new ArrayList<String>();
            if (hasWritePermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.WRITE_EXTERNAL_STORAGE);
            }

            if (hasReadPermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.READ_EXTERNAL_STORAGE);
            }

            if (hasCameraPermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.CAMERA);
            }
            if (!permissions.isEmpty()) {
                requestPermissions(permissions.toArray(new String[permissions.size()]), 111);
            }
        }


    }

    private File getFile() {
        File folder = new File("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos");
        if (!folder.exists()) {
            folder.mkdir();
        }

        mCurrentPhotoPath = createFileName();
        File image_file = new File(folder,mCurrentPhotoPath);
        return image_file;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode == CAM_REQUEST){
            copyFile("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos/" + mCurrentPhotoPath , getFilesDir().toString() + "/" + mCurrentPhotoPath);
            File d = new File("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos/" + mCurrentPhotoPath);
            d.delete();
            imageView.setImageDrawable(Drawable.createFromPath(getFilesDir().toString() + "/" + mCurrentPhotoPath));
        }
        if(requestCode == RESULT_LOAD_IMAGE){
            if(data != null){
                Uri selectedImage = data.getData();
                String[] filePathColumn = { MediaStore.Images.Media.DATA };
                Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
                cursor.moveToFirst();
                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                String picturePath = cursor.getString(columnIndex);
                cursor.close();
                mCurrentPhotoPath = createFileName();
                copyFile(picturePath, getFilesDir().toString() + "/" + mCurrentPhotoPath);
                imageView.setImageDrawable(Drawable.createFromPath(getFilesDir().toString() + "/" + mCurrentPhotoPath));
            }
        }

        super.onActivityResult(requestCode, resultCode, data);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 111: {
                for (int i = 0; i < permissions.length; i++) {
                    if (grantResults[i] == PackageManager.PERMISSION_GRANTED) {
                        System.out.println("Permissions --> " + "Permission Granted: " + permissions[i]);


                    } else if (grantResults[i] == PackageManager.PERMISSION_DENIED) {
                        System.out.println("Permissions --> " + "Permission Denied: " + permissions[i]);

                    }
                }
            }
            break;
            default: {
                super.onRequestPermissionsResult(requestCode, permissions, grantResults);
            }
        }
    }

    public void copyFile(String path1 , String path2){
        InputStream inStream = null;
        OutputStream outStream = null;
        try{

            File file1 =new File(path1);
            File file2 =new File(path2);

            inStream = new FileInputStream(file1);
            outStream = new FileOutputStream(file2); // for override file content
            //outStream = new FileOutputStream(file2,<strong>true</strong>); // for append file content

            byte[] buffer = new byte[1024];

            int length;
            while ((length = inStream.read(buffer)) > 0){
                outStream.write(buffer, 0, length);
            }

            if (inStream != null)inStream.close();
            if (outStream != null)outStream.close();

            System.out.println("File Copied..");
        }catch(IOException e){
            e.printStackTrace();
        }
    }
}

这是第二个活动的代码：

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.support.design.widget.Snackbar;

public class Add_Score extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add__score);
        final Button Next = (Button)findViewById(R.id.buttonNext);
        final Intent Add_Comment_Picture = new Intent(this, Add_Comment_Picture.class);

        Next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                String score = ((EditText) findViewById(R.id.editText)).getText().toString();
                String desc = ((EditText)findViewById(R.id.editTextDesc)).getText().toString();
                if(score.compareTo("") != 0 && desc.compareTo("") != 0){
                    startActivity(Add_Comment_Picture);
                    Add_Comment_Picture.putExtra("score", score);
                    Add_Comment_Picture.putExtra("desc" , desc );
                    startActivity(Add_Comment_Picture);
                }
                else{
                    Snackbar.make(v , "Please fill in the score and description" , Snackbar.LENGTH_LONG).show();
                }
            }
        });
    }
}

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.os.Build;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

public class Add_Comment_Picture extends AppCompatActivity {
    static final int CAM_REQUEST = 1;
    static final int RESULT_LOAD_IMAGE = 2;
    ImageView imageView;
    ImageButton button;
    ImageButton buttonGallery;
    String mCurrentPhotoPath;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add__comment__picture);
        button = (ImageButton) findViewById(R.id.imageButtonCamera);
        imageView = (ImageView) findViewById(R.id.imageView);
        buttonGallery = (ImageButton) findViewById(R.id.imageButtonGallery_f);


        Calendar c = Calendar.getInstance();

        String hours = Globals.getTimePadding(c.get(Calendar.HOUR));
        String minutes = Globals.getTimePadding(c.get(Calendar.MINUTE));
        String time = hours + ":" + minutes;
        String value = getIntent().getExtras().getString("score");
        String value2 = getIntent().getExtras().getString("desc");
        TextView scoreText = (TextView) findViewById(R.id.textViewScore);
        scoreText.setText("Score: " + value);
        TextView t = (TextView) findViewById(R.id.textViewDatec);
        t.setText(time);
        TextView descText = (TextView) findViewById(R.id.textViewDesc);
        descText.setText(value2);


        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent camera_intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                File file = getFile();
                camera_intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
                startActivityForResult(camera_intent, CAM_REQUEST);
            }
        });

        buttonGallery.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent intent_gallery = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                startActivityForResult(intent_gallery , RESULT_LOAD_IMAGE);
            }
        });

    }



    private String createFileName(){
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        return "JPEG_" + timeStamp + "_.jpg";
    }

    @Override
    protected void onStart() {
        super.onStart();

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

            int hasWritePermission = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE);
            int hasReadPermission = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
            int hasCameraPermission = checkSelfPermission(Manifest.permission.CAMERA);

            List<String> permissions = new ArrayList<String>();
            if (hasWritePermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.WRITE_EXTERNAL_STORAGE);
            }

            if (hasReadPermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.READ_EXTERNAL_STORAGE);
            }

            if (hasCameraPermission != PackageManager.PERMISSION_GRANTED) {
                permissions.add(Manifest.permission.CAMERA);
            }
            if (!permissions.isEmpty()) {
                requestPermissions(permissions.toArray(new String[permissions.size()]), 111);
            }
        }


    }

    private File getFile() {
        File folder = new File("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos");
        if (!folder.exists()) {
            folder.mkdir();
        }

        mCurrentPhotoPath = createFileName();
        File image_file = new File(folder,mCurrentPhotoPath);
        return image_file;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode == CAM_REQUEST){
            copyFile("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos/" + mCurrentPhotoPath , getFilesDir().toString() + "/" + mCurrentPhotoPath);
            File d = new File("sdcard/data/data/com.yuvaleliav1gmail.foodchain/photos/" + mCurrentPhotoPath);
            d.delete();
            imageView.setImageDrawable(Drawable.createFromPath(getFilesDir().toString() + "/" + mCurrentPhotoPath));
        }
        if(requestCode == RESULT_LOAD_IMAGE){
            if(data != null){
                Uri selectedImage = data.getData();
                String[] filePathColumn = { MediaStore.Images.Media.DATA };
                Cursor cursor = getContentResolver().query(selectedImage, filePathColumn, null, null, null);
                cursor.moveToFirst();
                int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
                String picturePath = cursor.getString(columnIndex);
                cursor.close();
                mCurrentPhotoPath = createFileName();
                copyFile(picturePath, getFilesDir().toString() + "/" + mCurrentPhotoPath);
                imageView.setImageDrawable(Drawable.createFromPath(getFilesDir().toString() + "/" + mCurrentPhotoPath));
            }
        }

        super.onActivityResult(requestCode, resultCode, data);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 111: {
                for (int i = 0; i < permissions.length; i++) {
                    if (grantResults[i] == PackageManager.PERMISSION_GRANTED) {
                        System.out.println("Permissions --> " + "Permission Granted: " + permissions[i]);


                    } else if (grantResults[i] == PackageManager.PERMISSION_DENIED) {
                        System.out.println("Permissions --> " + "Permission Denied: " + permissions[i]);

                    }
                }
            }
            break;
            default: {
                super.onRequestPermissionsResult(requestCode, permissions, grantResults);
            }
        }
    }

    public void copyFile(String path1 , String path2){
        InputStream inStream = null;
        OutputStream outStream = null;
        try{

            File file1 =new File(path1);
            File file2 =new File(path2);

            inStream = new FileInputStream(file1);
            outStream = new FileOutputStream(file2); // for override file content
            //outStream = new FileOutputStream(file2,<strong>true</strong>); // for append file content

            byte[] buffer = new byte[1024];

            int length;
            while ((length = inStream.read(buffer)) > 0){
                outStream.write(buffer, 0, length);
            }

            if (inStream != null)inStream.close();
            if (outStream != null)outStream.close();

            System.out.println("File Copied..");
        }catch(IOException e){
            e.printStackTrace();
        }
    }
}

---

您正在调用

startActivity

两次，一次是在添加额外内容之前，一次是在添加额外内容之后

startActivity(Add_Comment_Picture);
Add_Comment_Picture.putExtra("score", score);
Add_Comment_Picture.putExtra("desc" , desc );
startActivity(Add_Comment_Picture);

通过这种方式，您实际上是在开始活动之前，在意图中添加了额外的内容。只需删除第一个呼叫并保持如下状态：

Add_Comment_Picture.putExtra("score", score);
Add_Comment_Picture.putExtra("desc" , desc );
startActivity(Add_Comment_Picture);

这只是一条建议：用小写字母命名变量并使用驼峰大小写是一种常规做法（您可以称之为

Add\u Comment\u Picture

，而不是

addCommentPictureIntent

）。另外，当变量很多时，在末尾连接它所表示的类型是区分变量的一种好方法。您可以在线阅读更多关于约定的内容，但它们对于遵循约定并使代码更具可读性非常有用

---

您正在调用

startActivity

两次，一次是在添加额外内容之前，一次是在添加额外内容之后

startActivity(Add_Comment_Picture);
Add_Comment_Picture.putExtra("score", score);
Add_Comment_Picture.putExtra("desc" , desc );
startActivity(Add_Comment_Picture);

通过这种方式，您实际上是在开始活动之前，在意图中添加了额外的内容。只需删除第一个呼叫并保持如下状态：

Add_Comment_Picture.putExtra("score", score);
Add_Comment_Picture.putExtra("desc" , desc );
startActivity(Add_Comment_Picture);

这只是一条建议：用小写字母命名变量并使用驼峰大小写是一种常规做法（您可以称之为

Add\u Comment\u Picture

，而不是

addCommentPictureIntent

）。另外，当变量很多时，在末尾连接它所表示的类型是区分变量的一种好方法。您可以在线阅读更多关于约定的内容，但它们对于遵循约定并使代码更具可读性非常有用

---

这是

NPE

，所以我建议你去看看，以便更好地理解

NPE

在您的情况下，

bundle

是

null

，这意味着您正试图从

null

对象访问

字符串。因此，最好在访问之前检查
getIntent（）.getExtras（）
是否为
null
，以防止类似的崩溃

if(getIntent().getExtras() !=null){
    String value = getIntent().getExtras().getString("score");
    String value2 = getIntent().getExtras().getString("desc");
    ... 
}

或对于特定密钥的预先检查，您可以这样做

Bundle extras = getIntent().getExtras();
if(extras != null){
     if (extras.containsKey("score") && extras.containsKey("desc")){
        String value = getIntent().getExtras().getString("score");
        String value2 = getIntent().getExtras().getString("desc");
         ...
       }
  }

这是
NPE
，所以我建议你去看看，以便更好地理解
NPE

在您的情况下，
bundle
是
null
，这意味着您正试图从
null
对象访问
字符串。因此，最好在访问之前检查
getIntent（）.getExtras（）
是否为
null
，以防止类似的崩溃

if(getIntent().getExtras() !=null){
    String value = getIntent().getExtras().getString("score");
    String value2 = getIntent().getExtras().getString("desc");
    ... 
}

或对于特定密钥的预先检查，您可以这样做

Bundle extras = getIntent().getExtras();
if(extras != null){
     if (extras.containsKey("score") && extras.containsKey("desc")){
        String value = getIntent().getExtras().getString("score");
        String value2 = getIntent().getExtras().getString("desc");
         ...
       }
  }

使用下面的代码（您的问题是在放入额外内容之前开始活动）：

使用下面的代码（您的问题是在放入额外内容之前开始活动）：

可能重复的可能重复的可能重复的为什么你真的偷了我的答案，告诉我吧？@Vucko对不起，伙计。但我没有从任何人那里偷任何东西。我只是给出了我认为正确的答案。如果你把你的答案和我的答案相比较，我想你可以做到这一点。不管怎么说，我觉得“偷”这个词不太合适。我甚至不在乎，这太可怕了。如果你不在乎，你就不用“告诉我那件事”。如果你不在乎，你就不用“告诉我那件事”。我认为最可怕的是你的粗鲁。不管怎样，我只是关心尤瓦利亚夫的问题已经解决，如果尤瓦利亚夫将你的答案标记为已接受的答案，我将表示欢迎。你为什么真的偷了我的答案，告诉我吧？@Vucko抱歉的人。但我没有从任何人那里偷任何东西。我只是给出了我认为正确的答案。如果你把你的答案和我的答案相比较，我想你可以做到这一点。不管怎么说，我觉得“偷”这个词不太合适。我甚至不在乎，这太可怕了。如果你不在乎，你就不用“告诉我那件事”。如果你不在乎，你就不用“告诉我那件事”。我认为最可怕的是你的粗鲁。不管怎样，我只关心YuvalEliav的问题已经解决，如果YuvalEliav将您的答案标记为已接受的答案，我将表示欢迎。